[hackers] [flate] deflate += comments || nsz

changeset: 97:fd3836ea7105
user: nsz <nszabolcs_AT_gmail.com>
date: Tue Aug 11 14:19:18 2009 +0200
files: deflate.c
description:
deflate += comments

diff -r f7385ae4153e -r fd3836ea7105 deflate.c
--- a/deflate.c Tue Aug 11 13:48:57 2009 +0200
+++ b/deflate.c Tue Aug 11 14:19:18 2009 +0200
@@ -79,7 +79,7 @@
         ushort chain[MaxDist]; /* hash chain */
         LzCode lzbuf[LzSize]; /* literal run length, match len, match dist */
         LzCode *lz; /* current pos in lzbuf */
- int run; /* literal run length */
+ int nlit; /* literal run length */
         ushort lfreq[Nlitlen];
         ushort dfreq[Ndist];
         uchar dstbuf[DstSize];
@@ -277,6 +277,7 @@
         }
 }
 
+/* run length encode literal and dist code lengths into codes and extra */
 static int clencodes(uchar *codes, uchar *extra, uchar *llen, int nlit, uchar *dlen, int ndist) {
         int i, c, r, rr;
         int n = 0;
@@ -286,7 +287,6 @@
         for (i = 0; i < ndist; i++)
                 codes[nlit + i] = dlen[i];
         for (i = 0; i < nlit + ndist;) {
- /* run length encoding */
                 c = codes[i];
                 for (r = 1; i + r < nlit + ndist && codes[i + r] == c; r++);
                 i += r;
@@ -316,6 +316,7 @@
         return n;
 }
 
+/* compress block data into s->dstbuf using given codes */
 static void putblock(State *s, ushort *lcode, uchar *llen, ushort *dcode, uchar *dlen) {
         int n;
         LzCode *lz;
@@ -336,6 +337,7 @@
         putbits(s, lcode[EOB], llen[EOB]);
 }
 
+/* build code trees and select dynamic/fixed/uncompressed block compression */
 static void deflate_block(State *s) {
         uchar codes[Nlitlen + Ndist], extra[Nlitlen + Ndist];
         uchar llen[Nlitlen], dlen[Ndist], clen[Nclen];
@@ -365,7 +367,7 @@
         huffcodes(ccode, clen, Nclen);
         for (nclen = Nclen; nclen > 4 && clen[clenorder[nclen-1]] == 0; nclen--);
 
- /* calc size */
+ /* calc compressed size */
         uncsize = 3 + 16 + 8 * blocklen + (16 - 3 - s->nbits) % 8; /* byte aligned */
         fixsize = 3;
         dynsize = 3 + 5 + 5 + 4 + 3 * nclen;
@@ -443,6 +445,7 @@
 */
 }
 
+/* find n in base */
 static int bisect(ushort *base, int len, int n) {
         int lo = 0;
         int hi = len;
@@ -458,15 +461,17 @@
         return lo - 1;
 }
 
+/* add literal run length to lzbuf */
 static void flushlit(State *s) {
- if (s->run) {
+ if (s->nlit) {
                 s->lz->bits = LzLitFlag;
- s->lz->n = s->run;
+ s->lz->n = s->nlit;
                 s->lz++;
- s->run = 0;
+ s->nlit = 0;
         }
 }
 
+/* add match to lzbuf and update freq counts */
 static void recordmatch(State *s, Match m) {
         int n;
 
@@ -483,16 +488,18 @@
         s->dfreq[n]++;
 }
 
+/* update literal run length */
 static void recordlit(State *s, int c) {
- s->run++;
+ s->nlit++;
         s->lfreq[c]++;
 }
 
-/* multiplicative hash */
+/* multiplicative hash (using a prime close to golden ratio * 2^32) */
 static int gethash(uchar *p) {
         return (0x9e3779b1 * ((p[0]<<16) + (p[1]<<8) + p[2]) >> (32 - HashBits)) % HashSize;
 }
 
+/* update hash chain at the current position */
 static int updatechain(State *s) {
         int h, i;
 
@@ -507,6 +514,7 @@
         return i;
 }
 
+/* find longest match, mpos is the next in the hash chain */
 static Match getmatch(State *s, int mpos) {
         Match m = {0, MinMatch-1};
         int len;
@@ -538,16 +546,18 @@
         return m;
 }
 
+/* start a new block */
 static void newblock(State *s) {
         s->startpos = s->pos;
         s->dst = s->dstbegin = s->dstbuf;
         s->lz = s->lzbuf;
- s->run = 0;
+ s->nlit = 0;
         memset(s->lfreq, 0, sizeof(s->lfreq));
         memset(s->dfreq, 0, sizeof(s->dfreq));
         s->lfreq[EOB]++;
 }
 
+/* shift and fill win from s->src */
 static int fillwin(State *s) {
         int n, k;
 
@@ -576,6 +586,7 @@
         return 1;
 }
 
+/* check if the current block should be ended */
 static int endofblock(State *s) {
         if (s->avail == 0)
                 return 1;
@@ -585,6 +596,7 @@
         return 0;
 }
 
+/* deflate from s->src into s->dstbuf */
 static int deflate_state(State *s) {
         Match m;
         int head;
@@ -636,6 +648,7 @@
         }
 }
 
+/* alloc and init state */
 static State *alloc_state(void) {
         State *s = malloc(sizeof(State));
         int i;
Received on Tue Aug 11 2009 - 13:07:17 UTC