scuffed-code/icu4c/source/common/unicode/bytestream.h

// Copyright (C) 2009, International Business Machines
// Corporation and others. All Rights Reserved.
//
// Copyright 2007 Google Inc. All Rights Reserved.
// Author: sanjay@google.com (Sanjay Ghemawat)
//
// Abstract interface that consumes a sequence of bytes (ByteSink).
//
// Used so that we can write a single piece of code that can operate
// on a variety of output string types.
//
// Various implementations of this interface are provided:
//   ByteSink:
//      CheckedArrayByteSink    Write to a flat array, with bounds checking
//      StringByteSink          Write to an STL string

#ifndef __BYTESTREAM_H__
#define __BYTESTREAM_H__

/**
 * \file 
 * \brief C++ API: Interface for writing bytes, and implementation classes.
 */

#include "unicode/utypes.h"
#include "unicode/uobject.h"
#include "unicode/std_string.h"

U_NAMESPACE_BEGIN

/** 
 * A ByteSink can be filled with bytes
 * @draft ICU 4.2
 */
class U_COMMON_API ByteSink : public UMemory {
public:
  /**
   * @draft ICU 4.2
   */
  ByteSink() { }
  /**
   * @draft ICU 4.2
   */    
  virtual ~ByteSink() { }

  /**
   * Append "bytes[0,n-1]" to this.
   * @draft ICU 4.2
   */
  virtual void Append(const char* bytes, int32_t n) = 0;
 
 /**
  *  Returns a writable buffer for appending and writes the buffer's capacity to
  *  *result_capacity. Guarantees *result_capacity>=min_capacity.
  *  May return a pointer to the caller-owned scratch buffer which must have
  *  scratch_capacity>=min_capacity.
  *  The returned buffer is only valid until the next operation
  *  on this ByteSink.
  * 
  *  After writing at most *result_capacity bytes, call Append() with the
  *  pointer returned from this function and the number of bytes written.
  *  Many Append() implementations will avoid copying bytes if this function
  *  returned an internal buffer.
  * 
  *  Partial usage example:
  *   int32_t capacity;
  *   char* buffer = sink->GetAppendBuffer(..., &capacity);
  *   ... Write n bytes into buffer, with n <= capacity.
  *   sink->Append(buffer, n);
  *  In many implementations, that call to Append will avoid copying bytes.
  * 
  *  If the ByteSink allocates or reallocates an internal buffer, it should use
  *  the desired_capacity_hint if appropriate.
  *  If a caller cannot provide a reasonable guess at the desired capacity,
  *  it should pass desired_capacity_hint=0.
  * 
  *  If a non-scratch buffer is returned, the caller may only pass
  *  a prefix to it to Append().
  *  That is, it is not correct to pass an interior pointer to Append().
  * 
  *  The default implementation always returns the scratch buffer.
  *  @draft ICU 4.2
  */
  virtual char* GetAppendBuffer(int32_t min_capacity,
                                int32_t desired_capacity_hint,
                                char* scratch, int32_t scratch_capacity,
                                int32_t* result_capacity);

 /**
  *  Flush internal buffers.
  *  Some byte sinks use internal buffers or provide buffering
  *  and require calling Flush() at the end of the stream.
  *  The default implementation of Flush() does nothing.
  *  @draft ICU 4.2
  */
  virtual void Flush();

private:
  ByteSink(const ByteSink &); // copy constructor not implemented
  ByteSink &operator=(const ByteSink &); // assignment operator not implemented
};

// -------------------------------------------------------------
// Some standard implementations

/** 
 * Implementation of ByteSink that writes to a flat byte array,
 * with bounds-checking:
 * This sink will not write more than capacity bytes to outbuf.
 * If more than capacity bytes are Append()ed, then excess bytes are ignored,
 * and Overflowed() will return true.
 * Overflow does not cause a runtime error.
 * @draft ICU 4.2
 */
class U_COMMON_API CheckedArrayByteSink : public ByteSink {
public:
  /**
   * @draft ICU 4.2
   */
  CheckedArrayByteSink(char* outbuf, int32_t capacity);
  /**
   * @draft ICU 4.2
   */
  virtual void Append(const char* bytes, int32_t n);
  /**
   * @draft ICU 4.2
   */
  virtual char* GetAppendBuffer(int32_t min_capacity,
                                int32_t desired_capacity_hint,
                                char* scratch, int32_t scratch_capacity,
                                int32_t* result_capacity);
  /**
   * Returns the number of bytes actually written to the sink.
   * @draft ICU 4.2
   */
  int32_t NumberOfBytesWritten() const { return size_; }
  /**
   * Returns true if any bytes were discarded, i.e., if there was an
   * attempt to write more than 'capacity' bytes.
   * @draft ICU 4.2
   */
  UBool Overflowed() const { return overflowed_; }
private:
  char* outbuf_;
  const int32_t capacity_;
  int32_t size_;
  bool overflowed_;
  CheckedArrayByteSink(); ///< default constructor not implemented 
  CheckedArrayByteSink(const CheckedArrayByteSink &); ///< copy constructor not implemented
  CheckedArrayByteSink &operator=(const CheckedArrayByteSink &); ///< assignment operator not implemented
};

#if U_HAVE_STD_STRING

/** 
 * Implementation of ByteSink that writes to a "string".
 * @draft ICU 4.2
 */
template<typename StringClass>
class StringByteSink : public ByteSink {
 public:
  /**
   * @draft ICU 4.2
   */
  StringByteSink(StringClass* dest) : dest_(dest) { }
  /**
   * @draft ICU 4.2
   */
  virtual void Append(const char* data, int32_t n) { dest_->append(data, n); }
 private:
  StringClass* dest_;
  StringByteSink(); ///< default constructor not implemented 
  StringByteSink(const StringByteSink &); ///< copy constructor not implemented
  StringByteSink &operator=(const StringByteSink &); ///< assignment operator not implemented
};

#endif

U_NAMESPACE_END

#endif  // __BYTESTREAM_H__