1 // Copyright (C) 2009-2010, International Business Machines 2 // Corporation and others. All Rights Reserved. 3 // 4 // Copyright 2007 Google Inc. All Rights Reserved. 5 // Author: sanjay (at) google.com (Sanjay Ghemawat) 6 // 7 // Abstract interface that consumes a sequence of bytes (ByteSink). 8 // 9 // Used so that we can write a single piece of code that can operate 10 // on a variety of output string types. 11 // 12 // Various implementations of this interface are provided: 13 // ByteSink: 14 // CheckedArrayByteSink Write to a flat array, with bounds checking 15 // StringByteSink Write to an STL string 16 17 // This code is a contribution of Google code, and the style used here is 18 // a compromise between the original Google code and the ICU coding guidelines. 19 // For example, data types are ICU-ified (size_t,int->int32_t), 20 // and API comments doxygen-ified, but function names and behavior are 21 // as in the original, if possible. 22 // Assertion-style error handling, not available in ICU, was changed to 23 // parameter "pinning" similar to UnicodeString. 24 // 25 // In addition, this is only a partial port of the original Google code, 26 // limited to what was needed so far. The (nearly) complete original code 27 // is in the ICU svn repository at icuhtml/trunk/design/strings/contrib 28 // (see ICU ticket 6765, r25517). 29 30 #ifndef __BYTESTREAM_H__ 31 #define __BYTESTREAM_H__ 32 33 /** 34 * \file 35 * \brief C++ API: Interface for writing bytes, and implementation classes. 36 */ 37 38 #include "unicode/utypes.h" 39 #include "unicode/uobject.h" 40 #include "unicode/std_string.h" 41 42 U_NAMESPACE_BEGIN 43 44 /** 45 * A ByteSink can be filled with bytes. 46 * @stable ICU 4.2 47 */ 48 class U_COMMON_API ByteSink : public UMemory { 49 public: 50 /** 51 * Default constructor. 52 * @stable ICU 4.2 53 */ 54 ByteSink() { } 55 /** 56 * Virtual destructor. 57 * @stable ICU 4.2 58 */ 59 virtual ~ByteSink() { } 60 61 /** 62 * Append "bytes[0,n-1]" to this. 63 * @param bytes the pointer to the bytes 64 * @param n the number of bytes; must be non-negative 65 * @stable ICU 4.2 66 */ 67 virtual void Append(const char* bytes, int32_t n) = 0; 68 69 /** 70 * Returns a writable buffer for appending and writes the buffer's capacity to 71 * *result_capacity. Guarantees *result_capacity>=min_capacity. 72 * May return a pointer to the caller-owned scratch buffer which must have 73 * scratch_capacity>=min_capacity. 74 * The returned buffer is only valid until the next operation 75 * on this ByteSink. 76 * 77 * After writing at most *result_capacity bytes, call Append() with the 78 * pointer returned from this function and the number of bytes written. 79 * Many Append() implementations will avoid copying bytes if this function 80 * returned an internal buffer. 81 * 82 * Partial usage example: 83 * int32_t capacity; 84 * char* buffer = sink->GetAppendBuffer(..., &capacity); 85 * ... Write n bytes into buffer, with n <= capacity. 86 * sink->Append(buffer, n); 87 * In many implementations, that call to Append will avoid copying bytes. 88 * 89 * If the ByteSink allocates or reallocates an internal buffer, it should use 90 * the desired_capacity_hint if appropriate. 91 * If a caller cannot provide a reasonable guess at the desired capacity, 92 * it should pass desired_capacity_hint=0. 93 * 94 * If a non-scratch buffer is returned, the caller may only pass 95 * a prefix to it to Append(). 96 * That is, it is not correct to pass an interior pointer to Append(). 97 * 98 * The default implementation always returns the scratch buffer. 99 * 100 * @param min_capacity required minimum capacity of the returned buffer; 101 * must be non-negative 102 * @param desired_capacity_hint desired capacity of the returned buffer; 103 * must be non-negative 104 * @param scratch default caller-owned buffer 105 * @param scratch_capacity capacity of the scratch buffer 106 * @param result_capacity pointer to an integer which will be set to the 107 * capacity of the returned buffer 108 * @return a buffer with *result_capacity>=min_capacity 109 * @stable ICU 4.2 110 */ 111 virtual char* GetAppendBuffer(int32_t min_capacity, 112 int32_t desired_capacity_hint, 113 char* scratch, int32_t scratch_capacity, 114 int32_t* result_capacity); 115 116 /** 117 * Flush internal buffers. 118 * Some byte sinks use internal buffers or provide buffering 119 * and require calling Flush() at the end of the stream. 120 * The ByteSink should be ready for further Append() calls after Flush(). 121 * The default implementation of Flush() does nothing. 122 * @stable ICU 4.2 123 */ 124 virtual void Flush(); 125 126 private: 127 ByteSink(const ByteSink &); // copy constructor not implemented 128 ByteSink &operator=(const ByteSink &); // assignment operator not implemented 129 }; 130 131 // ------------------------------------------------------------- 132 // Some standard implementations 133 134 /** 135 * Implementation of ByteSink that writes to a flat byte array, 136 * with bounds-checking: 137 * This sink will not write more than capacity bytes to outbuf. 138 * If more than capacity bytes are Append()ed, then excess bytes are ignored, 139 * and Overflowed() will return true. 140 * Overflow does not cause a runtime error. 141 * @stable ICU 4.2 142 */ 143 class U_COMMON_API CheckedArrayByteSink : public ByteSink { 144 public: 145 /** 146 * Constructs a ByteSink that will write to outbuf[0..capacity-1]. 147 * @param outbuf buffer to write to 148 * @param capacity size of the buffer 149 * @stable ICU 4.2 150 */ 151 CheckedArrayByteSink(char* outbuf, int32_t capacity); 152 /** 153 * Returns the sink to its original state, without modifying the buffer. 154 * Useful for reusing both the buffer and the sink for multiple streams. 155 * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0 156 * and Overflowed()=FALSE. 157 * @return *this 158 * @draft ICU 4.6 159 */ 160 virtual CheckedArrayByteSink& Reset(); 161 /** 162 * Append "bytes[0,n-1]" to this. 163 * @param bytes the pointer to the bytes 164 * @param n the number of bytes; must be non-negative 165 * @stable ICU 4.2 166 */ 167 virtual void Append(const char* bytes, int32_t n); 168 /** 169 * Returns a writable buffer for appending and writes the buffer's capacity to 170 * *result_capacity. For details see the base class documentation. 171 * @param min_capacity required minimum capacity of the returned buffer; 172 * must be non-negative 173 * @param desired_capacity_hint desired capacity of the returned buffer; 174 * must be non-negative 175 * @param scratch default caller-owned buffer 176 * @param scratch_capacity capacity of the scratch buffer 177 * @param result_capacity pointer to an integer which will be set to the 178 * capacity of the returned buffer 179 * @return a buffer with *result_capacity>=min_capacity 180 * @stable ICU 4.2 181 */ 182 virtual char* GetAppendBuffer(int32_t min_capacity, 183 int32_t desired_capacity_hint, 184 char* scratch, int32_t scratch_capacity, 185 int32_t* result_capacity); 186 /** 187 * Returns the number of bytes actually written to the sink. 188 * @return number of bytes written to the buffer 189 * @stable ICU 4.2 190 */ 191 int32_t NumberOfBytesWritten() const { return size_; } 192 /** 193 * Returns true if any bytes were discarded, i.e., if there was an 194 * attempt to write more than 'capacity' bytes. 195 * @return TRUE if more than 'capacity' bytes were Append()ed 196 * @stable ICU 4.2 197 */ 198 UBool Overflowed() const { return overflowed_; } 199 /** 200 * Returns the number of bytes appended to the sink. 201 * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten() 202 * else they return the same number. 203 * @return number of bytes written to the buffer 204 * @draft ICU 4.6 205 */ 206 int32_t NumberOfBytesAppended() const { return appended_; } 207 private: 208 char* outbuf_; 209 const int32_t capacity_; 210 int32_t size_; 211 int32_t appended_; 212 UBool overflowed_; 213 CheckedArrayByteSink(); ///< default constructor not implemented 214 CheckedArrayByteSink(const CheckedArrayByteSink &); ///< copy constructor not implemented 215 CheckedArrayByteSink &operator=(const CheckedArrayByteSink &); ///< assignment operator not implemented 216 }; 217 218 #if U_HAVE_STD_STRING 219 220 /** 221 * Implementation of ByteSink that writes to a "string". 222 * The StringClass is usually instantiated with a std::string. 223 * @stable ICU 4.2 224 */ 225 template<typename StringClass> 226 class StringByteSink : public ByteSink { 227 public: 228 /** 229 * Constructs a ByteSink that will append bytes to the dest string. 230 * @param dest pointer to string object to append to 231 * @stable ICU 4.2 232 */ 233 StringByteSink(StringClass* dest) : dest_(dest) { } 234 /** 235 * Append "bytes[0,n-1]" to this. 236 * @param data the pointer to the bytes 237 * @param n the number of bytes; must be non-negative 238 * @stable ICU 4.2 239 */ 240 virtual void Append(const char* data, int32_t n) { dest_->append(data, n); } 241 private: 242 StringClass* dest_; 243 StringByteSink(); ///< default constructor not implemented 244 StringByteSink(const StringByteSink &); ///< copy constructor not implemented 245 StringByteSink &operator=(const StringByteSink &); ///< assignment operator not implemented 246 }; 247 248 #endif 249 250 U_NAMESPACE_END 251 252 #endif // __BYTESTREAM_H__ 253
