forked from lix-project/lix
* Path hashing.
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a09e66da5a
commit
2f04e7102e
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@ -148,10 +148,12 @@ static Hash computeDerived(Hash sourceHash, string targetName,
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throw Error("program " + progPath +
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" failed to create a result in " + targetPath);
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#if 0
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/* Remove write permission from the value. */
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int res = system(("chmod -R -w " + targetPath).c_str()); // !!! escaping
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if (WEXITSTATUS(res) != 0)
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throw Error("cannot remove write permission from " + targetPath);
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#endif
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} catch (exception &) {
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// system(("rm -rf " + targetPath).c_str());
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@ -159,7 +161,7 @@ static Hash computeDerived(Hash sourceHash, string targetName,
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}
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/* Hash the result. */
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Hash targetHash = hashFile(targetPath);
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Hash targetHash = hashPath(targetPath);
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/* Register targetHash -> targetPath. !!! this should be in
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values.cc. */
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141
src/hash.cc
141
src/hash.cc
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@ -1,9 +1,16 @@
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#include <iostream>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <dirent.h>
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#include <fcntl.h>
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extern "C" {
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#include "md5.h"
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}
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#include "hash.hh"
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#include <iostream>
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Hash::Hash()
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@ -88,3 +95,135 @@ Hash hashFile(const string & fileName)
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if (err) throw SysError("cannot hash file " + fileName);
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return hash;
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}
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struct HashSink : DumpSink
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{
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struct md5_ctx ctx;
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virtual void operator ()
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(const unsigned char * data, unsigned int len)
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{
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md5_process_bytes(data, len, &ctx);
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}
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};
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Hash hashPath(const string & path)
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{
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Hash hash;
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HashSink sink;
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md5_init_ctx(&sink.ctx);
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dumpPath(path, sink);
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md5_finish_ctx(&sink.ctx, hash.hash);
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return hash;
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}
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static void pad(unsigned int len, DumpSink & sink)
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{
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if (len % 8) {
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unsigned char zero[8];
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memset(zero, 0, sizeof(zero));
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sink(zero, 8 - (len % 8));
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}
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}
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static void writeInt(unsigned int n, DumpSink & sink)
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{
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unsigned char buf[8];
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memset(buf, 0, sizeof(buf));
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buf[0] = n & 0xff;
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buf[1] = (n >> 8) & 0xff;
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buf[2] = (n >> 16) & 0xff;
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buf[3] = (n >> 24) & 0xff;
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sink(buf, sizeof(buf));
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}
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static void writeString(const string & s, DumpSink & sink)
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{
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unsigned int len = s.length();
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writeInt(len, sink);
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sink((const unsigned char *) s.c_str(), len);
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pad(len, sink);
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}
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static void dumpEntries(const string & path, DumpSink & sink)
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{
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DIR * dir = opendir(path.c_str());
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if (!dir) throw SysError("opening directory " + path);
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struct dirent * dirent;
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/* !!! sort entries */
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while (errno = 0, dirent = readdir(dir)) {
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string name = dirent->d_name;
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if (name == "." || name == "..") continue;
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writeString("entry", sink);
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writeString("(", sink);
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writeString("name", sink);
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writeString(name, sink);
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writeString("file", sink);
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dumpPath(path + "/" + name, sink);
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writeString(")", sink);
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}
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if (errno) throw SysError("reading directory " + path);
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closedir(dir); /* !!! close on exception */
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}
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static void dumpContents(const string & path, unsigned int size,
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DumpSink & sink)
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{
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writeString("contents", sink);
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writeInt(size, sink);
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int fd = open(path.c_str(), O_RDONLY);
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if (!fd) throw SysError("opening file " + path);
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unsigned char buf[16384];
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unsigned int total = 0;
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ssize_t n;
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while ((n = read(fd, buf, sizeof(buf)))) {
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if (n == -1) throw SysError("reading file " + path);
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total += n;
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sink(buf, n);
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}
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if (total != size)
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throw SysError("file changed while reading it: " + path);
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pad(size, sink);
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close(fd); /* !!! close on exception */
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}
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void dumpPath(const string & path, DumpSink & sink)
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{
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cerr << path << endl;
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struct stat st;
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if (lstat(path.c_str(), &st))
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throw SysError("getting attributes of path " + path);
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writeString("(", sink);
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if (S_ISREG(st.st_mode)) {
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writeString("type", sink);
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writeString("regular", sink);
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dumpContents(path, st.st_size, sink);
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} else if (S_ISDIR(st.st_mode)) {
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writeString("type", sink);
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writeString("directory", sink);
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dumpEntries(path, sink);
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} else throw Error("unknown file type: " + path);
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writeString(")", sink);
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}
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19
src/hash.hh
19
src/hash.hh
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@ -50,6 +50,11 @@ Hash hashFile(const string & fileName);
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follows:
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hash(path) = md5(dump(path))
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*/
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Hash hashPath(const string & path);
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/* Dump a path as follows:
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IF path points to a REGULAR FILE:
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dump(path) = attrs(
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@ -60,7 +65,7 @@ Hash hashFile(const string & fileName);
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IF path points to a DIRECTORY:
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dump(path) = attrs(
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[ ("type", "directory")
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, ("entries", concat(map(f, entries(path))))
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, ("entries", concat(map(f, sort(entries(path)))))
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])
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where f(fn) = attrs(
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[ ("name", fn)
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@ -72,17 +77,25 @@ Hash hashFile(const string & fileName);
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attrs(as) = concat(map(attr, as)) + encN(0)
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attrs((a, b)) = encS(a) + encS(b)
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encS(s) = encN(len(s)) + s
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encS(s) = encN(len(s)) + s + (padding until next 64-bit boundary)
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encN(n) = 64-bit little-endian encoding of n.
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contents(path) = the contents of a regular file.
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sort(strings) = lexicographic sort by 8-bit value (strcmp).
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entries(path) = the entries of a directory, without `.' and
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`..'.
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`+' denotes string concatenation. */
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Hash hashPath(const string & path);
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struct DumpSink
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{
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virtual void operator () (const unsigned char * data, unsigned int len) = 0;
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};
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void dumpPath(const string & path, DumpSink & sink);
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#endif /* !__HASH_H */
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16
src/test.cc
16
src/test.cc
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@ -19,6 +19,15 @@ void evalTest(Expr e)
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}
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struct MySink : DumpSink
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{
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virtual void operator () (const unsigned char * data, unsigned int len)
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{
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cout.write((char *) data, len);
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}
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};
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void runTests()
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{
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/* Hashing. */
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@ -36,6 +45,13 @@ void runTests()
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abort();
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} catch (BadRefError err) { };
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/* Dumping. */
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#if 0
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MySink sink;
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dumpPath("scratch", sink);
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cout << (string) hashPath("scratch") << endl;
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#endif
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/* Set up the test environment. */
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@ -19,7 +19,7 @@ static string absValuePath(string s)
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Hash addValue(string path)
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{
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Hash hash = hashFile(path);
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Hash hash = hashPath(path);
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string name;
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if (queryDB(nixDB, dbRefs, hash, name)) {
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@ -72,8 +72,8 @@ string queryValuePath(Hash hash)
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if (queryDB(nixDB, dbRefs, hash, name)) {
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string fn = absValuePath(name);
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/* Verify that the file hasn't changed. !!! race */
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if (hashFile(fn) != hash)
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/* Verify that the file hasn't changed. !!! race !!! slow */
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if (hashPath(fn) != hash)
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throw Error("file " + fn + " is stale");
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return fn;
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