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#include "references.hh"
#include "hash.hh"
#include "util.hh"
#include "archive.hh"
#include <map>
#include <cstdlib>
#include <cassert>
#include <format>
namespace nix {
static unsigned int refLength = 32; /* characters */
static void search(const unsigned char * s, unsigned int len,
StringSet & hashes, StringSet & seen)
{
for (unsigned int i = 0; i + refLength <= len; ) {
int j;
bool match = true;
for (j = refLength - 1; j >= 0; --j)
if (base32Values[(unsigned char) s[i + j]] == -1) {
i += j + 1;
match = false;
break;
}
if (!match) continue;
string ref((const char *) s + i, refLength);
if (hashes.find(ref) != hashes.end()) {
debug(std::format("found reference to `{}' at offset `{}'", ref, i));
seen.insert(ref);
hashes.erase(ref);
}
++i;
}
}
struct RefScanSink : Sink
{
HashSink hashSink;
StringSet hashes;
StringSet seen;
string tail;
RefScanSink() : hashSink(htSHA256) { }
void operator () (const unsigned char * data, size_t len);
};
void RefScanSink::operator () (const unsigned char * data, size_t len)
{
hashSink(data, len);
/* It's possible that a reference spans the previous and current
fragment, so search in the concatenation of the tail of the
previous fragment and the start of the current fragment. */
string s = tail + string((const char *) data, len > refLength ? refLength : len);
search((const unsigned char *) s.data(), s.size(), hashes, seen);
search(data, len, hashes, seen);
unsigned int tailLen = len <= refLength ? len : refLength;
tail =
string(tail, tail.size() < refLength - tailLen ? 0 : tail.size() - (refLength - tailLen)) +
string((const char *) data + len - tailLen, tailLen);
}
PathSet scanForReferences(const string & path,
const PathSet & refs, HashResult & hash)
{
RefScanSink sink;
std::map<string, Path> backMap;
/* 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 (const auto& i : refs) {
string baseName = baseNameOf(i);
string::size_type pos = baseName.find('-');
if (pos == string::npos)
throw Error(std::format("bad reference `{}'", i));
string s = string(baseName, 0, pos);
assert(s.size() == refLength);
assert(backMap.find(s) == backMap.end());
// parseHash(htSHA256, s);
sink.hashes.insert(s);
backMap[s] = i;
}
/* Look for the hashes in the NAR dump of the path. */
dumpPath(path, sink);
/* Map the hashes found back to their store paths. */
PathSet found;
for (auto& i : sink.seen) {
std::map<string, Path>::iterator j;
if ((j = backMap.find(i)) == backMap.end()) abort();
found.insert(j->second);
}
hash = sink.hashSink.finish();
return found;
}
}
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