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8284370: Improve zlib usage
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Reviewed-by: bae
Backport-of: 46f42c72a92ffb035e84eb8e73bd6329ef006251
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@mrserb
mrserb authored and Yuri Nesterenko committed Jul 19, 2022
1 parent c06577b commit c16cc04
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Showing 3 changed files with 80 additions and 70 deletions.
75 changes: 55 additions & 20 deletions src/java.base/share/native/libzip/zlib/deflate.c
View file
Expand Up @@ -276,11 +276,6 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
int wrap = 1;
static const char my_version[] = ZLIB_VERSION;

ushf *overlay;
/* We overlay pending_buf and d_buf+l_buf. This works since the average
* output size for (length,distance) codes is <= 24 bits.
*/

if (version == Z_NULL || version[0] != my_version[0] ||
stream_size != sizeof(z_stream)) {
return Z_VERSION_ERROR;
Expand Down Expand Up @@ -350,9 +345,47 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,

s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */

overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2);
s->pending_buf = (uchf *) overlay;
s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L);
/* We overlay pending_buf and sym_buf. This works since the average size
* for length/distance pairs over any compressed block is assured to be 31
* bits or less.
*
* Analysis: The longest fixed codes are a length code of 8 bits plus 5
* extra bits, for lengths 131 to 257. The longest fixed distance codes are
* 5 bits plus 13 extra bits, for distances 16385 to 32768. The longest
* possible fixed-codes length/distance pair is then 31 bits total.
*
* sym_buf starts one-fourth of the way into pending_buf. So there are
* three bytes in sym_buf for every four bytes in pending_buf. Each symbol
* in sym_buf is three bytes -- two for the distance and one for the
* literal/length. As each symbol is consumed, the pointer to the next
* sym_buf value to read moves forward three bytes. From that symbol, up to
* 31 bits are written to pending_buf. The closest the written pending_buf
* bits gets to the next sym_buf symbol to read is just before the last
* code is written. At that time, 31*(n-2) bits have been written, just
* after 24*(n-2) bits have been consumed from sym_buf. sym_buf starts at
* 8*n bits into pending_buf. (Note that the symbol buffer fills when n-1
* symbols are written.) The closest the writing gets to what is unread is
* then n+14 bits. Here n is lit_bufsize, which is 16384 by default, and
* can range from 128 to 32768.
*
* Therefore, at a minimum, there are 142 bits of space between what is
* written and what is read in the overlain buffers, so the symbols cannot
* be overwritten by the compressed data. That space is actually 139 bits,
* due to the three-bit fixed-code block header.
*
* That covers the case where either Z_FIXED is specified, forcing fixed
* codes, or when the use of fixed codes is chosen, because that choice
* results in a smaller compressed block than dynamic codes. That latter
* condition then assures that the above analysis also covers all dynamic
* blocks. A dynamic-code block will only be chosen to be emitted if it has
* fewer bits than a fixed-code block would for the same set of symbols.
* Therefore its average symbol length is assured to be less than 31. So
* the compressed data for a dynamic block also cannot overwrite the
* symbols from which it is being constructed.
*/

s->pending_buf = (uchf *) ZALLOC(strm, s->lit_bufsize, 4);
s->pending_buf_size = (ulg)s->lit_bufsize * 4;

if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
s->pending_buf == Z_NULL) {
Expand All @@ -361,8 +394,12 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
deflateEnd (strm);
return Z_MEM_ERROR;
}
s->d_buf = overlay + s->lit_bufsize/sizeof(ush);
s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize;
s->sym_buf = s->pending_buf + s->lit_bufsize;
s->sym_end = (s->lit_bufsize - 1) * 3;
/* We avoid equality with lit_bufsize*3 because of wraparound at 64K
* on 16 bit machines and because stored blocks are restricted to
* 64K-1 bytes.
*/

s->level = level;
s->strategy = strategy;
Expand Down Expand Up @@ -573,7 +610,8 @@ int ZEXPORT deflatePrime (strm, bits, value)

if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
s = strm->state;
if ((Bytef *)(s->d_buf) < s->pending_out + ((Buf_size + 7) >> 3))
if (bits < 0 || bits > 16 ||
s->sym_buf < s->pending_out + ((Buf_size + 7) >> 3))
return Z_BUF_ERROR;
do {
put = Buf_size - s->bi_valid;
Expand Down Expand Up @@ -1132,7 +1170,6 @@ int ZEXPORT deflateCopy (dest, source)
#else
deflate_state *ds;
deflate_state *ss;
ushf *overlay;


if (deflateStateCheck(source) || dest == Z_NULL) {
Expand All @@ -1152,8 +1189,7 @@ int ZEXPORT deflateCopy (dest, source)
ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos));
ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos));
overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2);
ds->pending_buf = (uchf *) overlay;
ds->pending_buf = (uchf *) ZALLOC(dest, ds->lit_bufsize, 4);

if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
ds->pending_buf == Z_NULL) {
Expand All @@ -1167,8 +1203,7 @@ int ZEXPORT deflateCopy (dest, source)
zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);

ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush);
ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize;
ds->sym_buf = ds->pending_buf + ds->lit_bufsize;

ds->l_desc.dyn_tree = ds->dyn_ltree;
ds->d_desc.dyn_tree = ds->dyn_dtree;
Expand Down Expand Up @@ -1936,7 +1971,7 @@ local block_state deflate_fast(s, flush)
FLUSH_BLOCK(s, 1);
return finish_done;
}
if (s->last_lit)
if (s->sym_next)
FLUSH_BLOCK(s, 0);
return block_done;
}
Expand Down Expand Up @@ -2067,7 +2102,7 @@ local block_state deflate_slow(s, flush)
FLUSH_BLOCK(s, 1);
return finish_done;
}
if (s->last_lit)
if (s->sym_next)
FLUSH_BLOCK(s, 0);
return block_done;
}
Expand Down Expand Up @@ -2142,7 +2177,7 @@ local block_state deflate_rle(s, flush)
FLUSH_BLOCK(s, 1);
return finish_done;
}
if (s->last_lit)
if (s->sym_next)
FLUSH_BLOCK(s, 0);
return block_done;
}
Expand Down Expand Up @@ -2181,7 +2216,7 @@ local block_state deflate_huff(s, flush)
FLUSH_BLOCK(s, 1);
return finish_done;
}
if (s->last_lit)
if (s->sym_next)
FLUSH_BLOCK(s, 0);
return block_done;
}
25 changes: 11 additions & 14 deletions src/java.base/share/native/libzip/zlib/deflate.h
View file
Expand Up @@ -241,7 +241,7 @@ typedef struct internal_state {
/* Depth of each subtree used as tie breaker for trees of equal frequency
*/

uchf *l_buf; /* buffer for literals or lengths */
uchf *sym_buf; /* buffer for distances and literals/lengths */

uInt lit_bufsize;
/* Size of match buffer for literals/lengths. There are 4 reasons for
Expand All @@ -263,13 +263,8 @@ typedef struct internal_state {
* - I can't count above 4
*/

uInt last_lit; /* running index in l_buf */

ushf *d_buf;
/* Buffer for distances. To simplify the code, d_buf and l_buf have
* the same number of elements. To use different lengths, an extra flag
* array would be necessary.
*/
uInt sym_next; /* running index in sym_buf */
uInt sym_end; /* symbol table full when sym_next reaches this */

ulg opt_len; /* bit length of current block with optimal trees */
ulg static_len; /* bit length of current block with static trees */
Expand Down Expand Up @@ -349,20 +344,22 @@ void ZLIB_INTERNAL _tr_stored_block OF((deflate_state *s, charf *buf,

# define _tr_tally_lit(s, c, flush) \
{ uch cc = (c); \
s->d_buf[s->last_lit] = 0; \
s->l_buf[s->last_lit++] = cc; \
s->sym_buf[s->sym_next++] = 0; \
s->sym_buf[s->sym_next++] = 0; \
s->sym_buf[s->sym_next++] = cc; \
s->dyn_ltree[cc].Freq++; \
flush = (s->last_lit == s->lit_bufsize-1); \
flush = (s->sym_next == s->sym_end); \
}
# define _tr_tally_dist(s, distance, length, flush) \
{ uch len = (uch)(length); \
ush dist = (ush)(distance); \
s->d_buf[s->last_lit] = dist; \
s->l_buf[s->last_lit++] = len; \
s->sym_buf[s->sym_next++] = (uch)dist; \
s->sym_buf[s->sym_next++] = (uch)(dist >> 8); \
s->sym_buf[s->sym_next++] = len; \
dist--; \
s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
s->dyn_dtree[d_code(dist)].Freq++; \
flush = (s->last_lit == s->lit_bufsize-1); \
flush = (s->sym_next == s->sym_end); \
}
#else
# define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
Expand Down
50 changes: 14 additions & 36 deletions src/java.base/share/native/libzip/zlib/trees.c
View file
Expand Up @@ -440,7 +440,7 @@ local void init_block(s)

s->dyn_ltree[END_BLOCK].Freq = 1;
s->opt_len = s->static_len = 0L;
s->last_lit = s->matches = 0;
s->sym_next = s->matches = 0;
}

#define SMALLEST 1
Expand Down Expand Up @@ -971,7 +971,7 @@ void ZLIB_INTERNAL _tr_flush_block(s, buf, stored_len, last)

Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ",
opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len,
s->last_lit));
s->sym_next / 3));

if (static_lenb <= opt_lenb) opt_lenb = static_lenb;

Expand Down Expand Up @@ -1040,8 +1040,9 @@ int ZLIB_INTERNAL _tr_tally (s, dist, lc)
unsigned dist; /* distance of matched string */
unsigned lc; /* match length-MIN_MATCH or unmatched char (if dist==0) */
{
s->d_buf[s->last_lit] = (ush)dist;
s->l_buf[s->last_lit++] = (uch)lc;
s->sym_buf[s->sym_next++] = (uch)dist;
s->sym_buf[s->sym_next++] = (uch)(dist >> 8);
s->sym_buf[s->sym_next++] = (uch)lc;
if (dist == 0) {
/* lc is the unmatched char */
s->dyn_ltree[lc].Freq++;
Expand All @@ -1056,30 +1057,7 @@ int ZLIB_INTERNAL _tr_tally (s, dist, lc)
s->dyn_ltree[_length_code[lc]+LITERALS+1].Freq++;
s->dyn_dtree[d_code(dist)].Freq++;
}

#ifdef TRUNCATE_BLOCK
/* Try to guess if it is profitable to stop the current block here */
if ((s->last_lit & 0x1fff) == 0 && s->level > 2) {
/* Compute an upper bound for the compressed length */
ulg out_length = (ulg)s->last_lit*8L;
ulg in_length = (ulg)((long)s->strstart - s->block_start);
int dcode;
for (dcode = 0; dcode < D_CODES; dcode++) {
out_length += (ulg)s->dyn_dtree[dcode].Freq *
(5L+extra_dbits[dcode]);
}
out_length >>= 3;
Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
s->last_lit, in_length, out_length,
100L - out_length*100L/in_length));
if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1;
}
#endif
return (s->last_lit == s->lit_bufsize-1);
/* We avoid equality with lit_bufsize because of wraparound at 64K
* on 16 bit machines and because stored blocks are restricted to
* 64K-1 bytes.
*/
return (s->sym_next == s->sym_end);
}

/* ===========================================================================
Expand All @@ -1092,13 +1070,14 @@ local void compress_block(s, ltree, dtree)
{
unsigned dist; /* distance of matched string */
int lc; /* match length or unmatched char (if dist == 0) */
unsigned lx = 0; /* running index in l_buf */
unsigned sx = 0; /* running index in sym_buf */
unsigned code; /* the code to send */
int extra; /* number of extra bits to send */

if (s->last_lit != 0) do {
dist = s->d_buf[lx];
lc = s->l_buf[lx++];
if (s->sym_next != 0) do {
dist = s->sym_buf[sx++] & 0xff;
dist += (unsigned)(s->sym_buf[sx++] & 0xff) << 8;
lc = s->sym_buf[sx++];
if (dist == 0) {
send_code(s, lc, ltree); /* send a literal byte */
Tracecv(isgraph(lc), (stderr," '%c' ", lc));
Expand All @@ -1123,11 +1102,10 @@ local void compress_block(s, ltree, dtree)
}
} /* literal or match pair ? */

/* Check that the overlay between pending_buf and d_buf+l_buf is ok: */
Assert((uInt)(s->pending) < s->lit_bufsize + 2*lx,
"pendingBuf overflow");
/* Check that the overlay between pending_buf and sym_buf is ok: */
Assert(s->pending < s->lit_bufsize + sx, "pendingBuf overflow");

} while (lx < s->last_lit);
} while (sx < s->sym_next);

send_code(s, END_BLOCK, ltree);
}
Expand Down

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