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Improve the FileSystemObjectSink interface

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More invariants are enforced in the type, and less state needs to be
stored in the main sink itself. The method here is roughly that known as
"session types".

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
This commit is contained in:
John Ericson 2023-12-20 14:47:05 -05:00
parent 966d6fcd01
commit 6365bbfa81
9 changed files with 357 additions and 219 deletions
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130
src/libutil/git.cc
View file

@ -52,24 +52,22 @@ static std::string getString(Source & source, int n)
return v;
}
void parse(
void parseBlob(
FileSystemObjectSink & sink,
const Path & sinkPath,
Source & source,
std::function<SinkHook> hook,
bool executable,
const ExperimentalFeatureSettings & xpSettings)
{
xpSettings.require(Xp::GitHashing);
auto type = getString(source, 5);
if (type == "blob ") {
sink.createRegularFile(sinkPath);
sink.createRegularFile(sinkPath, [&](auto & crf) {
if (executable)
crf.isExecutable();
unsigned long long size = std::stoi(getStringUntil(source, 0));
sink.preallocateContents(size);
crf.preallocateContents(size);
unsigned long long left = size;
std::string buf;
@ -79,47 +77,91 @@ void parse(
checkInterrupt();
buf.resize(std::min((unsigned long long)buf.capacity(), left));
source(buf);
sink.receiveContents(buf);
crf(buf);
left -= buf.size();
}
});
}
void parseTree(
FileSystemObjectSink & sink,
const Path & sinkPath,
Source & source,
std::function<SinkHook> hook,
const ExperimentalFeatureSettings & xpSettings)
{
unsigned long long size = std::stoi(getStringUntil(source, 0));
unsigned long long left = size;
sink.createDirectory(sinkPath);
while (left) {
std::string perms = getStringUntil(source, ' ');
left -= perms.size();
left -= 1;
RawMode rawMode = std::stoi(perms, 0, 8);
auto modeOpt = decodeMode(rawMode);
if (!modeOpt)
throw Error("Unknown Git permission: %o", perms);
auto mode = std::move(*modeOpt);
std::string name = getStringUntil(source, '\0');
left -= name.size();
left -= 1;
std::string hashs = getString(source, 20);
left -= 20;
Hash hash(HashAlgorithm::SHA1);
std::copy(hashs.begin(), hashs.end(), hash.hash);
hook(name, TreeEntry {
.mode = mode,
.hash = hash,
});
}
}
ObjectType parseObjectType(
Source & source,
const ExperimentalFeatureSettings & xpSettings)
{
xpSettings.require(Xp::GitHashing);
auto type = getString(source, 5);
if (type == "blob ") {
return ObjectType::Blob;
} else if (type == "tree ") {
unsigned long long size = std::stoi(getStringUntil(source, 0));
unsigned long long left = size;
sink.createDirectory(sinkPath);
while (left) {
std::string perms = getStringUntil(source, ' ');
left -= perms.size();
left -= 1;
RawMode rawMode = std::stoi(perms, 0, 8);
auto modeOpt = decodeMode(rawMode);
if (!modeOpt)
throw Error("Unknown Git permission: %o", perms);
auto mode = std::move(*modeOpt);
std::string name = getStringUntil(source, '\0');
left -= name.size();
left -= 1;
std::string hashs = getString(source, 20);
left -= 20;
Hash hash(HashAlgorithm::SHA1);
std::copy(hashs.begin(), hashs.end(), hash.hash);
hook(name, TreeEntry {
.mode = mode,
.hash = hash,
});
if (mode == Mode::Executable)
sink.isExecutable();
}
return ObjectType::Tree;
} else throw Error("input doesn't look like a Git object");
}
void parse(
FileSystemObjectSink & sink,
const Path & sinkPath,
Source & source,
bool executable,
std::function<SinkHook> hook,
const ExperimentalFeatureSettings & xpSettings)
{
xpSettings.require(Xp::GitHashing);
auto type = parseObjectType(source, xpSettings);
switch (type) {
case ObjectType::Blob:
parseBlob(sink, sinkPath, source, executable, xpSettings);
break;
case ObjectType::Tree:
parseTree(sink, sinkPath, source, hook, xpSettings);
break;
default:
assert(false);
};
}
std::optional<Mode> convertMode(SourceAccessor::Type type)
{
@ -135,7 +177,7 @@ std::optional<Mode> convertMode(SourceAccessor::Type type)
void restore(FileSystemObjectSink & sink, Source & source, std::function<RestoreHook> hook)
{
parse(sink, "", source, [&](Path name, TreeEntry entry) {
parse(sink, "", source, false, [&](Path name, TreeEntry entry) {
auto [accessor, from] = hook(entry.hash);
auto stat = accessor->lstat(from);
auto gotOpt = convertMode(stat.type);