diff options
| -rw-r--r-- | archival/libunarchive/decompress_bunzip2.c | 49 |
1 files changed, 28 insertions, 21 deletions
diff --git a/archival/libunarchive/decompress_bunzip2.c b/archival/libunarchive/decompress_bunzip2.c index 3a5d23345..8d7746a79 100644 --- a/archival/libunarchive/decompress_bunzip2.c +++ b/archival/libunarchive/decompress_bunzip2.c @@ -492,15 +492,20 @@ static int get_next_block(bunzip_data *bd) int FAST_FUNC read_bunzip(bunzip_data *bd, char *outbuf, int len) { const uint32_t *dbuf; - int pos, current, previous, gotcount; + int pos, current, previous, out_count; + uint32_t CRC; - /* If last read was short due to end of file, return last block now */ - if (bd->writeCount < 0) return bd->writeCount; + /* If we already have error/end indicator, return it */ + if (bd->writeCount < 0) + return bd->writeCount; - gotcount = 0; + out_count = 0; dbuf = bd->dbuf; + + /* Register-cached state (hopefully): */ pos = bd->writePos; current = bd->writeCurrent; + CRC = bd->writeCRC; /* small loss on x86-32 (not enough regs), win on x86-64 */ /* We will always have pending decoded data to write into the output buffer unless this is the very first call (in which case we haven't @@ -514,8 +519,8 @@ int FAST_FUNC read_bunzip(bunzip_data *bd, char *outbuf, int len) /* Loop outputting bytes */ for (;;) { - /* If the output buffer is full, snapshot state and return */ - if (gotcount >= len) { + /* If the output buffer is full, save cached state and return */ + if (out_count >= len) { /* Unlikely branch. * Use of "goto" instead of keeping code here * helps compiler to realize this. */ @@ -523,17 +528,16 @@ int FAST_FUNC read_bunzip(bunzip_data *bd, char *outbuf, int len) } /* Write next byte into output buffer, updating CRC */ - outbuf[gotcount++] = current; - bd->writeCRC = (bd->writeCRC << 8) - ^ bd->crc32Table[(bd->writeCRC >> 24) ^ current]; + outbuf[out_count++] = current; + CRC = (CRC << 8) ^ bd->crc32Table[(CRC >> 24) ^ current]; /* Loop now if we're outputting multiple copies of this byte */ if (bd->writeCopies) { /* Unlikely branch */ /*--bd->writeCopies;*/ /*continue;*/ - /* Same, but (ab)using other existing --writeCopies operation. - * Luckily, this also compiles into just one branch insn: */ + /* Same, but (ab)using other existing --writeCopies operation + * (and this if() compiles into just test+branch pair): */ goto dec_writeCopies; } decode_next_byte: @@ -549,7 +553,7 @@ int FAST_FUNC read_bunzip(bunzip_data *bd, char *outbuf, int len) /* After 3 consecutive copies of the same byte, the 4th * is a repeat count. We count down from 4 instead * of counting up because testing for non-zero is faster */ - if (--bd->writeRunCountdown) { + if (--bd->writeRunCountdown != 0) { if (current != previous) bd->writeRunCountdown = 4; } else { @@ -568,11 +572,11 @@ int FAST_FUNC read_bunzip(bunzip_data *bd, char *outbuf, int len) } /* for(;;) */ /* Decompression of this input block completed successfully */ - bd->writeCRC = ~bd->writeCRC; - bd->totalCRC = ((bd->totalCRC << 1) | (bd->totalCRC >> 31)) ^ bd->writeCRC; + bd->writeCRC = CRC = ~CRC; + bd->totalCRC = ((bd->totalCRC << 1) | (bd->totalCRC >> 31)) ^ CRC; - /* If this block had a CRC error, force file level CRC error. */ - if (bd->writeCRC != bd->headerCRC) { + /* If this block had a CRC error, force file level CRC error */ + if (CRC != bd->headerCRC) { bd->totalCRC = bd->headerCRC + 1; return RETVAL_LAST_BLOCK; } @@ -581,23 +585,26 @@ int FAST_FUNC read_bunzip(bunzip_data *bd, char *outbuf, int len) /* Refill the intermediate buffer by Huffman-decoding next block of input */ { int r = get_next_block(bd); - if (r) { + if (r) { /* error/end */ bd->writeCount = r; - return (r != RETVAL_LAST_BLOCK) ? r : gotcount; + return (r != RETVAL_LAST_BLOCK) ? r : out_count; } } - bd->writeCRC = ~0; + CRC = ~0; pos = bd->writePos; current = bd->writeCurrent; goto decode_next_byte; outbuf_full: - /* Output buffer is full, snapshot state and return */ + /* Output buffer is full, save cached state and return */ bd->writePos = pos; bd->writeCurrent = current; + bd->writeCRC = CRC; + bd->writeCopies++; - return gotcount; + + return out_count; } /* Allocate the structure, read file header. If in_fd==-1, inbuf must contain |