Add FileUpdate tool, conditionally updates its output based on its input.
- Gratuitous and unused, but possibly useful one day.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77954 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/FileUpdate/FileUpdate.cpp b/utils/FileUpdate/FileUpdate.cpp
new file mode 100644
index 0000000..8d5d6b1
--- /dev/null
+++ b/utils/FileUpdate/FileUpdate.cpp
@@ -0,0 +1,86 @@
+//===- 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/raw_ostream.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);
+
+ // 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)
+ outs() << argv[0] << ": Not updating '" << OutputFilename
+ << "', contents match input.\n";
+ return 0;
+ }
+
+ delete Out;
+
+ // Otherwise, overwrite the output.
+ if (!Quiet)
+ outs() << argv[0] << ": Updating '" << OutputFilename
+ << "', contents changed.\n";
+ raw_fd_ostream OutStream(OutputFilename.c_str(), /*Binary=*/true,
+ /*Force=*/true, ErrorStr);
+ if (!ErrorStr.empty()) {
+ errs() << argv[0] << ": Unable to write output '"
+ << OutputFilename << "': " << ErrorStr << '\n';
+ return 1;
+ }
+
+ OutStream.write(In->getBufferStart(), In->getBufferSize());
+ OutStream.close();
+
+ if (OutStream.has_error()) {
+ errs() << argv[0] << ": Could not open output file '"
+ << OutputFilename << "': " << ErrorStr << '\n';
+ return 1;
+ }
+
+ return 0;
+}