1 /*
2 ** 2013-10-01
3 **
4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
6 **
7 ** May you do good and not evil.
8 ** May you find forgiveness for yourself and forgive others.
9 ** May you share freely, never taking more than you give.
10 **
11 ******************************************************************************
12 **
13 ** Compute hash signatures for every page of a database file. This utility
14 ** program is useful for analyzing the output logs generated by the
15 ** ext/misc/vfslog.c extension.
16 */
17 #include <stdio.h>
18 #include <string.h>
19 #include <assert.h>
20 #include <stdlib.h>
21
22 /*
23 ** Compute signature for a block of content.
24 **
25 ** For blocks of 16 or fewer bytes, the signature is just a hex dump of
26 ** the entire block.
27 **
28 ** For blocks of more than 16 bytes, the signature is a hex dump of the
29 ** first 8 bytes followed by a 64-bit has of the entire block.
30 */
vlogSignature(unsigned char * p,int n,char * zCksum)31 static void vlogSignature(unsigned char *p, int n, char *zCksum){
32 unsigned int s0 = 0, s1 = 0;
33 unsigned int *pI;
34 int i;
35 if( n<=16 ){
36 for(i=0; i<n; i++) sprintf(zCksum+i*2, "%02x", p[i]);
37 }else{
38 pI = (unsigned int*)p;
39 for(i=0; i<n-7; i+=8){
40 s0 += pI[0] + s1;
41 s1 += pI[1] + s0;
42 pI += 2;
43 }
44 for(i=0; i<8; i++) sprintf(zCksum+i*2, "%02x", p[i]);
45 sprintf(zCksum+i*2, "-%08x%08x", s0, s1);
46 }
47 }
48
49 /*
50 ** Open a file. Find its page size. Read each page, and compute and
51 ** display the page signature.
52 */
computeSigs(const char * zFilename)53 static void computeSigs(const char *zFilename){
54 FILE *in = fopen(zFilename, "rb");
55 unsigned pgsz;
56 size_t got;
57 unsigned n;
58 unsigned char aBuf[50];
59 unsigned char aPage[65536];
60
61 if( in==0 ){
62 fprintf(stderr, "cannot open \"%s\"\n", zFilename);
63 return;
64 }
65 got = fread(aBuf, 1, sizeof(aBuf), in);
66 if( got!=sizeof(aBuf) ){
67 goto endComputeSigs;
68 }
69 pgsz = aBuf[16]*256 + aBuf[17];
70 if( pgsz==1 ) pgsz = 65536;
71 if( (pgsz & (pgsz-1))!=0 ){
72 fprintf(stderr, "invalid page size: %02x%02x\n", aBuf[16], aBuf[17]);
73 goto endComputeSigs;
74 }
75 rewind(in);
76 for(n=1; (got=fread(aPage, 1, pgsz, in))==pgsz; n++){
77 vlogSignature(aPage, pgsz, aBuf);
78 printf("%4d: %s\n", n, aBuf);
79 }
80
81 endComputeSigs:
82 fclose(in);
83 }
84
85 /*
86 ** Find page signatures for all named files.
87 */
main(int argc,char ** argv)88 int main(int argc, char **argv){
89 int i;
90 for(i=1; i<argc; i++) computeSigs(argv[i]);
91 return 0;
92 }
93