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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 : #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 0 : 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 &); // copy constructor not implemented
130 : ByteSink &operator=(const ByteSink &); // assignment operator not implemented
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 0 : 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 : CheckedArrayByteSink(); ///< default constructor not implemented
221 : CheckedArrayByteSink(const CheckedArrayByteSink &); ///< copy constructor not implemented
222 : CheckedArrayByteSink &operator=(const CheckedArrayByteSink &); ///< assignment operator not implemented
223 : };
224 :
225 : /**
226 : * Implementation of ByteSink that writes to a "string".
227 : * The StringClass is usually instantiated with a std::string.
228 : * @stable ICU 4.2
229 : */
230 : template<typename StringClass>
231 : class StringByteSink : public ByteSink {
232 : public:
233 : /**
234 : * Constructs a ByteSink that will append bytes to the dest string.
235 : * @param dest pointer to string object to append to
236 : * @stable ICU 4.2
237 : */
238 : StringByteSink(StringClass* dest) : dest_(dest) { }
239 : /**
240 : * Append "bytes[0,n-1]" to this.
241 : * @param data the pointer to the bytes
242 : * @param n the number of bytes; must be non-negative
243 : * @stable ICU 4.2
244 : */
245 : virtual void Append(const char* data, int32_t n) { dest_->append(data, n); }
246 : private:
247 : StringClass* dest_;
248 : StringByteSink(); ///< default constructor not implemented
249 : StringByteSink(const StringByteSink &); ///< copy constructor not implemented
250 : StringByteSink &operator=(const StringByteSink &); ///< assignment operator not implemented
251 : };
252 :
253 : U_NAMESPACE_END
254 :
255 : #endif // __BYTESTREAM_H__
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