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91 lines
2.9 KiB
C++
91 lines
2.9 KiB
C++
//===--- FileSystem.cpp - Extra helpers for manipulating files ------------===//
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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 - 2016 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 http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#include "swift/Basic/FileSystem.h"
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#include "llvm/Support/FileSystem.h"
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#include "llvm/Support/Process.h"
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using namespace swift;
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namespace {
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class OpenFileRAII {
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static const int INVALID_FD = -1;
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public:
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int fd = INVALID_FD;
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~OpenFileRAII() {
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if (fd != INVALID_FD)
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llvm::sys::Process::SafelyCloseFileDescriptor(fd);
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}
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};
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}
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std::error_code swift::moveFileIfDifferent(const llvm::Twine &source,
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const llvm::Twine &destination) {
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namespace fs = llvm::sys::fs;
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// First check for a self-move.
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if (fs::equivalent(source, destination))
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return std::error_code();
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OpenFileRAII sourceFile;
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fs::file_status sourceStatus;
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if (std::error_code error = fs::openFileForRead(source, sourceFile.fd)) {
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// If we can't open the source file, fail.
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return error;
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}
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if (std::error_code error = fs::status(sourceFile.fd, sourceStatus)) {
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// If we can't stat the source file, fail.
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return error;
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}
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OpenFileRAII destFile;
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fs::file_status destStatus;
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bool couldReadDest = !fs::openFileForRead(destination, destFile.fd);
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if (couldReadDest)
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couldReadDest = !fs::status(destFile.fd, destStatus);
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// If we could read the destination file, and it matches the source file in
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// size, they may be the same. Do an actual comparison of the contents.
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if (couldReadDest && sourceStatus.getSize() == destStatus.getSize()) {
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uint64_t size = sourceStatus.getSize();
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bool same = false;
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if (size == 0) {
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same = true;
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} else {
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std::error_code sourceRegionErr;
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fs::mapped_file_region sourceRegion(sourceFile.fd,
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fs::mapped_file_region::readonly,
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size, 0, sourceRegionErr);
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if (sourceRegionErr)
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return sourceRegionErr;
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std::error_code destRegionErr;
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fs::mapped_file_region destRegion(destFile.fd,
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fs::mapped_file_region::readonly,
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size, 0, destRegionErr);
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if (!destRegionErr) {
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same = (0 == memcmp(sourceRegion.const_data(), destRegion.const_data(),
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size));
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}
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}
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// If the file contents are the same, we are done. Just delete the source.
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if (same)
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return fs::remove(source);
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}
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// If we get here, we weren't able to prove that the files are the same.
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return fs::rename(source, destination);
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}
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