Add a new memorybuffer class, to unify all the file reading code in the system

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36553 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/MemoryBuffer.h

@@ -0,0 +1,83 @@
+//===--- MemoryBuffer.h - Memory Buffer Interface ---------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Chris Lattner and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the MemoryBuffer interface.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_MEMORYBUFFER_H
+#define LLVM_SUPPORT_MEMORYBUFFER_H
+
+#include "llvm/Support/DataTypes.h"
+
+namespace llvm {
+
+/// MemoryBuffer - This interface provides simple read-only access to a block
+/// of memory, and provides simple methods for reading files and standard input
+/// into a memory buffer.  In addition to basic access to the characters in the
+/// file, this interface guarantees you can read one character past the end of
+/// the file, and that this character will read as '\0'.
+class MemoryBuffer {
+  const char *BufferStart; // Start of the buffer.
+  const char *BufferEnd;   // End of the buffer.
+
+  /// MustDeleteBuffer - True if we allocated this buffer.  If so, the
+  /// destructor must know the delete[] it.
+  bool MustDeleteBuffer;
+protected:
+  MemoryBuffer() : MustDeleteBuffer(false) {}
+  void init(const char *BufStart, const char *BufEnd);
+  void initCopyOf(const char *BufStart, const char *BufEnd);
+public:
+  virtual ~MemoryBuffer();
+  
+  const char *getBufferStart() const { return BufferStart; }
+  const char *getBufferEnd() const   { return BufferEnd; }
+  unsigned getBufferSize() const { return BufferEnd-BufferStart; }
+  
+  /// getBufferIdentifier - Return an identifier for this buffer, typically the
+  /// filename it was read from.
+  virtual const char *getBufferIdentifier() const {
+    return "Unknown buffer";
+  }
+
+  /// getFile - Open the specified file as a MemoryBuffer, returning a new
+  /// MemoryBuffer if successful, otherwise returning null.  If FileSize is
+  /// specified, this means that the client knows that the file exists and that
+  /// it has the specified size.
+  static MemoryBuffer *getFile(const char *FilenameStart, unsigned FnSize,
+                               int64_t FileSize = -1);
+
+  /// getMemBuffer - Open the specified memory range as a MemoryBuffer.  Note
+  /// that EndPtr[0] must be a null byte and be accessible!
+  static MemoryBuffer *getMemBuffer(const char *StartPtr, const char *EndPtr,
+                                    const char *BufferName = "");
+  
+  /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
+  /// is completely initialized to zeros.  Note that the caller should
+  /// initialize the memory allocated by this method.  The memory is owned by
+  /// the MemoryBuffer object.
+  static MemoryBuffer *getNewMemBuffer(unsigned Size,
+                                       const char *BufferName = "");
+  
+  /// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
+  /// that is not initialized.  Note that the caller should initialize the
+  /// memory allocated by this method.  The memory is owned by the MemoryBuffer
+  /// object.
+  static MemoryBuffer *getNewUninitMemBuffer(unsigned Size,
+                                             const char *BufferName = "");
+  
+  /// getSTDIN - Read all of stdin into a file buffer, and return it.  This
+  /// fails if stdin is empty.
+  static MemoryBuffer *getSTDIN();
+};
+
+} // end namespace llvm
+
+#endif