lix/src/libstore/local-binary-cache-store.cc
Eelco Dolstra bbe97dff8b Make the Store API more type-safe
Most functions now take a StorePath argument rather than a Path (which
is just an alias for std::string). The StorePath constructor ensures
that the path is syntactically correct (i.e. it looks like
<store-dir>/<base32-hash>-<name>). Similarly, functions like
buildPaths() now take a StorePathWithOutputs, rather than abusing Path
by adding a '!<outputs>' suffix.

Note that the StorePath type is implemented in Rust. This involves
some hackery to allow Rust values to be used directly in C++, via a
helper type whose destructor calls the Rust type's drop()
function. The main issue is the dynamic nature of C++ move semantics:
after we have moved a Rust value, we should not call the drop function
on the original value. So when we move a value, we set the original
value to bitwise zero, and the destructor only calls drop() if the
value is not bitwise zero. This should be sufficient for most types.

Also lots of minor cleanups to the C++ API to make it more modern
(e.g. using std::optional and std::string_view in some places).
2019-12-10 22:06:05 +01:00

106 lines
2.6 KiB
C++

#include "binary-cache-store.hh"
#include "globals.hh"
#include "nar-info-disk-cache.hh"
namespace nix {
class LocalBinaryCacheStore : public BinaryCacheStore
{
private:
Path binaryCacheDir;
public:
LocalBinaryCacheStore(
const Params & params, const Path & binaryCacheDir)
: BinaryCacheStore(params)
, binaryCacheDir(binaryCacheDir)
{
}
void init() override;
std::string getUri() override
{
return "file://" + binaryCacheDir;
}
protected:
bool fileExists(const std::string & path) override;
void upsertFile(const std::string & path,
const std::string & data,
const std::string & mimeType) override;
void getFile(const std::string & path, Sink & sink) override
{
try {
readFile(binaryCacheDir + "/" + path, sink);
} catch (SysError & e) {
if (e.errNo == ENOENT)
throw NoSuchBinaryCacheFile("file '%s' does not exist in binary cache", path);
}
}
StorePathSet queryAllValidPaths() override
{
StorePathSet paths;
for (auto & entry : readDirectory(binaryCacheDir)) {
if (entry.name.size() != 40 ||
!hasSuffix(entry.name, ".narinfo"))
continue;
paths.insert(parseStorePath(storeDir + "/" + entry.name.substr(0, entry.name.size() - 8)));
}
return paths;
}
};
void LocalBinaryCacheStore::init()
{
createDirs(binaryCacheDir + "/nar");
if (writeDebugInfo)
createDirs(binaryCacheDir + "/debuginfo");
BinaryCacheStore::init();
}
static void atomicWrite(const Path & path, const std::string & s)
{
Path tmp = path + ".tmp." + std::to_string(getpid());
AutoDelete del(tmp, false);
writeFile(tmp, s);
if (rename(tmp.c_str(), path.c_str()))
throw SysError(format("renaming '%1%' to '%2%'") % tmp % path);
del.cancel();
}
bool LocalBinaryCacheStore::fileExists(const std::string & path)
{
return pathExists(binaryCacheDir + "/" + path);
}
void LocalBinaryCacheStore::upsertFile(const std::string & path,
const std::string & data,
const std::string & mimeType)
{
atomicWrite(binaryCacheDir + "/" + path, data);
}
static RegisterStoreImplementation regStore([](
const std::string & uri, const Store::Params & params)
-> std::shared_ptr<Store>
{
if (getEnv("_NIX_FORCE_HTTP_BINARY_CACHE_STORE") == "1" ||
std::string(uri, 0, 7) != "file://")
return 0;
auto store = std::make_shared<LocalBinaryCacheStore>(params, std::string(uri, 7));
store->init();
return store;
});
}