michael@0: // Copyright (C) 2009-2012, International Business Machines
michael@0: // Corporation and others. All Rights Reserved.
michael@0: //
michael@0: // Copyright 2007 Google Inc. All Rights Reserved.
michael@0: // Author: sanjay@google.com (Sanjay Ghemawat)
michael@0: //
michael@0: // Abstract interface that consumes a sequence of bytes (ByteSink).
michael@0: //
michael@0: // Used so that we can write a single piece of code that can operate
michael@0: // on a variety of output string types.
michael@0: //
michael@0: // Various implementations of this interface are provided:
michael@0: //   ByteSink:
michael@0: //      CheckedArrayByteSink    Write to a flat array, with bounds checking
michael@0: //      StringByteSink          Write to an STL string
michael@0: 
michael@0: // This code is a contribution of Google code, and the style used here is
michael@0: // a compromise between the original Google code and the ICU coding guidelines.
michael@0: // For example, data types are ICU-ified (size_t,int->int32_t),
michael@0: // and API comments doxygen-ified, but function names and behavior are
michael@0: // as in the original, if possible.
michael@0: // Assertion-style error handling, not available in ICU, was changed to
michael@0: // parameter "pinning" similar to UnicodeString.
michael@0: //
michael@0: // In addition, this is only a partial port of the original Google code,
michael@0: // limited to what was needed so far. The (nearly) complete original code
michael@0: // is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
michael@0: // (see ICU ticket 6765, r25517).
michael@0: 
michael@0: #ifndef __BYTESTREAM_H__
michael@0: #define __BYTESTREAM_H__
michael@0: 
michael@0: /**
michael@0:  * \file
michael@0:  * \brief C++ API: Interface for writing bytes, and implementation classes.
michael@0:  */
michael@0: 
michael@0: #include "unicode/utypes.h"
michael@0: #include "unicode/uobject.h"
michael@0: #include "unicode/std_string.h"
michael@0: 
michael@0: U_NAMESPACE_BEGIN
michael@0: 
michael@0: /**
michael@0:  * A ByteSink can be filled with bytes.
michael@0:  * @stable ICU 4.2
michael@0:  */
michael@0: class U_COMMON_API ByteSink : public UMemory {
michael@0: public:
michael@0:   /**
michael@0:    * Default constructor.
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   ByteSink() { }
michael@0:   /**
michael@0:    * Virtual destructor.
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   virtual ~ByteSink();
michael@0: 
michael@0:   /**
michael@0:    * Append "bytes[0,n-1]" to this.
michael@0:    * @param bytes the pointer to the bytes
michael@0:    * @param n the number of bytes; must be non-negative
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   virtual void Append(const char* bytes, int32_t n) = 0;
michael@0: 
michael@0:   /**
michael@0:    * Returns a writable buffer for appending and writes the buffer's capacity to
michael@0:    * *result_capacity. Guarantees *result_capacity>=min_capacity.
michael@0:    * May return a pointer to the caller-owned scratch buffer which must have
michael@0:    * scratch_capacity>=min_capacity.
michael@0:    * The returned buffer is only valid until the next operation
michael@0:    * on this ByteSink.
michael@0:    *
michael@0:    * After writing at most *result_capacity bytes, call Append() with the
michael@0:    * pointer returned from this function and the number of bytes written.
michael@0:    * Many Append() implementations will avoid copying bytes if this function
michael@0:    * returned an internal buffer.
michael@0:    *
michael@0:    * Partial usage example:
michael@0:    *  int32_t capacity;
michael@0:    *  char* buffer = sink->GetAppendBuffer(..., &capacity);
michael@0:    *  ... Write n bytes into buffer, with n <= capacity.
michael@0:    *  sink->Append(buffer, n);
michael@0:    * In many implementations, that call to Append will avoid copying bytes.
michael@0:    *
michael@0:    * If the ByteSink allocates or reallocates an internal buffer, it should use
michael@0:    * the desired_capacity_hint if appropriate.
michael@0:    * If a caller cannot provide a reasonable guess at the desired capacity,
michael@0:    * it should pass desired_capacity_hint=0.
michael@0:    *
michael@0:    * If a non-scratch buffer is returned, the caller may only pass
michael@0:    * a prefix to it to Append().
michael@0:    * That is, it is not correct to pass an interior pointer to Append().
michael@0:    *
michael@0:    * The default implementation always returns the scratch buffer.
michael@0:    *
michael@0:    * @param min_capacity required minimum capacity of the returned buffer;
michael@0:    *                     must be non-negative
michael@0:    * @param desired_capacity_hint desired capacity of the returned buffer;
michael@0:    *                              must be non-negative
michael@0:    * @param scratch default caller-owned buffer
michael@0:    * @param scratch_capacity capacity of the scratch buffer
michael@0:    * @param result_capacity pointer to an integer which will be set to the
michael@0:    *                        capacity of the returned buffer
michael@0:    * @return a buffer with *result_capacity>=min_capacity
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   virtual char* GetAppendBuffer(int32_t min_capacity,
michael@0:                                 int32_t desired_capacity_hint,
michael@0:                                 char* scratch, int32_t scratch_capacity,
michael@0:                                 int32_t* result_capacity);
michael@0: 
michael@0:   /**
michael@0:    * Flush internal buffers.
michael@0:    * Some byte sinks use internal buffers or provide buffering
michael@0:    * and require calling Flush() at the end of the stream.
michael@0:    * The ByteSink should be ready for further Append() calls after Flush().
michael@0:    * The default implementation of Flush() does nothing.
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   virtual void Flush();
michael@0: 
michael@0: private:
michael@0:   ByteSink(const ByteSink &); // copy constructor not implemented
michael@0:   ByteSink &operator=(const ByteSink &); // assignment operator not implemented
michael@0: };
michael@0: 
michael@0: // -------------------------------------------------------------
michael@0: // Some standard implementations
michael@0: 
michael@0: /** 
michael@0:  * Implementation of ByteSink that writes to a flat byte array,
michael@0:  * with bounds-checking:
michael@0:  * This sink will not write more than capacity bytes to outbuf.
michael@0:  * If more than capacity bytes are Append()ed, then excess bytes are ignored,
michael@0:  * and Overflowed() will return true.
michael@0:  * Overflow does not cause a runtime error.
michael@0:  * @stable ICU 4.2
michael@0:  */
michael@0: class U_COMMON_API CheckedArrayByteSink : public ByteSink {
michael@0: public:
michael@0:   /**
michael@0:    * Constructs a ByteSink that will write to outbuf[0..capacity-1].
michael@0:    * @param outbuf buffer to write to
michael@0:    * @param capacity size of the buffer
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   CheckedArrayByteSink(char* outbuf, int32_t capacity);
michael@0:   /**
michael@0:    * Destructor.
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   virtual ~CheckedArrayByteSink();
michael@0:   /**
michael@0:    * Returns the sink to its original state, without modifying the buffer.
michael@0:    * Useful for reusing both the buffer and the sink for multiple streams.
michael@0:    * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0
michael@0:    * and Overflowed()=FALSE.
michael@0:    * @return *this
michael@0:    * @stable ICU 4.6
michael@0:    */
michael@0:   virtual CheckedArrayByteSink& Reset();
michael@0:   /**
michael@0:    * Append "bytes[0,n-1]" to this.
michael@0:    * @param bytes the pointer to the bytes
michael@0:    * @param n the number of bytes; must be non-negative
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   virtual void Append(const char* bytes, int32_t n);
michael@0:   /**
michael@0:    * Returns a writable buffer for appending and writes the buffer's capacity to
michael@0:    * *result_capacity. For details see the base class documentation.
michael@0:    * @param min_capacity required minimum capacity of the returned buffer;
michael@0:    *                     must be non-negative
michael@0:    * @param desired_capacity_hint desired capacity of the returned buffer;
michael@0:    *                              must be non-negative
michael@0:    * @param scratch default caller-owned buffer
michael@0:    * @param scratch_capacity capacity of the scratch buffer
michael@0:    * @param result_capacity pointer to an integer which will be set to the
michael@0:    *                        capacity of the returned buffer
michael@0:    * @return a buffer with *result_capacity>=min_capacity
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   virtual char* GetAppendBuffer(int32_t min_capacity,
michael@0:                                 int32_t desired_capacity_hint,
michael@0:                                 char* scratch, int32_t scratch_capacity,
michael@0:                                 int32_t* result_capacity);
michael@0:   /**
michael@0:    * Returns the number of bytes actually written to the sink.
michael@0:    * @return number of bytes written to the buffer
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   int32_t NumberOfBytesWritten() const { return size_; }
michael@0:   /**
michael@0:    * Returns true if any bytes were discarded, i.e., if there was an
michael@0:    * attempt to write more than 'capacity' bytes.
michael@0:    * @return TRUE if more than 'capacity' bytes were Append()ed
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   UBool Overflowed() const { return overflowed_; }
michael@0:   /**
michael@0:    * Returns the number of bytes appended to the sink.
michael@0:    * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten()
michael@0:    * else they return the same number.
michael@0:    * @return number of bytes written to the buffer
michael@0:    * @stable ICU 4.6
michael@0:    */
michael@0:   int32_t NumberOfBytesAppended() const { return appended_; }
michael@0: private:
michael@0:   char* outbuf_;
michael@0:   const int32_t capacity_;
michael@0:   int32_t size_;
michael@0:   int32_t appended_;
michael@0:   UBool overflowed_;
michael@0:   CheckedArrayByteSink(); ///< default constructor not implemented 
michael@0:   CheckedArrayByteSink(const CheckedArrayByteSink &); ///< copy constructor not implemented
michael@0:   CheckedArrayByteSink &operator=(const CheckedArrayByteSink &); ///< assignment operator not implemented
michael@0: };
michael@0: 
michael@0: #if U_HAVE_STD_STRING
michael@0: 
michael@0: /** 
michael@0:  * Implementation of ByteSink that writes to a "string".
michael@0:  * The StringClass is usually instantiated with a std::string.
michael@0:  * @stable ICU 4.2
michael@0:  */
michael@0: template<typename StringClass>
michael@0: class StringByteSink : public ByteSink {
michael@0:  public:
michael@0:   /**
michael@0:    * Constructs a ByteSink that will append bytes to the dest string.
michael@0:    * @param dest pointer to string object to append to
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   StringByteSink(StringClass* dest) : dest_(dest) { }
michael@0:   /**
michael@0:    * Append "bytes[0,n-1]" to this.
michael@0:    * @param data the pointer to the bytes
michael@0:    * @param n the number of bytes; must be non-negative
michael@0:    * @stable ICU 4.2
michael@0:    */
michael@0:   virtual void Append(const char* data, int32_t n) { dest_->append(data, n); }
michael@0:  private:
michael@0:   StringClass* dest_;
michael@0:   StringByteSink(); ///< default constructor not implemented 
michael@0:   StringByteSink(const StringByteSink &); ///< copy constructor not implemented
michael@0:   StringByteSink &operator=(const StringByteSink &); ///< assignment operator not implemented
michael@0: };
michael@0: 
michael@0: #endif
michael@0: 
michael@0: U_NAMESPACE_END
michael@0: 
michael@0: #endif  // __BYTESTREAM_H__