From 3ffe95d46ec6ac2625e6fed49c356699513a3cbf Mon Sep 17 00:00:00 2001
From: Robert Spalek <robert@ucw.cz>
Date: Fri, 16 Jul 2004 10:25:49 +0000
Subject: [PATCH] added adler32 functions

---
 lib/lizard-safe.c | 21 +++++++++++++++++++++
 lib/lizard.h      |  3 +++
 2 files changed, 24 insertions(+)

diff --git a/lib/lizard-safe.c b/lib/lizard-safe.c
index 88e9aebd..40a5aa3d 100644
--- a/lib/lizard-safe.c
+++ b/lib/lizard-safe.c
@@ -103,3 +103,24 @@ lizard_decompress_safe(byte *in, struct lizard_buffer *buf, uns expected_length)
   signal_handler[SIGSEGV] = old_handler;
   return ptr;
 }
+
+#define BASE 65521 /* largest prime smaller than 65536 */
+
+inline uns
+update_adler32(uns adler, byte *ptr, uns len)
+  /* taken from RFC1950 */
+{
+  uns s1 = adler & 0xffff;
+  uns s2 = (adler >> 16) & 0xffff;
+  for (uns n = 0; n < len; n++) {
+    s1 = (s1 + ptr[n]) % BASE;
+    s2 = (s2 + s1)     % BASE;
+  }
+  return (s2 << 16) + s1;
+}
+
+uns
+adler32(byte *ptr, uns len)
+{
+  return update_adler32(1, ptr, len);
+}
diff --git a/lib/lizard.h b/lib/lizard.h
index 51f46bad..838d683f 100644
--- a/lib/lizard.h
+++ b/lib/lizard.h
@@ -37,4 +37,7 @@ struct lizard_buffer *lizard_alloc(void);
 void lizard_free(struct lizard_buffer *buf);
 byte *lizard_decompress_safe(byte *in, struct lizard_buffer *buf, uns expected_length);
 
+uns update_adler32(uns adler, byte *ptr, uns len);
+uns adler32(byte *ptr, uns len);
+
 #endif
-- 
2.39.5