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git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@625 212acab6-be3b-0410-9dea-997c60f758d6

Source/crc32.c

@@ -0,0 +1,34 @@
+#include "exehead/config.h"
+#ifdef NSIS_CONFIG_CRC_SUPPORT
+
+// this is based on the (slow,small) CRC32 implementation from zlib.
+
+static unsigned long crc_table[256];
+
+static void make_crc_table()
+{
+  unsigned long c;
+  int n, k;
+
+  for (n = 0; n < 256; n++)
+  {
+    c = (unsigned long)n;
+    for (k = 0; k < 8; k++) c = (c >> 1) ^ (c & 1 ? 0xedb88320L : 0);
+    crc_table[n] = c;
+  }
+}
+
+
+// actually CRC32, but we put it in here so we don't
+// have to modify the other code.
+unsigned long CRC32(unsigned long crc, const unsigned char *buf, unsigned int len)
+{
+    if (!crc_table[1]) make_crc_table();
+    crc = crc ^ 0xffffffffL;
+    while (len-- > 0) {
+      crc = crc_table[(crc ^ (*buf++)) & 0xff] ^ (crc >> 8);    
+    }
+    return crc ^ 0xffffffffL;
+}
+
+#endif