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block_read: Only allocate in_buf when needed #20

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block_read: Only allocate in_buf when needed #20

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35 changes: 21 additions & 14 deletions libmpq/mpq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -897,25 +897,38 @@ int32_t libmpq__block_read(mpq_archive_s *mpq_archive, uint32_t file_number, uin
block_offset = mpq_archive->mpq_block[mpq_archive->mpq_map[file_number].block_table_indices].offset + (((long long)mpq_archive->mpq_block_ex[mpq_archive->mpq_map[file_number].block_table_indices].offset_high) << 32) + mpq_archive->mpq_file[file_number]->packed_offset[block_number];
in_size = mpq_archive->mpq_file[file_number]->packed_offset[block_number + 1] - mpq_archive->mpq_file[file_number]->packed_offset[block_number];

/* get implosion status. */
libmpq__file_imploded(mpq_archive, file_number, &imploded);

/* get compression status. */
libmpq__file_compressed(mpq_archive, file_number, &compressed);

/* check if we can avoid allocating a temporary buffer. */
const uint8_t use_in_buf_as_out = in_size <= out_size && (!compressed || in_size == out_size) && !imploded;

/* seek in file. */
if (fseeko(mpq_archive->fp, block_offset + mpq_archive->archive_offset, SEEK_SET) < 0) {

/* something with seek in file failed. */
return LIBMPQ_ERROR_SEEK;
}

/* allocate memory for the read buffer. */
if ((in_buf = calloc(1, in_size)) == NULL) {
if (use_in_buf_as_out) {
in_buf = out_buf;
} else {
/* allocate memory for the read buffer. */
if ((in_buf = calloc(1, in_size)) == NULL) {

/* memory allocation problem. */
return LIBMPQ_ERROR_MALLOC;
/* memory allocation problem. */
return LIBMPQ_ERROR_MALLOC;
}
}

/* read block from file. */
if (fread(in_buf, 1, in_size, mpq_archive->fp) != in_size) {

/* free buffers. */
free(in_buf);
if (!use_in_buf_as_out) free(in_buf);

/* something on reading block failed. */
return LIBMPQ_ERROR_READ;
Expand All @@ -941,26 +954,20 @@ int32_t libmpq__block_read(mpq_archive_s *mpq_archive, uint32_t file_number, uin
}
}

/* get compression status. */
libmpq__file_compressed(mpq_archive, file_number, &compressed);

/* check if file is compressed. */
if (compressed) {

/* decompress block. */
if ((tb = libmpq__decompress_block(in_buf, in_size, out_buf, out_size, LIBMPQ_FLAG_COMPRESS_MULTI)) < 0) {

/* free temporary buffer. */
free(in_buf);
if (!use_in_buf_as_out) free(in_buf);

/* something on decompressing block failed. */
return LIBMPQ_ERROR_UNPACK;
}
}

/* get implosion status. */
libmpq__file_imploded(mpq_archive, file_number, &imploded);

/* check if file is imploded. */
if (imploded) {

Expand Down Expand Up @@ -991,15 +998,15 @@ int32_t libmpq__block_read(mpq_archive_s *mpq_archive, uint32_t file_number, uin
if ((tb = libmpq__decompress_block(in_buf, in_size, out_buf, out_size, LIBMPQ_FLAG_COMPRESS_NONE)) < 0) {

/* free temporary buffer. */
free(in_buf);
if (!use_in_buf_as_out) free(in_buf);

/* something on decompressing block failed. */
return LIBMPQ_ERROR_UNPACK;
}
}

/* free read buffer. */
free(in_buf);
if (!use_in_buf_as_out) free(in_buf);

/* check for null pointer. */
if (transferred != NULL) {
Expand Down