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 // Copyright (C) 2009-2012, 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

 // This code is a contribution of Google code, and the style used here is

 // a compromise between the original Google code and the ICU coding guidelines.

 // For example, data types are ICU-ified (size_t,int->int32_t),

 // and API comments doxygen-ified, but function names and behavior are

 // as in the original, if possible.

 // Assertion-style error handling, not available in ICU, was changed to

 // parameter "pinning" similar to UnicodeString.

 //

 // In addition, this is only a partial port of the original Google code,

 // limited to what was needed so far. The (nearly) complete original code

 // is in the ICU svn repository at icuhtml/trunk/design/strings/contrib

 // (see ICU ticket 6765, r25517).

 #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.

  * @stable ICU 4.2

  */

 class U_COMMON_API ByteSink : public UMemory {

 public:

   /**

    * Default constructor.

    * @stable ICU 4.2

    */

   ByteSink() { }

   /**

    * Virtual destructor.

    * @stable ICU 4.2

    */

   virtual ~ByteSink();

   /**

    * Append "bytes[0,n-1]" to this.

    * @param bytes the pointer to the bytes

    * @param n the number of bytes; must be non-negative

    * @stable 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.

    *

    * @param min_capacity required minimum capacity of the returned buffer;

    *                     must be non-negative

    * @param desired_capacity_hint desired capacity of the returned buffer;

    *                              must be non-negative

    * @param scratch default caller-owned buffer

    * @param scratch_capacity capacity of the scratch buffer

    * @param result_capacity pointer to an integer which will be set to the

    *                        capacity of the returned buffer

    * @return a buffer with *result_capacity>=min_capacity

    * @stable 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 ByteSink should be ready for further Append() calls after Flush().

    * The default implementation of Flush() does nothing.

    * @stable 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.

  * @stable ICU 4.2

  */

 class U_COMMON_API CheckedArrayByteSink : public ByteSink {

 public:

   /**

    * Constructs a ByteSink that will write to outbuf[0..capacity-1].

    * @param outbuf buffer to write to

    * @param capacity size of the buffer

    * @stable ICU 4.2

    */

   CheckedArrayByteSink(char* outbuf, int32_t capacity);

   /**

    * Destructor.

    * @stable ICU 4.2

    */

   virtual ~CheckedArrayByteSink();

   /**

    * Returns the sink to its original state, without modifying the buffer.

    * Useful for reusing both the buffer and the sink for multiple streams.

    * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0

    * and Overflowed()=FALSE.

    * @return *this

    * @stable ICU 4.6

    */

   virtual CheckedArrayByteSink& Reset();

   /**

    * Append "bytes[0,n-1]" to this.

    * @param bytes the pointer to the bytes

    * @param n the number of bytes; must be non-negative

    * @stable ICU 4.2

    */

   virtual void Append(const char* bytes, int32_t n);

   /**

    * Returns a writable buffer for appending and writes the buffer's capacity to

    * *result_capacity. For details see the base class documentation.

    * @param min_capacity required minimum capacity of the returned buffer;

    *                     must be non-negative

    * @param desired_capacity_hint desired capacity of the returned buffer;

    *                              must be non-negative

    * @param scratch default caller-owned buffer

    * @param scratch_capacity capacity of the scratch buffer

    * @param result_capacity pointer to an integer which will be set to the

    *                        capacity of the returned buffer

    * @return a buffer with *result_capacity>=min_capacity

    * @stable 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.

    * @return number of bytes written to the buffer

    * @stable 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.

    * @return TRUE if more than 'capacity' bytes were Append()ed

    * @stable ICU 4.2

    */

   UBool Overflowed() const { return overflowed_; }

   /**

    * Returns the number of bytes appended to the sink.

    * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten()

    * else they return the same number.

    * @return number of bytes written to the buffer

    * @stable ICU 4.6

    */

   int32_t NumberOfBytesAppended() const { return appended_; }

 private:

   char* outbuf_;

   const int32_t capacity_;

   int32_t size_;

   int32_t appended_;

   UBool 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".

  * The StringClass is usually instantiated with a std::string.

  * @stable ICU 4.2

  */

 template<typename StringClass>

 class StringByteSink : public ByteSink {

  public:

   /**

    * Constructs a ByteSink that will append bytes to the dest string.

    * @param dest pointer to string object to append to

    * @stable ICU 4.2

    */

   StringByteSink(StringClass* dest) : dest_(dest) { }

   /**

    * Append "bytes[0,n-1]" to this.

    * @param data the pointer to the bytes

    * @param n the number of bytes; must be non-negative

    * @stable 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__