Initial import

third_party/zlib/adler32.c

@@ -0,0 +1,161 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:4;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=4 sts=4 sw=4 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 1995-2016 Mark Adler                                               │
+│ Copyright 2017 The Chromium Authors                                          │
+│ Use of this source code is governed by the BSD-style licenses that can       │
+│ be found in the third_party/zlib/LICENSE file.                               │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/dce.h"
+#include "libc/nexgen32e/x86feature.h"
+#include "third_party/zlib/internal.h"
+#include "third_party/zlib/zutil.h"
+
+asm(".ident\t\"\\n\\n\
+zlib (zlib License)\\n\
+Copyright 1995-2017 Jean-loup Gailly and Mark Adler\"");
+asm(".include \"libc/disclaimer.inc\"");
+
+#define BASE 65521U /* largest prime smaller than 65536 */
+#define NMAX 5552   /* largest n such that 255n(n+1)/2+(n+1)(BASE-1)<=2^32-1 */
+
+#define DO1(buf, i)    \
+  {                    \
+    adler += (buf)[i]; \
+    sum2 += adler;     \
+  }
+#define DO2(buf, i) \
+  DO1(buf, i);      \
+  DO1(buf, i + 1);
+#define DO4(buf, i) \
+  DO2(buf, i);      \
+  DO2(buf, i + 2);
+#define DO8(buf, i) \
+  DO4(buf, i);      \
+  DO4(buf, i + 4);
+#define DO16(buf) \
+  DO8(buf, 0);    \
+  DO8(buf, 8);
+
+/* use NO_DIVIDE if your processor does not do division in hardware --
+   try it both ways to see which is faster */
+#ifdef NO_DIVIDE
+/* note that this assumes BASE is 65521, where 65536 % 65521 == 15
+   (thank you to John Reiser for pointing this out) */
+#define CHOP(a)                  \
+  do {                           \
+    unsigned long tmp = a >> 16; \
+    a &= 0xffffUL;               \
+    a += (tmp << 4) - tmp;       \
+  } while (0)
+#define MOD28(a)              \
+  do {                        \
+    CHOP(a);                  \
+    if (a >= BASE) a -= BASE; \
+  } while (0)
+#define MOD(a) \
+  do {         \
+    CHOP(a);   \
+    MOD28(a);  \
+  } while (0)
+#define MOD63(a)                            \
+  do { /* this assumes a is not negative */ \
+    int64_t tmp = a >> 32;                  \
+    a &= 0xffffffffL;                       \
+    a += (tmp << 8) - (tmp << 5) + tmp;     \
+    tmp = a >> 16;                          \
+    a &= 0xffffL;                           \
+    a += (tmp << 4) - tmp;                  \
+    tmp = a >> 16;                          \
+    a &= 0xffffL;                           \
+    a += (tmp << 4) - tmp;                  \
+    if (a >= BASE) a -= BASE;               \
+  } while (0)
+#else
+#define MOD(a)   a %= BASE
+#define MOD28(a) a %= BASE
+#define MOD63(a) a %= BASE
+#endif
+
+uLong adler32_z(uLong adler, const Bytef *buf, size_t len) {
+  return adler32(adler, buf, len);
+}
+
+uLong adler32(uLong adler, const Bytef *buf, uInt len) {
+  unsigned long sum2;
+  unsigned n;
+  if (!IsTiny() && X86_HAVE(SSSE3) && buf && len >= 64) {
+    return adler32_simd_(adler, buf, len);
+  }
+  /* split Adler-32 into component sums */
+  sum2 = (adler >> 16) & 0xffff;
+  adler &= 0xffff;
+  /* in case user likes doing a byte at a time, keep it fast */
+  if (len == 1) {
+    adler += buf[0];
+    if (adler >= BASE) adler -= BASE;
+    sum2 += adler;
+    if (sum2 >= BASE) sum2 -= BASE;
+    return adler | (sum2 << 16);
+  }
+  /* initial Adler-32 value (deferred check for len == 1 speed) */
+  if (buf == Z_NULL) return 1L;
+  /* in case short lengths are provided, keep it somewhat fast */
+  if (len < 16) {
+    while (len--) {
+      adler += *buf++;
+      sum2 += adler;
+    }
+    if (adler >= BASE) adler -= BASE;
+    MOD28(sum2); /* only added so many BASE's */
+    return adler | (sum2 << 16);
+  }
+  /* do length NMAX blocks -- requires just one modulo operation */
+  while (len >= NMAX) {
+    len -= NMAX;
+    n = NMAX / 16; /* NMAX is divisible by 16 */
+    do {
+      DO16(buf); /* 16 sums unrolled */
+      buf += 16;
+    } while (--n);
+    MOD(adler);
+    MOD(sum2);
+  }
+  /* do remaining bytes (less than NMAX, still just one modulo) */
+  if (len) { /* avoid modulos if none remaining */
+    while (len >= 16) {
+      len -= 16;
+      DO16(buf);
+      buf += 16;
+    }
+    while (len--) {
+      adler += *buf++;
+      sum2 += adler;
+    }
+    MOD(adler);
+    MOD(sum2);
+  }
+  /* return recombined sums */
+  return adler | (sum2 << 16);
+}
+
+uLong adler32_combine(uLong adler1, uLong adler2, int64_t len2) {
+  unsigned long sum1;
+  unsigned long sum2;
+  unsigned rem;
+  /* for negative len, return invalid adler32 as a clue for debugging */
+  if (len2 < 0) return 0xffffffffUL;
+  /* the derivation of this formula is left as an exercise for the reader */
+  MOD63(len2); /* assumes len2 >= 0 */
+  rem = (unsigned)len2;
+  sum1 = adler1 & 0xffff;
+  sum2 = rem * sum1;
+  MOD(sum2);
+  sum1 += (adler2 & 0xffff) + BASE - 1;
+  sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;
+  if (sum1 >= BASE) sum1 -= BASE;
+  if (sum1 >= BASE) sum1 -= BASE;
+  if (sum2 >= ((unsigned long)BASE << 1)) sum2 -= ((unsigned long)BASE << 1);
+  if (sum2 >= BASE) sum2 -= BASE;
+  return sum1 | (sum2 << 16);
+}