/*
*******************************************************************************
* Copyright (C) 2011, International Business Machines
* Corporation and others. All Rights Reserved.
*******************************************************************************
* file name: appendable.h
* encoding: US-ASCII
* tab size: 8 (not used)
* indentation:4
*
* created on: 2010dec07
* created by: Markus W. Scherer
*/
#ifndef __APPENDABLE_H__
#define __APPENDABLE_H__
/**
* \file
* \brief C++ API: Appendable class: Sink for Unicode code points and 16-bit code units (UChars).
*/
#include "unicode/utypes.h"
#include "unicode/uobject.h"
U_NAMESPACE_BEGIN
class UnicodeString;
/**
* Base class for objects to which Unicode characters and strings can be appended.
* Combines elements of Java Appendable and ICU4C ByteSink.
*
* This class can be used in APIs where it does not matter whether the actual destination is
* a UnicodeString, a UChar[] array, a UnicodeSet, or any other object
* that receives and processes characters and/or strings.
*
* Implementation classes must implement at least appendCodeUnit(UChar).
* The base class provides default implementations for the other methods.
*
* The methods do not take UErrorCode parameters.
* If an error occurs (e.g., out-of-memory),
* in addition to returning FALSE from failing operations,
* the implementation must prevent unexpected behavior (e.g., crashes)
* from further calls and should make the error condition available separately
* (e.g., store a UErrorCode, make/keep a UnicodeString bogus).
* @draft ICU 4.8
*/
class U_COMMON_API Appendable : public UObject {
public:
/**
* Appends a 16-bit code unit.
* @param c code unit
* @return TRUE if the operation succeeded
* @draft ICU 4.8
*/
virtual UBool appendCodeUnit(UChar c) = 0;
/**
* Appends a code point.
* The default implementation calls appendCodeUnit(UChar) once or twice.
* @param c code point 0..0x10ffff
* @return TRUE if the operation succeeded
* @draft ICU 4.8
*/
virtual UBool appendCodePoint(UChar32 c);
/**
* Appends a string.
* The default implementation calls appendCodeUnit(UChar) for each code unit.
* @param s string, must not be NULL if length!=0
* @param length string length, or -1 if NUL-terminated
* @return TRUE if the operation succeeded
* @draft ICU 4.8
*/
virtual UBool appendString(const UChar *s, int32_t length);
/**
* Tells the object that the caller is going to append roughly
* appendCapacity UChars. A subclass might use this to pre-allocate
* a larger buffer if necessary.
* The default implementation does nothing. (It always returns TRUE.)
* @param appendCapacity estimated number of UChars that will be appended
* @return TRUE if the operation succeeded
* @draft ICU 4.8
*/
virtual UBool reserveAppendCapacity(int32_t appendCapacity);
/**
* Returns a writable buffer for appending and writes the buffer's capacity to
* *resultCapacity. Guarantees *resultCapacity>=minCapacity.
* May return a pointer to the caller-owned scratch buffer which must have
* scratchCapacity>=minCapacity.
* The returned buffer is only valid until the next operation
* on this Appendable.
*
* After writing at most *resultCapacity UChars, call appendString() with the
* pointer returned from this function and the number of UChars written.
* Many appendString() implementations will avoid copying UChars if this function
* returned an internal buffer.
*
* Partial usage example:
* \code
* int32_t capacity;
* UChar* buffer = app.getAppendBuffer(..., &capacity);
* ... Write n UChars into buffer, with n <= capacity.
* app.appendString(buffer, n);
* \endcode
* In many implementations, that call to append will avoid copying UChars.
*
* If the Appendable allocates or reallocates an internal buffer, it should use
* the desiredCapacityHint if appropriate.
* If a caller cannot provide a reasonable guess at the desired capacity,
* it should pass desiredCapacityHint=0.
*
* If a non-scratch buffer is returned, the caller may only pass
* a prefix to it to appendString().
* That is, it is not correct to pass an interior pointer to appendString().
*
* The default implementation always returns the scratch buffer.
*
* @param minCapacity required minimum capacity of the returned buffer;
* must be non-negative
* @param desiredCapacityHint desired capacity of the returned buffer;
* must be non-negative
* @param scratch default caller-owned buffer
* @param scratchCapacity capacity of the scratch buffer
* @param resultCapacity pointer to an integer which will be set to the
* capacity of the returned buffer
* @return a buffer with *resultCapacity>=minCapacity
* @draft ICU 4.8
*/
virtual UChar *getAppendBuffer(int32_t minCapacity,
int32_t desiredCapacityHint,
UChar *scratch, int32_t scratchCapacity,
int32_t *resultCapacity);
private:
// No ICU "poor man's RTTI" for this class nor its subclasses.
virtual UClassID getDynamicClassID() const;
};
/**
* An Appendable implementation which writes to a UnicodeString.
*
* This class is not intended for public subclassing.
* @draft ICU 4.8
*/
class U_COMMON_API UnicodeStringAppendable : public Appendable {
public:
/**
* Aliases the UnicodeString (keeps its reference) for writing.
* @param s The UnicodeString to which this Appendable will write.
* @draft ICU 4.8
*/
explicit UnicodeStringAppendable(UnicodeString &s) : str(s) {}
/**
* Appends a 16-bit code unit to the string.
* @param c code unit
* @return TRUE if the operation succeeded
* @draft ICU 4.8
*/
virtual UBool appendCodeUnit(UChar c);
/**
* Appends a code point to the string.
* @param c code point 0..0x10ffff
* @return TRUE if the operation succeeded
* @draft ICU 4.8
*/
virtual UBool appendCodePoint(UChar32 c);
/**
* Appends a string to the UnicodeString.
* @param s string, must not be NULL if length!=0
* @param length string length, or -1 if NUL-terminated
* @return TRUE if the operation succeeded
* @draft ICU 4.8
*/
virtual UBool appendString(const UChar *s, int32_t length);
/**
* Tells the UnicodeString that the caller is going to append roughly
* appendCapacity UChars.
* @param appendCapacity estimated number of UChars that will be appended
* @return TRUE if the operation succeeded
* @draft ICU 4.8
*/
virtual UBool reserveAppendCapacity(int32_t appendCapacity);
/**
* Returns a writable buffer for appending and writes the buffer's capacity to
* *resultCapacity. Guarantees *resultCapacity>=minCapacity.
* May return a pointer to the caller-owned scratch buffer which must have
* scratchCapacity>=minCapacity.
* The returned buffer is only valid until the next write operation
* on the UnicodeString.
*
* For details see Appendable::getAppendBuffer().
*
* @param minCapacity required minimum capacity of the returned buffer;
* must be non-negative
* @param desiredCapacityHint desired capacity of the returned buffer;
* must be non-negative
* @param scratch default caller-owned buffer
* @param scratchCapacity capacity of the scratch buffer
* @param resultCapacity pointer to an integer which will be set to the
* capacity of the returned buffer
* @return a buffer with *resultCapacity>=minCapacity
* @draft ICU 4.8
*/
virtual UChar *getAppendBuffer(int32_t minCapacity,
int32_t desiredCapacityHint,
UChar *scratch, int32_t scratchCapacity,
int32_t *resultCapacity);
private:
UnicodeString &str;
};
U_NAMESPACE_END
#endif // __APPENDABLE_H__