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#include "references.hh"
#include "hash.hh"
#include "util.hh"
#include "archive.hh"
#include <map>
#include <cstdlib>
#include <mutex>
namespace nix {
static unsigned int refLength = 32; /* characters */
static void search(const unsigned char * s, size_t len,
StringSet & hashes, StringSet & seen)
{
static std::once_flag initialised;
static bool isBase32[256];
std::call_once(initialised, [](){
for (unsigned int i = 0; i < 256; ++i) isBase32[i] = false;
for (unsigned int i = 0; i < base32Chars.size(); ++i)
isBase32[(unsigned char) base32Chars[i]] = true;
});
for (size_t i = 0; i + refLength <= len; ) {
int j;
bool match = true;
for (j = refLength - 1; j >= 0; --j)
if (!isBase32[(unsigned char) s[i + j]]) {
i += j + 1;
match = false;
break;
}
if (!match) continue;
string ref((const char *) s + i, refLength);
if (hashes.erase(ref)) {
debug(format("found reference to '%1%' at offset '%2%'")
% ref % i);
seen.insert(ref);
}
++i;
}
}
struct RefScanSink : Sink
{
StringSet hashes;
StringSet seen;
string tail;
RefScanSink() { }
void operator () (std::string_view data) override
{
/* 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 + std::string(data, 0, refLength);
search((const unsigned char *) s.data(), s.size(), hashes, seen);
search((const unsigned char *) data.data(), data.size(), hashes, seen);
size_t tailLen = data.size() <= refLength ? data.size() : refLength;
tail = std::string(tail, tail.size() < refLength - tailLen ? 0 : tail.size() - (refLength - tailLen));
tail.append({data.data() + data.size() - tailLen, tailLen});
}
};
std::pair<StorePathSet, HashResult> scanForReferences(
const string & path,
const StorePathSet & refs)
{
HashSink hashSink { htSHA256 };
auto found = scanForReferences(hashSink, path, refs);
auto hash = hashSink.finish();
return std::pair<StorePathSet, HashResult>(found, hash);
}
StorePathSet scanForReferences(
Sink & toTee,
const Path & path,
const StorePathSet & refs)
{
RefScanSink refsSink;
TeeSink sink { refsSink, toTee };
std::map<std::string, StorePath> backMap;
for (auto & i : refs) {
std::string hashPart(i.hashPart());
auto inserted = backMap.emplace(hashPart, i).second;
assert(inserted);
refsSink.hashes.insert(hashPart);
}
/* Look for the hashes in the NAR dump of the path. */
dumpPath(path, sink);
/* Map the hashes found back to their store paths. */
StorePathSet found;
for (auto & i : refsSink.seen) {
auto j = backMap.find(i);
assert(j != backMap.end());
found.insert(j->second);
}
return found;
}
RewritingSink::RewritingSink(const std::string & from, const std::string & to, Sink & nextSink)
: from(from), to(to), nextSink(nextSink)
{
assert(from.size() == to.size());
}
void RewritingSink::operator () (std::string_view data)
{
std::string s(prev);
s.append(data);
size_t j = 0;
while ((j = s.find(from, j)) != string::npos) {
matches.push_back(pos + j);
s.replace(j, from.size(), to);
}
prev = s.size() < from.size() ? s : std::string(s, s.size() - from.size() + 1, from.size() - 1);
auto consumed = s.size() - prev.size();
pos += consumed;
if (consumed) nextSink(s.substr(0, consumed));
}
void RewritingSink::flush()
{
if (prev.empty()) return;
pos += prev.size();
nextSink(prev);
prev.clear();
}
HashModuloSink::HashModuloSink(HashType ht, const std::string & modulus)
: hashSink(ht)
, rewritingSink(modulus, std::string(modulus.size(), 0), hashSink)
{
}
void HashModuloSink::operator () (std::string_view data)
{
rewritingSink(data);
}
HashResult HashModuloSink::finish()
{
rewritingSink.flush();
/* Hash the positions of the self-references. This ensures that a
NAR with self-references and a NAR with some of the
self-references already zeroed out do not produce a hash
collision. FIXME: proof. */
for (auto & pos : rewritingSink.matches)
hashSink(fmt("|%d", pos));
auto h = hashSink.finish();
return {h.first, rewritingSink.pos};
}
}
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