104 lines
2.9 KiB
C++
104 lines
2.9 KiB
C++
#ifndef lint
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static char rcsid[] = "@(#$Id: pathhash.cpp,v 1.4 2006-11-15 14:57:53 dockes Exp $ (C) 2005 J.F.Dockes";
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#endif
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/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the
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* Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#include <stdio.h>
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#include "pathhash.h"
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#include "md5.h"
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#include "base64.h"
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#ifndef NO_NAMESPACES
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using std::string;
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namespace Rcl {
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#endif /* NO_NAMESPACES */
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#ifdef PATHHASH_HEX
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static void md5hexprint(const unsigned char hash[16], string &out)
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{
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out.erase();
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out.reserve(33);
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static const char hex[]="0123456789abcdef";
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for (int i = 0; i < 16; i++) {
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out.append(1, hex[hash[i] >> 4]);
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out.append(1, hex[hash[i] & 0x0f]);
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}
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}
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#endif
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// Size of the hashed result (base64 of 16 bytes of md5, minus 2 pad chars)
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#define HASHLEN 22
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// Convert longish paths by truncating and appending hash of path
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// The full length of the base64-encoded (minus pad) of the md5 is 22 chars
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// We append this to the truncated path
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void pathHash(const std::string &path, std::string &phash, unsigned int maxlen)
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{
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if (maxlen < HASHLEN) {
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fprintf(stderr, "pathHash: internal error: requested len too small\n");
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abort();
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}
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if (path.length() <= maxlen) {
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phash = path;
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return;
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}
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// Compute the md5
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unsigned char chash[16];
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MD5_CTX ctx;
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MD5Init(&ctx);
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MD5Update(&ctx, (const unsigned char *)(path.c_str()+maxlen-HASHLEN),
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path.length() - (maxlen - HASHLEN));
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MD5Final(chash, &ctx);
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#if 0
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string hex;
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md5hexprint(chash, hex);
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printf("hex [%s]\n", hex.c_str());
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#endif
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// Encode it to ascii. This shouldn't be strictly necessary as
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// xapian terms can be binary
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string hash;
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base64_encode(string((char *)chash, 16), hash);
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// We happen to know there will be 2 pad chars in there, that we
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// don't need as this won't ever be decoded. Resulting length is 22
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hash.resize(hash.length() - 2);
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// Truncate path and append hash
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phash = path.substr(0, maxlen - HASHLEN) + hash;
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}
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#ifndef NO_NAMESPACES
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}
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#endif // NO_NAMESPACES
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#ifdef TEST_PATHHASH
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#include <stdio.h>
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int main(int argc, char **argv)
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{
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string path="/usr/lib/toto.cpp";
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string hash;
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pathHash(path, hash);
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printf("hash [%s]\n", hash.c_str());
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}
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#endif // TEST_PATHHASH
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