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/raw_ostream.h"
20
#include "llvm/System/Signals.h"
24
Quiet("quiet", cl::desc("Don't print unnecessary status information"),
27
static cl::opt<std::string>
28
InputFilename("input-file", cl::desc("Input file (defaults to stdin)"),
29
cl::init("-"), cl::value_desc("filename"));
31
static cl::opt<std::string>
32
OutputFilename(cl::Positional, cl::desc("<output-file>"), cl::Required);
34
int main(int argc, char **argv) {
35
sys::PrintStackTraceOnErrorSignal();
36
PrettyStackTraceProgram X(argc, argv);
37
cl::ParseCommandLineOptions(argc, argv);
39
// Get the input data.
42
MemoryBuffer::getFileOrSTDIN(InputFilename.c_str(), &ErrorStr);
44
errs() << argv[0] << ": error: Unable to get input '"
45
<< InputFilename << "': " << ErrorStr << '\n';
49
// Get the output data.
50
MemoryBuffer *Out = MemoryBuffer::getFile(OutputFilename.c_str(), &ErrorStr);
52
// If the output exists and the contents match, we are done.
53
if (Out && In->getBufferSize() == Out->getBufferSize() &&
54
memcmp(In->getBufferStart(), Out->getBufferStart(),
55
Out->getBufferSize()) == 0) {
57
outs() << argv[0] << ": Not updating '" << OutputFilename
58
<< "', contents match input.\n";
64
// Otherwise, overwrite the output.
66
outs() << argv[0] << ": Updating '" << OutputFilename
67
<< "', contents changed.\n";
68
raw_fd_ostream OutStream(OutputFilename.c_str(), ErrorStr,
69
raw_fd_ostream::F_Binary);
70
if (!ErrorStr.empty()) {
71
errs() << argv[0] << ": Unable to write output '"
72
<< OutputFilename << "': " << ErrorStr << '\n';
76
OutStream.write(In->getBufferStart(), In->getBufferSize());
79
if (OutStream.has_error()) {
80
errs() << argv[0] << ": Could not open output file '"
81
<< OutputFilename << "': " << ErrorStr << '\n';