tvl-depot/src/libstore/export-import.cc
Eelco Dolstra fa125b9b28
TeeSink: Pre-reserve string space
When receiving a very large file, this can prevent the string from
having tobe copied, which temporarily doubles memory consumption.
2017-03-01 16:16:04 +01:00

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#include "store-api.hh"
#include "archive.hh"
#include "worker-protocol.hh"
#include <algorithm>
namespace nix {
struct HashAndWriteSink : Sink
{
Sink & writeSink;
HashSink hashSink;
HashAndWriteSink(Sink & writeSink) : writeSink(writeSink), hashSink(htSHA256)
{
}
virtual void operator () (const unsigned char * data, size_t len)
{
writeSink(data, len);
hashSink(data, len);
}
Hash currentHash()
{
return hashSink.currentHash().first;
}
};
void Store::exportPaths(const Paths & paths, Sink & sink)
{
Paths sorted = topoSortPaths(PathSet(paths.begin(), paths.end()));
std::reverse(sorted.begin(), sorted.end());
std::string doneLabel("paths exported");
logger->incExpected(doneLabel, sorted.size());
for (auto & path : sorted) {
Activity act(*logger, lvlInfo, format("exporting path %s") % path);
sink << 1;
exportPath(path, sink);
logger->incProgress(doneLabel);
}
sink << 0;
}
void Store::exportPath(const Path & path, Sink & sink)
{
auto info = queryPathInfo(path);
HashAndWriteSink hashAndWriteSink(sink);
narFromPath(path, hashAndWriteSink);
/* Refuse to export paths that have changed. This prevents
filesystem corruption from spreading to other machines.
Don't complain if the stored hash is zero (unknown). */
Hash hash = hashAndWriteSink.currentHash();
if (hash != info->narHash && info->narHash != Hash(info->narHash.type))
throw Error(format("hash of path %1% has changed from %2% to %3%!") % path
% printHash(info->narHash) % printHash(hash));
hashAndWriteSink << exportMagic << path << info->references << info->deriver << 0;
}
Paths Store::importPaths(Source & source, std::shared_ptr<FSAccessor> accessor, bool dontCheckSigs)
{
Paths res;
while (true) {
auto n = readNum<uint64_t>(source);
if (n == 0) break;
if (n != 1) throw Error("input doesn't look like something created by nix-store --export");
/* Extract the NAR from the source. */
TeeSink tee(source);
parseDump(tee, tee.source);
uint32_t magic = readInt(source);
if (magic != exportMagic)
throw Error("Nix archive cannot be imported; wrong format");
ValidPathInfo info;
info.path = readStorePath(*this, source);
Activity act(*logger, lvlInfo, format("importing path %s") % info.path);
info.references = readStorePaths<PathSet>(*this, source);
info.deriver = readString(source);
if (info.deriver != "") assertStorePath(info.deriver);
info.narHash = hashString(htSHA256, *tee.source.data);
info.narSize = tee.source.data->size();
// Ignore optional legacy signature.
if (readInt(source) == 1)
readString(source);
addToStore(info, tee.source.data, false, dontCheckSigs, accessor);
res.push_back(info.path);
}
return res;
}
}