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comparison: src/ucx/cx/buffer.h

src/ucx/cx/buffer.h

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1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
3 *
4 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 /**
30 * \file buffer.h
31 *
32 * \brief Advanced buffer implementation.
33 *
34 * Instances of CxBuffer can be used to read from or to write to like one
35 * would do with a stream.
36 *
37 * Some features for convenient use of the buffer
38 * can be enabled. See the documentation of the macro constants for more
39 * information.
40 *
41 * \author Mike Becker
42 * \author Olaf Wintermann
43 * \version 3.0
44 * \copyright 2-Clause BSD License
45 */
46
47 #ifndef UCX_BUFFER_H
48 #define UCX_BUFFER_H
49
50 #include "common.h"
51 #include "allocator.h"
52
53 #ifdef __cplusplus
54 extern "C" {
55 #endif
56
57 /**
58 * No buffer features enabled (all flags cleared).
59 */
60 #define CX_BUFFER_DEFAULT 0x00
61
62 /**
63 * If this flag is enabled, the buffer will automatically free its contents when destroyed.
64 */
65 #define CX_BUFFER_FREE_CONTENTS 0x01
66
67 /**
68 * If this flag is enabled, the buffer will automatically extends its capacity.
69 */
70 #define CX_BUFFER_AUTO_EXTEND 0x02
71
72 /** Structure for the UCX buffer data. */
73 typedef struct {
74 /** A pointer to the buffer contents. */
75 union {
76 /**
77 * Data is interpreted as text.
78 */
79 char *space;
80 /**
81 * Data is interpreted as binary.
82 */
83 unsigned char *bytes;
84 };
85 /** The allocator to use for automatic memory management. */
86 CxAllocator const *allocator;
87 /** Current position of the buffer. */
88 size_t pos;
89 /** Current capacity (i.e. maximum size) of the buffer. */
90 size_t capacity;
91 /** Current size of the buffer content. */
92 size_t size;
93 /**
94 * The buffer may not extend beyond this threshold before starting to flush.
95 * Default is \c SIZE_MAX (flushing disabled when auto extension is enabled).
96 */
97 size_t flush_threshold;
98 /**
99 * The block size for the elements to flush.
100 * Default is 4096 bytes.
101 */
102 size_t flush_blksize;
103 /**
104 * The maximum number of blocks to flush in one cycle.
105 * Zero disables flushing entirely (this is the default).
106 * Set this to \c SIZE_MAX to flush the entire buffer.
107 *
108 * @attention if the maximum number of blocks multiplied with the block size
109 * is smaller than the expected contents written to this buffer within one write
110 * operation, multiple flush cycles are performed after that write.
111 * That means the total number of blocks flushed after one write to this buffer may
112 * be larger than \c flush_blkmax.
113 */
114 size_t flush_blkmax;
115
116 /**
117 * The write function used for flushing.
118 * If NULL, the flushed content gets discarded.
119 */
120 cx_write_func flush_func;
121
122 /**
123 * The target for \c flush_func.
124 */
125 void *flush_target;
126
127 /**
128 * Flag register for buffer features.
129 * @see #CX_BUFFER_DEFAULT
130 * @see #CX_BUFFER_FREE_CONTENTS
131 * @see #CX_BUFFER_AUTO_EXTEND
132 */
133 int flags;
134 } cx_buffer_s;
135
136 /**
137 * UCX buffer.
138 */
139 typedef cx_buffer_s CxBuffer;
140
141 /**
142 * Initializes a fresh buffer.
143 *
144 * \note You may provide \c NULL as argument for \p space.
145 * Then this function will allocate the space and enforce
146 * the #CX_BUFFER_FREE_CONTENTS flag.
147 *
148 * @param buffer the buffer to initialize
149 * @param space pointer to the memory area, or \c NULL to allocate
150 * new memory
151 * @param capacity the capacity of the buffer
152 * @param allocator the allocator this buffer shall use for automatic memory management
153 * @param flags buffer features (see cx_buffer_s.flags)
154 * @return zero on success, non-zero if a required allocation failed
155 */
156 __attribute__((__nonnull__(1, 4)))
157 int cxBufferInit(
158 CxBuffer *buffer,
159 void *space,
160 size_t capacity,
161 CxAllocator const *allocator,
162 int flags
163 );
164
165 /**
166 * Destroys the buffer contents.
167 *
168 * Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
169 *
170 * @param buffer the buffer which contents shall be destroyed
171 */
172 __attribute__((__nonnull__))
173 void cxBufferDestroy(CxBuffer *buffer);
174
175 /**
176 * Shifts the contents of the buffer by the given offset.
177 *
178 * If the offset is positive, the contents are shifted to the right.
179 * If auto extension is enabled, the buffer grows, if necessary.
180 * In case the auto extension fails, this function returns a non-zero value and
181 * no contents are changed.
182 * If auto extension is disabled, the contents that do not fit into the buffer
183 * are discarded.
184 *
185 * If the offset is negative, the contents are shifted to the left where the
186 * first \p shift bytes are discarded.
187 * The new size of the buffer is the old size minus the absolute shift value.
188 * If this value is larger than the buffer size, the buffer is emptied (but
189 * not cleared, see the security note below).
190 *
191 * The buffer position gets shifted alongside with the content but is kept
192 * within the boundaries of the buffer.
193 *
194 * \note For situations where \c off_t is not large enough, there are specialized cxBufferShiftLeft() and
195 * cxBufferShiftRight() functions using a \c size_t as parameter type.
196 *
197 * \attention
198 * Security Note: The shifting operation does \em not erase the previously occupied memory cells.
199 * But you can easily do that manually, e.g. by calling
200 * <code>memset(buffer->bytes, 0, shift)</code> for a right shift or
201 * <code>memset(buffer->bytes + buffer->size, 0, buffer->capacity - buffer->size)</code>
202 * for a left shift.
203 *
204 * @param buffer the buffer
205 * @param shift the shift offset (negative means left shift)
206 * @return 0 on success, non-zero if a required auto-extension fails
207 */
208 __attribute__((__nonnull__))
209 int cxBufferShift(
210 CxBuffer *buffer,
211 off_t shift
212 );
213
214 /**
215 * Shifts the buffer to the right.
216 * See cxBufferShift() for details.
217 *
218 * @param buffer the buffer
219 * @param shift the shift offset
220 * @return 0 on success, non-zero if a required auto-extension fails
221 * @see cxBufferShift()
222 */
223 __attribute__((__nonnull__))
224 int cxBufferShiftRight(
225 CxBuffer *buffer,
226 size_t shift
227 );
228
229 /**
230 * Shifts the buffer to the left.
231 * See cxBufferShift() for details.
232 *
233 * \note Since a left shift cannot fail due to memory allocation problems, this
234 * function always returns zero.
235 *
236 * @param buffer the buffer
237 * @param shift the positive shift offset
238 * @return always zero
239 * @see cxBufferShift()
240 */
241 __attribute__((__nonnull__))
242 int cxBufferShiftLeft(
243 CxBuffer *buffer,
244 size_t shift
245 );
246
247
248 /**
249 * Moves the position of the buffer.
250 *
251 * The new position is relative to the \p whence argument.
252 *
253 * \li \c SEEK_SET marks the start of the buffer.
254 * \li \c SEEK_CUR marks the current position.
255 * \li \c SEEK_END marks the end of the buffer.
256 *
257 * With an offset of zero, this function sets the buffer position to zero
258 * (\c SEEK_SET), the buffer size (\c SEEK_END) or leaves the buffer position
259 * unchanged (\c SEEK_CUR).
260 *
261 * @param buffer the buffer
262 * @param offset position offset relative to \p whence
263 * @param whence one of \c SEEK_SET, \c SEEK_CUR or \c SEEK_END
264 * @return 0 on success, non-zero if the position is invalid
265 *
266 */
267 __attribute__((__nonnull__))
268 int cxBufferSeek(
269 CxBuffer *buffer,
270 off_t offset,
271 int whence
272 );
273
274 /**
275 * Clears the buffer by resetting the position and deleting the data.
276 *
277 * The data is deleted by zeroing it with a call to memset().
278 *
279 * @param buffer the buffer to be cleared
280 */
281 __attribute__((__nonnull__))
282 void cxBufferClear(CxBuffer *buffer);
283
284 /**
285 * Tests, if the buffer position has exceeded the buffer capacity.
286 *
287 * @param buffer the buffer to test
288 * @return non-zero, if the current buffer position has exceeded the last
289 * available byte of the buffer.
290 */
291 __attribute__((__nonnull__))
292 int cxBufferEof(CxBuffer const *buffer);
293
294
295 /**
296 * Ensures that the buffer has a minimum capacity.
297 *
298 * If the current capacity is not sufficient, the buffer will be extended.
299 *
300 * @param buffer the buffer
301 * @param capacity the minimum required capacity for this buffer
302 * @return 0 on success or a non-zero value on failure
303 */
304 __attribute__((__nonnull__))
305 int cxBufferMinimumCapacity(
306 CxBuffer *buffer,
307 size_t capacity
308 );
309
310 /**
311 * Writes data to a CxBuffer.
312 *
313 * If flushing is enabled and the buffer needs to flush, the data is flushed to
314 * the target until the target signals that it cannot take more data by
315 * returning zero via the respective write function. In that case, the remaining
316 * data in this buffer is shifted to the beginning of this buffer so that the
317 * newly available space can be used to append as much data as possible. This
318 * function only stops writing more elements, when the flush target and this
319 * buffer are both incapable of taking more data or all data has been written.
320 * The number returned by this function is the total number of elements that
321 * could be written during the process. It does not necessarily mean that those
322 * elements are still in this buffer, because some of them could have also be
323 * flushed already.
324 *
325 * If automatic flushing is not enabled, the position of the buffer is increased
326 * by the number of bytes written.
327 *
328 * \note The signature is compatible with the fwrite() family of functions.
329 *
330 * @param ptr a pointer to the memory area containing the bytes to be written
331 * @param size the length of one element
332 * @param nitems the element count
333 * @param buffer the CxBuffer to write to
334 * @return the total count of elements written
335 */
336 __attribute__((__nonnull__))
337 size_t cxBufferWrite(
338 void const *ptr,
339 size_t size,
340 size_t nitems,
341 CxBuffer *buffer
342 );
343
344 /**
345 * Reads data from a CxBuffer.
346 *
347 * The position of the buffer is increased by the number of bytes read.
348 *
349 * \note The signature is compatible with the fread() family of functions.
350 *
351 * @param ptr a pointer to the memory area where to store the read data
352 * @param size the length of one element
353 * @param nitems the element count
354 * @param buffer the CxBuffer to read from
355 * @return the total number of elements read
356 */
357 __attribute__((__nonnull__))
358 size_t cxBufferRead(
359 void *ptr,
360 size_t size,
361 size_t nitems,
362 CxBuffer *buffer
363 );
364
365 /**
366 * Writes a character to a buffer.
367 *
368 * The least significant byte of the argument is written to the buffer. If the
369 * end of the buffer is reached and #CX_BUFFER_AUTO_EXTEND feature is enabled,
370 * the buffer capacity is extended by cxBufferMinimumCapacity(). If the feature is
371 * disabled or buffer extension fails, \c EOF is returned.
372 *
373 * On successful write, the position of the buffer is increased.
374 *
375 * @param buffer the buffer to write to
376 * @param c the character to write
377 * @return the byte that has bean written or \c EOF when the end of the stream is
378 * reached and automatic extension is not enabled or not possible
379 */
380 __attribute__((__nonnull__))
381 int cxBufferPut(
382 CxBuffer *buffer,
383 int c
384 );
385
386 /**
387 * Writes a string to a buffer.
388 *
389 * @param buffer the buffer
390 * @param str the zero-terminated string
391 * @return the number of bytes written
392 */
393 __attribute__((__nonnull__))
394 size_t cxBufferPutString(
395 CxBuffer *buffer,
396 const char *str
397 );
398
399 /**
400 * Gets a character from a buffer.
401 *
402 * The current position of the buffer is increased after a successful read.
403 *
404 * @param buffer the buffer to read from
405 * @return the character or \c EOF, if the end of the buffer is reached
406 */
407 __attribute__((__nonnull__))
408 int cxBufferGet(CxBuffer *buffer);
409
410 #ifdef __cplusplus
411 }
412 #endif
413
414 #endif /* UCX_BUFFER_H */

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