forgot to commit for some time... :(

1 files changed, 89 insertions, 0 deletions

diff --git a/pagerank.c b/pagerank.c
new file mode 100644
index 0000000..ec62ec8
--- /dev/null
+++ b/pagerank.c
@@ -0,0 +1,89 @@
+/******************************************************************************
+Filename     : pagerank.c
+Description  : Google PageRank Checksum Algorithm 
+Author       : http://zhiwei.li/
+Log          : Ver 0.1 2005-9-13  first release
+               Ver 1.0 2005-10-19  fixed :final character bug
+               Ver 1.1 2006-10-05  refine code
+               Ver 1.2 2008-8-20   use boolean type
+******************************************************************************/
+
+#include <stdio.h>
+#include <stdbool.h>
+
+int ConvertStrToInt(char *pStr, int Init, int Factor)
+{
+    while (*pStr) {
+        Init *= Factor;
+        Init += *pStr++;
+    }
+    return Init;
+}
+
+int HashURL(char *pStr)
+{
+    unsigned int C1, C2, T1, T2;
+
+    C1 = ConvertStrToInt(pStr, 0x1505, 0x21);
+    C2 = ConvertStrToInt(pStr, 0, 0x1003F);
+    C1 >>= 2;
+    C1 = ((C1 >> 4) & 0x3FFFFC0) | (C1 & 0x3F);
+    C1 = ((C1 >> 4) & 0x3FFC00) | (C1 & 0x3FF);
+    C1 = ((C1 >> 4) & 0x3C000) | (C1 & 0x3FFF);
+
+    T1 = (C1 & 0x3C0) << 4;
+    T1 |= C1 & 0x3C;
+    T1 = (T1 << 2) | (C2 & 0xF0F);
+
+    T2 = (C1 & 0xFFFFC000) << 4;
+    T2 |= C1 & 0x3C00;
+    T2 = (T2 << 0xA) | (C2 & 0xF0F0000);
+
+    return (T1 | T2);
+}
+
+char CheckHash(unsigned int HashInt)
+{
+    int Check = 0;
+    bool Flag = false;
+    int Remainder;
+
+    do {
+        Remainder = HashInt % 10;
+        HashInt /= 10;
+        if (Flag){
+            Remainder += Remainder;
+            Remainder = (Remainder / 10) + (Remainder % 10);
+        }
+        Check += Remainder;
+        Flag = !Flag;
+    } while( 0 != HashInt);
+
+    Check %= 10;
+    if (0 != Check) {
+        Check = 10 - Check;
+        if (Flag) {
+            if (1 == (Check % 2)) {
+                Check += 9;
+            }
+            Check >>= 1;
+        }
+    }
+    Check += 0x30;
+    return Check;
+}
+
+int main(int argc, char* argv[])
+{
+    unsigned int HashInt;
+
+    if (argc != 2) {
+        printf("Usage: %s [URL]\n",argv[0]);
+        return 1;
+    }
+
+    HashInt = HashURL(argv[1]);
+    printf("Checksum=7%c%u\n", CheckHash(HashInt), HashInt);
+    return 0;
+}
+