Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10'

git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10

third_party/nix/src/libstore/references.cc

@@ -0,0 +1,122 @@
+#include "references.hh"
+#include "hash.hh"
+#include "util.hh"
+#include "archive.hh"
+
+#include <map>
+#include <cstdlib>
+
+
+namespace nix {
+
+
+static unsigned int refLength = 32; /* characters */
+
+
+static void search(const unsigned char * s, size_t len,
+    StringSet & hashes, StringSet & seen)
+{
+    static bool initialised = false;
+    static bool isBase32[256];
+    if (!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;
+        initialised = 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.find(ref) != hashes.end()) {
+            debug(format("found reference to '%1%' at offset '%2%'")
+                  % 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);
+
+    size_t 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 (auto & i : refs) {
+        string baseName = baseNameOf(i);
+        string::size_type pos = baseName.find('-');
+        if (pos == string::npos)
+            throw Error(format("bad reference '%1%'") % 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;
+}
+
+
+}