add a new raw_ostream class which is an extremely high performance ostream that

can *only* output data (no seeking, reading, etc).  This is adapted from the
clang "-E outputter", and is roughly 10% faster than stdio on darwin and 30%
(or more) faster than std::ostream.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54855 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/raw_ostream.h

@@ -0,0 +1,170 @@
+//===--- raw_ostream.h - Raw output stream ---------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines the raw_ostream class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_RAW_OSTREAM_H
+#define LLVM_SUPPORT_RAW_OSTREAM_H
+
+#include <string>
+
+namespace llvm {
+
+/// raw_ostream - This class implements an extremely fast bulk output stream
+/// that can *only* output to a stream.  It does not support seeking, reopening,
+/// rewinding, line buffered disciplines etc. It is a simple buffer that outputs
+/// a chunk at a time.
+class raw_ostream {
+protected:
+  char *OutBufStart, *OutBufEnd, *OutBufCur;
+public:
+  raw_ostream() {
+    // Start out ready to flush.
+    OutBufStart = OutBufEnd = OutBufCur = 0;
+  }
+  virtual ~raw_ostream() {}
+  
+  //===--------------------------------------------------------------------===//
+  // Configuration Interface
+  //===--------------------------------------------------------------------===//
+  
+  /// SetBufferSize - Set the internal buffer size to the specified amount
+  /// instead of the default.
+  void SetBufferSize(unsigned Size) {
+    assert(Size >= 64 &&
+           "Buffer size must be somewhat large for invariants to hold");
+    flush();
+    
+    delete [] OutBufStart;
+    OutBufStart = new char[Size];
+    OutBufEnd = OutBufStart+Size;
+    OutBufCur = OutBufStart;
+  }
+  
+  //===--------------------------------------------------------------------===//
+  // Data Output Interface
+  //===--------------------------------------------------------------------===//
+  
+  void flush() {
+    if (OutBufCur != OutBufStart)
+      flush_impl();
+  }
+  
+  raw_ostream &operator<<(char C) {
+    if (OutBufCur >= OutBufEnd)
+      flush_impl();
+    *OutBufCur++ = C;
+    return *this;
+  }
+  
+  raw_ostream &operator<<(const char *Str) {
+    return OutputData(Str, strlen(Str));
+  }
+  
+  raw_ostream &OutputData(const char *Ptr, unsigned Size) {
+    if (OutBufCur+Size > OutBufEnd)
+      flush_impl();
+    
+    // Handle short strings specially, memcpy isn't very good at very short
+    // strings.
+    switch (Size) {
+//    case 4: OutBufCur[3] = Ptr[3]; // FALL THROUGH
+    case 3: OutBufCur[2] = Ptr[2]; // FALL THROUGH
+    case 2: OutBufCur[1] = Ptr[1]; // FALL THROUGH
+    case 1: OutBufCur[0] = Ptr[0]; // FALL THROUGH
+    case 0: break;
+    default:
+      // Normally the string to emit is shorter than the buffer.
+      if (Size <= unsigned(OutBufEnd-OutBufStart)) {
+        memcpy(OutBufCur, Ptr, Size);
+        break;
+      }
+
+      // If emitting a string larger than our buffer, emit in chunks.  In this
+      // case we know that we just flushed the buffer.
+      while (Size) {
+        unsigned NumToEmit = OutBufEnd-OutBufStart;
+        if (Size < NumToEmit) NumToEmit = Size;
+        assert(OutBufCur == OutBufStart);
+        memcpy(OutBufStart, Ptr, NumToEmit);
+        Ptr += NumToEmit;
+        OutBufCur = OutBufStart + NumToEmit;
+        flush_impl();
+      }
+      break;
+    }
+    OutBufCur += Size;
+    return *this;
+  }
+  
+  //===--------------------------------------------------------------------===//
+  // Subclass Interface
+  //===--------------------------------------------------------------------===//
+
+protected:
+  
+  /// flush_impl - The is the piece of the class that is implemented by
+  /// subclasses.  This outputs the currently buffered data and resets the
+  /// buffer to empty.
+  virtual void flush_impl() = 0;
+  
+  /// HandleFlush - A stream's implementation of flush should call this after
+  /// emitting the bytes to the data sink.
+  void HandleFlush() {
+    if (OutBufStart == 0)
+      SetBufferSize(4096);
+    OutBufCur = OutBufStart;
+  }
+private:
+  // An out of line virtual method to provide a home for the class vtable.
+  virtual void handle();
+};
+  
+/// raw_fd_ostream - A raw_ostream that writes to a file descriptor.
+///
+class raw_fd_ostream : public raw_ostream {
+  int FD;
+  bool ShouldClose;
+public:
+  /// raw_fd_ostream - Open the specified file for writing.  If an error occurs,
+  /// information about the error is put into ErrorInfo, and the stream should
+  /// be immediately destroyed.
+  raw_fd_ostream(const char *Filename, std::string &ErrorInfo);
+  
+  /// raw_fd_ostream ctor - FD is the file descriptor that this writes to.  If
+  /// ShouldClose is true, this closes the file when 
+  raw_fd_ostream(int fd, bool shouldClose) : FD(fd), ShouldClose(shouldClose) {}
+  
+  ~raw_fd_ostream();
+    
+  /// flush_impl - The is the piece of the class that is implemented by
+  /// subclasses.  This outputs the currently buffered data and resets the
+  /// buffer to empty.
+  virtual void flush_impl();
+};
+  
+class raw_stdout_ostream : public raw_fd_ostream {
+  // An out of line virtual method to provide a home for the class vtable.
+  virtual void handle();
+public:
+  raw_stdout_ostream();
+};
+
+class raw_stderr_ostream : public raw_fd_ostream {
+  // An out of line virtual method to provide a home for the class vtable.
+  virtual void handle();
+public:
+  raw_stderr_ostream();
+};
+  
+} // end llvm namespace
+
+#endif

lib/Support/raw_ostream.cpp

@@ -0,0 +1,64 @@
+//===--- raw_ostream.cpp - Implement the raw_ostream classes --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This implements support for bulk buffered stream output.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+#if !defined(_MSC_VER)
+#include <fcntl.h>
+#else
+#include <io.h>
+#define open(x,y,z) _open(x,y)
+#define write(fd, start, size) _write(fd, start, size)
+#define close(fd) _close(fd)
+#endif
+
+// An out of line virtual method to provide a home for the class vtable.
+void raw_ostream::handle() {}
+
+//===----------------------------------------------------------------------===//
+//  raw_fd_ostream
+//===----------------------------------------------------------------------===//
+
+/// raw_fd_ostream - Open the specified file for writing.  If an error occurs,
+/// information about the error is put into ErrorInfo, and the stream should
+/// be immediately destroyed.
+raw_fd_ostream::raw_fd_ostream(const char *Filename, std::string &ErrorInfo) {
+  FD = open(Filename, O_WRONLY|O_CREAT|O_TRUNC, 0644);
+  if (FD < 0) {
+    ErrorInfo = "Error opening output file '" + std::string(Filename) + "'";
+    ShouldClose = false;
+  } else {
+    ShouldClose = true;
+  }
+}
+
+raw_fd_ostream::~raw_fd_ostream() {
+  flush();
+  if (ShouldClose)
+    close(FD);
+}
+
+void raw_fd_ostream::flush_impl() {
+  if (OutBufCur-OutBufStart)
+    write(FD, OutBufStart, OutBufCur-OutBufStart);
+  HandleFlush();
+}
+
+
+raw_stdout_ostream::raw_stdout_ostream():raw_fd_ostream(STDOUT_FILENO, false) {}
+raw_stderr_ostream::raw_stderr_ostream():raw_fd_ostream(STDERR_FILENO, false) {}
+
+// An out of line virtual method to provide a home for the class vtable.
+void raw_stdout_ostream::handle() {}
+void raw_stderr_ostream::handle() {}