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a5955fc682
This separates the “do these two files have the same contents?” logic from the “move or delete” logic in `moveFileIfDifferent()`, creating a useful helper function. It also ties the special-case behavior for the `destination` parameter to a flag, since we have a use where we won’t want that.
89 lines
3.3 KiB
C++
89 lines
3.3 KiB
C++
//===--- FileSystem.h - Extra helpers for manipulating files ----*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_BASIC_FILESYSTEM_H
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#define SWIFT_BASIC_FILESYSTEM_H
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include <system_error>
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namespace llvm {
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class raw_pwrite_stream;
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class Twine;
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}
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namespace llvm {
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namespace vfs {
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class FileSystem;
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}
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}
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namespace swift {
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/// Invokes \p action with a raw_ostream that refers to a temporary file,
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/// which is then renamed into place as \p outputPath when the action
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/// completes.
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///
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/// If a temporary file cannot be created for whatever reason, \p action will
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/// be invoked with a stream directly opened at \p outputPath. Otherwise, if
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/// there is already a file at \p outputPath, it will not be overwritten if
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/// the new contents are identical.
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///
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/// If the process is interrupted with a signal, any temporary file will be
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/// removed.
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///
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/// As a special case, an output path of "-" is treated as referring to
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/// stdout.
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std::error_code atomicallyWritingToFile(
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llvm::StringRef outputPath,
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llvm::function_ref<void(llvm::raw_pwrite_stream &)> action);
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/// Moves a file from \p source to \p destination, unless there is already
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/// a file at \p destination that contains the same data as \p source.
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///
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/// In the latter case, the file at \p source is deleted. If an error occurs,
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/// the file at \p source will still be present at \p source.
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std::error_code moveFileIfDifferent(const llvm::Twine &source,
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const llvm::Twine &destination);
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enum class FileDifference : uint8_t {
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/// The source and destination paths refer to the exact same file.
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IdenticalFile,
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/// The source and destination paths refer to separate files with identical
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/// contents.
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SameContents,
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/// The source and destination paths refer to separate files with different
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/// contents.
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DifferentContents
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};
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/// Compares the files at \p source and \p destination to determine if they
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/// are the exact same files, different files with the same contents, or
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/// different files with different contents. If \p allowDestinationErrors is
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/// set, file system errors relating to the \p destination file return a
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/// \c DifferentFile result, rather than an error.
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llvm::ErrorOr<FileDifference>
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areFilesDifferent(const llvm::Twine &source, const llvm::Twine &destination,
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bool allowDestinationErrors);
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namespace vfs {
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llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
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getFileOrSTDIN(llvm::vfs::FileSystem &FS,
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const llvm::Twine &Name, int64_t FileSize = -1,
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bool RequiresNullTerminator = true, bool IsVolatile = false);
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} // end namespace vfs
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} // end namespace swift
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#endif // SWIFT_BASIC_FILESYSTEM_H
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