From c924079d6066547e52669517f62c4270f367521c Mon Sep 17 00:00:00 2001
From: ChatN0ir <lacostejustin2@gmail.com>
Date: Sun, 13 Oct 2019 12:13:00 +0200
Subject: [PATCH] Implemented CRC-32 Checksum-Algorithm

---
 hash/hash.c         | 26 +++++++++++++++++++++++++-
 hash/hash.h         |  7 +++++++
 hash/test_program.c |  1 +
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/hash/hash.c b/hash/hash.c
index 220bb5ca..8f202d4b 100644
--- a/hash/hash.c
+++ b/hash/hash.c
@@ -60,4 +60,28 @@ int adler_32(char s[])
         i++;
     }
     return (b << 16) | a;
-}
\ No newline at end of file
+}
+
+/* crc32 Hash-Algorithm*/
+
+int crc32(char string[])
+{
+    int i = 0;
+    unsigned int cur_crc, masking;
+
+    cur_crc = 0xFFFFFFFF;
+
+    while(string[i] != '\0')
+    {
+        unsigned int byte = string[i];
+        cur_crc = cur_crc ^ byte;
+        for(int j = 8; j > 0; --j)
+        {
+            masking = -(cur_crc & 1);
+            cur_crc = (cur_crc >> 1) ^ (0xEDB88320 & masking);
+        }
+        i++;
+    }
+
+    return -cur_crc;
+}
diff --git a/hash/hash.h b/hash/hash.h
index 7497b1b2..1f0722ff 100644
--- a/hash/hash.h
+++ b/hash/hash.h
@@ -40,4 +40,11 @@ char xor8(char[]);
 */
 int adler_32(char[]);
 
+/*
+    crc32: implements the crc-32 hash-algorithm
+    returns the checksum byte for the passed byte
+*/
+int crc32(char[]);
+
+
 #endif
\ No newline at end of file
diff --git a/hash/test_program.c b/hash/test_program.c
index f9dcd299..54439e8e 100644
--- a/hash/test_program.c
+++ b/hash/test_program.c
@@ -15,6 +15,7 @@ int main(void)
     printf("djb2: %s --> %lld\n", s, djb2(s));
     printf("xor8: %s --> %i\n", s, xor8(s)); /* 8 bit */
     printf("adler_32: %s --> %i\n", s, adler_32(s)); /* 32 bit */
+    printf("crc32: %s --> %i\n", s, crc32(s));
 
     return 0;
 }
\ No newline at end of file