#ifndef lint
static char rcsid[] = "@(#$Id: pathhash.cpp,v 1.2 2005-11-24 07:16:15 dockes Exp $ (C) 2005 J.F.Dockes";
#endif
#include <stdio.h>
#include "pathhash.h"
#include "md5.h"
#include "base64.h"
#ifndef NO_NAMESPACES
using std::string;
#endif /* NO_NAMESPACES */
#ifdef PATHHASH_HEX
static void md5hexprint(const unsigned char hash[16], string &out)
{
out.erase();
out.reserve(33);
static const char hex[]="0123456789abcdef";
for (int i = 0; i < 16; i++) {
out.append(1, hex[hash[i] >> 4]);
out.append(1, hex[hash[i] & 0x0f]);
}
}
#endif
// Size of the hashed result (base64 of 16 bytes of md5, minus 2 pad chars)
#define HASHLEN 22
// Convert longish paths by truncating and appending hash of path
// The full length of the base64-encoded (minus pad) of the md5 is 22 chars
// We append this to the truncated path
void pathHash(const std::string &path, std::string &phash, unsigned int maxlen)
{
if (maxlen < HASHLEN) {
fprintf(stderr, "pathHash: internal error: requested len too small\n");
abort();
}
if (path.length() <= maxlen) {
phash = path;
return;
}
// Compute the md5
unsigned char chash[16];
MD5_CTX ctx;
MD5Init(&ctx);
MD5Update(&ctx, (const unsigned char *)(path.c_str()+maxlen-HASHLEN),
path.length() - (maxlen - HASHLEN));
MD5Final(chash, &ctx);
#if 0
string hex;
md5hexprint(chash, hex);
printf("hex [%s]\n", hex.c_str());
#endif
// Encode it to ascii. This shouldn't be strictly necessary as
// xapian terms can be binary
string hash;
base64_encode(string((char *)chash, 16), hash);
// We happen to know there will be 2 pad chars in there, that we
// don't need as this won't ever be decoded. Resulting length is 22
hash.resize(hash.length() - 2);
// Truncate path and append hash
phash = path.substr(0, maxlen - HASHLEN) + hash;
}
#ifdef TEST_PATHHASH
#include <stdio.h>
int main(int argc, char **argv)
{
string path="/usr/lib/toto.cpp";
string hash;
pathHash(path, hash);
printf("hash [%s]\n", hash.c_str());
}
#endif // TEST_PATHHASH