merging --rsyncable support ?

[Mike Frysinger]

some distros have been carrying an --rsyncable patch for quite some time (the
Fedora version is below).  could this possibly be merged into mainline ?
-mike

diff -up gzip-1.3.13/deflate.c.rsync gzip-1.3.13/deflate.c
--- gzip-1.3.13/deflate.c.rsync 2009-09-26 20:43:28.000000000 +0200
+++ gzip-1.3.13/deflate.c       2009-12-01 16:14:24.656387546 +0100
@@ -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 near 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
@@ -310,6 +320,10 @@ 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;
@@ -546,6 +560,8 @@ 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;
 
@@ -573,13 +589,46 @@ 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
@@ -590,7 +639,7 @@ 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;
@@ -620,6 +669,7 @@ local off_t deflate_fast()
 
             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.
              */
@@ -648,9 +698,14 @@ 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
@@ -724,6 +779,7 @@ off_t deflate()
              */
             lookahead -= prev_length-1;
             prev_length -= 2;
+            RSYNC_ROLL(strstart, prev_length+1);
             do {
                 strstart++;
                 INSERT_STRING(strstart, hash_head);
@@ -736,24 +792,40 @@ 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--;
         }
diff -up gzip-1.3.13/doc/gzip.texi.rsync gzip-1.3.13/doc/gzip.texi
--- gzip-1.3.13/doc/gzip.texi.rsync     2009-09-28 11:08:16.000000000 +0200
+++ gzip-1.3.13/doc/gzip.texi   2009-12-01 16:14:24.664394713 +0100
@@ -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}).
 
address@hidden --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
diff -up gzip-1.3.13/gzip.c.rsync gzip-1.3.13/gzip.c
--- gzip-1.3.13/gzip.c.rsync    2009-09-26 20:56:02.000000000 +0200
+++ gzip-1.3.13/gzip.c  2009-12-01 16:18:17.121387126 +0100
@@ -229,6 +229,7 @@ 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[] =
   {
@@ -282,6 +283,7 @@ 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 }
 };
 
@@ -363,6 +365,7 @@ 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.",
  "",
@@ -493,6 +496,9 @@ int main (argc, argv)
            recursive = 1;
 #endif
            break;
+
+         case 'R':
+           rsync = 1; break;
        case 'S':
 #ifdef NO_MULTIPLE_DOTS
             if (*optarg == '.') optarg++;
diff -up gzip-1.3.13/gzip.h.rsync gzip-1.3.13/gzip.h
--- gzip-1.3.13/gzip.h.rsync    2009-09-26 20:43:28.000000000 +0200
+++ gzip-1.3.13/gzip.h  2009-12-01 16:14:24.664394713 +0100
@@ -158,6 +158,7 @@ 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 */
@@ -306,7 +307,7 @@ off_t deflate OF((void));
         /* in trees.c */
 void ct_init     OF((ush *attr, int *method));
 int  ct_tally    OF((int dist, int lc));
-off_t flush_block OF((char *buf, ulg stored_len, int eof));
+off_t flush_block OF((char *buf, ulg stored_len, int pad, int eof)); 
 
         /* in bits.c */
 void     bi_init    OF((file_t zipfile));
diff -up gzip-1.3.13/trees.c.rsync gzip-1.3.13/trees.c
--- gzip-1.3.13/trees.c.rsync   2009-09-26 20:43:28.000000000 +0200
+++ gzip-1.3.13/trees.c 2009-12-01 16:14:24.655388257 +0100
@@ -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;

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