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gitlstree.cc
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gitlstree.cc
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/*
* A prototype tool to mount git filesystem by parsing output of 'git
* ls-tree -l -r REVISION'.
`git-ls-tree -l -r` output contains lines like:
100644 blob f313668af32ea3447a594ae1e7d8ac9841fbae7b sound/README
and that should be mostly enough to obtain information to create a
mount-able filesystem.
*/
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <unordered_map>
#include <iostream>
#include <memory>
#include <vector>
#define FUSE_USE_VERSION 32
#include "concurrency_limit.h"
#include "git_cat_file.h"
#include "gitlstree.h"
#include "ostream_vector.h"
#include "scoped_timer.h"
#include "strutil.h"
using std::lock_guard;
using std::make_unique;
using std::mutex;
using std::string;
using std::unique_ptr;
using std::unordered_map;
using std::vector;
namespace gitlstree {
namespace {
class GitHeadHandler : public directory_container::File {
public:
GitHeadHandler(const std::string& rev, GitTree* parent)
: rev_(rev + "\n"), // Has a terminating newline.
parent_(parent) {}
virtual ~GitHeadHandler() {}
virtual int Getattr(struct stat* stbuf) override {
stbuf->st_uid = getuid();
stbuf->st_gid = getgid();
stbuf->st_mode = S_IFREG | S_IRUSR | S_IWUSR;
stbuf->st_size = rev_.size();
stbuf->st_nlink = 1;
return 0;
}
virtual ssize_t Read(char* target, size_t size, off_t offset) override {
if (offset != 0) {
return -EIO;
}
if (size <= rev_.size()) {
return -EIO;
}
memcpy(target, rev_.c_str(), rev_.size() + 1);
return rev_.size() + 1;
}
virtual int Open() override { return 0; }
virtual int Release() override { return 0; }
private:
std::string rev_;
GitTree* parent_;
DISALLOW_COPY_AND_ASSIGN(GitHeadHandler);
};
} // namespace
int FileElement::Getattr(struct stat* stbuf) {
stbuf->st_uid = getuid();
stbuf->st_gid = getgid();
if (attribute_ == S_IFLNK) {
// symbolic link.
static_assert(S_IFLNK == 0120000, "symlink stat attribute wrong.");
stbuf->st_mode = S_IFLNK | 0644;
} else {
stbuf->st_mode = S_IFREG | attribute_;
}
stbuf->st_size = size_;
stbuf->st_nlink = 1;
return 0;
}
// Maybe run remote command if ssh spec is available.
string GitTree::RunGitCommand(const vector<string>& commands, int* exit_code,
const std::string& log_tag) {
constexpr bool verbose = false;
if (verbose) {
std::cout << "Command: " << commands << std::endl;
}
scoped_timer::ScopedTimer time(log_tag);
if (!ssh_.empty()) {
string command;
for (const auto& s : commands) {
command += s + " ";
}
ScopedConcurrencyLimit l(command);
return PopenAndReadOrDie2(
{"ssh", ssh_, string("cd ") + gitdir_ + " && " + command}, nullptr,
exit_code);
} else {
return PopenAndReadOrDie2(commands, &gitdir_, exit_code);
}
}
bool GitTree::LoadDirectory(
const string& ref, directory_container::DirectoryContainer* container) {
int exit_code;
int exit_code_revparse;
string hash{RunGitCommand({"git", "rev-parse", ref}, &exit_code_revparse,
"rev-parse")};
// truncate the final newline.
hash.resize(hash.size() - 1);
if (exit_code_revparse != 0) {
std::cerr << "Could not resolve " << ref << std::endl;
return false;
}
string git_ls_tree(RunGitCommand({"git", "ls-tree", "-l", "-r", hash},
&exit_code, "lstree"));
if (exit_code != 0) {
// Failed to load directory.
return false;
}
const vector<string> lines = SplitStringUsing(git_ls_tree, '\n', true);
for (const auto& line : lines) {
const vector<string> elements = SplitStringUsing(line, ' ', true);
// TODO split with tab too.
// TODO
if (elements.size() == 4) {
const vector<string> elements3 =
SplitStringUsing(elements[3], '\t', false);
assert(elements3.size() == 2);
const string& file_path = elements3[1];
const string& sha1 = elements[2];
mode_t attribute = strtol(elements[0].c_str(), nullptr, 8);
size_t size = atoi(elements3[0].c_str());
assert(file_path[0] != '/'); // git ls-tree do not start with /.
container->add(string("/") + file_path,
make_unique<FileElement>(attribute, sha1, size, this));
}
}
container->add("/.status", make_unique<scoped_timer::StatusHandler>());
container->add("/.git/HEAD", make_unique<GitHeadHandler>(hash, this));
return true;
}
/* static */
std::unique_ptr<GitTree> GitTree::NewGitTree(
const string& my_gitdir, const string& hash, const string& maybe_ssh,
const string& cached_dir,
directory_container::DirectoryContainer* container) {
unique_ptr<GitTree> g{new GitTree(my_gitdir, maybe_ssh, cached_dir)};
if (g->LoadDirectory(hash, container)) {
return g;
} else {
return nullptr;
}
}
GitTree::GitTree(const string& my_gitdir, const string& maybe_ssh,
const string& cached_dir)
: gitdir_(my_gitdir),
ssh_(maybe_ssh),
cache_(cached_dir),
git_cat_file_(
maybe_ssh.empty()
? std::make_unique<GitCatFile::GitCatFileProcess>(&my_gitdir)
: std::make_unique<GitCatFile::GitCatFileProcess>(my_gitdir,
ssh_)) {
cache_.Gc();
}
GitTree::~GitTree() {}
FileElement::FileElement(int attribute, const string& sha1, int size,
GitTree* parent)
: attribute_(attribute), sha1_(sha1), size_(size), parent_(parent) {}
int FileElement::maybe_cat_file_locked() {
if (!memory_) {
memory_ = parent_->cache().get(sha1_, [this](string* ret) -> bool {
try {
*ret = parent_->git_cat_file()->Request(sha1_);
} catch (GitCatFile::GitCatFileProcess::ObjectNotFoundException& e) {
// If the object was not found, caching the result is not useful.
abort();
return false;
}
return true;
});
if (!memory_) {
// If still failed, something failed in the process.
abort();
return -EIO;
}
}
assert(!!memory_);
return 0;
}
int FileElement::Open() {
lock_guard<mutex> l(buf_mutex_);
return maybe_cat_file_locked();
}
ssize_t FileElement::Read(char* target, size_t size, off_t offset) {
lock_guard<mutex> l(buf_mutex_);
if (!memory_) {
// Dump some debug information.
std::cout << "file: " << sha1_ << std::endl;
parent_->cache().dump();
// Work around where RELEASE gets called before READ.
maybe_cat_file_locked();
}
assert(!!memory_); // This may happen if caching is broken.
if (offset < static_cast<off_t>(memory_->size())) {
if (offset + size > memory_->size()) size = memory_->size() - offset;
memcpy(target, memory_->memory_charp() + offset, size);
} else
size = 0;
return size;
}
ssize_t FileElement::Readlink(char* target, size_t size) {
lock_guard<mutex> l(buf_mutex_);
int e = maybe_cat_file_locked();
if (e != 0) return e;
if (size > memory_->size()) {
size = memory_->size();
target[size] = 0;
} else {
// TODO: is this an error condition that we can't fit in the final 0 ?
}
memcpy(target, memory_->memory_charp(), size);
return 0;
}
void FileElement::GetHash(char* hash) const { memcpy(hash, sha1_.data(), 40); }
int FileElement::Release() {
lock_guard<mutex> l(buf_mutex_);
// When your file name based map is destroyed that is not a good timing to
// destroy the cache.
// TODO add refcounting.
// parent_->cache().release(sha1_, memory_);
memory_ = nullptr;
return 0;
}
} // namespace gitlstree