Add read_stream_list()

[wimlib] / src / resource.c

/*
 * resource.c
 *
 * Read uncompressed and compressed metadata and file resources from a WIM file.
 */

/*
 * Copyright (C) 2012, 2013 Eric Biggers
 *
 * This file is part of wimlib, a library for working with WIM files.
 *
 * wimlib is free software; you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 3 of the License, or (at your option) any later
 * version.
 *
 * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * wimlib; if not, see http://www.gnu.org/licenses/.
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "wimlib.h"
#include "wimlib/endianness.h"
#include "wimlib/error.h"
#include "wimlib/file_io.h"
#include "wimlib/lookup_table.h"
#include "wimlib/resource.h"
#include "wimlib/sha1.h"

#ifdef __WIN32__
/* for read_win32_file_prefix(), read_win32_encrypted_file_prefix() */
#  include "wimlib/win32.h"
#endif

#ifdef WITH_NTFS_3G
/* for read_ntfs_file_prefix() */
#  include "wimlib/ntfs_3g.h"
#endif

#ifdef HAVE_ALLOCA_H
#  include <alloca.h>
#endif
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>

/*
 *                         Compressed WIM resources
 *
 * A compressed resource in a WIM consists of a number of compressed chunks,
 * each of which decompresses to a fixed chunk size (given in the WIM header;
 * usually 32768) except possibly the last, which always decompresses to any
 * remaining bytes.  In addition, immediately before the chunks, a table (the
 * "chunk table") provides the offset, in bytes relative to the end of the chunk
 * table, of the start of each compressed chunk, except for the first chunk
 * which is omitted as it always has an offset of 0.  Therefore, a compressed
 * resource with N chunks will have a chunk table with N - 1 entries.
 *
 * Additional information:
 *
 * - Entries in the chunk table are 4 bytes each, except if the uncompressed
 *   size of the resource is greater than 4 GiB, in which case the entries in
 *   the chunk table are 8 bytes each.  In either case, the entries are unsigned
 *   little-endian integers.
 *
 * - The chunk table is included in the compressed size of the resource provided
 *   in the corresponding entry in the WIM's stream lookup table.
 *
 * - The compressed size of a chunk is never greater than the uncompressed size.
 *   From the compressor's point of view, chunks that would have compressed to a
 *   size greater than or equal to their original size are in fact stored
 *   uncompressed.  From the decompresser's point of view, chunks with
 *   compressed size equal to their uncompressed size are in fact uncompressed.
 *
 * Furthermore, wimlib supports its own "pipable" WIM format, and for this the
 * structure of compressed resources was modified to allow piped reading and
 * writing.  To make sequential writing possible, the chunk table is placed
 * after the chunks rather than before the chunks, and to make sequential
 * reading possible, each chunk is prefixed with a 4-byte header giving its
 * compressed size as a 32-bit, unsigned, little-endian integer.  Otherwise the
 * details are the same.
 */


/* Decompress the specified chunk that uses the specified compression type
 * @ctype, part of a WIM with default chunk size @wim_chunk_size.  For LZX the
 * separate @wim_chunk_size is needed because it determines the window size used
 * for LZX compression.  */
static int
decompress(const void *cchunk, unsigned clen, void *uchunk, unsigned ulen,
           int ctype, u32 wim_chunk_size)
{
        switch (ctype) {
        case WIMLIB_COMPRESSION_TYPE_LZX:
                return wimlib_lzx_decompress2(cchunk, clen,
                                              uchunk, ulen, wim_chunk_size);
        case WIMLIB_COMPRESSION_TYPE_XPRESS:
                return wimlib_xpress_decompress(cchunk, clen,
                                                uchunk, ulen);
        case WIMLIB_COMPRESSION_TYPE_LZMS:
                return wimlib_lzms_decompress(cchunk, clen, uchunk, ulen);
        default:
                wimlib_assert(0);
                return -1;
        }
}

struct data_range {
        u64 offset;
        u64 size;
};

/* Alternate chunk table format for resources with WIM_RESHDR_FLAG_CONCAT set.
 */
struct alt_chunk_table_header_disk {
        /* Uncompressed size of the resource.  */
        le64 res_usize;

        /* Number of bytes each compressed chunk decompresses into, except
         * possibly the last which decompresses into the remainder.  */
        le32 chunk_size;

        /* ??? */
        le32 unknown;

        /* This header is directly followed by a table of compressed sizes of
         * the chunks.  */
} _packed_attribute;

/* Read data from a compressed WIM resource.  */
static int
read_compressed_wim_resource(const struct wim_resource_spec * const rspec,
                             const struct data_range * const ranges,
                             const size_t num_ranges,
                             const consume_data_callback_t cb,
                             void * const cb_ctx,
                             const bool raw_chunks_mode)
{
        int ret;
        int errno_save;

        u64 *chunk_offsets = NULL;
        u8 *ubuf = NULL;
        void *cbuf = NULL;
        bool chunk_offsets_malloced = false;
        bool ubuf_malloced = false;
        bool cbuf_malloced = false;

        /* Sanity checks  */
        wimlib_assert(rspec != NULL);
        wimlib_assert(rspec->ctype != WIMLIB_COMPRESSION_TYPE_NONE);
        wimlib_assert(is_power_of_2(rspec->cchunk_size));
        wimlib_assert(cb != NULL);
        wimlib_assert(num_ranges != 0);
        for (size_t i = 0; i < num_ranges; i++) {
                wimlib_assert(ranges[i].size != 0);
                wimlib_assert(ranges[i].offset + ranges[i].size >= ranges[i].size);
                wimlib_assert(ranges[i].offset + ranges[i].size <= rspec->uncompressed_size);
        }
        for (size_t i = 0; i < num_ranges - 1; i++)
                wimlib_assert(ranges[i].offset + ranges[i].size <= ranges[i + 1].offset);

        /* Get the offsets of the first and last bytes of the read.  */
        const u64 first_offset = ranges[0].offset;
        const u64 last_offset = ranges[num_ranges - 1].offset + ranges[num_ranges - 1].size - 1;

        /* Get the file descriptor for the WIM.  */
        struct filedes * const in_fd = &rspec->wim->in_fd;

        /* Determine if we're reading a pipable resource from a pipe or not.  */
        const bool is_pipe_read = !filedes_is_seekable(in_fd);

        /* Determine if the chunk table is in an altenate format.  */
        const bool alt_chunk_table = (rspec->flags & WIM_RESHDR_FLAG_CONCAT) && !is_pipe_read;

        /* Get the maximum size of uncompressed chunks in this resource, which
         * we require be a power of 2.  */
        u32 chunk_size;
        u64 cur_read_offset = rspec->offset_in_wim;
        if (alt_chunk_table) {
                /* Alternate chunk table format.  */
                struct alt_chunk_table_header_disk hdr;

                ret = full_pread(in_fd, &hdr, sizeof(hdr), cur_read_offset);
                if (ret)
                        goto read_error;
                cur_read_offset += sizeof(hdr);

                chunk_size = le32_to_cpu(hdr.chunk_size);

                if (!is_power_of_2(chunk_size)) {
                        ERROR("Invalid compressed resource: "
                              "expected power-of-2 chunk size (got %u)", chunk_size);
                        ret = WIMLIB_ERR_INVALID_CHUNK_SIZE;
                        goto out_free_memory;
                }
        } else {
                chunk_size = rspec->cchunk_size;
        }
        const u32 chunk_order = bsr32(chunk_size);

        /* Calculate the total number of chunks the resource is divided into.  */
        const u64 num_chunks = (rspec->uncompressed_size + chunk_size - 1) >> chunk_order;

        /* Calculate the 0-based indices of the first and last chunks containing
         * data that needs to be passed to the callback.  */
        const u64 first_needed_chunk = first_offset >> chunk_order;
        const u64 last_needed_chunk = last_offset >> chunk_order;

        /* Calculate the 0-based index of the first chunk that actually needs to
         * be read.  This is normally first_needed_chunk, but for pipe reads we
         * must always start from the 0th chunk.  */
        const u64 read_start_chunk = (is_pipe_read ? 0 : first_needed_chunk);

        /* Calculate the number of chunk offsets that are needed for the chunks
         * being read.  */
        const u64 num_needed_chunk_offsets =
                last_needed_chunk - read_start_chunk + 1 +
                (last_needed_chunk < num_chunks - 1);

        /* Calculate the number of entries in the chunk table.  Normally, it's
         * one less than the number of chunks, since the first chunk has no
         * entry.  But in the alternate chunk table format, the chunk entries
         * contain chunk sizes, not offsets, and there is one per chunk.  */
        const u64 num_chunk_entries = (alt_chunk_table ? num_chunks : num_chunks - 1);

        /* Set the size of each chunk table entry based on the resource's
         * uncompressed size.  XXX:  Does the alternate chunk table really
         * always have 4-byte entries?  */
        const u64 chunk_entry_size =
                (rspec->uncompressed_size > (1ULL << 32) && !alt_chunk_table)
                        ? 8 : 4;

        /* Calculate the size of the chunk table in bytes.  */
        const u64 chunk_table_size = num_chunk_entries * chunk_entry_size;

        /* Includes header  */
        const u64 chunk_table_full_size =
                (alt_chunk_table) ? chunk_table_size + sizeof(struct alt_chunk_table_header_disk)
                                  : chunk_table_size;

        if (!is_pipe_read) {
                /* Read the needed chunk table entries into memory and use them
                 * to initialize the chunk_offsets array.  */

                u64 first_chunk_entry_to_read;
                u64 last_chunk_entry_to_read;

                if (alt_chunk_table) {
                        /* The alternate chunk table contains chunk sizes, not
                         * offsets, so we always must read all preceding entries
                         * in order to determine offsets.  */
                        first_chunk_entry_to_read = 0;
                        last_chunk_entry_to_read = last_needed_chunk;
                } else {
                        /* Here we must account for the fact that the first
                         * chunk has no explicit chunk table entry.  */

                        if (read_start_chunk == 0)
                                first_chunk_entry_to_read = 0;
                        else
                                first_chunk_entry_to_read = read_start_chunk - 1;

                        if (last_needed_chunk == 0)
                                last_chunk_entry_to_read = 0;
                        else
                                last_chunk_entry_to_read = last_needed_chunk - 1;

                        if (last_needed_chunk < num_chunks - 1)
                                last_chunk_entry_to_read++;
                }

                const u64 num_chunk_entries_to_read =
                        last_chunk_entry_to_read - first_chunk_entry_to_read + 1;

                const u64 chunk_offsets_alloc_size =
                        max(num_chunk_entries_to_read,
                            num_needed_chunk_offsets) * sizeof(chunk_offsets[0]);

                if ((size_t)chunk_offsets_alloc_size != chunk_offsets_alloc_size)
                        goto oom;

                if (chunk_offsets_alloc_size <= STACK_MAX) {
                        chunk_offsets = alloca(chunk_offsets_alloc_size);
                } else {
                        chunk_offsets = MALLOC(chunk_offsets_alloc_size);
                        if (chunk_offsets == NULL)
                                goto oom;
                        chunk_offsets_malloced = true;
                }

                const size_t chunk_table_size_to_read =
                        num_chunk_entries_to_read * chunk_entry_size;

                const u64 file_offset_of_needed_chunk_entries =
                        cur_read_offset
                        + (first_chunk_entry_to_read * chunk_entry_size)
                        + (rspec->is_pipable ? (rspec->size_in_wim - chunk_table_size) : 0);

                void * const chunk_table_data =
                        (u8*)chunk_offsets +
                        chunk_offsets_alloc_size -
                        chunk_table_size_to_read;

                ret = full_pread(in_fd, chunk_table_data, chunk_table_size,
                                 file_offset_of_needed_chunk_entries);
                if (ret)
                        goto read_error;

                /* Now fill in chunk_offsets from the entries we have read in
                 * chunk_tab_data.  We break aliasing rules here to avoid having
                 * to allocate yet another array.  */
                typedef le64 __attribute__((may_alias)) aliased_le64_t;
                typedef le32 __attribute__((may_alias)) aliased_le32_t;
                u64 * chunk_offsets_p = chunk_offsets;

                if (alt_chunk_table) {
                        u64 cur_offset = 0;
                        aliased_le32_t *raw_entries = chunk_table_data;

                        for (size_t i = 0; i < num_chunk_entries_to_read; i++) {
                                u32 entry = le32_to_cpu(raw_entries[i]);
                                if (i >= read_start_chunk)
                                        *chunk_offsets_p++ = cur_offset;
                                cur_offset += entry;
                        }
                } else {
                        if (read_start_chunk == 0)
                                *chunk_offsets_p++ = 0;

                        if (chunk_entry_size == 4) {
                                aliased_le32_t *raw_entries = chunk_table_data;
                                for (size_t i = 0; i < num_chunk_entries_to_read; i++)
                                        *chunk_offsets_p++ = le32_to_cpu(raw_entries[i]);
                        } else {
                                aliased_le64_t *raw_entries = chunk_table_data;
                                for (size_t i = 0; i < num_chunk_entries_to_read; i++)
                                        *chunk_offsets_p++ = le64_to_cpu(raw_entries[i]);
                        }
                }

                /* Set offset to beginning of first chunk to read.  */
                cur_read_offset += chunk_offsets[0];
                if (rspec->is_pipable)
                        cur_read_offset += read_start_chunk * sizeof(struct pwm_chunk_hdr);
                else
                        cur_read_offset += chunk_table_size;
        }

        /* Allocate buffer for holding the uncompressed data of each chunk.  */
        if (chunk_size <= STACK_MAX) {
                ubuf = alloca(chunk_size);
        } else {
                ubuf = MALLOC(chunk_size);
                if (ubuf == NULL)
                        goto oom;
                ubuf_malloced = true;
        }

        /* Unless the raw compressed data was requested, allocate a temporary
         * buffer for reading compressed chunks, each of which can be at most
         * @chunk_size - 1 bytes.  This excludes compressed chunks that are a
         * full @chunk_size bytes, which are actually stored uncompressed.  */
        if (!raw_chunks_mode) {
                if (chunk_size - 1 <= STACK_MAX) {
                        cbuf = alloca(chunk_size - 1);
                } else {
                        cbuf = MALLOC(chunk_size - 1);
                        if (cbuf == NULL)
                                goto oom;
                        cbuf_malloced = true;
                }
        }

        /* Read and process each needed chunk.  */
        const struct data_range *cur_range = ranges;
        const struct data_range * const end_range = &ranges[num_ranges];
        u64 cur_range_pos = cur_range->offset;
        u64 cur_range_end = cur_range->offset + cur_range->size;

        for (u64 i = read_start_chunk; i <= last_needed_chunk; i++) {

                /* Calculate uncompressed size of next chunk.  */
                u32 chunk_usize;
                if ((i == num_chunks - 1) && (rspec->uncompressed_size & (chunk_size - 1)))
                        chunk_usize = (rspec->uncompressed_size & (chunk_size - 1));
                else
                        chunk_usize = chunk_size;

                /* Calculate compressed size of next chunk.  */
                u32 chunk_csize;
                if (is_pipe_read) {
                        struct pwm_chunk_hdr chunk_hdr;

                        ret = full_pread(in_fd, &chunk_hdr,
                                         sizeof(chunk_hdr), cur_read_offset);
                        if (ret)
                                goto read_error;
                        chunk_csize = le32_to_cpu(chunk_hdr.compressed_size);
                } else {
                        if (i == num_chunks - 1) {
                                chunk_csize = rspec->size_in_wim -
                                              chunk_table_full_size -
                                              chunk_offsets[i - read_start_chunk];
                                if (rspec->is_pipable)
                                        chunk_csize -= num_chunks * sizeof(struct pwm_chunk_hdr);
                        } else {
                                chunk_csize = chunk_offsets[i + 1 - read_start_chunk] -
                                              chunk_offsets[i - read_start_chunk];
                        }
                }
                if (chunk_csize == 0 || chunk_csize > chunk_usize) {
                        ERROR("Invalid chunk size in compressed resource!");
                        errno = EINVAL;
                        ret = WIMLIB_ERR_DECOMPRESSION;
                        goto out_free_memory;
                }
                if (rspec->is_pipable)
                        cur_read_offset += sizeof(struct pwm_chunk_hdr);

                /* Uncompressed offsets  */
                const u64 chunk_start_offset = i << chunk_order;
                const u64 chunk_end_offset = chunk_start_offset + chunk_usize;

                if (chunk_end_offset <= cur_range_pos) {

                        /* The next range does not require data in this chunk,
                         * so skip it.  */

                        cur_read_offset += chunk_csize;
                        if (is_pipe_read) {
                                u8 dummy;

                                ret = full_pread(in_fd, &dummy, 1, cur_read_offset - 1);
                                if (ret)
                                        goto read_error;
                        }
                } else {

                        /* Read the chunk and feed data to the callback
                         * function.  */
                        u8 *cb_buf;

                        ret = full_pread(in_fd,
                                         cbuf,
                                         chunk_csize,
                                         cur_read_offset);
                        if (ret)
                                goto read_error;

                        if (chunk_csize != chunk_usize && !raw_chunks_mode) {
                                ret = decompress(cbuf,
                                                 chunk_csize,
                                                 ubuf,
                                                 chunk_usize,
                                                 rspec->ctype,
                                                 chunk_size);
                                if (ret) {
                                        ERROR("Failed to decompress data!");
                                        ret = WIMLIB_ERR_DECOMPRESSION;
                                        errno = EINVAL;
                                        goto out_free_memory;
                                }
                                cb_buf = ubuf;
                        } else {
                                cb_buf = cbuf;
                        }
                        cur_read_offset += chunk_csize;

                        /* At least one range requires data in this chunk.
                         * However, the data fed to the callback function must
                         * not overlap range boundaries.  */
                        do {
                                size_t start, end, size;

                                start = cur_range_pos - chunk_start_offset;
                                end = min(cur_range_end, chunk_end_offset) - chunk_start_offset;
                                size = end - start;

                                if (raw_chunks_mode)
                                        ret = (*cb)(&cb_buf[0], chunk_csize, cb_ctx);
                                else
                                        ret = (*cb)(&cb_buf[start], size, cb_ctx);

                                if (ret)
                                        goto out_free_memory;

                                cur_range_pos += size;
                                if (cur_range_pos == cur_range_end) {
                                        if (++cur_range == end_range) {
                                                cur_range_pos = ~0ULL;
                                        } else {
                                                cur_range_pos = cur_range->offset;
                                                cur_range_end = cur_range->offset + cur_range->size;
                                        }
                                }
                        } while (cur_range_pos < chunk_end_offset);
                }
        }

        if (is_pipe_read
            && last_offset == rspec->uncompressed_size - 1
            && chunk_table_size)
        {
                u8 dummy;
                /* Skip chunk table at end of pipable resource.  */

                cur_read_offset += chunk_table_size;
                ret = full_pread(in_fd, &dummy, 1, cur_read_offset - 1);
                if (ret)
                        goto read_error;
        }
        ret = 0;
out_free_memory:
        errno_save = errno;
        if (chunk_offsets_malloced)
                FREE(chunk_offsets);
        if (ubuf_malloced)
                FREE(ubuf);
        if (cbuf_malloced)
                FREE(cbuf);
        errno = errno_save;
        return ret;

oom:
        ERROR("Not enough memory available to read size=%"PRIu64" bytes "
              "from compressed resource!", last_offset - first_offset + 1);
        errno = ENOMEM;
        ret = WIMLIB_ERR_NOMEM;
        goto out_free_memory;

read_error:
        ERROR_WITH_ERRNO("Error reading compressed file resource!");
        goto out_free_memory;
}

/* Read raw data from a file descriptor at the specified offset.  */
static int
read_raw_file_data(struct filedes *in_fd, u64 size, consume_data_callback_t cb,
                   u32 cb_chunk_size, void *ctx_or_buf, u64 offset)
{
        int ret;
        u8 *tmp_buf;
        bool tmp_buf_malloced = false;

        if (cb) {
                /* Send data to callback function in chunks.  */
                if (cb_chunk_size <= STACK_MAX) {
                        tmp_buf = alloca(cb_chunk_size);
                } else {
                        tmp_buf = MALLOC(cb_chunk_size);
                        if (tmp_buf == NULL) {
                                ret = WIMLIB_ERR_NOMEM;
                                goto out;
                        }
                        tmp_buf_malloced = true;
                }

                while (size) {
                        size_t bytes_to_read = min(cb_chunk_size, size);
                        ret = full_pread(in_fd, tmp_buf, bytes_to_read,
                                         offset);
                        if (ret)
                                goto read_error;
                        ret = cb(tmp_buf, bytes_to_read, ctx_or_buf);
                        if (ret)
                                goto out;
                        size -= bytes_to_read;
                        offset += bytes_to_read;
                }
        } else {
                /* Read data directly into buffer.  */
                ret = full_pread(in_fd, ctx_or_buf, size, offset);
                if (ret)
                        goto read_error;
        }
        ret = 0;
        goto out;

read_error:
        ERROR_WITH_ERRNO("Read error");
out:
        if (tmp_buf_malloced)
                FREE(tmp_buf);
        return ret;
}

static int
bufferer_cb(const void *chunk, size_t size, void *_ctx)
{
        u8 **buf_p = _ctx;

        *buf_p = mempcpy(*buf_p, chunk, size);
        return 0;
}

struct rechunker_context {
        u8 *buffer;
        u32 buffer_filled;
        u32 cb_chunk_size;

        const struct data_range *ranges;
        size_t num_ranges;
        size_t cur_range;
        u64 range_bytes_remaining;

        consume_data_callback_t cb;
        void *cb_ctx;
};

static int
rechunker_cb(const void *chunk, size_t size, void *_ctx)
{
        struct rechunker_context *ctx = _ctx;
        const u8 *chunkptr = chunk;
        size_t bytes_to_copy;
        int ret;

        wimlib_assert(ctx->cur_range != ctx->num_ranges);

        while (size) {
                bytes_to_copy = size;

                if (bytes_to_copy > ctx->cb_chunk_size - ctx->buffer_filled)
                        bytes_to_copy = ctx->cb_chunk_size - ctx->buffer_filled;

                if (bytes_to_copy > ctx->range_bytes_remaining - ctx->buffer_filled)
                        bytes_to_copy = ctx->range_bytes_remaining - ctx->buffer_filled;

                memcpy(&ctx->buffer[ctx->buffer_filled], chunkptr, bytes_to_copy);

                ctx->buffer_filled += bytes_to_copy;
                chunkptr += bytes_to_copy;
                size -= bytes_to_copy;
                ctx->range_bytes_remaining -= bytes_to_copy;

                if (ctx->buffer_filled == ctx->cb_chunk_size ||
                    ctx->range_bytes_remaining == 0)
                {
                        ret = (*ctx->cb)(ctx->buffer, ctx->buffer_filled, ctx->cb_ctx);
                        if (ret)
                                return ret;
                        ctx->buffer_filled = 0;

                        if (ctx->range_bytes_remaining == 0 &&
                            ++ctx->cur_range != ctx->num_ranges)
                                ctx->range_bytes_remaining = ctx->ranges[ctx->cur_range].size;
                }
        }
        return 0;
}

/*
 * read_partial_wim_resource()-
 *
 * Read a range of data from an uncompressed or compressed resource in a WIM
 * file.  Data is written into a buffer or fed into a callback function, as
 * documented in read_stream_prefix().
 *
 * By default, this function provides the uncompressed data of the resource, and
 * @size and @offset and interpreted relative to the uncompressed contents of
 * the resource.  This behavior can be modified by either of the following
 * flags:
 *
 * WIMLIB_READ_RESOURCE_FLAG_RAW_FULL:
 *      Read @size bytes at @offset of the raw contents of the compressed
 *      resource.  In the case of pipable resources, this excludes the stream
 *      header.  Exclusive with WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS.
 *
 * WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS:
 *      Read the raw compressed chunks of the compressed resource.  @size must
 *      be the full uncompressed size, @offset must be 0, and @cb_chunk_size
 *      must be the resource chunk size.
 *
 * Return values:
 *      WIMLIB_ERR_SUCCESS (0)
 *      WIMLIB_ERR_READ                   (errno set)
 *      WIMLIB_ERR_UNEXPECTED_END_OF_FILE (errno set to 0)
 *      WIMLIB_ERR_NOMEM                  (errno set to ENOMEM)
 *      WIMLIB_ERR_DECOMPRESSION          (errno set to EINVAL)
 *
 *      or other error code returned by the @cb function.
 */
int
read_partial_wim_resource(const struct wim_lookup_table_entry *lte,
                          u64 size, consume_data_callback_t cb,
                          u32 cb_chunk_size, void *ctx_or_buf,
                          int flags, u64 offset)
{
        const struct wim_resource_spec *rspec;
        struct filedes *in_fd;

        /* Verify parameters.  */
        wimlib_assert(lte->resource_location == RESOURCE_IN_WIM);
        rspec = lte->rspec;
        in_fd = &rspec->wim->in_fd;
        if (cb)
                wimlib_assert(is_power_of_2(cb_chunk_size));
        if (flags & WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS) {
                /* Raw chunks mode is subject to the restrictions noted.  */
                wimlib_assert(!lte_is_partial(lte));
                wimlib_assert(!(flags & WIMLIB_READ_RESOURCE_FLAG_RAW_FULL));
                wimlib_assert(cb_chunk_size == rspec->cchunk_size);
                wimlib_assert(size == lte->size);
                wimlib_assert(offset == 0);
        } else if (flags & WIMLIB_READ_RESOURCE_FLAG_RAW_FULL) {
                /* Raw full mode:  read must not overrun end of store size.  */
                wimlib_assert(!lte_is_partial(lte));
                wimlib_assert(offset + size >= size &&
                              offset + size <= rspec->size_in_wim);
        } else {
                /* Normal mode:  read must not overrun end of original size.  */
                wimlib_assert(offset + size >= size &&
                              offset + size <= lte->size);
        }

        DEBUG("Reading WIM resource: %"PRIu64" @ +%"PRIu64"[+%"PRIu64"] "
              "from %"PRIu64"(%"PRIu64") @ +%"PRIu64" "
              "(readflags 0x%08x, resflags 0x%02x%s)",
              size, offset, lte->offset_in_res,
              rspec->size_in_wim,
              rspec->uncompressed_size,
              rspec->offset_in_wim,
              flags, lte->flags,
              (rspec->is_pipable ? ", pipable" : ""));

        if ((flags & WIMLIB_READ_RESOURCE_FLAG_RAW_FULL) ||
            rspec->ctype == WIMLIB_COMPRESSION_TYPE_NONE)
        {
                return read_raw_file_data(in_fd,
                                          size,
                                          cb,
                                          cb_chunk_size,
                                          ctx_or_buf,
                                          rspec->offset_in_wim + lte->offset_in_res + offset);
        } else {
                bool raw_chunks;
                struct data_range range;
                consume_data_callback_t internal_cb;
                void *internal_cb_ctx;
                u8 *buf;
                bool rechunker_buf_malloced = false;
                struct rechunker_context *rechunker_ctx;
                int ret;

                if (size == 0)
                        return 0;

                range.offset = lte->offset_in_res + offset;
                range.size = size;
                raw_chunks = !!(flags & WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS);

                if (cb != NULL &&
                    cb_chunk_size == rspec->cchunk_size &&
                    !(rspec->flags & WIM_RESHDR_FLAG_CONCAT))
                {
                        internal_cb = cb;
                        internal_cb_ctx = ctx_or_buf;
                } else if (cb == NULL) {
                        buf = ctx_or_buf;
                        internal_cb = bufferer_cb;
                        internal_cb_ctx = &buf;
                } else {
                        rechunker_ctx = alloca(sizeof(struct rechunker_context));

                        if (cb_chunk_size <= STACK_MAX) {
                                rechunker_ctx->buffer = alloca(cb_chunk_size);
                        } else {
                                rechunker_ctx->buffer = MALLOC(cb_chunk_size);
                                if (rechunker_ctx->buffer == NULL)
                                        return WIMLIB_ERR_NOMEM;
                                rechunker_buf_malloced = true;
                        }
                        rechunker_ctx->buffer_filled = 0;
                        rechunker_ctx->cb_chunk_size = cb_chunk_size;

                        rechunker_ctx->ranges = &range;
                        rechunker_ctx->num_ranges = 1;
                        rechunker_ctx->cur_range = 0;
                        rechunker_ctx->range_bytes_remaining = range.size;

                        rechunker_ctx->cb = cb;
                        rechunker_ctx->cb_ctx = ctx_or_buf;

                        internal_cb = rechunker_cb;
                        internal_cb_ctx = rechunker_ctx;
                }

                ret = read_compressed_wim_resource(rspec, &range, 1,
                                                   internal_cb, internal_cb_ctx,
                                                   raw_chunks);
                if (rechunker_buf_malloced)
                        FREE(rechunker_ctx->buffer);

                return ret;
        }
}

int
read_partial_wim_stream_into_buf(const struct wim_lookup_table_entry *lte,
                                 size_t size, u64 offset, void *buf)
{
        return read_partial_wim_resource(lte, size, NULL, 0, buf, 0, offset);
}

static int
read_wim_stream_prefix(const struct wim_lookup_table_entry *lte, u64 size,
                       consume_data_callback_t cb, u32 cb_chunk_size,
                       void *ctx_or_buf, int flags)
{
        return read_partial_wim_resource(lte, size, cb, cb_chunk_size,
                                         ctx_or_buf, flags, 0);
}

#ifndef __WIN32__
/* This function handles reading stream data that is located in an external
 * file,  such as a file that has been added to the WIM image through execution
 * of a wimlib_add_command.
 *
 * This assumes the file can be accessed using the standard POSIX open(),
 * read(), and close().  On Windows this will not necessarily be the case (since
 * the file may need FILE_FLAG_BACKUP_SEMANTICS to be opened, or the file may be
 * encrypted), so Windows uses its own code for its equivalent case.
 */
static int
read_file_on_disk_prefix(const struct wim_lookup_table_entry *lte, u64 size,
                         consume_data_callback_t cb, u32 cb_chunk_size,
                         void *ctx_or_buf, int _ignored_flags)
{
        int ret;
        int raw_fd;
        struct filedes fd;

        wimlib_assert(size <= lte->size);
        DEBUG("Reading %"PRIu64" bytes from \"%"TS"\"", size, lte->file_on_disk);

        raw_fd = open(lte->file_on_disk, O_BINARY | O_RDONLY);
        if (raw_fd < 0) {
                ERROR_WITH_ERRNO("Can't open \"%"TS"\"", lte->file_on_disk);
                return WIMLIB_ERR_OPEN;
        }
        filedes_init(&fd, raw_fd);
        ret = read_raw_file_data(&fd, size, cb, cb_chunk_size, ctx_or_buf, 0);
        filedes_close(&fd);
        return ret;
}
#endif /* !__WIN32__ */

/* This function handles the trivial case of reading stream data that is, in
 * fact, already located in an in-memory buffer.  */
static int
read_buffer_prefix(const struct wim_lookup_table_entry *lte,
                   u64 size, consume_data_callback_t cb,
                   u32 cb_chunk_size, void *ctx_or_buf, int _ignored_flags)
{
        wimlib_assert(size <= lte->size);

        if (cb) {
                /* Feed the data into the callback function in
                 * appropriately-sized chunks.  */
                int ret;
                u32 chunk_size;

                for (u64 offset = 0; offset < size; offset += chunk_size) {
                        chunk_size = min(cb_chunk_size, size - offset);
                        ret = cb((const u8*)lte->attached_buffer + offset,
                                 chunk_size, ctx_or_buf);
                        if (ret)
                                return ret;
                }
        } else {
                /* Copy the data directly into the specified buffer.  */
                memcpy(ctx_or_buf, lte->attached_buffer, size);
        }
        return 0;
}

typedef int (*read_stream_prefix_handler_t)(const struct wim_lookup_table_entry *lte,
                                            u64 size, consume_data_callback_t cb,
                                            u32 cb_chunk_size, void *ctx_or_buf,
                                            int flags);

/*
 * read_stream_prefix()-
 *
 * Reads the first @size bytes from a generic "stream", which may be located in
 * any one of several locations, such as in a WIM file (compressed or
 * uncompressed), in an external file, or directly in an in-memory buffer.
 *
 * This function feeds the data either to a callback function (@cb != NULL,
 * passing it @ctx_or_buf), or write it directly into a buffer (@cb == NULL,
 * @ctx_or_buf specifies the buffer, which must have room for at least @size
 * bytes).
 *
 * When (@cb != NULL), @cb_chunk_size specifies the maximum size of data chunks
 * to feed the callback function.  @cb_chunk_size must be positive, and if the
 * stream is in a WIM file, must be a power of 2.  All chunks, except possibly
 * the last one, will be this size.  If (@cb == NULL), @cb_chunk_size is
 * ignored.
 *
 * If the stream is located in a WIM file, @flags can be set as documented in
 * read_partial_wim_resource().  Otherwise @flags are ignored.
 *
 * Returns 0 on success; nonzero on error.  A nonzero value will be returned if
 * the stream data cannot be successfully read (for a number of different
 * reasons, depending on the stream location), or if a callback function was
 * specified and it returned nonzero.
 */
int
read_stream_prefix(const struct wim_lookup_table_entry *lte, u64 size,
                   consume_data_callback_t cb, u32 cb_chunk_size,
                   void *ctx_or_buf, int flags)
{
        /* This function merely verifies several preconditions, then passes
         * control to an appropriate function for understanding each possible
         * stream location.  */
        static const read_stream_prefix_handler_t handlers[] = {
                [RESOURCE_IN_WIM]             = read_wim_stream_prefix,
        #ifdef __WIN32__
                [RESOURCE_IN_FILE_ON_DISK]    = read_win32_file_prefix,
        #else
                [RESOURCE_IN_FILE_ON_DISK]    = read_file_on_disk_prefix,
        #endif
                [RESOURCE_IN_ATTACHED_BUFFER] = read_buffer_prefix,
        #ifdef WITH_FUSE
                [RESOURCE_IN_STAGING_FILE]    = read_file_on_disk_prefix,
        #endif
        #ifdef WITH_NTFS_3G
                [RESOURCE_IN_NTFS_VOLUME]     = read_ntfs_file_prefix,
        #endif
        #ifdef __WIN32__
                [RESOURCE_WIN32_ENCRYPTED]    = read_win32_encrypted_file_prefix,
        #endif
        };
        wimlib_assert(lte->resource_location < ARRAY_LEN(handlers)
                      && handlers[lte->resource_location] != NULL);
        wimlib_assert(cb == NULL || cb_chunk_size > 0);
        return handlers[lte->resource_location](lte, size, cb, cb_chunk_size,
                                                ctx_or_buf, flags);
}

/* Read the full uncompressed data of the specified stream into the specified
 * buffer, which must have space for at least lte->size bytes.  */
int
read_full_stream_into_buf(const struct wim_lookup_table_entry *lte, void *buf)
{
        return read_stream_prefix(lte, lte->size, NULL, 0, buf, 0);
}

/* Read the full uncompressed data of the specified stream.  A buffer sufficient
 * to hold the data is allocated and returned in @buf_ret.  */
int
read_full_stream_into_alloc_buf(const struct wim_lookup_table_entry *lte,
                                void **buf_ret)
{
        int ret;
        void *buf;

        if ((size_t)lte->size != lte->size) {
                ERROR("Can't read %"PRIu64" byte stream into "
                      "memory", lte->size);
                return WIMLIB_ERR_NOMEM;
        }

        buf = MALLOC(lte->size);
        if (buf == NULL)
                return WIMLIB_ERR_NOMEM;

        ret = read_full_stream_into_buf(lte, buf);
        if (ret) {
                FREE(buf);
                return ret;
        }

        *buf_ret = buf;
        return 0;
}

/* Retrieve the full uncompressed data of the specified WIM resource.  */
static int
wim_resource_spec_to_data(struct wim_resource_spec *rspec, void **buf_ret)
{
        int ret;
        struct wim_lookup_table_entry *lte;

        lte = new_lookup_table_entry();
        if (lte == NULL)
                return WIMLIB_ERR_NOMEM;

        lte->unhashed = 1;
        lte_bind_wim_resource_spec(lte, rspec);
        lte->flags = rspec->flags;
        lte->size = rspec->uncompressed_size;
        lte->offset_in_res = 0;

        ret = read_full_stream_into_alloc_buf(lte, buf_ret);

        lte_unbind_wim_resource_spec(lte);
        free_lookup_table_entry(lte);
        return ret;
}

/* Retrieve the full uncompressed data of the specified WIM resource.  */
int
wim_reshdr_to_data(const struct wim_reshdr *reshdr, WIMStruct *wim, void **buf_ret)
{
        DEBUG("offset_in_wim=%"PRIu64", size_in_wim=%"PRIu64", "
              "uncompressed_size=%"PRIu64,
              reshdr->offset_in_wim, reshdr->size_in_wim, reshdr->uncompressed_size);

        struct wim_resource_spec rspec;
        wim_res_hdr_to_spec(reshdr, wim, &rspec);
        return wim_resource_spec_to_data(&rspec, buf_ret);
}

struct read_stream_list_ctx {
        read_stream_list_begin_stream_t begin_stream;
        consume_data_callback_t consume_chunk;
        read_stream_list_end_stream_t end_stream;
        void *begin_stream_ctx;
        void *consume_chunk_ctx;
        void *end_stream_ctx;
        struct wim_lookup_table_entry *cur_stream;
        u64 cur_stream_offset;
        struct wim_lookup_table_entry *final_stream;
        size_t list_head_offset;
};

static int
read_stream_list_wrapper_cb(const void *chunk, size_t size, void *_ctx)
{
        struct read_stream_list_ctx *ctx = _ctx;
        int ret;

        if (ctx->cur_stream_offset == 0) {
                /* Starting a new stream.  */
                ret = (*ctx->begin_stream)(ctx->cur_stream, ctx->begin_stream_ctx);
                if (ret)
                        return ret;
        }

        ret = (*ctx->consume_chunk)(chunk, size, ctx->consume_chunk_ctx);
        if (ret)
                return ret;

        ctx->cur_stream_offset += size;

        if (ctx->cur_stream_offset == ctx->cur_stream->size) {
                /* Finished reading all the data for a stream; advance
                 * to the next one.  */
                ret = (*ctx->end_stream)(ctx->cur_stream, ctx->end_stream_ctx);
                if (ret)
                        return ret;

                if (ctx->cur_stream == ctx->final_stream)
                        return 0;

                struct list_head *cur = (struct list_head *)
                                ((u8*)ctx->cur_stream + ctx->list_head_offset);
                struct list_head *next = cur->next;

                ctx->cur_stream = (struct wim_lookup_table_entry *)
                                ((u8*)next - ctx->list_head_offset);

                ctx->cur_stream_offset = 0;
        }
        return 0;
}

/*
 * Read a list of streams, each of which may be in any supported location (e.g.
 * in a WIM or in an external file).  Unlike read_stream_prefix() or the
 * functions which call it, this function optimizes the case where multiple
 * streams are packed into a single compressed WIM resource and reads them all
 * consecutively, only decompressing the data one time.
 *
 * @stream_list
 *      List of streams (represented as `struct wim_lookup_table_entry's) to
 *      read.
 * @list_head_offset
 *      Offset of the `struct list_head' within each `struct
 *      wim_lookup_table_entry' that makes up the @stream_list.
 * @begin_stream
 *      Callback for starting to process a stream.
 * @consume_chunk
 *      Callback for receiving a chunk of stream data.
 * @end_stream
 *      Callback for finishing the processing of a stream.
 * @cb_chunk_size
 *      Size of chunks to provide to @consume_chunk.  For a given stream, all
 *      the chunks will be this size, except possibly the last which will be the
 *      remainder.
 * @cb_ctx
 *      Parameter to pass to the callback functions.
 *
 * Returns 0 on success; a nonzero error code on failure.  Failure can occur due
 * to an error reading the data or due to an error status being returned by any
 * of the callback functions.
 */
int
read_stream_list(struct list_head *stream_list,
                 size_t list_head_offset,
                 read_stream_list_begin_stream_t begin_stream,
                 consume_data_callback_t consume_chunk,
                 read_stream_list_end_stream_t end_stream,
                 u32 cb_chunk_size,
                 void *cb_ctx)
{
        int ret;
        struct list_head *cur, *next;
        struct wim_lookup_table_entry *lte;

        ret = sort_stream_list_by_sequential_order(stream_list, list_head_offset);
        if (ret)
                return ret;

        for (cur = stream_list->next, next = cur->next;
             cur != stream_list;
             cur = next, next = cur->next)
        {
                lte = (struct wim_lookup_table_entry*)((u8*)cur - list_head_offset);

                if (lte_is_partial(lte)) {

                        struct wim_lookup_table_entry *lte_next, *lte_last;
                        struct list_head *next2;
                        size_t stream_count;

                        /* The next stream is a proper sub-sequence of a WIM
                         * resource.  See if there are other streams in the same
                         * resource that need to be read.  Since
                         * sort_stream_list_by_sequential_order() sorted the
                         * streams by offset in the WIM, this can be determined
                         * by simply scanning forward in the list.  */

                        lte_last = lte;
                        stream_count = 1;
                        for (next2 = next;
                             next2 != stream_list
                             && (lte_next = (struct wim_lookup_table_entry*)
                                                ((u8*)next2 - list_head_offset),
                                 lte_next->resource_location == RESOURCE_IN_WIM
                                 && lte_next->rspec == lte->rspec);
                             next2 = next2->next)
                        {
                                lte_last = lte_next;
                                stream_count++;
                        }
                        if (stream_count > 1) {
                                /* Reading multiple streams combined into a
                                 * single WIM resource.  They are in the stream
                                 * list, sorted by offset; @lte specifies the
                                 * first stream in the resource that needs to be
                                 * read and @lte_last specifies the last stream
                                 * in the resource that needs to be read.  */

                                next = next2;

                                struct data_range ranges[stream_count];

                                {
                                        struct list_head *next3;
                                        size_t i;
                                        struct wim_lookup_table_entry *lte_cur;

                                        next3 = cur;
                                        for (i = 0; i < stream_count; i++) {
                                                lte_cur = (struct wim_lookup_table_entry*)
                                                        ((u8*)next3 - list_head_offset);
                                                ranges[i].offset = lte_cur->offset_in_res;
                                                ranges[i].size = lte_cur->size;
                                                next3 = next3->next;
                                        }
                                }

                                struct rechunker_context rechunker_ctx = {
                                        .buffer = MALLOC(cb_chunk_size),
                                        .buffer_filled = 0,
                                        .cb_chunk_size = cb_chunk_size,
                                        .ranges = ranges,
                                        .num_ranges = stream_count,
                                        .cur_range = 0,
                                        .range_bytes_remaining = ranges[0].size,
                                        .cb = consume_chunk,
                                        .cb_ctx = cb_ctx,
                                };

                                if (rechunker_ctx.buffer == NULL)
                                        return WIMLIB_ERR_NOMEM;

                                struct read_stream_list_ctx ctx = {
                                        .begin_stream           = begin_stream,
                                        .begin_stream_ctx       = cb_ctx,
                                        .consume_chunk          = rechunker_cb,
                                        .consume_chunk_ctx      = &rechunker_ctx,
                                        .end_stream             = end_stream,
                                        .end_stream_ctx         = cb_ctx,
                                        .cur_stream             = lte,
                                        .cur_stream_offset      = 0,
                                        .final_stream           = lte_last,
                                        .list_head_offset       = list_head_offset,
                                };

                                ret = read_compressed_wim_resource(lte->rspec,
                                                                   ranges,
                                                                   stream_count,
                                                                   read_stream_list_wrapper_cb,
                                                                   &ctx,
                                                                   false);
                                FREE(rechunker_ctx.buffer);
                                if (ret)
                                        return ret;
                                continue;
                        }
                }
                ret = (*begin_stream)(lte, cb_ctx);
                if (ret)
                        return ret;

                ret = read_stream_prefix(lte, lte->size, consume_chunk,
                                         cb_chunk_size, cb_ctx, 0);
                if (ret)
                        return ret;

                ret = (*end_stream)(lte, cb_ctx);
                if (ret)
                        return ret;
        }
        return 0;
}

struct extract_ctx {
        SHA_CTX sha_ctx;
        consume_data_callback_t extract_chunk;
        void *extract_chunk_arg;
};

static int
extract_chunk_sha1_wrapper(const void *chunk, size_t chunk_size, void *_ctx)
{
        struct extract_ctx *ctx = _ctx;

        sha1_update(&ctx->sha_ctx, chunk, chunk_size);
        return ctx->extract_chunk(chunk, chunk_size, ctx->extract_chunk_arg);
}

/* Extracts the first @size bytes of a stream to somewhere.  In the process, the
 * SHA1 message digest of the uncompressed stream is checked if the full stream
 * is being extracted.
 *
 * @extract_chunk is a function that will be called to extract each chunk of the
 * stream.  */
int
extract_stream(const struct wim_lookup_table_entry *lte, u64 size,
               consume_data_callback_t extract_chunk, void *extract_chunk_arg)
{
        int ret;
        if (size == lte->size) {
                /* Do SHA1 */
                struct extract_ctx ctx;
                ctx.extract_chunk = extract_chunk;
                ctx.extract_chunk_arg = extract_chunk_arg;
                sha1_init(&ctx.sha_ctx);
                ret = read_stream_prefix(lte, size,
                                         extract_chunk_sha1_wrapper,
                                         lte_cchunk_size(lte),
                                         &ctx, 0);
                if (ret == 0) {
                        u8 hash[SHA1_HASH_SIZE];
                        sha1_final(hash, &ctx.sha_ctx);
                        if (!hashes_equal(hash, lte->hash)) {
                                if (wimlib_print_errors) {
                                        ERROR("Invalid SHA1 message digest "
                                              "on the following WIM stream:");
                                        print_lookup_table_entry(lte, stderr);
                                        if (lte->resource_location == RESOURCE_IN_WIM)
                                                ERROR("The WIM file appears to be corrupt!");
                                }
                                ret = WIMLIB_ERR_INVALID_RESOURCE_HASH;
                        }
                }
        } else {
                /* Don't do SHA1 */
                ret = read_stream_prefix(lte, size, extract_chunk,
                                         lte_cchunk_size(lte),
                                         extract_chunk_arg, 0);
        }
        return ret;
}

static int
extract_wim_chunk_to_fd(const void *buf, size_t len, void *_fd_p)
{
        struct filedes *fd = _fd_p;
        int ret = full_write(fd, buf, len);
        if (ret)
                ERROR_WITH_ERRNO("Error writing to file descriptor");
        return ret;
}

/* Extract the first @size bytes of the specified stream to the specified file
 * descriptor.  If @size is the full size of the stream, its SHA1 message digest
 * is also checked.  */
int
extract_stream_to_fd(const struct wim_lookup_table_entry *lte,
                     struct filedes *fd, u64 size)
{
        return extract_stream(lte, size, extract_wim_chunk_to_fd, fd);
}


static int
sha1_chunk(const void *buf, size_t len, void *ctx)
{
        sha1_update(ctx, buf, len);
        return 0;
}

/* Calculate the SHA1 message digest of a stream, storing it in @lte->hash.  */
int
sha1_stream(struct wim_lookup_table_entry *lte)
{
        int ret;
        SHA_CTX sha_ctx;

        sha1_init(&sha_ctx);
        ret = read_stream_prefix(lte, lte->size,
                                 sha1_chunk, lte_cchunk_size(lte),
                                 &sha_ctx, 0);
        if (ret == 0)
                sha1_final(lte->hash, &sha_ctx);

        return ret;
}

/* Convert a WIM resource header to a stand-alone resource specification.  */
void
wim_res_hdr_to_spec(const struct wim_reshdr *reshdr, WIMStruct *wim,
                    struct wim_resource_spec *spec)
{
        spec->wim = wim;
        spec->offset_in_wim = reshdr->offset_in_wim;
        spec->size_in_wim = reshdr->size_in_wim;
        spec->uncompressed_size = reshdr->uncompressed_size;
        INIT_LIST_HEAD(&spec->lte_list);
        spec->flags = reshdr->flags;
        spec->is_pipable = wim_is_pipable(wim);
        if (spec->flags & (WIM_RESHDR_FLAG_COMPRESSED | WIM_RESHDR_FLAG_CONCAT)) {
                spec->ctype = wim->compression_type;
                spec->cchunk_size = wim->chunk_size;
        } else {
                spec->ctype = WIMLIB_COMPRESSION_TYPE_NONE;
                spec->cchunk_size = 0;
        }
}

/* Convert a stand-alone resource specification to a WIM resource header.  */
void
wim_res_spec_to_hdr(const struct wim_resource_spec *rspec,
                    struct wim_reshdr *reshdr)
{
        reshdr->offset_in_wim     = rspec->offset_in_wim;
        reshdr->size_in_wim       = rspec->size_in_wim;
        reshdr->flags             = rspec->flags;
        reshdr->uncompressed_size = rspec->uncompressed_size;
}

/* Translates a WIM resource header from the on-disk format into an in-memory
 * format.  */
int
get_wim_reshdr(const struct wim_reshdr_disk *disk_reshdr,
               struct wim_reshdr *reshdr)
{
        reshdr->offset_in_wim = le64_to_cpu(disk_reshdr->offset_in_wim);
        reshdr->size_in_wim = (((u64)disk_reshdr->size_in_wim[0] <<  0) |
                              ((u64)disk_reshdr->size_in_wim[1] <<  8) |
                              ((u64)disk_reshdr->size_in_wim[2] << 16) |
                              ((u64)disk_reshdr->size_in_wim[3] << 24) |
                              ((u64)disk_reshdr->size_in_wim[4] << 32) |
                              ((u64)disk_reshdr->size_in_wim[5] << 40) |
                              ((u64)disk_reshdr->size_in_wim[6] << 48));
        reshdr->uncompressed_size = le64_to_cpu(disk_reshdr->uncompressed_size);
        reshdr->flags = disk_reshdr->flags;

        /* Truncate numbers to 62 bits to avoid possible overflows.  */
        if (reshdr->offset_in_wim & 0xc000000000000000ULL)
                return WIMLIB_ERR_INVALID_LOOKUP_TABLE_ENTRY;

        if (reshdr->uncompressed_size & 0xc000000000000000ULL)
                return WIMLIB_ERR_INVALID_LOOKUP_TABLE_ENTRY;

        return 0;
}

/* Translates a WIM resource header from an in-memory format into the on-disk
 * format.  */
void
put_wim_reshdr(const struct wim_reshdr *reshdr,
               struct wim_reshdr_disk *disk_reshdr)
{
        disk_reshdr->size_in_wim[0] = reshdr->size_in_wim  >>  0;
        disk_reshdr->size_in_wim[1] = reshdr->size_in_wim  >>  8;
        disk_reshdr->size_in_wim[2] = reshdr->size_in_wim  >> 16;
        disk_reshdr->size_in_wim[3] = reshdr->size_in_wim  >> 24;
        disk_reshdr->size_in_wim[4] = reshdr->size_in_wim  >> 32;
        disk_reshdr->size_in_wim[5] = reshdr->size_in_wim  >> 40;
        disk_reshdr->size_in_wim[6] = reshdr->size_in_wim  >> 48;
        disk_reshdr->flags = reshdr->flags;
        disk_reshdr->offset_in_wim = cpu_to_le64(reshdr->offset_in_wim);
        disk_reshdr->uncompressed_size = cpu_to_le64(reshdr->uncompressed_size);
}