1//===- FileSystemStatCache.cpp - Caching for 'stat' calls -----------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the FileSystemStatCache interface.
10//
11//===----------------------------------------------------------------------===//
12
13#include "clang/Basic/FileSystemStatCache.h"
14#include "llvm/Support/ErrorOr.h"
15#include "llvm/Support/Path.h"
16#include "llvm/Support/VirtualFileSystem.h"
17#include <utility>
18
19using namespace clang;
20
21void FileSystemStatCache::anchor() {}
22
23/// FileSystemStatCache::get - Get the 'stat' information for the specified
24/// path, using the cache to accelerate it if possible. This returns true if
25/// the path does not exist or false if it exists.
26///
27/// If isFile is true, then this lookup should only return success for files
28/// (not directories). If it is false this lookup should only return
29/// success for directories (not files). On a successful file lookup, the
30/// implementation can optionally fill in FileDescriptor with a valid
31/// descriptor and the client guarantees that it will close it.
32std::error_code FileSystemStatCache::get(StringRef Path,
33 llvm::vfs::Status &Status, bool isFile,
34 std::unique_ptr<llvm::vfs::File> *F,
35 FileSystemStatCache *Cache,
36 llvm::vfs::FileSystem &FS,
37 bool IsText) {
38 bool isForDir = !isFile;
39 std::error_code RetCode;
40
41 // If we have a cache, use it to resolve the stat query.
42 if (Cache)
43 RetCode = Cache->getStat(Path, Status, isFile, F, FS);
44 else if (isForDir || !F) {
45 // If this is a directory or a file descriptor is not needed and we have
46 // no cache, just go to the file system.
47 llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = FS.status(Path);
48 if (!StatusOrErr) {
49 RetCode = StatusOrErr.getError();
50 } else {
51 Status = *StatusOrErr;
52 }
53 } else {
54 // Otherwise, we have to go to the filesystem. We can always just use
55 // 'stat' here, but (for files) the client is asking whether the file exists
56 // because it wants to turn around and *open* it. It is more efficient to
57 // do "open+fstat" on success than it is to do "stat+open".
58 //
59 // Because of this, check to see if the file exists with 'open'. If the
60 // open succeeds, use fstat to get the stat info.
61 auto OwnedFile =
62 IsText ? FS.openFileForRead(Path) : FS.openFileForReadBinary(Path);
63
64 if (!OwnedFile) {
65 // If the open fails, our "stat" fails.
66 RetCode = OwnedFile.getError();
67 } else {
68 // Otherwise, the open succeeded. Do an fstat to get the information
69 // about the file. We'll end up returning the open file descriptor to the
70 // client to do what they please with it.
71 llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = (*OwnedFile)->status();
72 if (StatusOrErr) {
73 Status = *StatusOrErr;
74 *F = std::move(*OwnedFile);
75 } else {
76 // fstat rarely fails. If it does, claim the initial open didn't
77 // succeed.
78 *F = nullptr;
79 RetCode = StatusOrErr.getError();
80 }
81 }
82 }
83
84 // If the path doesn't exist, return failure.
85 if (RetCode)
86 return RetCode;
87
88 // If the path exists, make sure that its "directoryness" matches the clients
89 // demands.
90 if (Status.isDirectory() != isForDir) {
91 // If not, close the file if opened.
92 if (F)
93 *F = nullptr;
94 return std::make_error_code(
95 e: Status.isDirectory() ?
96 std::errc::is_a_directory : std::errc::not_a_directory);
97 }
98
99 return std::error_code();
100}
101
102std::error_code
103MemorizeStatCalls::getStat(StringRef Path, llvm::vfs::Status &Status,
104 bool isFile,
105 std::unique_ptr<llvm::vfs::File> *F,
106 llvm::vfs::FileSystem &FS) {
107 auto err = get(Path, Status, isFile, F, Cache: nullptr, FS);
108 if (err) {
109 // Do not cache failed stats, it is easy to construct common inconsistent
110 // situations if we do, and they are not important for PCH performance
111 // (which currently only needs the stats to construct the initial
112 // FileManager entries).
113 return err;
114 }
115
116 // Cache file 'stat' results and directories with absolutely paths.
117 if (!Status.isDirectory() || llvm::sys::path::is_absolute(path: Path))
118 StatCalls[Path] = Status;
119
120 return std::error_code();
121}
122