1 // 2016 and later: Unicode, Inc. and others. 2 // License & terms of use: http://www.unicode.org/copyright.html 3 // Copyright (C) 2009-2012, International Business Machines 4 // Corporation and others. All Rights Reserved. 5 // 6 // Copyright 2007 Google Inc. All Rights Reserved. 7 // Author: sanjay (at) google.com (Sanjay Ghemawat) 8 // 9 // Abstract interface that consumes a sequence of bytes (ByteSink). 10 // 11 // Used so that we can write a single piece of code that can operate 12 // on a variety of output string types. 13 // 14 // Various implementations of this interface are provided: 15 // ByteSink: 16 // CheckedArrayByteSink Write to a flat array, with bounds checking 17 // StringByteSink Write to an STL string 18 19 // This code is a contribution of Google code, and the style used here is 20 // a compromise between the original Google code and the ICU coding guidelines. 21 // For example, data types are ICU-ified (size_t,int->int32_t), 22 // and API comments doxygen-ified, but function names and behavior are 23 // as in the original, if possible. 24 // Assertion-style error handling, not available in ICU, was changed to 25 // parameter "pinning" similar to UnicodeString. 26 // 27 // In addition, this is only a partial port of the original Google code, 28 // limited to what was needed so far. The (nearly) complete original code 29 // is in the ICU svn repository at icuhtml/trunk/design/strings/contrib 30 // (see ICU ticket 6765, r25517). 31 32 #ifndef __BYTESTREAM_H__ 33 #define __BYTESTREAM_H__ 34 35 /** 36 * \file 37 * \brief C++ API: Interface for writing bytes, and implementation classes. 38 */ 39 40 #include "unicode/utypes.h" 41 #include "unicode/uobject.h" 42 #include "unicode/std_string.h" 43 44 U_NAMESPACE_BEGIN 45 46 /** 47 * A ByteSink can be filled with bytes. 48 * @stable ICU 4.2 49 */ 50 class U_COMMON_API ByteSink : public UMemory { 51 public: 52 /** 53 * Default constructor. 54 * @stable ICU 4.2 55 */ 56 ByteSink() { } 57 /** 58 * Virtual destructor. 59 * @stable ICU 4.2 60 */ 61 virtual ~ByteSink(); 62 63 /** 64 * Append "bytes[0,n-1]" to this. 65 * @param bytes the pointer to the bytes 66 * @param n the number of bytes; must be non-negative 67 * @stable ICU 4.2 68 */ 69 virtual void Append(const char* bytes, int32_t n) = 0; 70 71 /** 72 * Returns a writable buffer for appending and writes the buffer's capacity to 73 * *result_capacity. Guarantees *result_capacity>=min_capacity. 74 * May return a pointer to the caller-owned scratch buffer which must have 75 * scratch_capacity>=min_capacity. 76 * The returned buffer is only valid until the next operation 77 * on this ByteSink. 78 * 79 * After writing at most *result_capacity bytes, call Append() with the 80 * pointer returned from this function and the number of bytes written. 81 * Many Append() implementations will avoid copying bytes if this function 82 * returned an internal buffer. 83 * 84 * Partial usage example: 85 * int32_t capacity; 86 * char* buffer = sink->GetAppendBuffer(..., &capacity); 87 * ... Write n bytes into buffer, with n <= capacity. 88 * sink->Append(buffer, n); 89 * In many implementations, that call to Append will avoid copying bytes. 90 * 91 * If the ByteSink allocates or reallocates an internal buffer, it should use 92 * the desired_capacity_hint if appropriate. 93 * If a caller cannot provide a reasonable guess at the desired capacity, 94 * it should pass desired_capacity_hint=0. 95 * 96 * If a non-scratch buffer is returned, the caller may only pass 97 * a prefix to it to Append(). 98 * That is, it is not correct to pass an interior pointer to Append(). 99 * 100 * The default implementation always returns the scratch buffer. 101 * 102 * @param min_capacity required minimum capacity of the returned buffer; 103 * must be non-negative 104 * @param desired_capacity_hint desired capacity of the returned buffer; 105 * must be non-negative 106 * @param scratch default caller-owned buffer 107 * @param scratch_capacity capacity of the scratch buffer 108 * @param result_capacity pointer to an integer which will be set to the 109 * capacity of the returned buffer 110 * @return a buffer with *result_capacity>=min_capacity 111 * @stable ICU 4.2 112 */ 113 virtual char* GetAppendBuffer(int32_t min_capacity, 114 int32_t desired_capacity_hint, 115 char* scratch, int32_t scratch_capacity, 116 int32_t* result_capacity); 117 118 /** 119 * Flush internal buffers. 120 * Some byte sinks use internal buffers or provide buffering 121 * and require calling Flush() at the end of the stream. 122 * The ByteSink should be ready for further Append() calls after Flush(). 123 * The default implementation of Flush() does nothing. 124 * @stable ICU 4.2 125 */ 126 virtual void Flush(); 127 128 private: 129 ByteSink(const ByteSink &) = delete; 130 ByteSink &operator=(const ByteSink &) = delete; 131 }; 132 133 // ------------------------------------------------------------- 134 // Some standard implementations 135 136 /** 137 * Implementation of ByteSink that writes to a flat byte array, 138 * with bounds-checking: 139 * This sink will not write more than capacity bytes to outbuf. 140 * If more than capacity bytes are Append()ed, then excess bytes are ignored, 141 * and Overflowed() will return true. 142 * Overflow does not cause a runtime error. 143 * @stable ICU 4.2 144 */ 145 class U_COMMON_API CheckedArrayByteSink : public ByteSink { 146 public: 147 /** 148 * Constructs a ByteSink that will write to outbuf[0..capacity-1]. 149 * @param outbuf buffer to write to 150 * @param capacity size of the buffer 151 * @stable ICU 4.2 152 */ 153 CheckedArrayByteSink(char* outbuf, int32_t capacity); 154 /** 155 * Destructor. 156 * @stable ICU 4.2 157 */ 158 virtual ~CheckedArrayByteSink(); 159 /** 160 * Returns the sink to its original state, without modifying the buffer. 161 * Useful for reusing both the buffer and the sink for multiple streams. 162 * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0 163 * and Overflowed()=FALSE. 164 * @return *this 165 * @stable ICU 4.6 166 */ 167 virtual CheckedArrayByteSink& Reset(); 168 /** 169 * Append "bytes[0,n-1]" to this. 170 * @param bytes the pointer to the bytes 171 * @param n the number of bytes; must be non-negative 172 * @stable ICU 4.2 173 */ 174 virtual void Append(const char* bytes, int32_t n); 175 /** 176 * Returns a writable buffer for appending and writes the buffer's capacity to 177 * *result_capacity. For details see the base class documentation. 178 * @param min_capacity required minimum capacity of the returned buffer; 179 * must be non-negative 180 * @param desired_capacity_hint desired capacity of the returned buffer; 181 * must be non-negative 182 * @param scratch default caller-owned buffer 183 * @param scratch_capacity capacity of the scratch buffer 184 * @param result_capacity pointer to an integer which will be set to the 185 * capacity of the returned buffer 186 * @return a buffer with *result_capacity>=min_capacity 187 * @stable ICU 4.2 188 */ 189 virtual char* GetAppendBuffer(int32_t min_capacity, 190 int32_t desired_capacity_hint, 191 char* scratch, int32_t scratch_capacity, 192 int32_t* result_capacity); 193 /** 194 * Returns the number of bytes actually written to the sink. 195 * @return number of bytes written to the buffer 196 * @stable ICU 4.2 197 */ 198 int32_t NumberOfBytesWritten() const { return size_; } 199 /** 200 * Returns true if any bytes were discarded, i.e., if there was an 201 * attempt to write more than 'capacity' bytes. 202 * @return TRUE if more than 'capacity' bytes were Append()ed 203 * @stable ICU 4.2 204 */ 205 UBool Overflowed() const { return overflowed_; } 206 /** 207 * Returns the number of bytes appended to the sink. 208 * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten() 209 * else they return the same number. 210 * @return number of bytes written to the buffer 211 * @stable ICU 4.6 212 */ 213 int32_t NumberOfBytesAppended() const { return appended_; } 214 private: 215 char* outbuf_; 216 const int32_t capacity_; 217 int32_t size_; 218 int32_t appended_; 219 UBool overflowed_; 220 221 CheckedArrayByteSink() = delete; 222 CheckedArrayByteSink(const CheckedArrayByteSink &) = delete; 223 CheckedArrayByteSink &operator=(const CheckedArrayByteSink &) = delete; 224 }; 225 226 /** 227 * Implementation of ByteSink that writes to a "string". 228 * The StringClass is usually instantiated with a std::string. 229 * @stable ICU 4.2 230 */ 231 template<typename StringClass> 232 class StringByteSink : public ByteSink { 233 public: 234 /** 235 * Constructs a ByteSink that will append bytes to the dest string. 236 * @param dest pointer to string object to append to 237 * @stable ICU 4.2 238 */ 239 StringByteSink(StringClass* dest) : dest_(dest) { } 240 /** 241 * Constructs a ByteSink that reserves append capacity and will append bytes to the dest string. 242 * 243 * @param dest pointer to string object to append to 244 * @param initialAppendCapacity capacity beyond dest->length() to be reserve()d 245 * @stable ICU 60 246 */ 247 StringByteSink(StringClass* dest, int32_t initialAppendCapacity) : dest_(dest) { 248 if (initialAppendCapacity > 0 && 249 (uint32_t)initialAppendCapacity > (dest->capacity() - dest->length())) { 250 dest->reserve(dest->length() + initialAppendCapacity); 251 } 252 } 253 /** 254 * Append "bytes[0,n-1]" to this. 255 * @param data the pointer to the bytes 256 * @param n the number of bytes; must be non-negative 257 * @stable ICU 4.2 258 */ 259 virtual void Append(const char* data, int32_t n) { dest_->append(data, n); } 260 private: 261 StringClass* dest_; 262 263 StringByteSink() = delete; 264 StringByteSink(const StringByteSink &) = delete; 265 StringByteSink &operator=(const StringByteSink &) = delete; 266 }; 267 268 U_NAMESPACE_END 269 270 #endif // __BYTESTREAM_H__ 271
