-static
-int
-deflate_block(BGZF* fp, int block_length)
-{
- // Deflate the block in fp->uncompressed_block into fp->compressed_block.
- // Also adds an extra field that stores the compressed block length.
-
- byte* buffer = fp->compressed_block;
- int buffer_size = fp->compressed_block_size;
-
- // Init gzip header
- buffer[0] = GZIP_ID1;
- buffer[1] = GZIP_ID2;
- buffer[2] = CM_DEFLATE;
- buffer[3] = FLG_FEXTRA;
- buffer[4] = 0; // mtime
- buffer[5] = 0;
- buffer[6] = 0;
- buffer[7] = 0;
- buffer[8] = 0;
- buffer[9] = OS_UNKNOWN;
- buffer[10] = BGZF_XLEN;
- buffer[11] = 0;
- buffer[12] = BGZF_ID1;
- buffer[13] = BGZF_ID2;
- buffer[14] = BGZF_LEN;
- buffer[15] = 0;
- buffer[16] = 0; // placeholder for block length
- buffer[17] = 0;
-
- // loop to retry for blocks that do not compress enough
- int input_length = block_length;
- int compressed_length = 0;
- while (1) {
- int compress_level = fp->is_uncompressed? 0 : Z_DEFAULT_COMPRESSION;
- z_stream zs;
- zs.zalloc = NULL;
- zs.zfree = NULL;
- zs.next_in = fp->uncompressed_block;
- zs.avail_in = input_length;
- zs.next_out = (void*)&buffer[BLOCK_HEADER_LENGTH];
- zs.avail_out = buffer_size - BLOCK_HEADER_LENGTH - BLOCK_FOOTER_LENGTH;
-
- int status = deflateInit2(&zs, compress_level, Z_DEFLATED,
- GZIP_WINDOW_BITS, Z_DEFAULT_MEM_LEVEL, Z_DEFAULT_STRATEGY);
- if (status != Z_OK) {
- report_error(fp, "deflate init failed");
- return -1;
- }
- status = deflate(&zs, Z_FINISH);
- if (status != Z_STREAM_END) {
- deflateEnd(&zs);
- if (status == Z_OK) {
- // Not enough space in buffer.
- // Can happen in the rare case the input doesn't compress enough.
- // Reduce the amount of input until it fits.
- input_length -= 1024;
- if (input_length <= 0) {
- // should never happen
- report_error(fp, "input reduction failed");
- return -1;
- }
- continue;
- }
- report_error(fp, "deflate failed");
- return -1;
- }
- status = deflateEnd(&zs);
- if (status != Z_OK) {
- report_error(fp, "deflate end failed");
- return -1;
- }
- compressed_length = zs.total_out;
- compressed_length += BLOCK_HEADER_LENGTH + BLOCK_FOOTER_LENGTH;
- if (compressed_length > MAX_BLOCK_SIZE) {
- // should never happen
- report_error(fp, "deflate overflow");
- return -1;
- }
- break;
- }