michael@0: /*
michael@0: *******************************************************************************
michael@0: *   Copyright (C) 2011-2012, International Business Machines
michael@0: *   Corporation and others.  All Rights Reserved.
michael@0: *******************************************************************************
michael@0: *   file name:  appendable.h
michael@0: *   encoding:   US-ASCII
michael@0: *   tab size:   8 (not used)
michael@0: *   indentation:4
michael@0: *
michael@0: *   created on: 2010dec07
michael@0: *   created by: Markus W. Scherer
michael@0: */
michael@0: 
michael@0: #ifndef __APPENDABLE_H__
michael@0: #define __APPENDABLE_H__
michael@0: 
michael@0: /**
michael@0:  * \file
michael@0:  * \brief C++ API: Appendable class: Sink for Unicode code points and 16-bit code units (UChars).
michael@0:  */
michael@0: 
michael@0: #include "unicode/utypes.h"
michael@0: #include "unicode/uobject.h"
michael@0: 
michael@0: U_NAMESPACE_BEGIN
michael@0: 
michael@0: class UnicodeString;
michael@0: 
michael@0: /**
michael@0:  * Base class for objects to which Unicode characters and strings can be appended.
michael@0:  * Combines elements of Java Appendable and ICU4C ByteSink.
michael@0:  *
michael@0:  * This class can be used in APIs where it does not matter whether the actual destination is
michael@0:  * a UnicodeString, a UChar[] array, a UnicodeSet, or any other object
michael@0:  * that receives and processes characters and/or strings.
michael@0:  *
michael@0:  * Implementation classes must implement at least appendCodeUnit(UChar).
michael@0:  * The base class provides default implementations for the other methods.
michael@0:  *
michael@0:  * The methods do not take UErrorCode parameters.
michael@0:  * If an error occurs (e.g., out-of-memory),
michael@0:  * in addition to returning FALSE from failing operations,
michael@0:  * the implementation must prevent unexpected behavior (e.g., crashes)
michael@0:  * from further calls and should make the error condition available separately
michael@0:  * (e.g., store a UErrorCode, make/keep a UnicodeString bogus).
michael@0:  * @stable ICU 4.8
michael@0:  */
michael@0: class U_COMMON_API Appendable : public UObject {
michael@0: public:
michael@0:     /**
michael@0:      * Destructor.
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     ~Appendable();
michael@0: 
michael@0:     /**
michael@0:      * Appends a 16-bit code unit.
michael@0:      * @param c code unit
michael@0:      * @return TRUE if the operation succeeded
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UBool appendCodeUnit(UChar c) = 0;
michael@0: 
michael@0:     /**
michael@0:      * Appends a code point.
michael@0:      * The default implementation calls appendCodeUnit(UChar) once or twice.
michael@0:      * @param c code point 0..0x10ffff
michael@0:      * @return TRUE if the operation succeeded
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UBool appendCodePoint(UChar32 c);
michael@0: 
michael@0:     /**
michael@0:      * Appends a string.
michael@0:      * The default implementation calls appendCodeUnit(UChar) for each code unit.
michael@0:      * @param s string, must not be NULL if length!=0
michael@0:      * @param length string length, or -1 if NUL-terminated
michael@0:      * @return TRUE if the operation succeeded
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UBool appendString(const UChar *s, int32_t length);
michael@0: 
michael@0:     /**
michael@0:      * Tells the object that the caller is going to append roughly
michael@0:      * appendCapacity UChars. A subclass might use this to pre-allocate
michael@0:      * a larger buffer if necessary.
michael@0:      * The default implementation does nothing. (It always returns TRUE.)
michael@0:      * @param appendCapacity estimated number of UChars that will be appended
michael@0:      * @return TRUE if the operation succeeded
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UBool reserveAppendCapacity(int32_t appendCapacity);
michael@0: 
michael@0:     /**
michael@0:      * Returns a writable buffer for appending and writes the buffer's capacity to
michael@0:      * *resultCapacity. Guarantees *resultCapacity>=minCapacity.
michael@0:      * May return a pointer to the caller-owned scratch buffer which must have
michael@0:      * scratchCapacity>=minCapacity.
michael@0:      * The returned buffer is only valid until the next operation
michael@0:      * on this Appendable.
michael@0:      *
michael@0:      * After writing at most *resultCapacity UChars, call appendString() with the
michael@0:      * pointer returned from this function and the number of UChars written.
michael@0:      * Many appendString() implementations will avoid copying UChars if this function
michael@0:      * returned an internal buffer.
michael@0:      *
michael@0:      * Partial usage example:
michael@0:      * \code
michael@0:      *  int32_t capacity;
michael@0:      *  UChar* buffer = app.getAppendBuffer(..., &capacity);
michael@0:      *  ... Write n UChars into buffer, with n <= capacity.
michael@0:      *  app.appendString(buffer, n);
michael@0:      * \endcode
michael@0:      * In many implementations, that call to append will avoid copying UChars.
michael@0:      *
michael@0:      * If the Appendable allocates or reallocates an internal buffer, it should use
michael@0:      * the desiredCapacityHint if appropriate.
michael@0:      * If a caller cannot provide a reasonable guess at the desired capacity,
michael@0:      * it should pass desiredCapacityHint=0.
michael@0:      *
michael@0:      * If a non-scratch buffer is returned, the caller may only pass
michael@0:      * a prefix to it to appendString().
michael@0:      * That is, it is not correct to pass an interior pointer to appendString().
michael@0:      *
michael@0:      * The default implementation always returns the scratch buffer.
michael@0:      *
michael@0:      * @param minCapacity required minimum capacity of the returned buffer;
michael@0:      *                    must be non-negative
michael@0:      * @param desiredCapacityHint desired capacity of the returned buffer;
michael@0:      *                            must be non-negative
michael@0:      * @param scratch default caller-owned buffer
michael@0:      * @param scratchCapacity capacity of the scratch buffer
michael@0:      * @param resultCapacity pointer to an integer which will be set to the
michael@0:      *                       capacity of the returned buffer
michael@0:      * @return a buffer with *resultCapacity>=minCapacity
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UChar *getAppendBuffer(int32_t minCapacity,
michael@0:                                    int32_t desiredCapacityHint,
michael@0:                                    UChar *scratch, int32_t scratchCapacity,
michael@0:                                    int32_t *resultCapacity);
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * An Appendable implementation which writes to a UnicodeString.
michael@0:  *
michael@0:  * This class is not intended for public subclassing.
michael@0:  * @stable ICU 4.8
michael@0:  */
michael@0: class U_COMMON_API UnicodeStringAppendable : public Appendable {
michael@0: public:
michael@0:     /**
michael@0:      * Aliases the UnicodeString (keeps its reference) for writing.
michael@0:      * @param s The UnicodeString to which this Appendable will write.
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     explicit UnicodeStringAppendable(UnicodeString &s) : str(s) {}
michael@0: 
michael@0:     /**
michael@0:      * Destructor.
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     ~UnicodeStringAppendable();
michael@0: 
michael@0:     /**
michael@0:      * Appends a 16-bit code unit to the string.
michael@0:      * @param c code unit
michael@0:      * @return TRUE if the operation succeeded
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UBool appendCodeUnit(UChar c);
michael@0: 
michael@0:     /**
michael@0:      * Appends a code point to the string.
michael@0:      * @param c code point 0..0x10ffff
michael@0:      * @return TRUE if the operation succeeded
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UBool appendCodePoint(UChar32 c);
michael@0: 
michael@0:     /**
michael@0:      * Appends a string to the UnicodeString.
michael@0:      * @param s string, must not be NULL if length!=0
michael@0:      * @param length string length, or -1 if NUL-terminated
michael@0:      * @return TRUE if the operation succeeded
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UBool appendString(const UChar *s, int32_t length);
michael@0: 
michael@0:     /**
michael@0:      * Tells the UnicodeString that the caller is going to append roughly
michael@0:      * appendCapacity UChars.
michael@0:      * @param appendCapacity estimated number of UChars that will be appended
michael@0:      * @return TRUE if the operation succeeded
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UBool reserveAppendCapacity(int32_t appendCapacity);
michael@0: 
michael@0:     /**
michael@0:      * Returns a writable buffer for appending and writes the buffer's capacity to
michael@0:      * *resultCapacity. Guarantees *resultCapacity>=minCapacity.
michael@0:      * May return a pointer to the caller-owned scratch buffer which must have
michael@0:      * scratchCapacity>=minCapacity.
michael@0:      * The returned buffer is only valid until the next write operation
michael@0:      * on the UnicodeString.
michael@0:      *
michael@0:      * For details see Appendable::getAppendBuffer().
michael@0:      *
michael@0:      * @param minCapacity required minimum capacity of the returned buffer;
michael@0:      *                    must be non-negative
michael@0:      * @param desiredCapacityHint desired capacity of the returned buffer;
michael@0:      *                            must be non-negative
michael@0:      * @param scratch default caller-owned buffer
michael@0:      * @param scratchCapacity capacity of the scratch buffer
michael@0:      * @param resultCapacity pointer to an integer which will be set to the
michael@0:      *                       capacity of the returned buffer
michael@0:      * @return a buffer with *resultCapacity>=minCapacity
michael@0:      * @stable ICU 4.8
michael@0:      */
michael@0:     virtual UChar *getAppendBuffer(int32_t minCapacity,
michael@0:                                    int32_t desiredCapacityHint,
michael@0:                                    UChar *scratch, int32_t scratchCapacity,
michael@0:                                    int32_t *resultCapacity);
michael@0: 
michael@0: private:
michael@0:     UnicodeString &str;
michael@0: };
michael@0: 
michael@0: U_NAMESPACE_END
michael@0: 
michael@0: #endif  // __APPENDABLE_H__