lix/src/libstore/references.cc
Eelco Dolstra d58a11e019 * Shorten SHA-256 hashes used in store path name generation to 160
bits, then encode them in a radix-32 representation (using digits
  and letters except e, o, u, and t).  This produces store paths like
  /nix/store/4i0zb0z7f88mwghjirkz702a71dcfivn-aterm-2.3.1.  The nice
  thing about this is that the hash part of the file name is still 32
  characters, as before with MD5.

  (Of course, shortening SHA-256 to 160 bits makes it no better than
  SHA-160 in theory, but hopefully it's a bit more resistant to
  attacks; it's certainly a lot slower.)
2005-01-14 16:04:03 +00:00

106 lines
2.6 KiB
C++

#include <cerrno>
#include <map>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dirent.h>
#include <fcntl.h>
#include "references.hh"
#include "hash.hh"
static void search(const string & s,
Strings & ids, Strings & seen)
{
for (Strings::iterator i = ids.begin();
i != ids.end(); )
{
checkInterrupt();
if (s.find(*i) == string::npos)
i++;
else {
debug(format("found reference to `%1%'") % *i);
seen.push_back(*i);
i = ids.erase(i);
}
}
}
void checkPath(const string & path,
Strings & ids, Strings & seen)
{
checkInterrupt();
struct stat st;
if (lstat(path.c_str(), &st))
throw SysError(format("getting attributes of path `%1%'") % path);
if (S_ISDIR(st.st_mode)) {
Strings names = readDirectory(path);
for (Strings::iterator i = names.begin(); i != names.end(); i++) {
search(*i, ids, seen);
checkPath(path + "/" + *i, ids, seen);
}
}
else if (S_ISREG(st.st_mode)) {
debug(format("checking `%1%'") % path);
AutoCloseFD fd = open(path.c_str(), O_RDONLY);
if (fd == -1) throw SysError(format("opening file `%1%'") % path);
unsigned char * buf = new unsigned char[st.st_size];
readFull(fd, buf, st.st_size);
search(string((char *) buf, st.st_size), ids, seen);
delete buf; /* !!! autodelete */
}
else if (S_ISLNK(st.st_mode))
search(readLink(path), ids, seen);
else throw Error(format("unknown file type: %1%") % path);
}
Strings filterReferences(const string & path, const Strings & paths)
{
map<string, string> backMap;
Strings ids;
Strings seen;
/* For efficiency (and a higher hit rate), just search for the
hash part of the file name. (This assumes that all references
have the form `HASH-bla'). */
for (Strings::const_iterator i = paths.begin();
i != paths.end(); i++)
{
string baseName = baseNameOf(*i);
unsigned int pos = baseName.find('-');
if (pos == string::npos)
throw Error(format("bad reference `%1%'") % *i);
string s = string(baseName, 0, pos);
// parseHash(htSHA256, s);
ids.push_back(s);
backMap[s] = *i;
}
checkPath(path, ids, seen);
Strings found;
for (Strings::iterator i = seen.begin(); i != seen.end(); i++)
{
map<string, string>::iterator j;
if ((j = backMap.find(*i)) == backMap.end()) abort();
found.push_back(j->second);
}
return found;
}