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// 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
// 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.
* @draft ICU 4.2
*/
class U_COMMON_API ByteSink : public UMemory {
public:
/**
* Default constructor.
* @draft ICU 4.2
*/
ByteSink() { }
/**
* Virtual destructor.
* @draft 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
* @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.
*
* @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
* @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:
/**
* Constructs a ByteSink that will write to outbuf[0..capacity-1].
* @param outbuf buffer to write to
* @param capacity size of the buffer
* @draft ICU 4.2
*/
CheckedArrayByteSink(char* outbuf, int32_t capacity);
/**
* Append "bytes[0,n-1]" to this.
* @param bytes the pointer to the bytes
* @param n the number of bytes; must be non-negative
* @draft 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
* @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.
* @return number of bytes written to the buffer
* @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.
* @return TRUE if more than 'capacity' bytes were Append()ed
* @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".
* The StringClass is usually instantiated with a std::string.
* @draft 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
* @draft ICU 4.2
*/
StringByteSink(StringClass* dest) : dest_(dest) { }
/**
* Append "bytes[0,n-1]" to this.
* @param bytes the pointer to the bytes
* @param n the number of bytes; must be non-negative
* @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__