Commit c267ef7 for zlib
commit c267ef7306fe9fc1399833e3556cd9798dec2eb0
Author: Mark Adler <git@madler.net>
Date: Mon Jan 5 01:15:38 2026 -0600
Use atomics to build inflate fixed tables once.
This moves the once code from crc32.c to zutil.c, and uses it also
for building the inflate fixed tables when BUILDFIXED is defined.
The fixed tables are now housed in inftrees.c, shared by inflate.c
and infback.c. The once() function is now external, and so is
renamed to z_once() to avoid name collisions.
If either BUILDFIXED or DYNAMIC_CRC_TABLE is defined, and atomics
are not available, then a warning is issued noting that zlib is not
thread-safe.
diff --git a/FAQ b/FAQ
index b6b11bd..57dd4f5 100644
--- a/FAQ
+++ b/FAQ
@@ -156,6 +156,10 @@ The latest zlib FAQ is at http://zlib.net/zlib_faq.html
library memory allocation routines by default. zlib's *Init* functions
allow for the application to provide custom memory allocation routines.
+ If the non-default BUILDFIXED or DYNAMIC_CRC_TABLE defines are used on a
+ system without atomics (e.g. pre-C11), then inflate() and crc32() will not
+ be thread safe.
+
Of course, you should only operate on any given zlib or gzip stream from a
single thread at a time.
diff --git a/README b/README
index 02259d4..17b70fc 100644
--- a/README
+++ b/README
@@ -1,8 +1,8 @@
ZLIB DATA COMPRESSION LIBRARY
zlib 1.3.1.2 is a general purpose data compression library. All the code is
-thread safe. The data format used by the zlib library is described by RFCs
-(Request for Comments) 1950 to 1952 at
+thread safe (though see the FAQ for caveats). The data format used by the zlib
+library is described by RFCs (Request for Comments) 1950 to 1952 at
https://datatracker.ietf.org/doc/html/rfc1950 (zlib format), rfc1951 (deflate
format) and rfc1952 (gzip format).
diff --git a/crc32.c b/crc32.c
index 33d8c79..630049f 100644
--- a/crc32.c
+++ b/crc32.c
@@ -204,83 +204,8 @@ local z_crc_t FAR crc_table[256];
local void write_table64(FILE *, const z_word_t FAR *, int);
#endif /* MAKECRCH */
-/*
- Define a once() function depending on the availability of atomics. If this is
- compiled with DYNAMIC_CRC_TABLE defined, and if CRCs will be computed in
- multiple threads, and if atomics are not available, then get_crc_table() must
- be called to initialize the tables and must return before any threads are
- allowed to compute or combine CRCs.
- */
-
-/* Definition of once functionality. */
-typedef struct once_s once_t;
-
-/* Check for the availability of atomics. */
-#if defined(__STDC__) && __STDC_VERSION__ >= 201112L && \
- !defined(__STDC_NO_ATOMICS__)
-
-#include <stdatomic.h>
-
-/* Structure for once(), which must be initialized with ONCE_INIT. */
-struct once_s {
- atomic_flag begun;
- atomic_int done;
-};
-#define ONCE_INIT {ATOMIC_FLAG_INIT, 0}
-
-/*
- Run the provided init() function exactly once, even if multiple threads
- invoke once() at the same time. The state must be a once_t initialized with
- ONCE_INIT.
- */
-local void once(once_t *state, void (*init)(void)) {
- if (!atomic_load(&state->done)) {
- if (atomic_flag_test_and_set(&state->begun))
- while (!atomic_load(&state->done))
- ;
- else {
- init();
- atomic_store(&state->done, 1);
- }
- }
-}
-
-#else /* no atomics */
-
-/* Structure for once(), which must be initialized with ONCE_INIT. */
-struct once_s {
- volatile int begun;
- volatile int done;
-};
-#define ONCE_INIT {0, 0}
-
-/* Test and set. Alas, not atomic, but tries to minimize the period of
- vulnerability. */
-local int test_and_set(int volatile *flag) {
- int was;
-
- was = *flag;
- *flag = 1;
- return was;
-}
-
-/* Run the provided init() function once. This is not thread-safe. */
-local void once(once_t *state, void (*init)(void)) {
- if (!state->done) {
- if (test_and_set(&state->begun))
- while (!state->done)
- ;
- else {
- init();
- state->done = 1;
- }
- }
-}
-
-#endif
-
/* State for once(). */
-local once_t made = ONCE_INIT;
+local z_once_t made = Z_ONCE_INIT;
/*
Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
@@ -548,7 +473,7 @@ local void braid(z_crc_t ltl[][256], z_word_t big[][256], int n, int w) {
*/
const z_crc_t FAR * ZEXPORT get_crc_table(void) {
#ifdef DYNAMIC_CRC_TABLE
- once(&made, make_crc_table);
+ z_once(&made, make_crc_table);
#endif /* DYNAMIC_CRC_TABLE */
return (const z_crc_t FAR *)crc_table;
}
@@ -585,7 +510,7 @@ unsigned long ZEXPORT crc32_z(unsigned long crc, const unsigned char FAR *buf,
if (buf == Z_NULL) return 0;
#ifdef DYNAMIC_CRC_TABLE
- once(&made, make_crc_table);
+ z_once(&made, make_crc_table);
#endif /* DYNAMIC_CRC_TABLE */
/* Pre-condition the CRC */
@@ -697,7 +622,7 @@ unsigned long ZEXPORT crc32_z(unsigned long crc, const unsigned char FAR *buf,
if (buf == Z_NULL) return 0;
#ifdef DYNAMIC_CRC_TABLE
- once(&made, make_crc_table);
+ z_once(&made, make_crc_table);
#endif /* DYNAMIC_CRC_TABLE */
/* Pre-condition the CRC */
@@ -1022,7 +947,7 @@ uLong ZEXPORT crc32_combine64(uLong crc1, uLong crc2, z_off64_t len2) {
if (len2 < 0)
return 0;
#ifdef DYNAMIC_CRC_TABLE
- once(&made, make_crc_table);
+ z_once(&made, make_crc_table);
#endif /* DYNAMIC_CRC_TABLE */
return multmodp(x2nmodp(len2, 3), crc1) ^ (crc2 & 0xffffffff);
}
@@ -1037,7 +962,7 @@ uLong ZEXPORT crc32_combine_gen64(z_off64_t len2) {
if (len2 < 0)
return 0;
#ifdef DYNAMIC_CRC_TABLE
- once(&made, make_crc_table);
+ z_once(&made, make_crc_table);
#endif /* DYNAMIC_CRC_TABLE */
return x2nmodp(len2, 3);
}
diff --git a/infback.c b/infback.c
index 5608530..518bf3e 100644
--- a/infback.c
+++ b/infback.c
@@ -63,57 +63,6 @@ int ZEXPORT inflateBackInit_(z_streamp strm, int windowBits,
return Z_OK;
}
-/*
- Return state with length and distance decoding tables and index sizes set to
- fixed code decoding. Normally this returns fixed tables from inffixed.h.
- If BUILDFIXED is defined, then instead this routine builds the tables the
- first time it's called, and returns those tables the first time and
- thereafter. This reduces the size of the code by about 2K bytes, in
- exchange for a little execution time. However, BUILDFIXED should not be
- used for threaded applications, since the rewriting of the tables and virgin
- may not be thread-safe.
- */
-local void fixedtables(struct inflate_state FAR *state) {
-#ifdef BUILDFIXED
- static int virgin = 1;
- static code *lenfix, *distfix;
- static code fixed[544];
-
- /* build fixed huffman tables if first call (may not be thread safe) */
- if (virgin) {
- unsigned sym, bits;
- static code *next;
-
- /* literal/length table */
- sym = 0;
- while (sym < 144) state->lens[sym++] = 8;
- while (sym < 256) state->lens[sym++] = 9;
- while (sym < 280) state->lens[sym++] = 7;
- while (sym < 288) state->lens[sym++] = 8;
- next = fixed;
- lenfix = next;
- bits = 9;
- inflate_table(LENS, state->lens, 288, &(next), &(bits), state->work);
-
- /* distance table */
- sym = 0;
- while (sym < 32) state->lens[sym++] = 5;
- distfix = next;
- bits = 5;
- inflate_table(DISTS, state->lens, 32, &(next), &(bits), state->work);
-
- /* do this just once */
- virgin = 0;
- }
-#else /* !BUILDFIXED */
-# include "inffixed.h"
-#endif /* BUILDFIXED */
- state->lencode = lenfix;
- state->lenbits = 9;
- state->distcode = distfix;
- state->distbits = 5;
-}
-
/* Macros for inflateBack(): */
/* Load returned state from inflate_fast() */
@@ -293,7 +242,7 @@ int ZEXPORT inflateBack(z_streamp strm, in_func in, void FAR *in_desc,
state->mode = STORED;
break;
case 1: /* fixed block */
- fixedtables(state);
+ inflate_fixed(state);
Tracev((stderr, "inflate: fixed codes block%s\n",
state->last ? " (last)" : ""));
state->mode = LEN; /* decode codes */
diff --git a/inffixed.h b/inffixed.h
index d628327..05ce88e 100644
--- a/inffixed.h
+++ b/inffixed.h
@@ -1,94 +1,94 @@
- /* inffixed.h -- table for decoding fixed codes
- * Generated automatically by makefixed().
- */
+/* inffixed.h -- table for decoding fixed codes
+ * Generated automatically by makefixed().
+ */
- /* WARNING: this file should *not* be used by applications.
- It is part of the implementation of this library and is
- subject to change. Applications should only use zlib.h.
- */
+/* WARNING: this file should *not* be used by applications.
+ It is part of the implementation of this library and is
+ subject to change. Applications should only use zlib.h.
+ */
- static const code lenfix[512] = {
- {96,7,0},{0,8,80},{0,8,16},{20,8,115},{18,7,31},{0,8,112},{0,8,48},
- {0,9,192},{16,7,10},{0,8,96},{0,8,32},{0,9,160},{0,8,0},{0,8,128},
- {0,8,64},{0,9,224},{16,7,6},{0,8,88},{0,8,24},{0,9,144},{19,7,59},
- {0,8,120},{0,8,56},{0,9,208},{17,7,17},{0,8,104},{0,8,40},{0,9,176},
- {0,8,8},{0,8,136},{0,8,72},{0,9,240},{16,7,4},{0,8,84},{0,8,20},
- {21,8,227},{19,7,43},{0,8,116},{0,8,52},{0,9,200},{17,7,13},{0,8,100},
- {0,8,36},{0,9,168},{0,8,4},{0,8,132},{0,8,68},{0,9,232},{16,7,8},
- {0,8,92},{0,8,28},{0,9,152},{20,7,83},{0,8,124},{0,8,60},{0,9,216},
- {18,7,23},{0,8,108},{0,8,44},{0,9,184},{0,8,12},{0,8,140},{0,8,76},
- {0,9,248},{16,7,3},{0,8,82},{0,8,18},{21,8,163},{19,7,35},{0,8,114},
- {0,8,50},{0,9,196},{17,7,11},{0,8,98},{0,8,34},{0,9,164},{0,8,2},
- {0,8,130},{0,8,66},{0,9,228},{16,7,7},{0,8,90},{0,8,26},{0,9,148},
- {20,7,67},{0,8,122},{0,8,58},{0,9,212},{18,7,19},{0,8,106},{0,8,42},
- {0,9,180},{0,8,10},{0,8,138},{0,8,74},{0,9,244},{16,7,5},{0,8,86},
- {0,8,22},{64,8,0},{19,7,51},{0,8,118},{0,8,54},{0,9,204},{17,7,15},
- {0,8,102},{0,8,38},{0,9,172},{0,8,6},{0,8,134},{0,8,70},{0,9,236},
- {16,7,9},{0,8,94},{0,8,30},{0,9,156},{20,7,99},{0,8,126},{0,8,62},
- {0,9,220},{18,7,27},{0,8,110},{0,8,46},{0,9,188},{0,8,14},{0,8,142},
- {0,8,78},{0,9,252},{96,7,0},{0,8,81},{0,8,17},{21,8,131},{18,7,31},
- {0,8,113},{0,8,49},{0,9,194},{16,7,10},{0,8,97},{0,8,33},{0,9,162},
- {0,8,1},{0,8,129},{0,8,65},{0,9,226},{16,7,6},{0,8,89},{0,8,25},
- {0,9,146},{19,7,59},{0,8,121},{0,8,57},{0,9,210},{17,7,17},{0,8,105},
- {0,8,41},{0,9,178},{0,8,9},{0,8,137},{0,8,73},{0,9,242},{16,7,4},
- {0,8,85},{0,8,21},{16,8,258},{19,7,43},{0,8,117},{0,8,53},{0,9,202},
- {17,7,13},{0,8,101},{0,8,37},{0,9,170},{0,8,5},{0,8,133},{0,8,69},
- {0,9,234},{16,7,8},{0,8,93},{0,8,29},{0,9,154},{20,7,83},{0,8,125},
- {0,8,61},{0,9,218},{18,7,23},{0,8,109},{0,8,45},{0,9,186},{0,8,13},
- {0,8,141},{0,8,77},{0,9,250},{16,7,3},{0,8,83},{0,8,19},{21,8,195},
- {19,7,35},{0,8,115},{0,8,51},{0,9,198},{17,7,11},{0,8,99},{0,8,35},
- {0,9,166},{0,8,3},{0,8,131},{0,8,67},{0,9,230},{16,7,7},{0,8,91},
- {0,8,27},{0,9,150},{20,7,67},{0,8,123},{0,8,59},{0,9,214},{18,7,19},
- {0,8,107},{0,8,43},{0,9,182},{0,8,11},{0,8,139},{0,8,75},{0,9,246},
- {16,7,5},{0,8,87},{0,8,23},{64,8,0},{19,7,51},{0,8,119},{0,8,55},
- {0,9,206},{17,7,15},{0,8,103},{0,8,39},{0,9,174},{0,8,7},{0,8,135},
- {0,8,71},{0,9,238},{16,7,9},{0,8,95},{0,8,31},{0,9,158},{20,7,99},
- {0,8,127},{0,8,63},{0,9,222},{18,7,27},{0,8,111},{0,8,47},{0,9,190},
- {0,8,15},{0,8,143},{0,8,79},{0,9,254},{96,7,0},{0,8,80},{0,8,16},
- {20,8,115},{18,7,31},{0,8,112},{0,8,48},{0,9,193},{16,7,10},{0,8,96},
- {0,8,32},{0,9,161},{0,8,0},{0,8,128},{0,8,64},{0,9,225},{16,7,6},
- {0,8,88},{0,8,24},{0,9,145},{19,7,59},{0,8,120},{0,8,56},{0,9,209},
- {17,7,17},{0,8,104},{0,8,40},{0,9,177},{0,8,8},{0,8,136},{0,8,72},
- {0,9,241},{16,7,4},{0,8,84},{0,8,20},{21,8,227},{19,7,43},{0,8,116},
- {0,8,52},{0,9,201},{17,7,13},{0,8,100},{0,8,36},{0,9,169},{0,8,4},
- {0,8,132},{0,8,68},{0,9,233},{16,7,8},{0,8,92},{0,8,28},{0,9,153},
- {20,7,83},{0,8,124},{0,8,60},{0,9,217},{18,7,23},{0,8,108},{0,8,44},
- {0,9,185},{0,8,12},{0,8,140},{0,8,76},{0,9,249},{16,7,3},{0,8,82},
- {0,8,18},{21,8,163},{19,7,35},{0,8,114},{0,8,50},{0,9,197},{17,7,11},
- {0,8,98},{0,8,34},{0,9,165},{0,8,2},{0,8,130},{0,8,66},{0,9,229},
- {16,7,7},{0,8,90},{0,8,26},{0,9,149},{20,7,67},{0,8,122},{0,8,58},
- {0,9,213},{18,7,19},{0,8,106},{0,8,42},{0,9,181},{0,8,10},{0,8,138},
- {0,8,74},{0,9,245},{16,7,5},{0,8,86},{0,8,22},{64,8,0},{19,7,51},
- {0,8,118},{0,8,54},{0,9,205},{17,7,15},{0,8,102},{0,8,38},{0,9,173},
- {0,8,6},{0,8,134},{0,8,70},{0,9,237},{16,7,9},{0,8,94},{0,8,30},
- {0,9,157},{20,7,99},{0,8,126},{0,8,62},{0,9,221},{18,7,27},{0,8,110},
- {0,8,46},{0,9,189},{0,8,14},{0,8,142},{0,8,78},{0,9,253},{96,7,0},
- {0,8,81},{0,8,17},{21,8,131},{18,7,31},{0,8,113},{0,8,49},{0,9,195},
- {16,7,10},{0,8,97},{0,8,33},{0,9,163},{0,8,1},{0,8,129},{0,8,65},
- {0,9,227},{16,7,6},{0,8,89},{0,8,25},{0,9,147},{19,7,59},{0,8,121},
- {0,8,57},{0,9,211},{17,7,17},{0,8,105},{0,8,41},{0,9,179},{0,8,9},
- {0,8,137},{0,8,73},{0,9,243},{16,7,4},{0,8,85},{0,8,21},{16,8,258},
- {19,7,43},{0,8,117},{0,8,53},{0,9,203},{17,7,13},{0,8,101},{0,8,37},
- {0,9,171},{0,8,5},{0,8,133},{0,8,69},{0,9,235},{16,7,8},{0,8,93},
- {0,8,29},{0,9,155},{20,7,83},{0,8,125},{0,8,61},{0,9,219},{18,7,23},
- {0,8,109},{0,8,45},{0,9,187},{0,8,13},{0,8,141},{0,8,77},{0,9,251},
- {16,7,3},{0,8,83},{0,8,19},{21,8,195},{19,7,35},{0,8,115},{0,8,51},
- {0,9,199},{17,7,11},{0,8,99},{0,8,35},{0,9,167},{0,8,3},{0,8,131},
- {0,8,67},{0,9,231},{16,7,7},{0,8,91},{0,8,27},{0,9,151},{20,7,67},
- {0,8,123},{0,8,59},{0,9,215},{18,7,19},{0,8,107},{0,8,43},{0,9,183},
- {0,8,11},{0,8,139},{0,8,75},{0,9,247},{16,7,5},{0,8,87},{0,8,23},
- {64,8,0},{19,7,51},{0,8,119},{0,8,55},{0,9,207},{17,7,15},{0,8,103},
- {0,8,39},{0,9,175},{0,8,7},{0,8,135},{0,8,71},{0,9,239},{16,7,9},
- {0,8,95},{0,8,31},{0,9,159},{20,7,99},{0,8,127},{0,8,63},{0,9,223},
- {18,7,27},{0,8,111},{0,8,47},{0,9,191},{0,8,15},{0,8,143},{0,8,79},
- {0,9,255}
- };
+static const code lenfix[512] = {
+ {96,7,0},{0,8,80},{0,8,16},{20,8,115},{18,7,31},{0,8,112},{0,8,48},
+ {0,9,192},{16,7,10},{0,8,96},{0,8,32},{0,9,160},{0,8,0},{0,8,128},
+ {0,8,64},{0,9,224},{16,7,6},{0,8,88},{0,8,24},{0,9,144},{19,7,59},
+ {0,8,120},{0,8,56},{0,9,208},{17,7,17},{0,8,104},{0,8,40},{0,9,176},
+ {0,8,8},{0,8,136},{0,8,72},{0,9,240},{16,7,4},{0,8,84},{0,8,20},
+ {21,8,227},{19,7,43},{0,8,116},{0,8,52},{0,9,200},{17,7,13},{0,8,100},
+ {0,8,36},{0,9,168},{0,8,4},{0,8,132},{0,8,68},{0,9,232},{16,7,8},
+ {0,8,92},{0,8,28},{0,9,152},{20,7,83},{0,8,124},{0,8,60},{0,9,216},
+ {18,7,23},{0,8,108},{0,8,44},{0,9,184},{0,8,12},{0,8,140},{0,8,76},
+ {0,9,248},{16,7,3},{0,8,82},{0,8,18},{21,8,163},{19,7,35},{0,8,114},
+ {0,8,50},{0,9,196},{17,7,11},{0,8,98},{0,8,34},{0,9,164},{0,8,2},
+ {0,8,130},{0,8,66},{0,9,228},{16,7,7},{0,8,90},{0,8,26},{0,9,148},
+ {20,7,67},{0,8,122},{0,8,58},{0,9,212},{18,7,19},{0,8,106},{0,8,42},
+ {0,9,180},{0,8,10},{0,8,138},{0,8,74},{0,9,244},{16,7,5},{0,8,86},
+ {0,8,22},{64,8,0},{19,7,51},{0,8,118},{0,8,54},{0,9,204},{17,7,15},
+ {0,8,102},{0,8,38},{0,9,172},{0,8,6},{0,8,134},{0,8,70},{0,9,236},
+ {16,7,9},{0,8,94},{0,8,30},{0,9,156},{20,7,99},{0,8,126},{0,8,62},
+ {0,9,220},{18,7,27},{0,8,110},{0,8,46},{0,9,188},{0,8,14},{0,8,142},
+ {0,8,78},{0,9,252},{96,7,0},{0,8,81},{0,8,17},{21,8,131},{18,7,31},
+ {0,8,113},{0,8,49},{0,9,194},{16,7,10},{0,8,97},{0,8,33},{0,9,162},
+ {0,8,1},{0,8,129},{0,8,65},{0,9,226},{16,7,6},{0,8,89},{0,8,25},
+ {0,9,146},{19,7,59},{0,8,121},{0,8,57},{0,9,210},{17,7,17},{0,8,105},
+ {0,8,41},{0,9,178},{0,8,9},{0,8,137},{0,8,73},{0,9,242},{16,7,4},
+ {0,8,85},{0,8,21},{16,8,258},{19,7,43},{0,8,117},{0,8,53},{0,9,202},
+ {17,7,13},{0,8,101},{0,8,37},{0,9,170},{0,8,5},{0,8,133},{0,8,69},
+ {0,9,234},{16,7,8},{0,8,93},{0,8,29},{0,9,154},{20,7,83},{0,8,125},
+ {0,8,61},{0,9,218},{18,7,23},{0,8,109},{0,8,45},{0,9,186},{0,8,13},
+ {0,8,141},{0,8,77},{0,9,250},{16,7,3},{0,8,83},{0,8,19},{21,8,195},
+ {19,7,35},{0,8,115},{0,8,51},{0,9,198},{17,7,11},{0,8,99},{0,8,35},
+ {0,9,166},{0,8,3},{0,8,131},{0,8,67},{0,9,230},{16,7,7},{0,8,91},
+ {0,8,27},{0,9,150},{20,7,67},{0,8,123},{0,8,59},{0,9,214},{18,7,19},
+ {0,8,107},{0,8,43},{0,9,182},{0,8,11},{0,8,139},{0,8,75},{0,9,246},
+ {16,7,5},{0,8,87},{0,8,23},{64,8,0},{19,7,51},{0,8,119},{0,8,55},
+ {0,9,206},{17,7,15},{0,8,103},{0,8,39},{0,9,174},{0,8,7},{0,8,135},
+ {0,8,71},{0,9,238},{16,7,9},{0,8,95},{0,8,31},{0,9,158},{20,7,99},
+ {0,8,127},{0,8,63},{0,9,222},{18,7,27},{0,8,111},{0,8,47},{0,9,190},
+ {0,8,15},{0,8,143},{0,8,79},{0,9,254},{96,7,0},{0,8,80},{0,8,16},
+ {20,8,115},{18,7,31},{0,8,112},{0,8,48},{0,9,193},{16,7,10},{0,8,96},
+ {0,8,32},{0,9,161},{0,8,0},{0,8,128},{0,8,64},{0,9,225},{16,7,6},
+ {0,8,88},{0,8,24},{0,9,145},{19,7,59},{0,8,120},{0,8,56},{0,9,209},
+ {17,7,17},{0,8,104},{0,8,40},{0,9,177},{0,8,8},{0,8,136},{0,8,72},
+ {0,9,241},{16,7,4},{0,8,84},{0,8,20},{21,8,227},{19,7,43},{0,8,116},
+ {0,8,52},{0,9,201},{17,7,13},{0,8,100},{0,8,36},{0,9,169},{0,8,4},
+ {0,8,132},{0,8,68},{0,9,233},{16,7,8},{0,8,92},{0,8,28},{0,9,153},
+ {20,7,83},{0,8,124},{0,8,60},{0,9,217},{18,7,23},{0,8,108},{0,8,44},
+ {0,9,185},{0,8,12},{0,8,140},{0,8,76},{0,9,249},{16,7,3},{0,8,82},
+ {0,8,18},{21,8,163},{19,7,35},{0,8,114},{0,8,50},{0,9,197},{17,7,11},
+ {0,8,98},{0,8,34},{0,9,165},{0,8,2},{0,8,130},{0,8,66},{0,9,229},
+ {16,7,7},{0,8,90},{0,8,26},{0,9,149},{20,7,67},{0,8,122},{0,8,58},
+ {0,9,213},{18,7,19},{0,8,106},{0,8,42},{0,9,181},{0,8,10},{0,8,138},
+ {0,8,74},{0,9,245},{16,7,5},{0,8,86},{0,8,22},{64,8,0},{19,7,51},
+ {0,8,118},{0,8,54},{0,9,205},{17,7,15},{0,8,102},{0,8,38},{0,9,173},
+ {0,8,6},{0,8,134},{0,8,70},{0,9,237},{16,7,9},{0,8,94},{0,8,30},
+ {0,9,157},{20,7,99},{0,8,126},{0,8,62},{0,9,221},{18,7,27},{0,8,110},
+ {0,8,46},{0,9,189},{0,8,14},{0,8,142},{0,8,78},{0,9,253},{96,7,0},
+ {0,8,81},{0,8,17},{21,8,131},{18,7,31},{0,8,113},{0,8,49},{0,9,195},
+ {16,7,10},{0,8,97},{0,8,33},{0,9,163},{0,8,1},{0,8,129},{0,8,65},
+ {0,9,227},{16,7,6},{0,8,89},{0,8,25},{0,9,147},{19,7,59},{0,8,121},
+ {0,8,57},{0,9,211},{17,7,17},{0,8,105},{0,8,41},{0,9,179},{0,8,9},
+ {0,8,137},{0,8,73},{0,9,243},{16,7,4},{0,8,85},{0,8,21},{16,8,258},
+ {19,7,43},{0,8,117},{0,8,53},{0,9,203},{17,7,13},{0,8,101},{0,8,37},
+ {0,9,171},{0,8,5},{0,8,133},{0,8,69},{0,9,235},{16,7,8},{0,8,93},
+ {0,8,29},{0,9,155},{20,7,83},{0,8,125},{0,8,61},{0,9,219},{18,7,23},
+ {0,8,109},{0,8,45},{0,9,187},{0,8,13},{0,8,141},{0,8,77},{0,9,251},
+ {16,7,3},{0,8,83},{0,8,19},{21,8,195},{19,7,35},{0,8,115},{0,8,51},
+ {0,9,199},{17,7,11},{0,8,99},{0,8,35},{0,9,167},{0,8,3},{0,8,131},
+ {0,8,67},{0,9,231},{16,7,7},{0,8,91},{0,8,27},{0,9,151},{20,7,67},
+ {0,8,123},{0,8,59},{0,9,215},{18,7,19},{0,8,107},{0,8,43},{0,9,183},
+ {0,8,11},{0,8,139},{0,8,75},{0,9,247},{16,7,5},{0,8,87},{0,8,23},
+ {64,8,0},{19,7,51},{0,8,119},{0,8,55},{0,9,207},{17,7,15},{0,8,103},
+ {0,8,39},{0,9,175},{0,8,7},{0,8,135},{0,8,71},{0,9,239},{16,7,9},
+ {0,8,95},{0,8,31},{0,9,159},{20,7,99},{0,8,127},{0,8,63},{0,9,223},
+ {18,7,27},{0,8,111},{0,8,47},{0,9,191},{0,8,15},{0,8,143},{0,8,79},
+ {0,9,255}
+};
- static const code distfix[32] = {
- {16,5,1},{23,5,257},{19,5,17},{27,5,4097},{17,5,5},{25,5,1025},
- {21,5,65},{29,5,16385},{16,5,3},{24,5,513},{20,5,33},{28,5,8193},
- {18,5,9},{26,5,2049},{22,5,129},{64,5,0},{16,5,2},{23,5,385},
- {19,5,25},{27,5,6145},{17,5,7},{25,5,1537},{21,5,97},{29,5,24577},
- {16,5,4},{24,5,769},{20,5,49},{28,5,12289},{18,5,13},{26,5,3073},
- {22,5,193},{64,5,0}
- };
+static const code distfix[32] = {
+ {16,5,1},{23,5,257},{19,5,17},{27,5,4097},{17,5,5},{25,5,1025},
+ {21,5,65},{29,5,16385},{16,5,3},{24,5,513},{20,5,33},{28,5,8193},
+ {18,5,9},{26,5,2049},{22,5,129},{64,5,0},{16,5,2},{23,5,385},
+ {19,5,25},{27,5,6145},{17,5,7},{25,5,1537},{21,5,97},{29,5,24577},
+ {16,5,4},{24,5,769},{20,5,49},{28,5,12289},{18,5,13},{26,5,3073},
+ {22,5,193},{64,5,0}
+};
diff --git a/inflate.c b/inflate.c
index 301b5e7..623c95b 100644
--- a/inflate.c
+++ b/inflate.c
@@ -85,12 +85,6 @@
#include "inflate.h"
#include "inffast.h"
-#ifdef MAKEFIXED
-# ifndef BUILDFIXED
-# define BUILDFIXED
-# endif
-#endif
-
local int inflateStateCheck(z_streamp strm) {
struct inflate_state FAR *state;
if (strm == Z_NULL ||
@@ -240,118 +234,6 @@ int ZEXPORT inflatePrime(z_streamp strm, int bits, int value) {
return Z_OK;
}
-/*
- Return state with length and distance decoding tables and index sizes set to
- fixed code decoding. Normally this returns fixed tables from inffixed.h.
- If BUILDFIXED is defined, then instead this routine builds the tables the
- first time it's called, and returns those tables the first time and
- thereafter. This reduces the size of the code by about 2K bytes, in
- exchange for a little execution time. However, BUILDFIXED should not be
- used for threaded applications, since the rewriting of the tables and virgin
- may not be thread-safe.
- */
-local void fixedtables(struct inflate_state FAR *state) {
-#ifdef BUILDFIXED
- static int virgin = 1;
- static code *lenfix, *distfix;
- static code fixed[544];
-
- /* build fixed huffman tables if first call (may not be thread safe) */
- if (virgin) {
- unsigned sym, bits;
- static code *next;
-
- /* literal/length table */
- sym = 0;
- while (sym < 144) state->lens[sym++] = 8;
- while (sym < 256) state->lens[sym++] = 9;
- while (sym < 280) state->lens[sym++] = 7;
- while (sym < 288) state->lens[sym++] = 8;
- next = fixed;
- lenfix = next;
- bits = 9;
- inflate_table(LENS, state->lens, 288, &(next), &(bits), state->work);
-
- /* distance table */
- sym = 0;
- while (sym < 32) state->lens[sym++] = 5;
- distfix = next;
- bits = 5;
- inflate_table(DISTS, state->lens, 32, &(next), &(bits), state->work);
-
- /* do this just once */
- virgin = 0;
- }
-#else /* !BUILDFIXED */
-# include "inffixed.h"
-#endif /* BUILDFIXED */
- state->lencode = lenfix;
- state->lenbits = 9;
- state->distcode = distfix;
- state->distbits = 5;
-}
-
-#ifdef MAKEFIXED
-#include <stdio.h>
-
-/*
- Write out the inffixed.h that is #include'd above. Defining MAKEFIXED also
- defines BUILDFIXED, so the tables are built on the fly. makefixed() writes
- those tables to stdout, which would be piped to inffixed.h. A small program
- can simply call makefixed to do this:
-
- void makefixed(void);
-
- int main(void)
- {
- makefixed();
- return 0;
- }
-
- Then that can be linked with zlib built with MAKEFIXED defined and run:
-
- a.out > inffixed.h
- */
-void makefixed(void)
-{
- unsigned low, size;
- struct inflate_state state;
-
- fixedtables(&state);
- puts(" /* inffixed.h -- table for decoding fixed codes");
- puts(" * Generated automatically by makefixed().");
- puts(" */");
- puts("");
- puts(" /* WARNING: this file should *not* be used by applications.");
- puts(" It is part of the implementation of this library and is");
- puts(" subject to change. Applications should only use zlib.h.");
- puts(" */");
- puts("");
- size = 1U << 9;
- printf(" static const code lenfix[%u] = {", size);
- low = 0;
- for (;;) {
- if ((low % 7) == 0) printf("\n ");
- printf("{%u,%u,%d}", (low & 127) == 99 ? 64 : state.lencode[low].op,
- state.lencode[low].bits, state.lencode[low].val);
- if (++low == size) break;
- putchar(',');
- }
- puts("\n };");
- size = 1U << 5;
- printf("\n static const code distfix[%u] = {", size);
- low = 0;
- for (;;) {
- if ((low % 6) == 0) printf("\n ");
- printf("{%u,%u,%d}", state.distcode[low].op, state.distcode[low].bits,
- state.distcode[low].val);
- if (++low == size) break;
- putchar(',');
- }
- puts("\n };");
-}
-#endif /* MAKEFIXED */
-
/*
Update the window with the last wsize (normally 32K) bytes written before
returning. If window does not exist yet, create it. This is only called
@@ -841,7 +723,7 @@ int ZEXPORT inflate(z_streamp strm, int flush) {
state->mode = STORED;
break;
case 1: /* fixed block */
- fixedtables(state);
+ inflate_fixed(state);
Tracev((stderr, "inflate: fixed codes block%s\n",
state->last ? " (last)" : ""));
state->mode = LEN_; /* decode codes */
diff --git a/inftrees.c b/inftrees.c
index f7849a7..c050f8b 100644
--- a/inftrees.c
+++ b/inftrees.c
@@ -5,6 +5,7 @@
#include "zutil.h"
#include "inftrees.h"
+#include "inflate.h"
#define MAXBITS 15
@@ -297,3 +298,116 @@ int ZLIB_INTERNAL inflate_table(codetype type, unsigned short FAR *lens,
*bits = root;
return 0;
}
+
+#ifdef BUILDFIXED
+/*
+ If this is compiled with BUILDFIXED defined, and if inflate will be used in
+ multiple threads, and if atomics are not available, then inflate() must be
+ called with a fixed block (e.g. 0x03 0x00) to initialize the tables and must
+ return before any other threads are allowed to call inflate.
+ */
+
+static code *lenfix, *distfix;
+static code fixed[544];
+
+/* State for z_once(). */
+local z_once_t built = Z_ONCE_INIT;
+
+local void buildtables(void) {
+ unsigned sym, bits;
+ static code *next;
+ unsigned short lens[288], work[288];
+
+ /* literal/length table */
+ sym = 0;
+ while (sym < 144) lens[sym++] = 8;
+ while (sym < 256) lens[sym++] = 9;
+ while (sym < 280) lens[sym++] = 7;
+ while (sym < 288) lens[sym++] = 8;
+ next = fixed;
+ lenfix = next;
+ bits = 9;
+ inflate_table(LENS, lens, 288, &(next), &(bits), work);
+
+ /* distance table */
+ sym = 0;
+ while (sym < 32) lens[sym++] = 5;
+ distfix = next;
+ bits = 5;
+ inflate_table(DISTS, lens, 32, &(next), &(bits), work);
+}
+#else /* !BUILDFIXED */
+# include "inffixed.h"
+#endif /* BUILDFIXED */
+
+/*
+ Return state with length and distance decoding tables and index sizes set to
+ fixed code decoding. Normally this returns fixed tables from inffixed.h.
+ If BUILDFIXED is defined, then instead this routine builds the tables the
+ first time it's called, and returns those tables the first time and
+ thereafter. This reduces the size of the code by about 2K bytes, in
+ exchange for a little execution time. However, BUILDFIXED should not be
+ used for threaded applications if atomics are not available, as it will
+ not be thread-safe.
+ */
+void inflate_fixed(struct inflate_state FAR *state) {
+#ifdef BUILDFIXED
+ z_once(&built, buildtables);
+#endif /* BUILDFIXED */
+ state->lencode = lenfix;
+ state->lenbits = 9;
+ state->distcode = distfix;
+ state->distbits = 5;
+}
+
+#ifdef MAKEFIXED
+#include <stdio.h>
+
+/*
+ Write out the inffixed.h that will be #include'd above. Defining MAKEFIXED
+ also defines BUILDFIXED, so the tables are built on the fly. main() writes
+ those tables to stdout, which would directed to inffixed.h. Compile this
+ along with zutil.c:
+
+ cc -DMAKEFIXED -o fix inftrees.c zutil.c
+ ./fix > inffixed.h
+ */
+int main(void) {
+ unsigned low, size;
+ struct inflate_state state;
+
+ inflate_fixed(&state);
+ puts("/* inffixed.h -- table for decoding fixed codes");
+ puts(" * Generated automatically by makefixed().");
+ puts(" */");
+ puts("");
+ puts("/* WARNING: this file should *not* be used by applications.");
+ puts(" It is part of the implementation of this library and is");
+ puts(" subject to change. Applications should only use zlib.h.");
+ puts(" */");
+ puts("");
+ size = 1U << 9;
+ printf("static const code lenfix[%u] = {", size);
+ low = 0;
+ for (;;) {
+ if ((low % 7) == 0) printf("\n ");
+ printf("{%u,%u,%d}", (low & 127) == 99 ? 64 : state.lencode[low].op,
+ state.lencode[low].bits, state.lencode[low].val);
+ if (++low == size) break;
+ putchar(',');
+ }
+ puts("\n};");
+ size = 1U << 5;
+ printf("\nstatic const code distfix[%u] = {", size);
+ low = 0;
+ for (;;) {
+ if ((low % 6) == 0) printf("\n ");
+ printf("{%u,%u,%d}", state.distcode[low].op, state.distcode[low].bits,
+ state.distcode[low].val);
+ if (++low == size) break;
+ putchar(',');
+ }
+ puts("\n};");
+ return 0;
+}
+#endif /* MAKEFIXED */
diff --git a/inftrees.h b/inftrees.h
index 396f74b..00ec96e 100644
--- a/inftrees.h
+++ b/inftrees.h
@@ -60,3 +60,5 @@ typedef enum {
int ZLIB_INTERNAL inflate_table(codetype type, unsigned short FAR *lens,
unsigned codes, code FAR * FAR *table,
unsigned FAR *bits, unsigned short FAR *work);
+struct inflate_state;
+void ZLIB_INTERNAL inflate_fixed(struct inflate_state FAR *state);
diff --git a/zconf.h b/zconf.h
index 7d936c7..524192a 100644
--- a/zconf.h
+++ b/zconf.h
@@ -131,6 +131,7 @@
# define inflate_copyright z_inflate_copyright
# define inflate_fast z_inflate_fast
# define inflate_table z_inflate_table
+# define inflate_fixed z_inflate_fixed
# ifndef Z_SOLO
# define uncompress z_uncompress
# define uncompress2 z_uncompress2
diff --git a/zconf.h.in b/zconf.h.in
index 7d936c7..524192a 100644
--- a/zconf.h.in
+++ b/zconf.h.in
@@ -131,6 +131,7 @@
# define inflate_copyright z_inflate_copyright
# define inflate_fast z_inflate_fast
# define inflate_table z_inflate_table
+# define inflate_fixed z_inflate_fixed
# ifndef Z_SOLO
# define uncompress z_uncompress
# define uncompress2 z_uncompress2
diff --git a/zlib.map b/zlib.map
index e267d82..aba65ab 100644
--- a/zlib.map
+++ b/zlib.map
@@ -11,9 +11,11 @@ ZLIB_1.2.0 {
inflate_copyright;
inflate_fast;
inflate_table;
+ inflate_fixed;
zcalloc;
zcfree;
z_errmsg;
+ z_once;
gz_error;
gz_intmax;
_*;
diff --git a/zutil.c b/zutil.c
index 6e8a369..3a94e91 100644
--- a/zutil.c
+++ b/zutil.c
@@ -305,3 +305,61 @@ void ZLIB_INTERNAL zcfree(voidpf opaque, voidpf ptr) {
#endif /* MY_ZCALLOC */
#endif /* !Z_SOLO */
+
+#if defined(BUILDFIXED) || defined(DYNAMIC_CRC_TABLE)
+/*
+ Define a z_once() function depending on the availability of atomics.
+ */
+
+/* Check for the availability of atomics. */
+#if defined(__STDC__) && __STDC_VERSION__ >= 201112L && \
+ !defined(__STDC_NO_ATOMICS__)
+
+#include <stdatomic.h>
+
+/*
+ Run the provided init() function exactly once, even if multiple threads
+ invoke once() at the same time. The state must be a once_t initialized with
+ Z_ONCE_INIT.
+ */
+void z_once(z_once_t *state, void (*init)(void)) {
+ if (!atomic_load(&state->done)) {
+ if (atomic_flag_test_and_set(&state->begun))
+ while (!atomic_load(&state->done))
+ ;
+ else {
+ init();
+ atomic_store(&state->done, 1);
+ }
+ }
+}
+
+#else /* no atomics */
+
+#warning zlib not thread-safe
+
+/* Test and set. Alas, not atomic, but tries to limit the period of
+ vulnerability. */
+local int test_and_set(int volatile *flag) {
+ int was;
+
+ was = *flag;
+ *flag = 1;
+ return was;
+}
+
+/* Run the provided init() function once. This is not thread-safe. */
+void z_once(z_once_t *state, void (*init)(void)) {
+ if (!state->done) {
+ if (test_and_set(&state->begun))
+ while (!state->done)
+ ;
+ else {
+ init();
+ state->done = 1;
+ }
+ }
+}
+
+#endif
+#endif
diff --git a/zutil.h b/zutil.h
index 27ca693..94fa1af 100644
--- a/zutil.h
+++ b/zutil.h
@@ -254,4 +254,30 @@ extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
#define ZSWAP32(q) ((((q) >> 24) & 0xff) + (((q) >> 8) & 0xff00) + \
(((q) & 0xff00) << 8) + (((q) & 0xff) << 24))
+#ifdef MAKEFIXED
+# ifndef BUILDFIXED
+# define BUILDFIXED
+# endif
+#endif
+#if defined(BUILDFIXED) || defined(DYNAMIC_CRC_TABLE)
+/* Structure for z_once(), which must be initialized with Z_ONCE_INIT. */
+typedef struct z_once_s z_once_t;
+void ZLIB_INTERNAL z_once(z_once_t *state, void (*init)(void));
+#if defined(__STDC__) && __STDC_VERSION__ >= 201112L && \
+ !defined(__STDC_NO_ATOMICS__)
+#include <stdatomic.h>
+struct z_once_s {
+ atomic_flag begun;
+ atomic_int done;
+};
+#define Z_ONCE_INIT {ATOMIC_FLAG_INIT, 0}
+#else /* no atomics! */
+struct z_once_s {
+ volatile int begun;
+ volatile int done;
+};
+#define Z_ONCE_INIT {0, 0}
+#endif
+#endif
+
#endif /* ZUTIL_H */