1 //===- FileUpdate.cpp - Conditionally update a file -----------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // FileUpdate is a utility for conditionally updating a file from its input
11 // based on whether the input differs from the output. It is used to avoid
12 // unnecessary modifications in a build system.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/Support/CommandLine.h"
17 #include "llvm/Support/MemoryBuffer.h"
18 #include "llvm/Support/PrettyStackTrace.h"
19 #include "llvm/Support/ToolOutputFile.h"
20 #include "llvm/Support/Signals.h"
21 #include "llvm/Support/system_error.h"
25 Quiet("quiet", cl::desc("Don't print unnecessary status information"),
28 static cl::opt<std::string>
29 InputFilename("input-file", cl::desc("Input file (defaults to stdin)"),
30 cl::init("-"), cl::value_desc("filename"));
32 static cl::opt<std::string>
33 OutputFilename(cl::Positional, cl::desc("<output-file>"), cl::Required);
35 int main(int argc, char **argv) {
36 sys::PrintStackTraceOnErrorSignal();
37 PrettyStackTraceProgram X(argc, argv);
38 cl::ParseCommandLineOptions(argc, argv);
40 if (OutputFilename == "-") {
41 errs() << argv[0] << ": error: Can't update standard output\n";
45 // Get the input data.
48 MemoryBuffer::getFileOrSTDIN(InputFilename.c_str(), ec);
50 errs() << argv[0] << ": error: Unable to get input '"
51 << InputFilename << "': " << ec.message() << '\n';
55 // Get the output data.
56 MemoryBuffer *Out = MemoryBuffer::getFile(OutputFilename.c_str(), ec);
58 // If the output exists and the contents match, we are done.
59 if (Out && In->getBufferSize() == Out->getBufferSize() &&
60 memcmp(In->getBufferStart(), Out->getBufferStart(),
61 Out->getBufferSize()) == 0) {
63 errs() << argv[0] << ": Not updating '" << OutputFilename
64 << "', contents match input.\n";
70 // Otherwise, overwrite the output.
72 errs() << argv[0] << ": Updating '" << OutputFilename
73 << "', contents changed.\n";
75 tool_output_file OutStream(OutputFilename.c_str(), ErrorStr,
76 raw_fd_ostream::F_Binary);
77 if (!ErrorStr.empty()) {
78 errs() << argv[0] << ": Unable to write output '"
79 << OutputFilename << "': " << ErrorStr << '\n';
83 OutStream.os().write(In->getBufferStart(), In->getBufferSize());