/*
** SPDX-License-Identifier: BSD-3-Clause
** Copyright Contributors to the OpenEXR Project.
*/

#include "openexr_chunkio.h"

#include "internal_coding.h"
#include "internal_structs.h"
#include "internal_util.h"
#include "internal_xdr.h"
#include "internal_file.h"

#include <limits.h>
#include <string.h>

/**************************************/

exr_result_t extract_chunk_table (
    exr_const_context_t   ctxt,
    exr_const_priv_part_t part,
    uint64_t**            chunktable,
    uint64_t*             chunkminoffset);

/**************************************/

static exr_result_t
validate_and_compute_tile_chunk_off (
    exr_const_context_t   ctxt,
    exr_const_priv_part_t part,
    int                   tilex,
    int                   tiley,
    int                   levelx,
    int                   levely,
    int32_t*              chunkoffout)
{
    int                        numx, numy;
    const exr_attr_tiledesc_t* tiledesc;
    int64_t                    chunkoff = 0;

    if (!part->tiles || part->num_tile_levels_x <= 0 ||
        part->num_tile_levels_y <= 0 || !part->tile_level_tile_count_x ||
        !part->tile_level_tile_count_y)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_MISSING_REQ_ATTR,
            "Tile descriptor data missing or corrupt");
    }

    if (tilex < 0 || tiley < 0 || levelx < 0 || levely < 0)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid tile indices provided (%d, %d, level %d, %d)",
            tilex,
            tiley,
            levelx,
            levely);

    tiledesc = part->tiles->tiledesc;
    switch (EXR_GET_TILE_LEVEL_MODE ((*tiledesc)))
    {
        case EXR_TILE_ONE_LEVEL:
        case EXR_TILE_MIPMAP_LEVELS:
            if (levelx != levely)
            {
                return ctxt->print_error (
                    ctxt,
                    EXR_ERR_INVALID_ARGUMENT,
                    "Request for tile (%d, %d) level (%d, %d), but single level and mipmap tiles must have same level x and y",
                    tilex,
                    tiley,
                    levelx,
                    levely);
            }
            if (levelx >= part->num_tile_levels_x)
            {
                return ctxt->print_error (
                    ctxt,
                    EXR_ERR_INVALID_ARGUMENT,
                    "Request for tile (%d, %d) level %d, but level past available levels (%d)",
                    tilex,
                    tiley,
                    levelx,
                    part->num_tile_levels_x);
            }

            numx = part->tile_level_tile_count_x[levelx];
            numy = part->tile_level_tile_count_y[levelx];

            if (tilex >= numx || tiley >= numy)
            {
                return ctxt->print_error (
                    ctxt,
                    EXR_ERR_INVALID_ARGUMENT,
                    "Request for tile (%d, %d) level %d, but level only has %d x %d tiles",
                    tilex,
                    tiley,
                    levelx,
                    numx,
                    numy);
            }

            for (int l = 0; l < levelx; ++l)
                chunkoff +=
                    ((int64_t) part->tile_level_tile_count_x[l] *
                     (int64_t) part->tile_level_tile_count_y[l]);
            chunkoff += tiley * numx + tilex;
            break;

        case EXR_TILE_RIPMAP_LEVELS:
            if (levelx >= part->num_tile_levels_x)
            {
                return ctxt->print_error (
                    ctxt,
                    EXR_ERR_INVALID_ARGUMENT,
                    "Request for tile (%d, %d) level %d, %d, but x level past available levels (%d)",
                    tilex,
                    tiley,
                    levelx,
                    levely,
                    part->num_tile_levels_x);
            }
            if (levely >= part->num_tile_levels_y)
            {
                return ctxt->print_error (
                    ctxt,
                    EXR_ERR_INVALID_ARGUMENT,
                    "Request for tile (%d, %d) level %d, %d, but y level past available levels (%d)",
                    tilex,
                    tiley,
                    levelx,
                    levely,
                    part->num_tile_levels_y);
            }

            numx = part->tile_level_tile_count_x[levelx];
            numy = part->tile_level_tile_count_y[levely];

            if (tilex >= numx || tiley >= numy)
            {
                return ctxt->print_error (
                    ctxt,
                    EXR_ERR_INVALID_ARGUMENT,
                    "Request for tile (%d, %d) at rip level %d, %d level only has %d x %d tiles",
                    tilex,
                    tiley,
                    levelx,
                    levely,
                    numx,
                    numy);
            }

            for (int ly = 0; ly < levely; ++ly)
            {
                for (int lx = 0; lx < part->num_tile_levels_x; ++lx)
                {
                    chunkoff +=
                        ((int64_t) part->tile_level_tile_count_x[lx] *
                         (int64_t) part->tile_level_tile_count_y[ly]);
                }
            }
            for (int lx = 0; lx < levelx; ++lx)
            {
                chunkoff +=
                    ((int64_t) part->tile_level_tile_count_x[lx] *
                     (int64_t) numy);
            }
            chunkoff += tiley * numx + tilex;
            break;
        case EXR_TILE_LAST_TYPE:
        default:
            return ctxt->print_error (
                ctxt, EXR_ERR_UNKNOWN, "Invalid tile description");
    }

    if (chunkoff >= part->chunk_count)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_UNKNOWN,
            "Invalid tile chunk offset %" PRId64 " (%d avail)",
            chunkoff,
            part->chunk_count);
    }

    *chunkoffout = (int32_t) chunkoff;
    return EXR_ERR_SUCCESS;
}

/**************************************/

struct priv_chunk_leader
{
    int32_t partnum;
    union
    {
        int32_t scanline_y;
        struct
        {
            int32_t tile_x;
            int32_t tile_y;
            int32_t level_x;
            int32_t level_y;
        };
    };
    uint8_t _pad[4];
    uint64_t packed_size;
};

static exr_result_t
extract_chunk_leader (
    exr_const_context_t       ctxt,
    exr_const_priv_part_t     part,
    int                       partnum,
    uint64_t                  offset,
    uint64_t*                 next_offset,
    struct priv_chunk_leader* leaderdata)
{
    exr_result_t rv = EXR_ERR_SUCCESS;
    int32_t      data[6];
    uint64_t     nextoffset = offset;
    int          rdcnt, ntoread;
    int64_t      maxval = (int64_t) INT_MAX; // 2GB

    if (ctxt->file_size > 0) maxval = ctxt->file_size;

    if (part->storage_mode == EXR_STORAGE_SCANLINE ||
        part->storage_mode == EXR_STORAGE_DEEP_SCANLINE)
    {
        ntoread = (ctxt->is_multipart) ? 2 : 1;
        if (part->storage_mode != EXR_STORAGE_DEEP_SCANLINE) ++ntoread;
    }
    else if (part->storage_mode == EXR_STORAGE_DEEP_TILED)
    {
        if (ctxt->is_multipart)
            ntoread = 5;
        else
            ntoread = 4;
    }
    else if (ctxt->is_multipart)
        ntoread = 6;
    else
        ntoread = 5;

    rv = ctxt->do_read (
        ctxt,
        data,
        (size_t) ntoread * sizeof (int32_t),
        &nextoffset,
        NULL,
        EXR_MUST_READ_ALL);
    if (rv != EXR_ERR_SUCCESS) return rv;

    priv_to_native32 (data, ntoread);

    rdcnt = 0;
    if (ctxt->is_multipart)
    {
        if (data[rdcnt] != partnum)
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Invalid part number reconstructing chunk table: expect %d, found %d",
                partnum,
                data[rdcnt]);
        }
        leaderdata->partnum = partnum;
        ++rdcnt;
    }
    else
        leaderdata->partnum = 0;

    if (part->storage_mode == EXR_STORAGE_SCANLINE ||
        part->storage_mode == EXR_STORAGE_DEEP_SCANLINE)
    {
        leaderdata->scanline_y = data[rdcnt];
    }
    else
    {
        leaderdata->tile_x  = data[rdcnt++];
        leaderdata->tile_y  = data[rdcnt++];
        leaderdata->level_x = data[rdcnt++];
        leaderdata->level_y = data[rdcnt];
    }

    if (part->storage_mode == EXR_STORAGE_DEEP_SCANLINE ||
        part->storage_mode == EXR_STORAGE_DEEP_TILED)
    {
        int64_t deep_data[3];

        rv = ctxt->do_read (
            ctxt,
            deep_data,
            3 * sizeof (int64_t),
            &nextoffset,
            NULL,
            EXR_MUST_READ_ALL);

        if (rv != EXR_ERR_SUCCESS) return rv;
        priv_to_native64 (deep_data, 3);

        if (deep_data[0] < 0 || (deep_data[0] == 0 && (deep_data[1] != 0 || deep_data[2] != 0)))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Invalid chunk size reconstructing chunk table: found out of range sample count %" PRId64,
                deep_data[0]);
        }
        if (deep_data[1] < 0 || deep_data[1] > maxval ||
            (deep_data[1] == 0 && deep_data[2] != 0))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Invalid chunk size reconstructing chunk table: found out of range %" PRId64,
                deep_data[1]);
        }
        leaderdata->packed_size = (uint64_t) deep_data[0] + (uint64_t) deep_data[1];
    }
    else
    {
        ++rdcnt;

        if (data[rdcnt] < 0 || data[rdcnt] > maxval)
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Invalid chunk size reconstructing chunk table: found out of range %d",
                data[rdcnt]);
        }
        leaderdata->packed_size = (uint64_t) data[rdcnt];
    }
    nextoffset += leaderdata->packed_size;

    *next_offset = nextoffset;
    return rv;
}

static exr_result_t
extract_chunk_size (
    exr_const_context_t   ctxt,
    exr_const_priv_part_t part,
    int                   partnum,
    uint64_t              offset,
    uint64_t*             next_offset)
{
    struct priv_chunk_leader leader;

    return extract_chunk_leader (
        ctxt, part, partnum, offset, next_offset, &leader);
}

/**************************************/

static exr_result_t
read_and_validate_chunk_leader (
    exr_const_context_t   ctxt,
    exr_const_priv_part_t part,
    int                   partnum,
    uint64_t              offset,
    int*                  indexio,
    uint64_t*             next_offset)
{
    exr_result_t             rv = EXR_ERR_SUCCESS;
    struct priv_chunk_leader leader;

    rv = extract_chunk_leader (
        ctxt, part, partnum, offset, next_offset, &leader);
    if (rv != EXR_ERR_SUCCESS) return rv;

    if (part->storage_mode == EXR_STORAGE_SCANLINE ||
        part->storage_mode == EXR_STORAGE_DEEP_SCANLINE)
    {
        int64_t chunk = (int64_t) leader.scanline_y;
        chunk -= (int64_t) part->data_window.min.y;
        chunk /= part->lines_per_chunk;

        // scanlines can be more strict about the ordering
        if (*indexio != (int)chunk || chunk < 0 || chunk >= part->chunk_count)
            rv = ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Invalid chunk index: %" PRId64
                " reading scanline %d (datawindow min %d) with lines per chunk %d",
                chunk,
                leader.scanline_y,
                part->data_window.min.y,
                part->lines_per_chunk);

        *indexio = (int) chunk;
    }
    else
    {
        // because of random order, just go with it if the coordinates look sane
        int32_t cidx = 0;

        rv = validate_and_compute_tile_chunk_off (
            ctxt,
            part,
            leader.tile_x,
            leader.tile_y,
            leader.level_x,
            leader.level_y,
            &cidx);

        *indexio = cidx;
    }

    return rv;
}

// this should behave the same as the old ImfMultiPartInputFile
static exr_result_t
reconstruct_chunk_table (
    exr_const_context_t ctxt, exr_const_priv_part_t part, uint64_t* chunktable)
{
    exr_result_t          rv          = EXR_ERR_SUCCESS;
    exr_result_t          firstfailrv = EXR_ERR_SUCCESS;
    uint64_t              offset_start, chunk_start, max_offset;
    uint64_t*             curctable;
    exr_const_priv_part_t curpart = NULL;
    int                   found_ci, computed_ci, partnum = 0;
    size_t                chunkbytes;

    curpart      = ctxt->parts[ctxt->num_parts - 1];
    offset_start = curpart->chunk_table_offset;
    offset_start += sizeof (uint64_t) * (uint64_t) curpart->chunk_count;

    curpart = ctxt->parts[partnum];
    while (curpart != part)
    {
        ++partnum;
        curpart = ctxt->parts[partnum];
    }

    max_offset = (uint64_t) -1;
    if (ctxt->file_size > 0) max_offset = (uint64_t) ctxt->file_size;

    // for multi-part, need to start at the first part and extract everything, then
    // work our way back up to this one, then grab the end of the previous part
    if (partnum > 0)
    {
        curpart = ctxt->parts[partnum - 1];
        rv      = extract_chunk_table (ctxt, curpart, &curctable, &chunk_start);
        if (rv != EXR_ERR_SUCCESS) return rv;

        chunk_start = offset_start;
        for (int ci = 0; ci < curpart->chunk_count; ++ci)
        {
            if (curctable[ci] > chunk_start && curctable[ci] < max_offset)
                chunk_start = curctable[ci];
        }

        rv = extract_chunk_size (
            ctxt, curpart, partnum - 1, chunk_start, &offset_start);
        if (rv != EXR_ERR_SUCCESS) return rv;
    }

    chunkbytes = (size_t) part->chunk_count * sizeof (uint64_t);
    curctable  = (uint64_t*) ctxt->alloc_fn (chunkbytes);
    if (!curctable) return EXR_ERR_OUT_OF_MEMORY;

    memset (curctable, 0, chunkbytes);

    for (int ci = 0; ci < part->chunk_count; ++ci)
    {
        if (chunktable[ci] >= offset_start && chunktable[ci] < max_offset)
        {
            offset_start = chunktable[ci];
        }
        chunk_start = offset_start;
        computed_ci = ci;
        if (part->lineorder == EXR_LINEORDER_DECREASING_Y)
            computed_ci = part->chunk_count - (ci + 1);
        found_ci = computed_ci;

        rv = read_and_validate_chunk_leader (
            ctxt, part, partnum, chunk_start, &found_ci, &offset_start);
        if (rv != EXR_ERR_SUCCESS)
        {
            chunk_start = 0;
            if (firstfailrv == EXR_ERR_SUCCESS) firstfailrv = rv;
        }

        if (found_ci >= 0 && found_ci < part->chunk_count)
        {
            if (curctable[found_ci] == 0) curctable[found_ci] = chunk_start;
        }
    }
    if (firstfailrv == EXR_ERR_SUCCESS)
    {
        memcpy (chunktable, curctable, chunkbytes);
    }
    else
    {
        for (int ci = 0; ci < part->chunk_count; ++ci)
        {
            if ( curctable[ci] != 0 )
                chunktable[ci] = curctable[ci];
        }
    }
    ctxt->free_fn (curctable);

    return firstfailrv;
}

exr_result_t
exr_get_chunk_table_offset (
    exr_const_context_t ctxt, int part_index, uint64_t* chunk_offset_out)
{
    EXR_LOCK_WRITE_AND_DEFINE_PART (part_index);

    if (!chunk_offset_out)
        return EXR_UNLOCK_WRITE_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_INVALID_ARGUMENT));

    *chunk_offset_out = part->chunk_table_offset;
    return EXR_UNLOCK_WRITE_AND_RETURN (EXR_ERR_SUCCESS);
}

exr_result_t
extract_chunk_table (
    exr_const_context_t   ctxt,
    exr_const_priv_part_t part,
    uint64_t**            chunktable,
    uint64_t*             chunkminoffset)
{
    uint64_t* ctable     = NULL;
    uint64_t  chunkoff   = part->chunk_table_offset;
    uint64_t  chunkbytes = sizeof (uint64_t) * (uint64_t) part->chunk_count;

    *chunkminoffset = chunkoff + chunkbytes;

    ctable = (uint64_t*) atomic_load (
        EXR_CONST_CAST (atomic_uintptr_t*, &(part->chunk_table)));
    if (ctable == NULL)
    {
        int64_t      nread = 0;
        uintptr_t    eptr = 0, nptr = 0;
        int          complete = 1;
        uint64_t     maxoff   = ((uint64_t) -1);
        exr_result_t rv;

        if (part->chunk_count <= 0)
            return ctxt->report_error (
                ctxt, EXR_ERR_INVALID_ARGUMENT, "Invalid file with no chunks");

        /* some of the stream-based objects can't reliably check the file size
         * so the C++ layer also had an arbitrary stop at 2^20 chunk entries
         * which seems safe...
         */
        if (part->chunk_count > (1024 * 1024) ||
            (ctxt->file_size > 0 &&
             chunkbytes + chunkoff > (uint64_t) ctxt->file_size))
            return ctxt->print_error (
                ctxt,
                EXR_ERR_INVALID_ARGUMENT,
                "chunk table size (%" PRIu64 ") too big for file size (%" PRId64
                ")",
                chunkbytes,
                ctxt->file_size);

        ctable = (uint64_t*) ctxt->alloc_fn (chunkbytes);
        if (ctable == NULL)
            return ctxt->standard_error (ctxt, EXR_ERR_OUT_OF_MEMORY);

        rv = ctxt->do_read (
            ctxt, ctable, chunkbytes, &chunkoff, &nread, EXR_MUST_READ_ALL);
        if (rv != EXR_ERR_SUCCESS)
        {
            ctxt->free_fn (ctable);
            ctable = (uint64_t*) UINTPTR_MAX;
        }
        else if (!ctxt->disable_chunk_reconstruct)
        {
            // could convert table all at once, but need to check if the
            // file is incomplete (i.e. crashed during write and didn't
            // get a complete chunk table), so just do them one at a time
            if (ctxt->file_size > 0) maxoff = (uint64_t) ctxt->file_size;
            for (int ci = 0; ci < part->chunk_count; ++ci)
            {
                uint64_t cchunk = one_to_native64 (ctable[ci]);
                if (cchunk < chunkoff || cchunk >= maxoff) complete = 0;
                ctable[ci] = cchunk;
            }

            if (!complete)
            {
                // The c++ side would basically fail as soon as it
                // failed, but would otherwise swallow all errors, and
                // then just let the reads fail later. We will do
                // something similar, except when in strict mode, we
                // will fail with a corrupt chunk immediately.
                rv = reconstruct_chunk_table (ctxt, part, ctable);
                if (rv != EXR_ERR_SUCCESS)
                {
                    if (ctxt->strict_header)
                    {
                        ctxt->free_fn (ctable);
                        ctable = (uint64_t*) UINTPTR_MAX;
                        rv     = ctxt->report_error (
                            ctxt,
                            EXR_ERR_BAD_CHUNK_LEADER,
                            "Incomplete / corrupt chunk table, unable to reconstruct");
                    }
                    else
                        rv = EXR_ERR_SUCCESS;
                }
            }
        }
        else { priv_to_native64 (ctable, part->chunk_count); }

        nptr = (uintptr_t) ctable;
        // see if we win or not
        if (!atomic_compare_exchange_strong (
                EXR_CONST_CAST (atomic_uintptr_t*, &(part->chunk_table)),
                &eptr,
                nptr))
        {
            if (nptr != UINTPTR_MAX) ctxt->free_fn (ctable);
            ctable = (uint64_t*) eptr;
            if (ctable == NULL)
                return ctxt->standard_error (ctxt, EXR_ERR_OUT_OF_MEMORY);
        }
    }

    *chunktable = ctable;
    return ((uintptr_t) ctable) == UINTPTR_MAX ? EXR_ERR_BAD_CHUNK_LEADER
                                               : EXR_ERR_SUCCESS;
}

/**************************************/

static exr_result_t
alloc_chunk_table (
    exr_const_context_t ctxt, exr_const_priv_part_t part, uint64_t** chunktable)
{
    uint64_t* ctable = NULL;

    /* we have the lock, but to access the type, we'll use the atomic function anyway */
    ctable = (uint64_t*) atomic_load (
        EXR_CONST_CAST (atomic_uintptr_t*, &(part->chunk_table)));
    if (ctable == NULL)
    {
        uint64_t  chunkbytes = sizeof (uint64_t) * (uint64_t) part->chunk_count;
        uintptr_t eptr = 0, nptr = 0;

        ctable = (uint64_t*) ctxt->alloc_fn (chunkbytes);
        if (ctable == NULL)
            return ctxt->standard_error (ctxt, EXR_ERR_OUT_OF_MEMORY);
        memset (ctable, 0, chunkbytes);

        nptr = (uintptr_t) ctable;
        if (!atomic_compare_exchange_strong (
                EXR_CONST_CAST (atomic_uintptr_t*, &(part->chunk_table)),
                &eptr,
                nptr))
        {
            ctxt->free_fn (ctable);
            ctable = (uint64_t*) eptr;
            if (ctable == NULL)
                return ctxt->standard_error (ctxt, EXR_ERR_OUT_OF_MEMORY);
        }
    }
    *chunktable = ctable;
    return EXR_ERR_SUCCESS;
}

/**************************************/

static uint64_t
compute_chunk_unpack_size (
    int x, int y, int width, int height, int lpc, exr_const_priv_part_t part)
{
    uint64_t unpacksize = 0;
    if (part->chan_has_line_sampling || height != lpc)
    {
        const exr_attr_chlist_t* chanlist = part->channels->chlist;
        for (int c = 0; c < chanlist->num_channels; ++c)
        {
            const exr_attr_chlist_entry_t* curc = (chanlist->entries + c);
            uint64_t chansz = ((curc->pixel_type == EXR_PIXEL_HALF) ? 2 : 4);

            chansz *=
                (uint64_t) compute_sampled_width (width, curc->x_sampling, x);
            chansz *=
                (uint64_t) compute_sampled_height (height, curc->y_sampling, y);

            unpacksize += chansz;
        }
    }
    else
        unpacksize = part->unpacked_size_per_chunk;
    return unpacksize;
}

/**************************************/

exr_result_t
exr_chunk_default_initialize (
    exr_context_t ctxt, int part_index,
    const exr_attr_box2i_t *box,
    int levelx, int levely,
    exr_chunk_info_t* cinfo)
{
    exr_result_t     rv = EXR_ERR_SUCCESS;
    exr_attr_box2i_t dw;
    int              miny, cidx, lpc;
    exr_priv_part_t  part;

    if (!cinfo) return EXR_ERR_INVALID_ARGUMENT;
    if (!box) return EXR_ERR_INVALID_ARGUMENT;

    if (!ctxt) return EXR_ERR_MISSING_CONTEXT_ARG;

    if (part_index < 0 || part_index >= ctxt->num_parts)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_ARGUMENT_OUT_OF_RANGE,
            "Part index (%d) out of range",
            part_index);

    /* TODO: Double check need for a lock? */
    part = ctxt->parts[part_index];

    dw = part->data_window;
    if (box->min.y < dw.min.y || box->min.y > dw.max.y)
        return EXR_ERR_INVALID_ARGUMENT;

    if (ctxt->mode == EXR_CONTEXT_TEMPORARY)
    {
        part->chunk_count = internal_exr_compute_chunk_offset_size (part);
    }

    if (part->storage_mode == EXR_STORAGE_SCANLINE ||
        part->storage_mode == EXR_STORAGE_DEEP_SCANLINE ||
        (ctxt->mode == EXR_CONTEXT_TEMPORARY && !(part->tiles)))
    {
        lpc  = part->lines_per_chunk;
        cidx = box->min.y - dw.min.y;
        if (lpc > 1) cidx /= lpc;

        // do we need to invert this when reading decreasing y? it appears not
        //if (part->lineorder == EXR_LINEORDER_DECREASING_Y)
        //    cidx = part->chunk_count - (cidx + 1);
        miny = dw.min.y + cidx * lpc;

        if (cidx < 0 || cidx >= part->chunk_count)
            return EXR_ERR_INVALID_ARGUMENT;

        cinfo->idx         = cidx;
        if (part->storage_mode == EXR_STORAGE_LAST_TYPE &&
            ctxt->mode == EXR_CONTEXT_TEMPORARY)
            cinfo->type = (uint8_t) EXR_STORAGE_SCANLINE;
        else
            cinfo->type = (uint8_t) part->storage_mode;
        cinfo->compression = (uint8_t) part->comp_type;
        cinfo->start_x     = dw.min.x;
        cinfo->start_y     = miny;
        cinfo->width       = dw.max.x - dw.min.x + 1;
        cinfo->height      = lpc;
        if (miny < dw.min.y)
        {
            cinfo->start_y = dw.min.y;
            cinfo->height -= dw.min.y - miny;
        }
        else if (((int64_t)miny + (int64_t)lpc) > (int64_t)dw.max.y)
        {
            cinfo->height = dw.max.y - miny + 1;
        }
        cinfo->level_x = 0;
        cinfo->level_y = 0;

        cinfo->unpacked_size = compute_chunk_unpack_size (
            dw.min.x, miny, cinfo->width, cinfo->height, lpc, part);
    }
    else if (part->tiles)
    {
        const exr_attr_chlist_t*   chanlist;
        const exr_attr_tiledesc_t* tiledesc;
        int                        tilew, tileh;
        uint64_t                   texels, unpacksize = 0;
        int64_t                    tend, dend;
        int                        tilex, tiley;

        tiledesc = part->tiles->tiledesc;

        tilew = (int) (tiledesc->x_size);
        tileh = (int) (tiledesc->y_size);

        tilex = (box->min.x - dw.min.x) / tilew;
        tiley = (box->min.y - dw.min.y) / tileh;

        cidx = 0;
        rv   = validate_and_compute_tile_chunk_off (
            ctxt, part, tilex, tiley, levelx, levely, &cidx);
        if (rv != EXR_ERR_SUCCESS) return rv;

        dend  = ((int64_t) part->tile_level_tile_size_x[levelx]);
        tend  = ((int64_t) tilew) * ((int64_t) (tilex + 1));
        if (tend > dend)
        {
            tend -= dend;
            if (tend < tilew) tilew = tilew - ((int) tend);
        }

        dend  = ((int64_t) part->tile_level_tile_size_y[levely]);
        tend  = ((int64_t) tileh) * ((int64_t) (tiley + 1));
        if (tend > dend)
        {
            tend -= dend;
            if (tend < tileh) tileh = tileh - ((int) tend);
        }

        cinfo->idx         = cidx;
        if (part->storage_mode == EXR_STORAGE_LAST_TYPE &&
            ctxt->mode == EXR_CONTEXT_TEMPORARY)
            cinfo->type = (uint8_t) EXR_STORAGE_TILED;
        else
            cinfo->type = (uint8_t) part->storage_mode;
        cinfo->compression = (uint8_t) part->comp_type;
        cinfo->start_x     = tilex;
        cinfo->start_y     = tiley;
        cinfo->height      = tileh;
        cinfo->width       = tilew;
        if (levelx > 255 || levely > 255)
            return EXR_ERR_ATTR_SIZE_MISMATCH;

        cinfo->level_x = (uint8_t) levelx;
        cinfo->level_y = (uint8_t) levely;

        chanlist = part->channels->chlist;
        texels   = (uint64_t) tilew * (uint64_t) tileh;
        for (int c = 0; c < chanlist->num_channels; ++c)
        {
            const exr_attr_chlist_entry_t* curc = (chanlist->entries + c);
            unpacksize +=
                texels * (uint64_t) ((curc->pixel_type == EXR_PIXEL_HALF) ? 2 : 4);
        }
        cinfo->unpacked_size = unpacksize;
    }

    return rv;
}

/**************************************/

exr_result_t
exr_read_scanline_chunk_info (
    exr_const_context_t ctxt, int part_index, int y, exr_chunk_info_t* cinfo)
{
    exr_result_t     rv;
    int              miny, cidx, rdcnt, lpc;
    int32_t          data[3];
    int64_t          ddata[3];
    int64_t          fsize;
    uint64_t         chunkmin, dataoff;
    exr_attr_box2i_t dw;
    uint64_t*        ctable;

    EXR_READONLY_AND_DEFINE_PART (part_index);

    if (!cinfo) return ctxt->standard_error (ctxt, EXR_ERR_INVALID_ARGUMENT);

    if (part->storage_mode != EXR_STORAGE_SCANLINE &&
        part->storage_mode != EXR_STORAGE_DEEP_SCANLINE)
    {
        return ctxt->standard_error (ctxt, EXR_ERR_SCAN_TILE_MIXEDAPI);
    }

    dw = part->data_window;
    if (y < dw.min.y || y > dw.max.y)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid request for scanline %d outside range of data window (%d - %d)",
            y,
            dw.min.y,
            dw.max.y);
    }

    lpc  = part->lines_per_chunk;
    cidx = y - dw.min.y;
    if (lpc > 1) cidx /= lpc;

    // do we need to invert this when reading decreasing y? it appears not
    //if (part->lineorder == EXR_LINEORDER_DECREASING_Y)
    //    cidx = part->chunk_count - (cidx + 1);
    miny = dw.min.y + cidx * lpc;

    if (cidx < 0 || cidx >= part->chunk_count)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid request for scanline %d in chunk %d outside chunk count %d",
            y,
            cidx,
            part->chunk_count);
    }

    cinfo->idx         = cidx;
    cinfo->type        = (uint8_t) part->storage_mode;
    cinfo->compression = (uint8_t) part->comp_type;
    cinfo->start_x     = dw.min.x;
    cinfo->start_y     = miny;
    cinfo->width       = dw.max.x - dw.min.x + 1;
    cinfo->height      = lpc;
    if (miny < dw.min.y)
    {
        cinfo->start_y = dw.min.y;
        cinfo->height -= dw.min.y - miny;
    }
    else if (((int64_t)miny + (int64_t)lpc) > (int64_t)dw.max.y)
    {
        cinfo->height = dw.max.y - miny + 1;
    }
    cinfo->level_x = 0;
    cinfo->level_y = 0;

    /* need to read from the file to get the packed chunk size */
    rv = extract_chunk_table (ctxt, part, &ctable, &chunkmin);
    if (rv != EXR_ERR_SUCCESS) return rv;

    fsize = ctxt->file_size;

    dataoff = ctable[cidx];

    /* known behavior for partial files */
    if (dataoff == 0)
        return EXR_ERR_INCOMPLETE_CHUNK_TABLE;

    if (dataoff < chunkmin || (fsize > 0 && dataoff > (uint64_t) fsize))
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_BAD_CHUNK_LEADER,
            "Corrupt chunk offset table: scanline %d, chunk index %d recorded at file offset %" PRIu64,
            y,
            cidx,
            dataoff);
    }

    /* TODO: Look at collapsing this into extract_chunk_leader, only
     * issue is more concrete error messages */
    /* multi part files have the part for validation */
    rdcnt = (ctxt->is_multipart) ? 2 : 1;
    /* deep has 64-bit data, so be variable about what we read */
    if (part->storage_mode != EXR_STORAGE_DEEP_SCANLINE) ++rdcnt;

    rv = ctxt->do_read (
        ctxt,
        data,
        (size_t) (rdcnt) * sizeof (int32_t),
        &dataoff,
        NULL,
        EXR_MUST_READ_ALL);

    if (rv != EXR_ERR_SUCCESS) return rv;

    priv_to_native32 (data, rdcnt);

    rdcnt = 0;
    if (ctxt->is_multipart)
    {
        if (data[rdcnt] != part_index)
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Preparing read scanline %d (chunk %d), found corrupt leader: part says %d, expected %d",
                y,
                cidx,
                data[rdcnt],
                part_index);
        }
        ++rdcnt;
    }
    if (miny != data[rdcnt])
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_BAD_CHUNK_LEADER,
            "Preparing to read scanline %d (chunk %d), found corrupt leader: scanline says %d, expected %d",
            y,
            cidx,
            data[rdcnt],
            miny);
    }

    if (part->storage_mode == EXR_STORAGE_DEEP_SCANLINE)
    {
        rv = ctxt->do_read (
            ctxt,
            ddata,
            3 * sizeof (int64_t),
            &dataoff,
            NULL,
            EXR_MUST_READ_ALL);
        if (rv != EXR_ERR_SUCCESS) { return rv; }
        priv_to_native64 (ddata, 3);

        if (ddata[0] < 0 || ddata[0] > (int64_t) INT_MAX)
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Preparing to read scanline %d (chunk %d), found corrupt leader: invalid sample table size %" PRId64,
                y,
                cidx,
                ddata[0]);
        }
        if (ddata[1] < 0 || ddata[1] > (int64_t) INT_MAX)
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Preparing to read scanline %d (chunk %d), found corrupt leader: invalid packed data size %" PRId64,
                y,
                cidx,
                ddata[1]);
        }
        if (ddata[2] < 0 || ddata[2] > (int64_t) INT_MAX)
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Preparing to scanline %d (chunk %d), found corrupt leader: unsupported unpacked data size %" PRId64,
                y,
                cidx,
                ddata[2]);
        }

        cinfo->sample_count_data_offset = dataoff;
        cinfo->sample_count_table_size  = (uint64_t) ddata[0];
        cinfo->data_offset              = dataoff + (uint64_t) ddata[0];
        cinfo->packed_size              = (uint64_t) ddata[1];
        cinfo->unpacked_size            = (uint64_t) ddata[2];

        /*
         * uncompressed reads don't have same checks as compressed, so
         * pre-check that the data is of a valid size
         */
        chunkmin = ((uint64_t)cinfo->width * (uint64_t)cinfo->height) * sizeof(int32_t);
        if (part->comp_type == EXR_COMPRESSION_NONE &&
            cinfo->sample_count_table_size != chunkmin)
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Invalid deep sample count size, must be one entry per pixel: found %" PRIu64 " expected %" PRIu64,
                cinfo->sample_count_table_size, chunkmin);
        }

        if (fsize > 0 &&
            ((cinfo->sample_count_data_offset +
              cinfo->sample_count_table_size) > ((uint64_t) fsize) ||
             (cinfo->data_offset + cinfo->packed_size) > ((uint64_t) fsize)))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Preparing to scanline %d (chunk %d), found corrupt leader: sample table and data result in access past end of the file: sample table size %" PRId64
                " + data size %" PRId64 " larger than file %" PRId64,
                y,
                cidx,
                ddata[0],
                ddata[1],
                fsize);
        }
    }
    else
    {
        uint64_t unpacksize = compute_chunk_unpack_size (
            dw.min.x, miny, cinfo->width, cinfo->height, lpc, part);

        ++rdcnt;
        if (data[rdcnt] < 0 ||
            (uint64_t) data[rdcnt] > part->unpacked_size_per_chunk)
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Preparing to read scanline %d (chunk %d), found corrupt leader: packed data size says %" PRIu64
                ", must be between 0 and %" PRIu64,
                y,
                cidx,
                (uint64_t) data[rdcnt],
                part->unpacked_size_per_chunk);
        }

        cinfo->data_offset              = dataoff;
        cinfo->packed_size              = (uint64_t) data[rdcnt];
        cinfo->unpacked_size            = unpacksize;
        cinfo->sample_count_data_offset = 0;
        cinfo->sample_count_table_size  = 0;

        if (fsize > 0 &&
            (cinfo->data_offset + cinfo->packed_size) > ((uint64_t) fsize))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Preparing to read scanline %d (chunk %d), found corrupt leader: packed size %" PRIu64
                ", file offset %" PRIu64 ", size %" PRId64,
                y,
                cidx,
                cinfo->packed_size,
                cinfo->data_offset,
                fsize);
        }
    }

    if (cinfo->packed_size == 0 && cinfo->unpacked_size > 0)
        return ctxt->report_error (
            ctxt, EXR_ERR_INVALID_ARGUMENT, "Invalid packed size of 0");

    if (part->comp_type == EXR_COMPRESSION_NONE &&
        cinfo->packed_size != cinfo->unpacked_size)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_BAD_CHUNK_LEADER,
            "Mismatch between unpacked and packed size with uncompressed data: packed is %" PRIu64 "; unpacked is %" PRIu64,
            cinfo->packed_size, cinfo->unpacked_size);
    }

    return EXR_ERR_SUCCESS;
}

/**************************************/

exr_result_t
exr_read_tile_chunk_info (
    exr_const_context_t ctxt,
    int                 part_index,
    int                 tilex,
    int                 tiley,
    int                 levelx,
    int                 levely,
    exr_chunk_info_t*   cinfo)
{
    exr_result_t               rv;
    int32_t                    data[6];
    int32_t*                   tdata;
    int32_t                    cidx, ntoread;
    uint64_t                   chunkmin, dataoff;
    int64_t                    nread, fsize, tend, dend;
    const exr_attr_chlist_t*   chanlist;
    const exr_attr_tiledesc_t* tiledesc;
    int                        tilew, tileh;
    uint64_t                   texels, unpacksize = 0;
    uint64_t*                  ctable;
    EXR_READONLY_AND_DEFINE_PART (part_index);

    if (!cinfo) return ctxt->standard_error (ctxt, EXR_ERR_INVALID_ARGUMENT);

    if (part->storage_mode != EXR_STORAGE_TILED &&
        part->storage_mode != EXR_STORAGE_DEEP_TILED)
    {
        return ctxt->standard_error (ctxt, EXR_ERR_TILE_SCAN_MIXEDAPI);
    }

    cidx = 0;
    rv   = validate_and_compute_tile_chunk_off (
        ctxt, part, tilex, tiley, levelx, levely, &cidx);
    if (rv != EXR_ERR_SUCCESS) return rv;

    tiledesc = part->tiles->tiledesc;

    tilew = (int) (tiledesc->x_size);
    dend  = ((int64_t) part->tile_level_tile_size_x[levelx]);
    tend  = ((int64_t) tilew) * ((int64_t) (tilex + 1));
    if (tend > dend)
    {
        tend -= dend;
        if (tend < tilew) tilew = tilew - ((int) tend);
    }

    tileh = (int) (tiledesc->y_size);
    dend  = ((int64_t) part->tile_level_tile_size_y[levely]);
    tend  = ((int64_t) tileh) * ((int64_t) (tiley + 1));
    if (tend > dend)
    {
        tend -= dend;
        if (tend < tileh) tileh = tileh - ((int) tend);
    }

    cinfo->idx         = cidx;
    cinfo->type        = (uint8_t) part->storage_mode;
    cinfo->compression = (uint8_t) part->comp_type;
    cinfo->start_x     = tilex;
    cinfo->start_y     = tiley;
    cinfo->height      = tileh;
    cinfo->width       = tilew;
    if (levelx > 255 || levely > 255)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_ATTR_SIZE_MISMATCH,
            "Unable to represent tile level %d, %d in chunk structure",
            levelx,
            levely);

    cinfo->level_x = (uint8_t) levelx;
    cinfo->level_y = (uint8_t) levely;

    chanlist = part->channels->chlist;
    texels   = (uint64_t) tilew * (uint64_t) tileh;
    for (int c = 0; c < chanlist->num_channels; ++c)
    {
        const exr_attr_chlist_entry_t* curc = (chanlist->entries + c);
        unpacksize +=
            texels * (uint64_t) ((curc->pixel_type == EXR_PIXEL_HALF) ? 2 : 4);
    }

    rv = extract_chunk_table (ctxt, part, &ctable, &chunkmin);
    if (rv != EXR_ERR_SUCCESS) return rv;

    /* TODO: Look at collapsing this into extract_chunk_leader, only
     * issue is more concrete error messages */
    if (part->storage_mode == EXR_STORAGE_DEEP_TILED)
    {
        if (ctxt->is_multipart)
            ntoread = 5;
        else
            ntoread = 4;
    }
    else if (ctxt->is_multipart)
        ntoread = 6;
    else
        ntoread = 5;

    fsize = ctxt->file_size;

    dataoff = ctable[cidx];

    /* known behavior for partial files */
    if (dataoff == 0)
        return EXR_ERR_INCOMPLETE_CHUNK_TABLE;

    if (dataoff < chunkmin || (fsize > 0 && dataoff > (uint64_t) fsize))
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_BAD_CHUNK_LEADER,
            "Corrupt chunk offset table: tile (%d, %d), level (%d, %d), chunk index %d recorded at file offset %" PRIu64,
            tilex,
            tiley,
            levelx,
            levely,
            cidx,
            dataoff);
    }

    rv = ctxt->do_read (
        ctxt,
        data,
        (uint64_t) (ntoread) * sizeof (int32_t),
        &dataoff,
        &nread,
        EXR_MUST_READ_ALL);
    if (rv != EXR_ERR_SUCCESS)
    {
        return ctxt->print_error (
            ctxt,
            rv,
            "Unable to read information block for tile (%d, %d), level (%d, %d): request %" PRIu64
            " bytes from offset %" PRIu64 ", got %" PRIu64 " bytes",
            tilex,
            tiley,
            levelx,
            levely,
            (uint64_t) (ntoread) * sizeof (int32_t),
            ctable[cidx],
            (uint64_t) nread);
    }
    priv_to_native32 (data, ntoread);

    tdata = data;
    if (ctxt->is_multipart)
    {
        if (part_index != data[0])
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Corrupt tile (%d, %d), level (%d, %d) (chunk %d): bad part number (%d, expect %d)",
                tilex,
                tiley,
                levelx,
                levely,
                cidx,
                data[0],
                part_index);
        }
        ++tdata;
    }
    if (tdata[0] != tilex)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_BAD_CHUNK_LEADER,
            "Corrupt tile (%d, %d), level (%d, %d) (chunk %d): bad tile x coordinate (%d, expect %d)",
            tilex,
            tiley,
            levelx,
            levely,
            cidx,
            tdata[0],
            tilex);
    }
    if (tdata[1] != tiley)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_BAD_CHUNK_LEADER,
            "Corrupt tile (%d, %d), level (%d, %d) (chunk %d): bad tile Y coordinate (%d, expect %d)",
            tilex,
            tiley,
            levelx,
            levely,
            cidx,
            tdata[1],
            tiley);
    }
    if (tdata[2] != levelx)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_BAD_CHUNK_LEADER,
            "Corrupt tile (%d, %d), level (%d, %d) (chunk %d): bad tile mip/rip level X (%d, expect %d)",
            tilex,
            tiley,
            levelx,
            levely,
            cidx,
            tdata[2],
            levelx);
    }
    if (tdata[3] != levely)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_BAD_CHUNK_LEADER,
            "Corrupt tile (%d, %d), level (%d, %d) (chunk %d): bad tile mip/rip level Y (%d, expect %d)",
            tilex,
            tiley,
            levelx,
            levely,
            cidx,
            tdata[3],
            levely);
    }

    if (part->storage_mode == EXR_STORAGE_DEEP_TILED)
    {
        int64_t ddata[3];
        rv = ctxt->do_read (
            ctxt,
            ddata,
            3 * sizeof (int64_t),
            &dataoff,
            NULL,
            EXR_MUST_READ_ALL);
        if (rv != EXR_ERR_SUCCESS) { return rv; }
        priv_to_native64 (ddata, 3);

        /*
         * because of smaller tiles than base tile size, sample table
         * may be smaller than normal tile size, just check that it is
         * at least a multiple of int32_t
         */
        if (ddata[0] < 0 ||
            (part->comp_type == EXR_COMPRESSION_NONE &&
             0 != (ddata[0] % sizeof(int32_t))) ||
            (ddata[0] == 0 && (ddata[1] != 0 || ddata[2] != 0)))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Corrupt deep tile (%d, %d), level (%d, %d) (chunk %d): invalid sample table size %" PRId64,
                tilex,
                tiley,
                levelx,
                levely,
                cidx,
                ddata[0]);
        }

        /* not all compressors support 64-bit */
        if (ddata[1] < 0 || ddata[1] > (int64_t) INT32_MAX ||
            (ddata[1] == 0 && ddata[2] != 0))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Corrupt deep tile (%d, %d), level (%d, %d) (chunk %d): invalid packed data size %" PRId64,
                tilex,
                tiley,
                levelx,
                levely,
                cidx,
                ddata[1]);
        }

        if (ddata[2] < 0 || ddata[2] > (int64_t) INT32_MAX ||
            (ddata[2] == 0 && ddata[1] != 0))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Corrupt deep tile (%d, %d), level (%d, %d) (chunk %d): invalid unpacked size %" PRId64,
                tilex,
                tiley,
                levelx,
                levely,
                cidx,
                ddata[1]);
        }
        cinfo->sample_count_data_offset = dataoff;
        cinfo->sample_count_table_size  = (uint64_t) ddata[0];
        cinfo->packed_size              = (uint64_t) ddata[1];
        cinfo->unpacked_size            = (uint64_t) ddata[2];
        cinfo->data_offset              = dataoff + (uint64_t) ddata[0];

        if (fsize > 0 &&
            ((cinfo->sample_count_data_offset +
              cinfo->sample_count_table_size) > ((uint64_t) fsize) ||
             (cinfo->data_offset + cinfo->packed_size) > ((uint64_t) fsize)))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Corrupt deep tile (%d, %d), level (%d, %d) (chunk %d): access past end of the file: sample table size %" PRId64
                " + data size %" PRId64 " larger than file %" PRId64,
                tilex,
                tiley,
                levelx,
                levely,
                cidx,
                ddata[0],
                ddata[1],
                fsize);
        }
    }
    else
    {
        if (tdata[4] < 0 || ((uint64_t) tdata[4]) > unpacksize ||
            (tdata[4] == 0 && unpacksize != 0))
        {
            return ctxt->print_error (
                ctxt,
                EXR_ERR_BAD_CHUNK_LEADER,
                "Corrupt tile (%d, %d), level (%d, %d) (chunk %d): invalid packed size %d vs unpacked size %" PRIu64,
                tilex,
                tiley,
                levelx,
                levely,
                cidx,
                (int) tdata[4],
                unpacksize);
        }
        else if (fsize > 0)
        {
            uint64_t finpos = dataoff + (uint64_t) tdata[4];
            if (finpos > (uint64_t) fsize)
            {
                return ctxt->print_error (
                    ctxt,
                    EXR_ERR_BAD_CHUNK_LEADER,
                    "Corrupt tile (%d, %d), level (%d, %d) (chunk %d): access past end of file: packed size (%d) at offset %" PRIu64
                    " vs size of file %" PRId64,
                    tilex,
                    tiley,
                    levelx,
                    levely,
                    cidx,
                    (int) tdata[4],
                    dataoff,
                    fsize);
            }
        }

        cinfo->packed_size              = (uint64_t) tdata[4];
        cinfo->unpacked_size            = unpacksize;
        cinfo->data_offset              = dataoff;
        cinfo->sample_count_data_offset = 0;
        cinfo->sample_count_table_size  = 0;
    }

    if (cinfo->packed_size == 0 && cinfo->unpacked_size > 0)
        return ctxt->report_error (
            ctxt, EXR_ERR_INVALID_ARGUMENT, "Invalid packed size of 0");

    if (part->comp_type == EXR_COMPRESSION_NONE &&
       cinfo->packed_size != cinfo->unpacked_size)
    {
         return ctxt->print_error (
             ctxt,
             EXR_ERR_BAD_CHUNK_LEADER,
             "Mismatch between unpacked and packed size with uncompressed data: packed is %" PRIu64 "; unpacked is %" PRIu64,
             cinfo->packed_size, cinfo->unpacked_size);
    }



    return EXR_ERR_SUCCESS;
}

exr_result_t
exr_read_chunk (
    exr_const_context_t     ctxt,
    int                     part_index,
    const exr_chunk_info_t* cinfo,
    void*                   packed_data)
{
    exr_result_t                 rv;
    uint64_t                     dataoffset, toread;
    int64_t                      nread;
    enum _INTERNAL_EXR_READ_MODE rmode = EXR_MUST_READ_ALL;
    EXR_READONLY_AND_DEFINE_PART (part_index);

    if (!cinfo) return ctxt->standard_error (ctxt, EXR_ERR_INVALID_ARGUMENT);
    if (cinfo->packed_size > 0 && !packed_data)
        return ctxt->standard_error (ctxt, EXR_ERR_INVALID_ARGUMENT);

    if (cinfo->idx < 0 || cinfo->idx >= part->chunk_count)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "invalid chunk index (%d) vs part chunk count %d",
            cinfo->idx,
            part->chunk_count);
    if (cinfo->type != (uint8_t) part->storage_mode)
        return ctxt->report_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "mismatched storage type for chunk block info");
    if (cinfo->compression != (uint8_t) part->comp_type)
        return ctxt->report_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "mismatched compression type for chunk block info");

    dataoffset = cinfo->data_offset;
    if (ctxt->file_size > 0 && dataoffset > (uint64_t) ctxt->file_size)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "chunk block info data offset (%" PRIu64
            ") past end of file (%" PRId64 ")",
            dataoffset,
            ctxt->file_size);

    /* allow a short read if uncompressed */
    if (part->comp_type == EXR_COMPRESSION_NONE) rmode = EXR_ALLOW_SHORT_READ;

    toread = cinfo->packed_size;
    if (toread > 0)
    {
        nread = 0;
        rv    = ctxt->do_read (
            ctxt, packed_data, toread, &dataoffset, &nread, rmode);

        if (rmode == EXR_ALLOW_SHORT_READ &&
            nread >= 0 &&
            nread < (int64_t) toread)
            {
                memset (
                    ((uint8_t*) packed_data) + nread,
                        0,
                (size_t)(toread - (uint64_t)nread));
            }
    }
    else
        rv = EXR_ERR_SUCCESS;

    return rv;
}

/**************************************/

exr_result_t
exr_read_deep_chunk (
    exr_const_context_t     ctxt,
    int                     part_index,
    const exr_chunk_info_t* cinfo,
    void*                   packed_data,
    void*                   sample_data)
{
    exr_result_t                 rv;
    uint64_t                     dataoffset, toread;
    int64_t                      nread;
    enum _INTERNAL_EXR_READ_MODE rmode = EXR_MUST_READ_ALL;
    EXR_READONLY_AND_DEFINE_PART (part_index);

    if (!cinfo) return ctxt->standard_error (ctxt, EXR_ERR_INVALID_ARGUMENT);

    if (cinfo->idx < 0 || cinfo->idx >= part->chunk_count)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "invalid chunk index (%d) vs part chunk count %d",
            cinfo->idx,
            part->chunk_count);
    if (cinfo->type != (uint8_t) part->storage_mode)
        return ctxt->report_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "mismatched storage type for chunk block info");
    if (cinfo->compression != (uint8_t) part->comp_type)
        return ctxt->report_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "mismatched compression type for chunk block info");

    if (ctxt->file_size > 0 &&
        cinfo->sample_count_data_offset > (uint64_t) ctxt->file_size)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "chunk block info sample count offset (%" PRIu64
            ") past end of file (%" PRId64 ")",
            cinfo->sample_count_data_offset,
            ctxt->file_size);

    if (ctxt->file_size > 0 && cinfo->data_offset > (uint64_t) ctxt->file_size)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "chunk block info data offset (%" PRIu64
            ") past end of file (%" PRId64 ")",
            cinfo->data_offset,
            ctxt->file_size);

    rv = EXR_ERR_SUCCESS;
    if (sample_data && cinfo->sample_count_table_size > 0)
    {
        dataoffset = cinfo->sample_count_data_offset;
        toread     = cinfo->sample_count_table_size;
        nread      = 0;
        rv         = ctxt->do_read (
            ctxt, sample_data, toread, &dataoffset, &nread, rmode);
    }

    if (rv != EXR_ERR_SUCCESS) return rv;

    /* the on-disk sample count table is little-endian; convert to native so
     * callers receive host-order counts (matching unpacked pixel data) */
    if (sample_data && cinfo->sample_count_table_size > 0)
        priv_to_native32 (
            sample_data,
            (int) (cinfo->sample_count_table_size / sizeof (uint32_t)));

    if (packed_data && cinfo->packed_size > 0)
    {
        dataoffset = cinfo->data_offset;
        toread     = cinfo->packed_size;
        nread      = 0;
        rv         = ctxt->do_read (
            ctxt, packed_data, toread, &dataoffset, &nread, rmode);
    }

    return rv;
}

/**************************************/

/* pull most of the logic to here to avoid having to unlock at every
 * error exit point and re-use mostly shared logic */
static exr_result_t
write_scan_chunk (
    exr_context_t   ctxt,
    int             part_index,
    exr_priv_part_t part,
    int             y,
    const void*     packed_data,
    uint64_t        packed_size,
    uint64_t        unpacked_size,
    const void*     sample_data,
    uint64_t        sample_data_size)
{
    exr_result_t rv;
    int32_t      data[3];
    int32_t      psize;
    int          cidx, lpc, miny, wrcnt;
    uint64_t*    ctable;

    if (ctxt->mode != EXR_CONTEXT_WRITING_DATA)
    {
        if (ctxt->mode == EXR_CONTEXT_WRITE)
            return ctxt->standard_error (ctxt, EXR_ERR_HEADER_NOT_WRITTEN);
        return ctxt->standard_error (ctxt, EXR_ERR_NOT_OPEN_WRITE);
    }

    if (part->storage_mode == EXR_STORAGE_TILED ||
        part->storage_mode == EXR_STORAGE_DEEP_TILED)
    {
        return ctxt->standard_error (ctxt, EXR_ERR_SCAN_TILE_MIXEDAPI);
    }

    if (ctxt->cur_output_part != part_index)
        return ctxt->standard_error (ctxt, EXR_ERR_INCORRECT_PART);

    if (packed_size > 0 && !packed_data)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid packed data argument size %" PRIu64 " pointer %p",
            (uint64_t) packed_size,
            packed_data);

    if (part->storage_mode != EXR_STORAGE_DEEP_SCANLINE &&
        packed_size > (uint64_t) INT32_MAX)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Packed data size %" PRIu64 " too large (max %" PRIu64 ")",
            (uint64_t) packed_size,
            (uint64_t) INT32_MAX);
    psize = (int32_t) packed_size;

    if (part->storage_mode == EXR_STORAGE_DEEP_SCANLINE &&
        (!sample_data || sample_data_size == 0))
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid sample count data argument size %" PRIu64 " pointer %p",
            (uint64_t) sample_data_size,
            sample_data);

    if (y < part->data_window.min.y || y > part->data_window.max.y)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid attempt to write scanlines starting at %d outside range of data window (%d - %d)",
            y,
            part->data_window.min.y,
            part->data_window.max.y);
    }

    lpc  = part->lines_per_chunk;
    cidx = (y - part->data_window.min.y);
    if (lpc > 1) cidx /= lpc;

    //if (part->lineorder == EXR_LINEORDER_DECREASING_Y)
    //    cidx = part->chunk_count - (cidx + 1);

    miny = cidx * lpc + part->data_window.min.y;

    if (y != miny)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Attempt to write scanline %d which does not align with y dims (%d) for chunk index (%d)",
            y,
            miny,
            cidx);
    }

    if (cidx < 0 || cidx >= part->chunk_count)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Chunk index for scanline %d in chunk %d outside chunk count %d",
            y,
            cidx,
            part->chunk_count);
    }

    if (part->lineorder != EXR_LINEORDER_RANDOM_Y &&
        ctxt->last_output_chunk != (cidx - 1))
    {
        return ctxt->standard_error (ctxt, EXR_ERR_INCORRECT_CHUNK);
    }

    if (ctxt->is_multipart)
    {
        data[0] = part_index;
        data[1] = miny;
        if (part->storage_mode != EXR_STORAGE_DEEP_SCANLINE)
        {
            data[2] = psize;
            wrcnt   = 3;
        }
        else
            wrcnt = 2;
    }
    else
    {
        data[0] = miny;
        if (part->storage_mode != EXR_STORAGE_DEEP_SCANLINE)
        {
            data[1] = psize;
            wrcnt   = 2;
        }
        else
            wrcnt = 1;
    }
    priv_from_native32 (data, wrcnt);

    rv = alloc_chunk_table (ctxt, part, &ctable);
    if (rv != EXR_ERR_SUCCESS) return rv;

    ctable[cidx] = ctxt->output_file_offset;
    rv           = ctxt->do_write (
        ctxt,
        data,
        (uint64_t) (wrcnt) * sizeof (int32_t),
        &(ctxt->output_file_offset));
    if (rv == EXR_ERR_SUCCESS &&
        part->storage_mode == EXR_STORAGE_DEEP_SCANLINE)
    {
        int64_t ddata[3];
        ddata[0] = (int64_t) sample_data_size;
        ddata[1] = (int64_t) packed_size;
        ddata[2] = (int64_t) unpacked_size;
        rv       = ctxt->do_write (
            ctxt, ddata, 3 * sizeof (uint64_t), &(ctxt->output_file_offset));

        if (rv == EXR_ERR_SUCCESS)
            rv = ctxt->do_write (
                ctxt,
                sample_data,
                sample_data_size,
                &(ctxt->output_file_offset));
    }
    if (rv == EXR_ERR_SUCCESS && packed_size > 0)
        rv = ctxt->do_write (
            ctxt, packed_data, packed_size, &(ctxt->output_file_offset));

    if (rv == EXR_ERR_SUCCESS)
    {
        ++(ctxt->output_chunk_count);
        if (ctxt->output_chunk_count == part->chunk_count)
        {
            uint64_t chunkoff = part->chunk_table_offset;

            ++(ctxt->cur_output_part);
            if (ctxt->cur_output_part == ctxt->num_parts)
                ctxt->mode = EXR_CONTEXT_WRITE_FINISHED;
            ctxt->last_output_chunk  = -1;
            ctxt->output_chunk_count = 0;

            priv_from_native64 (ctable, part->chunk_count);
            rv = ctxt->do_write (
                ctxt,
                ctable,
                sizeof (uint64_t) * (uint64_t) (part->chunk_count),
                &chunkoff);
            /* just in case we look at it again? */
            priv_to_native64 (ctable, part->chunk_count);
        }
        else { ctxt->last_output_chunk = cidx; }
    }

    return rv;
}

/**************************************/

exr_result_t
exr_write_scanline_chunk_info (
    exr_context_t ctxt, int part_index, int y, exr_chunk_info_t* cinfo)
{
    exr_attr_box2i_t dw;
    int              lpc, miny, cidx;
    exr_chunk_info_t nil = {0};

    EXR_LOCK_AND_DEFINE_PART (part_index);

    if (!cinfo)
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_INVALID_ARGUMENT));

    if (part->storage_mode == EXR_STORAGE_TILED ||
        part->storage_mode == EXR_STORAGE_DEEP_TILED)
    {
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_SCAN_TILE_MIXEDAPI));
    }

    if (ctxt->mode != EXR_CONTEXT_WRITING_DATA)
    {
        if (ctxt->mode == EXR_CONTEXT_WRITE)
            return EXR_UNLOCK_AND_RETURN (
                ctxt->standard_error (ctxt, EXR_ERR_HEADER_NOT_WRITTEN));
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_NOT_OPEN_WRITE));
    }

    dw = part->data_window;
    if (y < dw.min.y || y > dw.max.y)
    {
        return EXR_UNLOCK_AND_RETURN (ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid request for scanline %d outside range of data window (%d - %d)",
            y,
            dw.min.y,
            dw.max.y));
    }

    lpc  = part->lines_per_chunk;
    cidx = (y - dw.min.y);
    if (lpc > 1) cidx /= lpc;

    //if (part->lineorder == EXR_LINEORDER_DECREASING_Y)
    //    cidx = part->chunk_count - (cidx + 1);
    miny = cidx * lpc + dw.min.y;

    if (cidx < 0 || cidx >= part->chunk_count)
    {
        return EXR_UNLOCK_AND_RETURN (ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid request for scanline %d in chunk %d outside chunk count %d",
            y,
            cidx,
            part->chunk_count));
    }

    *cinfo             = nil;
    cinfo->idx         = cidx;
    cinfo->type        = (uint8_t) part->storage_mode;
    cinfo->compression = (uint8_t) part->comp_type;
    cinfo->start_x     = dw.min.x;
    cinfo->start_y     = miny;
    cinfo->width       = dw.max.x - dw.min.x + 1;
    cinfo->height      = lpc;
    if (miny < dw.min.y)
    {
        cinfo->start_y = dw.min.y;
        cinfo->height -= (dw.min.y - miny);
    }
    else if ((miny + lpc) > dw.max.y) { cinfo->height = (dw.max.y - miny + 1); }
    cinfo->level_x = 0;
    cinfo->level_y = 0;

    cinfo->sample_count_data_offset = 0;
    cinfo->sample_count_table_size  = 0;
    cinfo->data_offset              = 0;
    cinfo->packed_size              = 0;
    cinfo->unpacked_size =
        compute_chunk_unpack_size (dw.min.x, y, cinfo->width, cinfo->height, lpc, part);

    return EXR_UNLOCK_AND_RETURN (EXR_ERR_SUCCESS);
}

/**************************************/

exr_result_t
exr_write_tile_chunk_info (
    exr_context_t     ctxt,
    int               part_index,
    int               tilex,
    int               tiley,
    int               levelx,
    int               levely,
    exr_chunk_info_t* cinfo)
{
    exr_result_t               rv;
    int                        cidx;
    const exr_attr_chlist_t*   chanlist;
    const exr_attr_tiledesc_t* tiledesc;
    int                        tilew, tileh;
    uint64_t                   unpacksize = 0;
    exr_chunk_info_t           nil        = {0};

    EXR_LOCK_AND_DEFINE_PART (part_index);

    if (!cinfo)
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_INVALID_ARGUMENT));

    if (part->storage_mode == EXR_STORAGE_SCANLINE ||
        part->storage_mode == EXR_STORAGE_DEEP_SCANLINE)
    {
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_TILE_SCAN_MIXEDAPI));
    }

    if (ctxt->mode != EXR_CONTEXT_WRITING_DATA)
    {
        if (ctxt->mode == EXR_CONTEXT_WRITE)
            return EXR_UNLOCK_AND_RETURN (
                ctxt->standard_error (ctxt, EXR_ERR_HEADER_NOT_WRITTEN));
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_NOT_OPEN_WRITE));
    }

    cidx = 0;
    rv   = validate_and_compute_tile_chunk_off (
        ctxt, part, tilex, tiley, levelx, levely, &cidx);
    if (rv != EXR_ERR_SUCCESS) return EXR_UNLOCK_AND_RETURN (rv);

    tiledesc = part->tiles->tiledesc;
    tilew    = part->tile_level_tile_size_x[levelx];
    if (tiledesc->x_size < (uint32_t) tilew) tilew = (int) tiledesc->x_size;
    tileh = part->tile_level_tile_size_y[levely];
    if (tiledesc->y_size < (uint32_t) tileh) tileh = (int) tiledesc->y_size;

    if (((int64_t) (tilex) * (int64_t) (tilew) + (int64_t) (tilew) +
         (int64_t) (part->data_window.min.x) - 1) >
        (int64_t) (part->data_window.max.x))
    {
        int64_t sz = (int64_t) (part->data_window.max.x) -
                     (int64_t) (part->data_window.min.x) + 1;
        tilew = (int) (sz - ((int64_t) (tilex) * (int64_t) (tilew)));
    }

    if (((int64_t) (tiley) * (int64_t) (tileh) + (int64_t) (tileh) +
         (int64_t) (part->data_window.min.y) - 1) >
        (int64_t) (part->data_window.max.y))
    {
        int64_t sz = (int64_t) (part->data_window.max.y) -
                     (int64_t) (part->data_window.min.y) + 1;
        tileh = (int) (sz - ((int64_t) (tiley) * (int64_t) (tileh)));
    }

    *cinfo             = nil;
    cinfo->idx         = cidx;
    cinfo->type        = (uint8_t) part->storage_mode;
    cinfo->compression = (uint8_t) part->comp_type;
    cinfo->start_x     = tilex;
    cinfo->start_y     = tiley;
    cinfo->height      = tileh;
    cinfo->width       = tilew;
    if (levelx > 255 || levely > 255)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_ATTR_SIZE_MISMATCH,
            "Unable to represent tile level %d, %d in chunk structure",
            levelx,
            levely);

    cinfo->level_x = (uint8_t) levelx;
    cinfo->level_y = (uint8_t) levely;

    chanlist = part->channels->chlist;
    for (int c = 0; c < chanlist->num_channels; ++c)
    {
        const exr_attr_chlist_entry_t* curc = (chanlist->entries + c);
        unpacksize += (uint64_t) (tilew) * (uint64_t) (tileh) *
                      (uint64_t) ((curc->pixel_type == EXR_PIXEL_HALF) ? 2 : 4);
    }

    cinfo->sample_count_data_offset = 0;
    cinfo->sample_count_table_size  = 0;
    cinfo->data_offset              = 0;
    cinfo->packed_size              = 0;
    cinfo->unpacked_size            = unpacksize;

    return EXR_UNLOCK_AND_RETURN (EXR_ERR_SUCCESS);
}

/**************************************/

exr_result_t
exr_write_scanline_chunk (
    exr_context_t ctxt,
    int           part_index,
    int           y,
    const void*   packed_data,
    uint64_t      packed_size)
{
    exr_result_t rv;
    EXR_LOCK_AND_DEFINE_PART (part_index);

    if (part->storage_mode == EXR_STORAGE_DEEP_SCANLINE)
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_USE_SCAN_DEEP_WRITE));

    rv = write_scan_chunk (
        ctxt, part_index, part, y, packed_data, packed_size, 0, NULL, 0);
    return EXR_UNLOCK_AND_RETURN (rv);
}

/**************************************/

exr_result_t
exr_write_deep_scanline_chunk (
    exr_context_t ctxt,
    int           part_index,
    int           y,
    const void*   packed_data,
    uint64_t      packed_size,
    uint64_t      unpacked_size,
    const void*   sample_data,
    uint64_t      sample_data_size)
{
    exr_result_t rv;
    EXR_LOCK_AND_DEFINE_PART (part_index);

    if (part->storage_mode == EXR_STORAGE_SCANLINE)
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_USE_SCAN_NONDEEP_WRITE));

    rv = write_scan_chunk (
        ctxt,
        part_index,
        part,
        y,
        packed_data,
        packed_size,
        unpacked_size,
        sample_data,
        sample_data_size);
    return EXR_UNLOCK_AND_RETURN (rv);
}

/**************************************/

/* pull most of the logic to here to avoid having to unlock at every
 * error exit point and re-use mostly shared logic */
static exr_result_t
write_tile_chunk (
    exr_context_t   ctxt,
    int             part_index,
    exr_priv_part_t part,
    int             tilex,
    int             tiley,
    int             levelx,
    int             levely,
    const void*     packed_data,
    uint64_t        packed_size,
    uint64_t        unpacked_size,
    const void*     sample_data,
    uint64_t        sample_data_size)
{
    exr_result_t rv;
    int32_t      data[6];
    int32_t      psize;
    int          cidx, wrcnt;
    uint64_t*    ctable;

    if (ctxt->mode != EXR_CONTEXT_WRITING_DATA)
    {
        if (ctxt->mode == EXR_CONTEXT_WRITE)
            return ctxt->standard_error (ctxt, EXR_ERR_HEADER_NOT_WRITTEN);
        return ctxt->standard_error (ctxt, EXR_ERR_NOT_OPEN_WRITE);
    }

    if (part->storage_mode == EXR_STORAGE_SCANLINE ||
        part->storage_mode == EXR_STORAGE_DEEP_SCANLINE)
    {
        return ctxt->standard_error (ctxt, EXR_ERR_TILE_SCAN_MIXEDAPI);
    }

    if (ctxt->cur_output_part != part_index)
        return ctxt->standard_error (ctxt, EXR_ERR_INCORRECT_PART);

    if (!packed_data || packed_size == 0)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid packed data argument size %" PRIu64 " pointer %p",
            (uint64_t) packed_size,
            packed_data);

    if (part->storage_mode != EXR_STORAGE_DEEP_TILED &&
        packed_size > (uint64_t) INT32_MAX)
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Packed data size %" PRIu64 " too large (max %" PRIu64 ")",
            (uint64_t) packed_size,
            (uint64_t) INT32_MAX);
    psize = (int32_t) packed_size;

    if (part->storage_mode == EXR_STORAGE_DEEP_TILED &&
        (!sample_data || sample_data_size == 0))
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Invalid sample count data argument size %" PRIu64 " pointer %p",
            (uint64_t) sample_data_size,
            sample_data);

    cidx = -1;
    rv   = validate_and_compute_tile_chunk_off (
        ctxt, part, tilex, tiley, levelx, levely, &cidx);
    if (rv != EXR_ERR_SUCCESS) return rv;

    if (cidx < 0 || cidx >= part->chunk_count)
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INVALID_ARGUMENT,
            "Chunk index for tile (%d, %d) at level (%d, %d) %d outside chunk count %d",
            tilex,
            tiley,
            levelx,
            levely,
            cidx,
            part->chunk_count);
    }

    if (part->lineorder != EXR_LINEORDER_RANDOM_Y &&
        ctxt->last_output_chunk != (cidx - 1))
    {
        return ctxt->print_error (
            ctxt,
            EXR_ERR_INCORRECT_CHUNK,
            "Chunk index %d is not the next chunk to be written (last %d)",
            cidx,
            ctxt->last_output_chunk);
    }

    wrcnt = 0;
    if (ctxt->is_multipart) { data[wrcnt++] = part_index; }
    data[wrcnt++] = tilex;
    data[wrcnt++] = tiley;
    data[wrcnt++] = levelx;
    data[wrcnt++] = levely;
    if (part->storage_mode != EXR_STORAGE_DEEP_TILED) data[wrcnt++] = psize;

    priv_from_native32 (data, wrcnt);

    rv = alloc_chunk_table (ctxt, part, &ctable);
    if (rv != EXR_ERR_SUCCESS) return rv;

    ctable[cidx] = ctxt->output_file_offset;
    rv           = ctxt->do_write (
        ctxt,
        data,
        (uint64_t) (wrcnt) * sizeof (int32_t),
        &(ctxt->output_file_offset));
    if (rv == EXR_ERR_SUCCESS && part->storage_mode == EXR_STORAGE_DEEP_TILED)
    {
        int64_t ddata[3];
        ddata[0] = (int64_t) sample_data_size;
        ddata[1] = (int64_t) packed_size;
        ddata[2] = (int64_t) unpacked_size;

        priv_from_native64 (ddata, 3);

        rv = ctxt->do_write (
            ctxt, ddata, 3 * sizeof (uint64_t), &(ctxt->output_file_offset));

        if (rv == EXR_ERR_SUCCESS)
            rv = ctxt->do_write (
                ctxt,
                sample_data,
                sample_data_size,
                &(ctxt->output_file_offset));
    }
    if (rv == EXR_ERR_SUCCESS)
        rv = ctxt->do_write (
            ctxt, packed_data, packed_size, &(ctxt->output_file_offset));

    if (rv == EXR_ERR_SUCCESS)
    {
        ++(ctxt->output_chunk_count);
        if (ctxt->output_chunk_count == part->chunk_count)
        {
            uint64_t chunkoff = part->chunk_table_offset;

            ++(ctxt->cur_output_part);
            if (ctxt->cur_output_part == ctxt->num_parts)
                ctxt->mode = EXR_CONTEXT_WRITE_FINISHED;
            ctxt->last_output_chunk  = -1;
            ctxt->output_chunk_count = 0;

            priv_from_native64 (ctable, part->chunk_count);
            rv = ctxt->do_write (
                ctxt,
                ctable,
                sizeof (uint64_t) * (uint64_t) (part->chunk_count),
                &chunkoff);
            /* just in case we look at it again? */
            priv_to_native64 (ctable, part->chunk_count);
        }
        else { ctxt->last_output_chunk = cidx; }
    }

    return rv;
}

/**************************************/

exr_result_t
exr_write_tile_chunk (
    exr_context_t ctxt,
    int           part_index,
    int           tilex,
    int           tiley,
    int           levelx,
    int           levely,
    const void*   packed_data,
    uint64_t      packed_size)
{
    exr_result_t rv;
    EXR_LOCK_AND_DEFINE_PART (part_index);

    if (part->storage_mode == EXR_STORAGE_DEEP_TILED)
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_USE_TILE_DEEP_WRITE));

    rv = write_tile_chunk (
        ctxt,
        part_index,
        part,
        tilex,
        tiley,
        levelx,
        levely,
        packed_data,
        packed_size,
        0,
        NULL,
        0);
    return EXR_UNLOCK_AND_RETURN (rv);
}

/**************************************/

exr_result_t
exr_write_deep_tile_chunk (
    exr_context_t ctxt,
    int           part_index,
    int           tilex,
    int           tiley,
    int           levelx,
    int           levely,
    const void*   packed_data,
    uint64_t      packed_size,
    uint64_t      unpacked_size,
    const void*   sample_data,
    uint64_t      sample_data_size)
{
    exr_result_t rv;
    EXR_LOCK_AND_DEFINE_PART (part_index);

    if (part->storage_mode == EXR_STORAGE_TILED)
        return EXR_UNLOCK_AND_RETURN (
            ctxt->standard_error (ctxt, EXR_ERR_USE_TILE_NONDEEP_WRITE));

    rv = write_tile_chunk (
        ctxt,
        part_index,
        part,
        tilex,
        tiley,
        levelx,
        levely,
        packed_data,
        packed_size,
        unpacked_size,
        sample_data,
        sample_data_size);
    return EXR_UNLOCK_AND_RETURN (rv);
}

/**************************************/

exr_result_t
internal_validate_next_chunk (
    exr_encode_pipeline_t* encode,
    exr_const_context_t    ctxt,
    exr_const_priv_part_t  part)
{
    exr_result_t rv = EXR_ERR_SUCCESS;
    int          cidx, lpc;

    if (ctxt->cur_output_part != encode->part_index)
        return ctxt->standard_error (ctxt, EXR_ERR_INCORRECT_PART);

    cidx = -1;

    if (part->storage_mode == EXR_STORAGE_TILED ||
        part->storage_mode == EXR_STORAGE_DEEP_TILED)
    {
        rv = validate_and_compute_tile_chunk_off (
            ctxt,
            part,
            encode->chunk.start_x,
            encode->chunk.start_y,
            encode->chunk.level_x,
            encode->chunk.level_y,
            &cidx);
    }
    else
    {
        lpc  = part->lines_per_chunk;
        cidx = (encode->chunk.start_y - part->data_window.min.y);
        if (lpc > 1) cidx /= lpc;

        //if (part->lineorder == EXR_LINEORDER_DECREASING_Y)
        //{
        //    cidx = part->chunk_count - (cidx + 1);
        //}
    }

    if (rv == EXR_ERR_SUCCESS)
    {
        if (cidx < 0 || cidx >= part->chunk_count)
        {
            rv = ctxt->print_error (
                ctxt,
                EXR_ERR_INVALID_ARGUMENT,
                "Chunk index for scanline %d in chunk %d outside chunk count %d",
                encode->chunk.start_y,
                cidx,
                part->chunk_count);
        }
        else if (
            part->lineorder != EXR_LINEORDER_RANDOM_Y &&
            ctxt->last_output_chunk != (cidx - 1))
        {
            rv = ctxt->print_error (
                ctxt,
                EXR_ERR_INCORRECT_CHUNK,
                "Attempt to write chunk %d, but last output chunk is %d",
                cidx,
                ctxt->last_output_chunk);
        }
    }
    return rv;
}
