// © 2016 and later: Unicode, Inc. and others. // License & terms of use: http://www.unicode.org/copyright.html // 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" #if U_SHOW_CPLUSPLUS_API #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; #ifndef U_HIDE_DRAFT_API /** * Appends n bytes to this. Same as Append(). * Call AppendU8() with u8"string literals" which are const char * in C++11 * but const char8_t * in C++20. * If the compiler does support char8_t as a distinct type, * then an AppendU8() overload for that is defined and will be chosen. * * @param bytes the pointer to the bytes * @param n the number of bytes; must be non-negative * @draft ICU 67 */ inline void AppendU8(const char* bytes, int32_t n) { Append(bytes, n); } #if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN) /** * Appends n bytes to this. Same as Append() but for a const char8_t * pointer. * Call AppendU8() with u8"string literals" which are const char * in C++11 * but const char8_t * in C++20. * If the compiler does support char8_t as a distinct type, * then this AppendU8() overload for that is defined and will be chosen. * * @param bytes the pointer to the bytes * @param n the number of bytes; must be non-negative * @draft ICU 67 */ inline void AppendU8(const char8_t* bytes, int32_t n) { Append(reinterpret_cast<const char*>(bytes), n); } #endif #endif // U_HIDE_DRAFT_API /** * 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 &) = delete; ByteSink &operator=(const ByteSink &) = delete; }; // ------------------------------------------------------------- // 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() = delete; CheckedArrayByteSink(const CheckedArrayByteSink &) = delete; CheckedArrayByteSink &operator=(const CheckedArrayByteSink &) = delete; }; /** * 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) { } /** * Constructs a ByteSink that reserves append capacity and will append bytes to the dest string. * * @param dest pointer to string object to append to * @param initialAppendCapacity capacity beyond dest->length() to be reserve()d * @stable ICU 60 */ StringByteSink(StringClass* dest, int32_t initialAppendCapacity) : dest_(dest) { if (initialAppendCapacity > 0 && (uint32_t)initialAppendCapacity > (dest->capacity() - dest->length())) { dest->reserve(dest->length() + initialAppendCapacity); } } /** * 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() = delete; StringByteSink(const StringByteSink &) = delete; StringByteSink &operator=(const StringByteSink &) = delete; }; U_NAMESPACE_END #endif /* U_SHOW_CPLUSPLUS_API */ #endif // __BYTESTREAM_H__