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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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72
src/libutil/fs-sink.cc
View file

@ -19,16 +19,12 @@ void copyRecursive(
case SourceAccessor::tRegular:
{
sink.createRegularFile(to);
if (stat.isExecutable)
sink.isExecutable();
LambdaSink sink2 {
[&](auto d) {
sink.receiveContents(d);
}
};
accessor.readFile(from, sink2, [&](uint64_t size) {
sink.preallocateContents(size);
sink.createRegularFile(to, [&](CreateRegularFileSink & crf) {
if (stat.isExecutable)
crf.isExecutable();
accessor.readFile(from, crf, [&](uint64_t size) {
crf.preallocateContents(size);
});
});
break;
}
@ -71,20 +67,24 @@ void RestoreSink::createDirectory(const Path & path)
throw SysError("creating directory '%1%'", p);
};
void RestoreSink::createRegularFile(const Path & path)
struct RestoreRegularFile : CreateRegularFileSink {
AutoCloseFD fd;
void operator () (std::string_view data) override;
void isExecutable() override;
void preallocateContents(uint64_t size) override;
};
void RestoreSink::createRegularFile(const Path & path, std::function<void(CreateRegularFileSink &)> func)
{
Path p = dstPath + path;
fd = open(p.c_str(), O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, 0666);
if (!fd) throw SysError("creating file '%1%'", p);
RestoreRegularFile crf;
crf.fd = open(p.c_str(), O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, 0666);
if (!crf.fd) throw SysError("creating file '%1%'", p);
func(crf);
}
void RestoreSink::closeRegularFile()
{
/* Call close explicitly to make sure the error is checked */
fd.close();
}
void RestoreSink::isExecutable()
void RestoreRegularFile::isExecutable()
{
struct stat st;
if (fstat(fd.get(), &st) == -1)
@ -93,7 +93,7 @@ void RestoreSink::isExecutable()
throw SysError("fchmod");
}
void RestoreSink::preallocateContents(uint64_t len)
void RestoreRegularFile::preallocateContents(uint64_t len)
{
if (!restoreSinkSettings.preallocateContents)
return;
@ -111,7 +111,7 @@ void RestoreSink::preallocateContents(uint64_t len)
#endif
}
void RestoreSink::receiveContents(std::string_view data)
void RestoreRegularFile::operator () (std::string_view data)
{
writeFull(fd.get(), data);
}
@ -122,4 +122,32 @@ void RestoreSink::createSymlink(const Path & path, const std::string & target)
nix::createSymlink(target, p);
}
void RegularFileSink::createRegularFile(const Path & path, std::function<void(CreateRegularFileSink &)> func)
{
struct CRF : CreateRegularFileSink {
RegularFileSink & back;
CRF(RegularFileSink & back) : back(back) {}
void operator () (std::string_view data) override
{
back.sink(data);
}
void isExecutable() override {}
} crf { *this };
func(crf);
}
void NullFileSystemObjectSink::createRegularFile(const Path & path, std::function<void(CreateRegularFileSink &)> func)
{
struct : CreateRegularFileSink {
void operator () (std::string_view data) override {}
void isExecutable() override {}
} crf;
// Even though `NullFileSystemObjectSink` doesn't do anything, it's important
// that we call the function, to e.g. advance the parser using this
// sink.
func(crf);
}
}