1 files changed, 78 insertions, 0 deletions
diff --git a/extmod/uzlib/adler32.c b/extmod/uzlib/adler32.c
new file mode 100644
index 0000000000..f99b2d7f40
--- /dev/null
+++ b/extmod/uzlib/adler32.c
@@ -0,0 +1,78 @@
+/*
+ * Adler-32 checksum
+ *
+ * Copyright (c) 2003 by Joergen Ibsen / Jibz
+ * All Rights Reserved
+ *
+ * http://www.ibsensoftware.com/
+ *
+ * This software is provided 'as-is', without any express
+ * or implied warranty.  In no event will the authors be
+ * held liable for any damages arising from the use of
+ * this software.
+ *
+ * Permission is granted to anyone to use this software
+ * for any purpose, including commercial applications,
+ * and to alter it and redistribute it freely, subject to
+ * the following restrictions:
+ *
+ * 1. The origin of this software must not be
+ *    misrepresented; you must not claim that you
+ *    wrote the original software. If you use this
+ *    software in a product, an acknowledgment in
+ *    the product documentation would be appreciated
+ *    but is not required.
+ *
+ * 2. Altered source versions must be plainly marked
+ *    as such, and must not be misrepresented as
+ *    being the original software.
+ *
+ * 3. This notice may not be removed or altered from
+ *    any source distribution.
+ */
+
+/*
+ * Adler-32 algorithm taken from the zlib source, which is
+ * Copyright (C) 1995-1998 Jean-loup Gailly and Mark Adler
+ */
+
+#include "tinf.h"
+
+#define A32_BASE 65521
+#define A32_NMAX 5552
+
+unsigned int tinf_adler32(const void *data, unsigned int length)
+{
+   const unsigned char *buf = (const unsigned char *)data;
+
+   unsigned int s1 = 1;
+   unsigned int s2 = 0;
+
+   while (length > 0)
+   {
+      int k = length < A32_NMAX ? length : A32_NMAX;
+      int i;
+
+      for (i = k / 16; i; --i, buf += 16)
+      {
+         s1 += buf[0];  s2 += s1; s1 += buf[1];  s2 += s1;
+         s1 += buf[2];  s2 += s1; s1 += buf[3];  s2 += s1;
+         s1 += buf[4];  s2 += s1; s1 += buf[5];  s2 += s1;
+         s1 += buf[6];  s2 += s1; s1 += buf[7];  s2 += s1;
+
+         s1 += buf[8];  s2 += s1; s1 += buf[9];  s2 += s1;
+         s1 += buf[10]; s2 += s1; s1 += buf[11]; s2 += s1;
+         s1 += buf[12]; s2 += s1; s1 += buf[13]; s2 += s1;
+         s1 += buf[14]; s2 += s1; s1 += buf[15]; s2 += s1;
+      }
+
+      for (i = k % 16; i; --i) { s1 += *buf++; s2 += s1; }
+
+      s1 %= A32_BASE;
+      s2 %= A32_BASE;
+
+      length -= k;
+   }
+
+   return (s2 << 16) | s1;
+}