Initial commit of new FileOutputBuffer support class.

Since the llvm::sys::fs::map_file_pages() support function it relies on
is not yet implemented on Windows, the unit tests for FileOutputBuffer 
are currently conditionalized to run only on unix.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161099 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 97 insertions, 0 deletions

diff --git a/include/llvm/Support/FileOutputBuffer.h b/include/llvm/Support/FileOutputBuffer.h
new file mode 100644
index 0000000..0f07164
--- /dev/null
+++ b/include/llvm/Support/FileOutputBuffer.h
@@ -0,0 +1,97 @@
+//=== FileOutputBuffer.h - File Output Buffer -------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Utility for creating a in-memory buffer that will be written to a file.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_FILEOUTPUTBUFFER_H
+#define LLVM_SUPPORT_FILEOUTPUTBUFFER_H
+
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/DataTypes.h"
+
+namespace llvm {
+
+class error_code;
+template<class T> class OwningPtr;
+
+/// FileOutputBuffer - This interface provides simple way to create an in-memory
+/// buffer which will be written to a file. During the lifetime of these 
+/// objects, the content or existence of the specified file is undefined. That
+/// is, creating an OutputBuffer for a file may immediately remove the file.
+/// If the FileOutputBuffer is committed, the target file's content will become 
+/// the buffer content at the time of the commit.  If the FileOutputBuffer is  
+/// not committed, the file will be deleted in the FileOutputBuffer destructor.
+class FileOutputBuffer {
+public:
+
+  enum  {
+    F_executable = 1  /// set the 'x' bit on the resulting file
+  }; 
+
+  /// Factory method to create an OutputBuffer object which manages a read/write
+  /// buffer of the specified size. When committed, the buffer will be written
+  /// to the file at the specified path.  
+  static error_code create(StringRef FilePath, size_t Size, 
+                           OwningPtr<FileOutputBuffer> &Result, 
+                           unsigned Flags=0);
+  
+
+  /// Returns a pointer to the start of the buffer.
+  uint8_t *getBufferStart() const {
+    return BufferStart;
+  }
+  
+  /// Returns a pointer to the end of the buffer.
+  uint8_t *getBufferEnd() const {
+    return BufferEnd;
+  }
+  
+  /// Returns size of the buffer.
+  size_t getBufferSize() const {
+    return BufferEnd - BufferStart;
+  }
+  
+  /// Returns path where file will show up if buffer is committed.
+  StringRef getPath() const {
+    return FinalPath;
+  }
+    
+  /// Flushes the content of the buffer to its file and deallocates the 
+  /// buffer.  If commit() is not called before this object's destructor
+  /// is called, the file is deleted in the destructor. The optional parameter
+  /// is used if it turns out you want the file size to be smaller than
+  /// initially requested.
+  error_code commit(int64_t NewSmallerSize = -1);
+  
+  /// If this object was previously committed, the destructor just deletes
+  /// this object.  If this object was not committed, the destructor
+  /// deallocates the buffer and the target file is never written.
+  ~FileOutputBuffer();
+
+  
+protected:
+  FileOutputBuffer(const FileOutputBuffer &); // DO NOT IMPLEMENT
+  FileOutputBuffer &operator=(const FileOutputBuffer &); // DO NOT IMPLEMENT
+  FileOutputBuffer(uint8_t *Start, uint8_t *End, 
+                    StringRef Path, StringRef TempPath);
+    
+  uint8_t            *BufferStart;
+  uint8_t            *BufferEnd;
+  SmallString<128>    FinalPath;
+  SmallString<128>    TempPath;
+};
+
+
+
+} // end namespace llvm
+
+#endif