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@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 42 #if U_SHOW_CPLUSPLUS_API 43 44 #include "unicode/uobject.h" 45 #include "unicode/std_string.h" 46 47 U_NAMESPACE_BEGIN 48 49 /** 50 * A ByteSink can be filled with bytes. 51 * @stable ICU 4.2 52 */ 53 class U_COMMON_API ByteSink : public UMemory { 54 public: 55 /** 56 * Default constructor. 57 * @stable ICU 4.2 58 */ ByteSink()59 ByteSink() { } 60 /** 61 * Virtual destructor. 62 * @stable ICU 4.2 63 */ 64 virtual ~ByteSink(); 65 66 /** 67 * Append "bytes[0,n-1]" to this. 68 * @param bytes the pointer to the bytes 69 * @param n the number of bytes; must be non-negative 70 * @stable ICU 4.2 71 */ 72 virtual void Append(const char* bytes, int32_t n) = 0; 73 74 /** 75 * Returns a writable buffer for appending and writes the buffer's capacity to 76 * *result_capacity. Guarantees *result_capacity>=min_capacity. 77 * May return a pointer to the caller-owned scratch buffer which must have 78 * scratch_capacity>=min_capacity. 79 * The returned buffer is only valid until the next operation 80 * on this ByteSink. 81 * 82 * After writing at most *result_capacity bytes, call Append() with the 83 * pointer returned from this function and the number of bytes written. 84 * Many Append() implementations will avoid copying bytes if this function 85 * returned an internal buffer. 86 * 87 * Partial usage example: 88 * int32_t capacity; 89 * char* buffer = sink->GetAppendBuffer(..., &capacity); 90 * ... Write n bytes into buffer, with n <= capacity. 91 * sink->Append(buffer, n); 92 * In many implementations, that call to Append will avoid copying bytes. 93 * 94 * If the ByteSink allocates or reallocates an internal buffer, it should use 95 * the desired_capacity_hint if appropriate. 96 * If a caller cannot provide a reasonable guess at the desired capacity, 97 * it should pass desired_capacity_hint=0. 98 * 99 * If a non-scratch buffer is returned, the caller may only pass 100 * a prefix to it to Append(). 101 * That is, it is not correct to pass an interior pointer to Append(). 102 * 103 * The default implementation always returns the scratch buffer. 104 * 105 * @param min_capacity required minimum capacity of the returned buffer; 106 * must be non-negative 107 * @param desired_capacity_hint desired capacity of the returned buffer; 108 * must be non-negative 109 * @param scratch default caller-owned buffer 110 * @param scratch_capacity capacity of the scratch buffer 111 * @param result_capacity pointer to an integer which will be set to the 112 * capacity of the returned buffer 113 * @return a buffer with *result_capacity>=min_capacity 114 * @stable ICU 4.2 115 */ 116 virtual char* GetAppendBuffer(int32_t min_capacity, 117 int32_t desired_capacity_hint, 118 char* scratch, int32_t scratch_capacity, 119 int32_t* result_capacity); 120 121 /** 122 * Flush internal buffers. 123 * Some byte sinks use internal buffers or provide buffering 124 * and require calling Flush() at the end of the stream. 125 * The ByteSink should be ready for further Append() calls after Flush(). 126 * The default implementation of Flush() does nothing. 127 * @stable ICU 4.2 128 */ 129 virtual void Flush(); 130 131 private: 132 ByteSink(const ByteSink &) = delete; 133 ByteSink &operator=(const ByteSink &) = delete; 134 }; 135 136 // ------------------------------------------------------------- 137 // Some standard implementations 138 139 /** 140 * Implementation of ByteSink that writes to a flat byte array, 141 * with bounds-checking: 142 * This sink will not write more than capacity bytes to outbuf. 143 * If more than capacity bytes are Append()ed, then excess bytes are ignored, 144 * and Overflowed() will return true. 145 * Overflow does not cause a runtime error. 146 * @stable ICU 4.2 147 */ 148 class U_COMMON_API CheckedArrayByteSink : public ByteSink { 149 public: 150 /** 151 * Constructs a ByteSink that will write to outbuf[0..capacity-1]. 152 * @param outbuf buffer to write to 153 * @param capacity size of the buffer 154 * @stable ICU 4.2 155 */ 156 CheckedArrayByteSink(char* outbuf, int32_t capacity); 157 /** 158 * Destructor. 159 * @stable ICU 4.2 160 */ 161 virtual ~CheckedArrayByteSink(); 162 /** 163 * Returns the sink to its original state, without modifying the buffer. 164 * Useful for reusing both the buffer and the sink for multiple streams. 165 * Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0 166 * and Overflowed()=FALSE. 167 * @return *this 168 * @stable ICU 4.6 169 */ 170 virtual CheckedArrayByteSink& Reset(); 171 /** 172 * Append "bytes[0,n-1]" to this. 173 * @param bytes the pointer to the bytes 174 * @param n the number of bytes; must be non-negative 175 * @stable ICU 4.2 176 */ 177 virtual void Append(const char* bytes, int32_t n); 178 /** 179 * Returns a writable buffer for appending and writes the buffer's capacity to 180 * *result_capacity. For details see the base class documentation. 181 * @param min_capacity required minimum capacity of the returned buffer; 182 * must be non-negative 183 * @param desired_capacity_hint desired capacity of the returned buffer; 184 * must be non-negative 185 * @param scratch default caller-owned buffer 186 * @param scratch_capacity capacity of the scratch buffer 187 * @param result_capacity pointer to an integer which will be set to the 188 * capacity of the returned buffer 189 * @return a buffer with *result_capacity>=min_capacity 190 * @stable ICU 4.2 191 */ 192 virtual char* GetAppendBuffer(int32_t min_capacity, 193 int32_t desired_capacity_hint, 194 char* scratch, int32_t scratch_capacity, 195 int32_t* result_capacity); 196 /** 197 * Returns the number of bytes actually written to the sink. 198 * @return number of bytes written to the buffer 199 * @stable ICU 4.2 200 */ NumberOfBytesWritten()201 int32_t NumberOfBytesWritten() const { return size_; } 202 /** 203 * Returns true if any bytes were discarded, i.e., if there was an 204 * attempt to write more than 'capacity' bytes. 205 * @return TRUE if more than 'capacity' bytes were Append()ed 206 * @stable ICU 4.2 207 */ Overflowed()208 UBool Overflowed() const { return overflowed_; } 209 /** 210 * Returns the number of bytes appended to the sink. 211 * If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten() 212 * else they return the same number. 213 * @return number of bytes written to the buffer 214 * @stable ICU 4.6 215 */ NumberOfBytesAppended()216 int32_t NumberOfBytesAppended() const { return appended_; } 217 private: 218 char* outbuf_; 219 const int32_t capacity_; 220 int32_t size_; 221 int32_t appended_; 222 UBool overflowed_; 223 224 CheckedArrayByteSink() = delete; 225 CheckedArrayByteSink(const CheckedArrayByteSink &) = delete; 226 CheckedArrayByteSink &operator=(const CheckedArrayByteSink &) = delete; 227 }; 228 229 /** 230 * Implementation of ByteSink that writes to a "string". 231 * The StringClass is usually instantiated with a std::string. 232 * @stable ICU 4.2 233 */ 234 template<typename StringClass> 235 class StringByteSink : public ByteSink { 236 public: 237 /** 238 * Constructs a ByteSink that will append bytes to the dest string. 239 * @param dest pointer to string object to append to 240 * @stable ICU 4.2 241 */ StringByteSink(StringClass * dest)242 StringByteSink(StringClass* dest) : dest_(dest) { } 243 /** 244 * Constructs a ByteSink that reserves append capacity and will append bytes to the dest string. 245 * 246 * @param dest pointer to string object to append to 247 * @param initialAppendCapacity capacity beyond dest->length() to be reserve()d 248 * @stable ICU 60 249 */ StringByteSink(StringClass * dest,int32_t initialAppendCapacity)250 StringByteSink(StringClass* dest, int32_t initialAppendCapacity) : dest_(dest) { 251 if (initialAppendCapacity > 0 && 252 (uint32_t)initialAppendCapacity > (dest->capacity() - dest->length())) { 253 dest->reserve(dest->length() + initialAppendCapacity); 254 } 255 } 256 /** 257 * Append "bytes[0,n-1]" to this. 258 * @param data the pointer to the bytes 259 * @param n the number of bytes; must be non-negative 260 * @stable ICU 4.2 261 */ Append(const char * data,int32_t n)262 virtual void Append(const char* data, int32_t n) { dest_->append(data, n); } 263 private: 264 StringClass* dest_; 265 266 StringByteSink() = delete; 267 StringByteSink(const StringByteSink &) = delete; 268 StringByteSink &operator=(const StringByteSink &) = delete; 269 }; 270 271 U_NAMESPACE_END 272 273 #endif /* U_SHOW_CPLUSPLUS_API */ 274 275 #endif // __BYTESTREAM_H__ 276