lix/src/libstore/nar-accessor.cc
Eelco Dolstra d62a9390fc Get rid of std::shared_ptr<std::string> and ref<std::string>
These were needed back in the pre-C++11 era because we didn't have
move semantics. But now we do.
2022-01-18 11:12:30 +01:00

282 lines
7.9 KiB
C++

#include "nar-accessor.hh"
#include "archive.hh"
#include "json.hh"
#include <map>
#include <stack>
#include <algorithm>
#include <nlohmann/json.hpp>
namespace nix {
struct NarMember
{
FSAccessor::Type type = FSAccessor::Type::tMissing;
bool isExecutable = false;
/* If this is a regular file, position of the contents of this
file in the NAR. */
uint64_t start = 0, size = 0;
std::string target;
/* If this is a directory, all the children of the directory. */
std::map<std::string, NarMember> children;
};
struct NarAccessor : public FSAccessor
{
std::optional<const std::string> nar;
GetNarBytes getNarBytes;
NarMember root;
struct NarIndexer : ParseSink, Source
{
NarAccessor & acc;
Source & source;
std::stack<NarMember *> parents;
bool isExec = false;
uint64_t pos = 0;
NarIndexer(NarAccessor & acc, Source & source)
: acc(acc), source(source)
{ }
void createMember(const Path & path, NarMember member)
{
size_t level = std::count(path.begin(), path.end(), '/');
while (parents.size() > level) parents.pop();
if (parents.empty()) {
acc.root = std::move(member);
parents.push(&acc.root);
} else {
if (parents.top()->type != FSAccessor::Type::tDirectory)
throw Error("NAR file missing parent directory of path '%s'", path);
auto result = parents.top()->children.emplace(baseNameOf(path), std::move(member));
parents.push(&result.first->second);
}
}
void createDirectory(const Path & path) override
{
createMember(path, {FSAccessor::Type::tDirectory, false, 0, 0});
}
void createRegularFile(const Path & path) override
{
createMember(path, {FSAccessor::Type::tRegular, false, 0, 0});
}
void isExecutable() override
{
parents.top()->isExecutable = true;
}
void preallocateContents(uint64_t size) override
{
assert(size <= std::numeric_limits<uint64_t>::max());
parents.top()->size = (uint64_t) size;
parents.top()->start = pos;
}
void receiveContents(std::string_view data) override
{ }
void createSymlink(const Path & path, const string & target) override
{
createMember(path,
NarMember{FSAccessor::Type::tSymlink, false, 0, 0, target});
}
size_t read(char * data, size_t len) override
{
auto n = source.read(data, len);
pos += n;
return n;
}
};
NarAccessor(std::string && _nar) : nar(_nar)
{
StringSource source(*nar);
NarIndexer indexer(*this, source);
parseDump(indexer, indexer);
}
NarAccessor(Source & source)
{
NarIndexer indexer(*this, source);
parseDump(indexer, indexer);
}
NarAccessor(const std::string & listing, GetNarBytes getNarBytes)
: getNarBytes(getNarBytes)
{
using json = nlohmann::json;
std::function<void(NarMember &, json &)> recurse;
recurse = [&](NarMember & member, json & v) {
std::string type = v["type"];
if (type == "directory") {
member.type = FSAccessor::Type::tDirectory;
for (auto i = v["entries"].begin(); i != v["entries"].end(); ++i) {
std::string name = i.key();
recurse(member.children[name], i.value());
}
} else if (type == "regular") {
member.type = FSAccessor::Type::tRegular;
member.size = v["size"];
member.isExecutable = v.value("executable", false);
member.start = v["narOffset"];
} else if (type == "symlink") {
member.type = FSAccessor::Type::tSymlink;
member.target = v.value("target", "");
} else return;
};
json v = json::parse(listing);
recurse(root, v);
}
NarMember * find(const Path & path)
{
Path canon = path == "" ? "" : canonPath(path);
NarMember * current = &root;
auto end = path.end();
for (auto it = path.begin(); it != end; ) {
// because it != end, the remaining component is non-empty so we need
// a directory
if (current->type != FSAccessor::Type::tDirectory) return nullptr;
// skip slash (canonPath above ensures that this is always a slash)
assert(*it == '/');
it += 1;
// lookup current component
auto next = std::find(it, end, '/');
auto child = current->children.find(std::string(it, next));
if (child == current->children.end()) return nullptr;
current = &child->second;
it = next;
}
return current;
}
NarMember & get(const Path & path) {
auto result = find(path);
if (result == nullptr)
throw Error("NAR file does not contain path '%1%'", path);
return *result;
}
Stat stat(const Path & path) override
{
auto i = find(path);
if (i == nullptr)
return {FSAccessor::Type::tMissing, 0, false};
return {i->type, i->size, i->isExecutable, i->start};
}
StringSet readDirectory(const Path & path) override
{
auto i = get(path);
if (i.type != FSAccessor::Type::tDirectory)
throw Error("path '%1%' inside NAR file is not a directory", path);
StringSet res;
for (auto & child : i.children)
res.insert(child.first);
return res;
}
std::string readFile(const Path & path, bool requireValidPath = true) override
{
auto i = get(path);
if (i.type != FSAccessor::Type::tRegular)
throw Error("path '%1%' inside NAR file is not a regular file", path);
if (getNarBytes) return getNarBytes(i.start, i.size);
assert(nar);
return std::string(*nar, i.start, i.size);
}
std::string readLink(const Path & path) override
{
auto i = get(path);
if (i.type != FSAccessor::Type::tSymlink)
throw Error("path '%1%' inside NAR file is not a symlink", path);
return i.target;
}
};
ref<FSAccessor> makeNarAccessor(std::string && nar)
{
return make_ref<NarAccessor>(std::move(nar));
}
ref<FSAccessor> makeNarAccessor(Source & source)
{
return make_ref<NarAccessor>(source);
}
ref<FSAccessor> makeLazyNarAccessor(const std::string & listing,
GetNarBytes getNarBytes)
{
return make_ref<NarAccessor>(listing, getNarBytes);
}
void listNar(JSONPlaceholder & res, ref<FSAccessor> accessor,
const Path & path, bool recurse)
{
auto st = accessor->stat(path);
auto obj = res.object();
switch (st.type) {
case FSAccessor::Type::tRegular:
obj.attr("type", "regular");
obj.attr("size", st.fileSize);
if (st.isExecutable)
obj.attr("executable", true);
if (st.narOffset)
obj.attr("narOffset", st.narOffset);
break;
case FSAccessor::Type::tDirectory:
obj.attr("type", "directory");
{
auto res2 = obj.object("entries");
for (auto & name : accessor->readDirectory(path)) {
if (recurse) {
auto res3 = res2.placeholder(name);
listNar(res3, accessor, path + "/" + name, true);
} else
res2.object(name);
}
}
break;
case FSAccessor::Type::tSymlink:
obj.attr("type", "symlink");
obj.attr("target", accessor->readLink(path));
break;
default:
throw Error("path '%s' does not exist in NAR", path);
}
}
}