Index: gzip-1.5/deflate.c =================================================================== --- gzip-1.5.orig/deflate.c +++ gzip-1.5/deflate.c @@ -131,6 +131,14 @@ #endif /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */ +#ifndef RSYNC_WIN +# define RSYNC_WIN 4096 +#endif +/* Size of rsync window, must be < MAX_DIST */ + +#define RSYNC_SUM_MATCH(sum) ((sum) % RSYNC_WIN == 0) +/* Whether window sum matches magic value */ + /* =========================================================================== * Local data used by the "longest match" routines. */ @@ -212,6 +220,8 @@ local int compr_level; unsigned good_match; /* Use a faster search when the previous match is longer than this */ +local ulg rsync_sum; /* rolling sum of rsync window */ +local ulg rsync_chunk_end; /* next rsync sequence point */ /* Values for max_lazy_match, good_match and max_chain_length, depending on * the desired pack level (0..9). The values given below have been tuned to @@ -314,6 +324,10 @@ void lm_init (pack_level, flags) #endif /* prev will be initialized on the fly */ + /* rsync params */ + rsync_chunk_end = 0xFFFFFFFFUL; + rsync_sum = 0; + /* Set the default configuration parameters: */ max_lazy_match = configuration_table[pack_level].max_lazy; @@ -550,6 +564,8 @@ local void fill_window() memcpy((char*)window, (char*)window+WSIZE, (unsigned)WSIZE); match_start -= WSIZE; strstart -= WSIZE; /* we now have strstart >= MAX_DIST: */ + if (rsync_chunk_end != 0xFFFFFFFFUL) + rsync_chunk_end -= WSIZE; block_start -= (long) WSIZE; @@ -579,13 +595,46 @@ local void fill_window() } } +local void rsync_roll(start, num) + unsigned start; + unsigned num; +{ + unsigned i; + + if (start < RSYNC_WIN) { + /* before window fills. */ + for (i = start; i < RSYNC_WIN; i++) { + if (i == start + num) return; + rsync_sum += (ulg)window[i]; + } + num -= (RSYNC_WIN - start); + start = RSYNC_WIN; + } + + /* buffer after window full */ + for (i = start; i < start+num; i++) { + /* New character in */ + rsync_sum += (ulg)window[i]; + /* Old character out */ + rsync_sum -= (ulg)window[i - RSYNC_WIN]; + if (rsync_chunk_end == 0xFFFFFFFFUL && RSYNC_SUM_MATCH(rsync_sum)) + rsync_chunk_end = i; + } +} + +/* =========================================================================== + * Set rsync_chunk_end if window sum matches magic value. + */ +#define RSYNC_ROLL(s, n) \ + do { if (rsync) rsync_roll((s), (n)); } while(0) + /* =========================================================================== * Flush the current block, with given end-of-file flag. * IN assertion: strstart is set to the end of the current match. */ #define FLUSH_BLOCK(eof) \ flush_block(block_start >= 0L ? (char*)&window[(unsigned)block_start] : \ - (char*)NULL, (long)strstart - block_start, (eof)) + (char*)NULL, (long)strstart - block_start, flush-1, (eof)) /* =========================================================================== * Processes a new input file and return its compressed length. This @@ -596,7 +645,7 @@ local void fill_window() local off_t deflate_fast() { IPos hash_head; /* head of the hash chain */ - int flush; /* set if current block must be flushed */ + int flush; /* set if current block must be flushed, 2=>and padded */ unsigned match_length = 0; /* length of best match */ prev_length = MIN_MATCH-1; @@ -625,7 +674,8 @@ local off_t deflate_fast() flush = ct_tally(strstart-match_start, match_length - MIN_MATCH); lookahead -= match_length; - + + RSYNC_ROLL(strstart, match_length); /* Insert new strings in the hash table only if the match length * is not too large. This saves time but degrades compression. */ @@ -654,9 +704,14 @@ local off_t deflate_fast() /* No match, output a literal byte */ Tracevv((stderr,"%c",window[strstart])); flush = ct_tally (0, window[strstart]); + RSYNC_ROLL(strstart, 1); lookahead--; strstart++; } + if (rsync && strstart > rsync_chunk_end) { + rsync_chunk_end = 0xFFFFFFFFUL; + flush = 2; + } if (flush) FLUSH_BLOCK(0), block_start = strstart; /* Make sure that we always have enough lookahead, except @@ -730,6 +785,7 @@ off_t deflate() */ lookahead -= prev_length-1; prev_length -= 2; + RSYNC_ROLL(strstart, prev_length+1); do { strstart++; INSERT_STRING(strstart, hash_head); @@ -742,24 +798,40 @@ off_t deflate() match_available = 0; match_length = MIN_MATCH-1; strstart++; - if (flush) FLUSH_BLOCK(0), block_start = strstart; + if (rsync && strstart > rsync_chunk_end) { + rsync_chunk_end = 0xFFFFFFFFUL; + flush = 2; + } + if (flush) FLUSH_BLOCK(0), block_start = strstart; } else if (match_available) { /* If there was no match at the previous position, output a * single literal. If there was a match but the current match * is longer, truncate the previous match to a single literal. */ Tracevv((stderr,"%c",window[strstart-1])); - if (ct_tally (0, window[strstart-1])) { - FLUSH_BLOCK(0), block_start = strstart; + flush = ct_tally (0, window[strstart-1]); + if (rsync && strstart > rsync_chunk_end) { + rsync_chunk_end = 0xFFFFFFFFUL; + flush = 2; } + if (flush) FLUSH_BLOCK(0), block_start = strstart; + RSYNC_ROLL(strstart, 1); strstart++; lookahead--; } else { /* There is no previous match to compare with, wait for * the next step to decide. */ + if (rsync && strstart > rsync_chunk_end) { + /* Reset huffman tree */ + rsync_chunk_end = 0xFFFFFFFFUL; + flush = 2; + FLUSH_BLOCK(0), block_start = strstart; + } + match_available = 1; + RSYNC_ROLL(strstart, 1); strstart++; lookahead--; } Index: gzip-1.5/doc/gzip.texi =================================================================== --- gzip-1.5.orig/doc/gzip.texi +++ gzip-1.5/doc/gzip.texi @@ -353,6 +353,14 @@ specified on the command line are direct into the directory and compress all the files it finds there (or decompress them in the case of @command{gunzip}). +@item --rsyncable +While compressing, synchronize the output occasionally based on the +input. This reduces compression by about 1 percent most cases, but +means that the @code{rsync} program can take advantage of similarities +in the uncompressed input when syncronizing two files compressed with +this flag. @code{gunzip} cannot tell the difference between a +compressed file created with this option, and one created without it. + @item --suffix @var{suf} @itemx -S @var{suf} Use suffix @var{suf} instead of @samp{.gz}. Any suffix can be Index: gzip-1.5/gzip.c =================================================================== --- gzip-1.5.orig/gzip.c +++ gzip-1.5/gzip.c @@ -213,6 +213,7 @@ int ofd; /* output fil unsigned insize; /* valid bytes in inbuf */ unsigned inptr; /* index of next byte to be processed in inbuf */ unsigned outcnt; /* bytes in output buffer */ +int rsync = 0; /* make ryncable chunks */ static int handled_sig[] = { @@ -270,7 +271,7 @@ static const struct option longopts[] = {"best", 0, 0, '9'}, /* compress better */ {"lzw", 0, 0, 'Z'}, /* make output compatible with old compress */ {"bits", 1, 0, 'b'}, /* max number of bits per code (implies -Z) */ - + {"rsyncable", 0, 0, 'R'}, /* make rsync-friendly archive */ { 0, 0, 0, 0 } }; @@ -353,6 +354,7 @@ local void help() " -Z, --lzw produce output compatible with old compress", " -b, --bits=BITS max number of bits per code (implies -Z)", #endif + " --rsyncable Make rsync-friendly archive", "", "With no FILE, or when FILE is -, read standard input.", "", @@ -482,6 +484,9 @@ int main (int argc, char **argv) recursive = 1; #endif break; + + case 'R': + rsync = 1; break; case 'S': #ifdef NO_MULTIPLE_DOTS if (*optarg == '.') optarg++; Index: gzip-1.5/gzip.h =================================================================== --- gzip-1.5.orig/gzip.h +++ gzip-1.5/gzip.h @@ -140,6 +140,7 @@ EXTERN(uch, window); /* Sliding extern unsigned insize; /* valid bytes in inbuf */ extern unsigned inptr; /* index of next byte to be processed in inbuf */ extern unsigned outcnt; /* bytes in output buffer */ +extern int rsync; /* deflate into rsyncable chunks */ extern off_t bytes_in; /* number of input bytes */ extern off_t bytes_out; /* number of output bytes */ @@ -287,7 +288,7 @@ extern off_t deflate (void); /* in trees.c */ extern void ct_init (ush *attr, int *method); extern int ct_tally (int dist, int lc); -extern off_t flush_block (char *buf, ulg stored_len, int eof); +extern off_t flush_block (char *buf, ulg stored_len, int pad, int eof); /* in bits.c */ extern void bi_init (file_t zipfile); Index: gzip-1.5/trees.c =================================================================== --- gzip-1.5.orig/trees.c +++ gzip-1.5/trees.c @@ -856,9 +856,10 @@ local void send_all_trees(lcodes, dcodes * trees or store, and output the encoded block to the zip file. This function * returns the total compressed length for the file so far. */ -off_t flush_block(buf, stored_len, eof) +off_t flush_block(buf, stored_len, pad, eof) char *buf; /* input block, or NULL if too old */ ulg stored_len; /* length of input block */ + int pad; /* pad output to byte boundary */ int eof; /* true if this is the last block for a file */ { ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ @@ -951,6 +952,10 @@ off_t flush_block(buf, stored_len, eof) Assert (input_len == bytes_in, "bad input size"); bi_windup(); compressed_len += 7; /* align on byte boundary */ + } else if (pad && (compressed_len % 8) != 0) { + send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */ + compressed_len = (compressed_len + 3 + 7) & ~7L; + copy_block(buf, 0, 1); /* with header */ } return compressed_len >> 3;