From 71e181512d1cd61d3865f93f5b85b208b5720ba5 Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Sun, 17 Jan 2016 16:05:16 +0000
Subject: add crc8

---
 src/include/gnunet_crypto_lib.h | 15 +++++++++++++++
 src/util/crypto_crc.c           | 30 ++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/src/include/gnunet_crypto_lib.h b/src/include/gnunet_crypto_lib.h
index 77b4d0452..23caade12 100644
--- a/src/include/gnunet_crypto_lib.h
+++ b/src/include/gnunet_crypto_lib.h
@@ -402,6 +402,19 @@ void
 GNUNET_CRYPTO_seed_weak_random (int32_t seed);
 
 
+/**
+ * @ingroup hash
+ * Calculate the checksum of a buffer in one step.
+ *
+ * @param buf buffer to calculate CRC over
+ * @param len number of bytes in @a buf
+ * @return crc8 value
+ */
+uint8_t
+GNUNET_CRYPTO_crc8_n (const void *buf,
+                      size_t len);
+
+
 /**
  * Perform an incremental step in a CRC16 (for TCP/IP) calculation.
  *
@@ -439,6 +452,8 @@ GNUNET_CRYPTO_crc16_n (const void *buf,
                        size_t len);
 
 
+
+
 /**
  * @ingroup hash
  * Compute the CRC32 checksum for the first len
diff --git a/src/util/crypto_crc.c b/src/util/crypto_crc.c
index ec2e80683..b5df01959 100644
--- a/src/util/crypto_crc.c
+++ b/src/util/crypto_crc.c
@@ -165,5 +165,35 @@ GNUNET_CRYPTO_crc16_n (const void *buf, size_t len)
 }
 
 
+/**
+ * @ingroup hash
+ * Calculate the checksum of a buffer in one step.
+ *
+ * @param buf buffer to calculate CRC over
+ * @param len number of bytes in @a buf
+ * @return crc8 value
+ */
+uint8_t
+GNUNET_CRYPTO_crc8_n (const void *buf,
+                      size_t len)
+{
+  const uint8_t *data = buf;
+  unsigned int crc = 0;
+  int i;
+  int j;
+
+  for (j = len; 0 != j; j--)
+  {
+    crc ^= (*data++ << 8);
+    for (i = 8; 0 != i; i--)
+    {
+      if (0 != (crc & 0x8000))
+        crc ^= (0x1070 << 3);
+      crc <<= 1;
+    }
+  }
+  return (uint8_t) (crc >> 8);
+}
+
 
 /* end of crypto_crc.c */
-- 
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