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93 lines
2.3 KiB
C
93 lines
2.3 KiB
C
/*
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** 2013-10-01
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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******************************************************************************
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**
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** Compute hash signatures for every page of a database file. This utility
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** program is useful for analyzing the output logs generated by the
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** ext/misc/vfslog.c extension.
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*/
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#include <stdio.h>
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#include <string.h>
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#include <assert.h>
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#include <stdlib.h>
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/*
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** Compute signature for a block of content.
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**
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** For blocks of 16 or fewer bytes, the signature is just a hex dump of
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** the entire block.
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**
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** For blocks of more than 16 bytes, the signature is a hex dump of the
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** first 8 bytes followed by a 64-bit has of the entire block.
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*/
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static void vlogSignature(unsigned char *p, int n, char *zCksum){
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unsigned int s0 = 0, s1 = 0;
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unsigned int *pI;
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int i;
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if( n<=16 ){
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for(i=0; i<n; i++) sprintf(zCksum+i*2, "%02x", p[i]);
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}else{
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pI = (unsigned int*)p;
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for(i=0; i<n-7; i+=8){
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s0 += pI[0] + s1;
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s1 += pI[1] + s0;
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pI += 2;
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}
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for(i=0; i<8; i++) sprintf(zCksum+i*2, "%02x", p[i]);
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sprintf(zCksum+i*2, "-%08x%08x", s0, s1);
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}
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}
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/*
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** Open a file. Find its page size. Read each page, and compute and
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** display the page signature.
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*/
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static void computeSigs(const char *zFilename){
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FILE *in = fopen(zFilename, "rb");
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unsigned pgsz;
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size_t got;
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unsigned n;
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unsigned char aBuf[50];
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unsigned char aPage[65536];
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if( in==0 ){
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fprintf(stderr, "cannot open \"%s\"\n", zFilename);
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return;
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}
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got = fread(aBuf, 1, sizeof(aBuf), in);
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if( got!=sizeof(aBuf) ){
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goto endComputeSigs;
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}
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pgsz = aBuf[16]*256 + aBuf[17];
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if( pgsz==1 ) pgsz = 65536;
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if( (pgsz & (pgsz-1))!=0 ){
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fprintf(stderr, "invalid page size: %02x%02x\n", aBuf[16], aBuf[17]);
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goto endComputeSigs;
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}
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rewind(in);
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for(n=1; (got=fread(aPage, 1, pgsz, in))==pgsz; n++){
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vlogSignature(aPage, pgsz, aBuf);
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printf("%4d: %s\n", n, aBuf);
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}
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endComputeSigs:
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fclose(in);
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}
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/*
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** Find page signatures for all named files.
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*/
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int main(int argc, char **argv){
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int i;
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for(i=1; i<argc; i++) computeSigs(argv[i]);
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return 0;
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}
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