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//===- FileUpdate.cpp - Conditionally update a file -----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// FileUpdate is a utility for conditionally updating a file from its input
// based on whether the input differs from the output. It is used to avoid
// unnecessary modifications in a build system.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/PrettyStackTrace.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/System/Signals.h"
using namespace llvm;
static cl::opt<bool>
Quiet("quiet", cl::desc("Don't print unnecessary status information"),
cl::init(false));
static cl::opt<std::string>
InputFilename("input-file", cl::desc("Input file (defaults to stdin)"),
cl::init("-"), cl::value_desc("filename"));
static cl::opt<std::string>
OutputFilename(cl::Positional, cl::desc("<output-file>"), cl::Required);
int main(int argc, char **argv) {
sys::PrintStackTraceOnErrorSignal();
PrettyStackTraceProgram X(argc, argv);
cl::ParseCommandLineOptions(argc, argv);
if (OutputFilename == "-") {
errs() << argv[0] << ": error: Can't update standard output\n";
return 1;
}
// Get the input data.
std::string ErrorStr;
MemoryBuffer *In =
MemoryBuffer::getFileOrSTDIN(InputFilename.c_str(), &ErrorStr);
if (In == 0) {
errs() << argv[0] << ": error: Unable to get input '"
<< InputFilename << "': " << ErrorStr << '\n';
return 1;
}
// Get the output data.
MemoryBuffer *Out = MemoryBuffer::getFile(OutputFilename.c_str(), &ErrorStr);
// If the output exists and the contents match, we are done.
if (Out && In->getBufferSize() == Out->getBufferSize() &&
memcmp(In->getBufferStart(), Out->getBufferStart(),
Out->getBufferSize()) == 0) {
if (!Quiet)
errs() << argv[0] << ": Not updating '" << OutputFilename
<< "', contents match input.\n";
return 0;
}
delete Out;
// Otherwise, overwrite the output.
if (!Quiet)
errs() << argv[0] << ": Updating '" << OutputFilename
<< "', contents changed.\n";
tool_output_file OutStream(OutputFilename.c_str(), ErrorStr,
raw_fd_ostream::F_Binary);
if (!ErrorStr.empty()) {
errs() << argv[0] << ": Unable to write output '"
<< OutputFilename << "': " << ErrorStr << '\n';
return 1;
}
OutStream.os().write(In->getBufferStart(), In->getBufferSize());
// Declare success.
OutStream.keep();
return 0;
}
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