clang 19.0.0git
FileSystemStatCache.cpp
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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
14#include "llvm/Support/Chrono.h"
15#include "llvm/Support/ErrorOr.h"
16#include "llvm/Support/Path.h"
17#include "llvm/Support/VirtualFileSystem.h"
18#include <utility>
19
20using namespace clang;
21
22void FileSystemStatCache::anchor() {}
23
24/// FileSystemStatCache::get - Get the 'stat' information for the specified
25/// path, using the cache to accelerate it if possible. This returns true if
26/// the path does not exist or false if it exists.
27///
28/// If isFile is true, then this lookup should only return success for files
29/// (not directories). If it is false this lookup should only return
30/// success for directories (not files). On a successful file lookup, the
31/// implementation can optionally fill in FileDescriptor with a valid
32/// descriptor and the client guarantees that it will close it.
33std::error_code
34FileSystemStatCache::get(StringRef Path, llvm::vfs::Status &Status,
35 bool isFile, std::unique_ptr<llvm::vfs::File> *F,
37 llvm::vfs::FileSystem &FS) {
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 = FS.openFileForRead(Path);
62
63 if (!OwnedFile) {
64 // If the open fails, our "stat" fails.
65 RetCode = OwnedFile.getError();
66 } else {
67 // Otherwise, the open succeeded. Do an fstat to get the information
68 // about the file. We'll end up returning the open file descriptor to the
69 // client to do what they please with it.
70 llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = (*OwnedFile)->status();
71 if (StatusOrErr) {
72 Status = *StatusOrErr;
73 *F = std::move(*OwnedFile);
74 } else {
75 // fstat rarely fails. If it does, claim the initial open didn't
76 // succeed.
77 *F = nullptr;
78 RetCode = StatusOrErr.getError();
79 }
80 }
81 }
82
83 // If the path doesn't exist, return failure.
84 if (RetCode)
85 return RetCode;
86
87 // If the path exists, make sure that its "directoryness" matches the clients
88 // demands.
89 if (Status.isDirectory() != isForDir) {
90 // If not, close the file if opened.
91 if (F)
92 *F = nullptr;
93 return std::make_error_code(
94 Status.isDirectory() ?
95 std::errc::is_a_directory : std::errc::not_a_directory);
96 }
97
98 return std::error_code();
99}
100
101std::error_code
102MemorizeStatCalls::getStat(StringRef Path, llvm::vfs::Status &Status,
103 bool isFile,
104 std::unique_ptr<llvm::vfs::File> *F,
105 llvm::vfs::FileSystem &FS) {
106 auto err = get(Path, Status, isFile, F, nullptr, FS);
107 if (err) {
108 // Do not cache failed stats, it is easy to construct common inconsistent
109 // situations if we do, and they are not important for PCH performance
110 // (which currently only needs the stats to construct the initial
111 // FileManager entries).
112 return err;
113 }
114
115 // Cache file 'stat' results and directories with absolutely paths.
116 if (!Status.isDirectory() || llvm::sys::path::is_absolute(Path))
117 StatCalls[Path] = Status;
118
119 return std::error_code();
120}
Defines the FileSystemStatCache interface.
Abstract interface for introducing a FileManager cache for 'stat' system calls, which is used by prec...
static std::error_code get(StringRef Path, llvm::vfs::Status &Status, bool isFile, std::unique_ptr< llvm::vfs::File > *F, FileSystemStatCache *Cache, llvm::vfs::FileSystem &FS)
Get the 'stat' information for the specified path, using the cache to accelerate it if possible.
llvm::StringMap< llvm::vfs::Status, llvm::BumpPtrAllocator > StatCalls
The set of stat() calls that have been seen.
std::error_code getStat(StringRef Path, llvm::vfs::Status &Status, bool isFile, std::unique_ptr< llvm::vfs::File > *F, llvm::vfs::FileSystem &FS) override
The type-property cache.
Definition: Type.cpp:4353
The JSON file list parser is used to communicate input to InstallAPI.