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thirdparty/libtomcrypt/misc/adler32.c

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+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ */
+#include "tomcrypt.h"
+
+/**
+   @file adler32.c
+   Adler-32 checksum algorithm
+   Written and placed in the public domain by Wei Dai
+   Adapted for libtomcrypt by Steffen Jaeckel
+*/
+#ifdef LTC_ADLER32
+
+static const unsigned long _adler32_base = 65521;
+
+void adler32_init(adler32_state *ctx)
+{
+   LTC_ARGCHKVD(ctx != NULL);
+   ctx->s[0] = 1;
+   ctx->s[1] = 0;
+}
+
+void adler32_update(adler32_state *ctx, const unsigned char *input, unsigned long length)
+{
+   unsigned long s1, s2;
+
+   LTC_ARGCHKVD(ctx != NULL);
+   LTC_ARGCHKVD(input != NULL);
+   s1 = ctx->s[0];
+   s2 = ctx->s[1];
+
+   if (length % 8 != 0) {
+      do {
+         s1 += *input++;
+         s2 += s1;
+         length--;
+      } while (length % 8 != 0);
+
+      if (s1 >= _adler32_base)
+         s1 -= _adler32_base;
+      s2 %= _adler32_base;
+   }
+
+   while (length > 0) {
+      s1 += input[0];
+      s2 += s1;
+      s1 += input[1];
+      s2 += s1;
+      s1 += input[2];
+      s2 += s1;
+      s1 += input[3];
+      s2 += s1;
+      s1 += input[4];
+      s2 += s1;
+      s1 += input[5];
+      s2 += s1;
+      s1 += input[6];
+      s2 += s1;
+      s1 += input[7];
+      s2 += s1;
+
+      length -= 8;
+      input += 8;
+
+      if (s1 >= _adler32_base)
+         s1 -= _adler32_base;
+      s2 %= _adler32_base;
+   }
+
+   LTC_ARGCHKVD(s1 < _adler32_base);
+   LTC_ARGCHKVD(s2 < _adler32_base);
+
+   ctx->s[0] = (unsigned short)s1;
+   ctx->s[1] = (unsigned short)s2;
+}
+
+void adler32_finish(adler32_state *ctx, void *hash, unsigned long size)
+{
+   unsigned char* h;
+
+   LTC_ARGCHKVD(ctx != NULL);
+   LTC_ARGCHKVD(hash != NULL);
+
+   h = hash;
+
+   switch (size) {
+      default:
+         h[3] = ctx->s[0] & 0x0ff;
+         /* FALLTHROUGH */
+      case 3:
+         h[2] = (ctx->s[0] >> 8) & 0x0ff;
+         /* FALLTHROUGH */
+      case 2:
+         h[1] = ctx->s[1] & 0x0ff;
+         /* FALLTHROUGH */
+      case 1:
+         h[0] = (ctx->s[1] >> 8) & 0x0ff;
+         /* FALLTHROUGH */
+      case 0:
+         ;
+   }
+}
+
+int adler32_test(void)
+{
+#ifndef LTC_TEST
+   return CRYPT_NOP;
+#else
+   const void* in = "libtomcrypt";
+   const unsigned char adler32[] = { 0x1b, 0xe8, 0x04, 0xba };
+   unsigned char out[4];
+   adler32_state ctx;
+   adler32_init(&ctx);
+   adler32_update(&ctx, in, strlen(in));
+   adler32_finish(&ctx, out, 4);
+   if (compare_testvector(adler32, 4, out, 4, "adler32", 0)) {
+      return CRYPT_FAIL_TESTVECTOR;
+   }
+   return CRYPT_OK;
+#endif
+}
+#endif
+
+/* ref:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */