4.20

7zip/Archive/7z_C/7zCrc.c

@@ -0,0 +1,76 @@
+/* 7zCrc.c */
+
+#include "7zCrc.h"
+
+#define kCrcPoly 0xEDB88320
+
+UInt32 g_CrcTable[256];
+
+void InitCrcTable()
+{
+  UInt32 i;
+  for (i = 0; i < 256; i++)
+  {
+    UInt32 r = i;
+    int j;
+    for (j = 0; j < 8; j++)
+      if (r & 1) 
+        r = (r >> 1) ^ kCrcPoly;
+      else     
+        r >>= 1;
+    g_CrcTable[i] = r;
+  }
+}
+
+void CrcInit(UInt32 *crc) { *crc = 0xFFFFFFFF; }
+UInt32 CrcGetDigest(UInt32 *crc) { return *crc ^ 0xFFFFFFFF; } 
+
+void CrcUpdateByte(UInt32 *crc, Byte b)
+{
+  *crc = g_CrcTable[((Byte)(*crc)) ^ b] ^ (*crc >> 8);
+}
+
+void CrcUpdateUInt16(UInt32 *crc, UInt16 v)
+{
+  CrcUpdateByte(crc, (Byte)v);
+  CrcUpdateByte(crc, (Byte)(v >> 8));
+}
+
+void CrcUpdateUInt32(UInt32 *crc, UInt32 v)
+{
+  int i;
+  for (i = 0; i < 4; i++)
+    CrcUpdateByte(crc, (Byte)(v >> (8 * i)));
+}
+
+void CrcUpdateUInt64(UInt32 *crc, UInt64 v)
+{
+  int i;
+  for (i = 0; i < 8; i++)
+  {
+    CrcUpdateByte(crc, (Byte)(v));
+    v >>= 8;
+  }
+}
+
+void CrcUpdate(UInt32 *crc, const void *data, size_t size)
+{
+  UInt32 v = *crc;
+  const Byte *p = (const Byte *)data;
+  for (; size > 0 ; size--, p++)
+    v = g_CrcTable[((Byte)(v)) ^ *p] ^ (v >> 8);
+  *crc = v;
+}
+
+UInt32 CrcCalculateDigest(const void *data, size_t size)
+{
+  UInt32 crc;
+  CrcInit(&crc);
+  CrcUpdate(&crc, data, size);
+  return CrcGetDigest(&crc);
+}
+
+int CrcVerifyDigest(UInt32 digest, const void *data, size_t size)
+{
+  return (CrcCalculateDigest(data, size) == digest);
+}