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comparison: ucx/cx/buffer.h

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
153 * memory management. If \c NULL, the default heap allocator will be used.
154 * @param flags buffer features (see cx_buffer_s.flags)
155 * @return zero on success, non-zero if a required allocation failed
156 */
157 __attribute__((__nonnull__(1)))
158 int cxBufferInit(
159 CxBuffer *buffer,
160 void *space,
161 size_t capacity,
162 CxAllocator const *allocator,
163 int flags
164 );
165
166 /**
167 * Allocates and initializes a fresh buffer.
168 *
169 * \note You may provide \c NULL as argument for \p space.
170 * Then this function will allocate the space and enforce
171 * the #CX_BUFFER_FREE_CONTENTS flag.
172 *
173 * @param space pointer to the memory area, or \c NULL to allocate
174 * new memory
175 * @param capacity the capacity of the buffer
176 * @param allocator the allocator to use for allocating the structure and the automatic
177 * memory management within the buffer. If \c NULL, the default heap allocator will be used.
178 * @param flags buffer features (see cx_buffer_s.flags)
179 * @return a pointer to the buffer on success, \c NULL if a required allocation failed
180 */
181 CxBuffer *cxBufferCreate(
182 void *space,
183 size_t capacity,
184 CxAllocator const *allocator,
185 int flags
186 );
187
188 /**
189 * Destroys the buffer contents.
190 *
191 * Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
192 * If you want to free the memory of the entire buffer, use cxBufferFree().
193 *
194 * @param buffer the buffer which contents shall be destroyed
195 * @see cxBufferInit()
196 */
197 __attribute__((__nonnull__))
198 void cxBufferDestroy(CxBuffer *buffer);
199
200 /**
201 * Deallocates the buffer.
202 *
203 * If the #CX_BUFFER_FREE_CONTENTS feature is enabled, this function also destroys
204 * the contents. If you \em only want to destroy the contents, use cxBufferDestroy().
205 *
206 * @param buffer the buffer to deallocate
207 * @see cxBufferCreate()
208 */
209 __attribute__((__nonnull__))
210 void cxBufferFree(CxBuffer *buffer);
211
212 /**
213 * Shifts the contents of the buffer by the given offset.
214 *
215 * If the offset is positive, the contents are shifted to the right.
216 * If auto extension is enabled, the buffer grows, if necessary.
217 * In case the auto extension fails, this function returns a non-zero value and
218 * no contents are changed.
219 * If auto extension is disabled, the contents that do not fit into the buffer
220 * are discarded.
221 *
222 * If the offset is negative, the contents are shifted to the left where the
223 * first \p shift bytes are discarded.
224 * The new size of the buffer is the old size minus the absolute shift value.
225 * If this value is larger than the buffer size, the buffer is emptied (but
226 * not cleared, see the security note below).
227 *
228 * The buffer position gets shifted alongside with the content but is kept
229 * within the boundaries of the buffer.
230 *
231 * \note For situations where \c off_t is not large enough, there are specialized cxBufferShiftLeft() and
232 * cxBufferShiftRight() functions using a \c size_t as parameter type.
233 *
234 * \attention
235 * Security Note: The shifting operation does \em not erase the previously occupied memory cells.
236 * But you can easily do that manually, e.g. by calling
237 * <code>memset(buffer->bytes, 0, shift)</code> for a right shift or
238 * <code>memset(buffer->bytes + buffer->size, 0, buffer->capacity - buffer->size)</code>
239 * for a left shift.
240 *
241 * @param buffer the buffer
242 * @param shift the shift offset (negative means left shift)
243 * @return 0 on success, non-zero if a required auto-extension fails
244 */
245 __attribute__((__nonnull__))
246 int cxBufferShift(
247 CxBuffer *buffer,
248 off_t shift
249 );
250
251 /**
252 * Shifts the buffer to the right.
253 * See cxBufferShift() for details.
254 *
255 * @param buffer the buffer
256 * @param shift the shift offset
257 * @return 0 on success, non-zero if a required auto-extension fails
258 * @see cxBufferShift()
259 */
260 __attribute__((__nonnull__))
261 int cxBufferShiftRight(
262 CxBuffer *buffer,
263 size_t shift
264 );
265
266 /**
267 * Shifts the buffer to the left.
268 * See cxBufferShift() for details.
269 *
270 * \note Since a left shift cannot fail due to memory allocation problems, this
271 * function always returns zero.
272 *
273 * @param buffer the buffer
274 * @param shift the positive shift offset
275 * @return always zero
276 * @see cxBufferShift()
277 */
278 __attribute__((__nonnull__))
279 int cxBufferShiftLeft(
280 CxBuffer *buffer,
281 size_t shift
282 );
283
284
285 /**
286 * Moves the position of the buffer.
287 *
288 * The new position is relative to the \p whence argument.
289 *
290 * \li \c SEEK_SET marks the start of the buffer.
291 * \li \c SEEK_CUR marks the current position.
292 * \li \c SEEK_END marks the end of the buffer.
293 *
294 * With an offset of zero, this function sets the buffer position to zero
295 * (\c SEEK_SET), the buffer size (\c SEEK_END) or leaves the buffer position
296 * unchanged (\c SEEK_CUR).
297 *
298 * @param buffer the buffer
299 * @param offset position offset relative to \p whence
300 * @param whence one of \c SEEK_SET, \c SEEK_CUR or \c SEEK_END
301 * @return 0 on success, non-zero if the position is invalid
302 *
303 */
304 __attribute__((__nonnull__))
305 int cxBufferSeek(
306 CxBuffer *buffer,
307 off_t offset,
308 int whence
309 );
310
311 /**
312 * Clears the buffer by resetting the position and deleting the data.
313 *
314 * The data is deleted by zeroing it with a call to memset().
315 *
316 * @param buffer the buffer to be cleared
317 */
318 __attribute__((__nonnull__))
319 void cxBufferClear(CxBuffer *buffer);
320
321 /**
322 * Tests, if the buffer position has exceeded the buffer capacity.
323 *
324 * @param buffer the buffer to test
325 * @return non-zero, if the current buffer position has exceeded the last
326 * available byte of the buffer.
327 */
328 __attribute__((__nonnull__))
329 int cxBufferEof(CxBuffer const *buffer);
330
331
332 /**
333 * Ensures that the buffer has a minimum capacity.
334 *
335 * If the current capacity is not sufficient, the buffer will be extended.
336 *
337 * @param buffer the buffer
338 * @param capacity the minimum required capacity for this buffer
339 * @return 0 on success or a non-zero value on failure
340 */
341 __attribute__((__nonnull__))
342 int cxBufferMinimumCapacity(
343 CxBuffer *buffer,
344 size_t capacity
345 );
346
347 /**
348 * Writes data to a CxBuffer.
349 *
350 * If flushing is enabled and the buffer needs to flush, the data is flushed to
351 * the target until the target signals that it cannot take more data by
352 * returning zero via the respective write function. In that case, the remaining
353 * data in this buffer is shifted to the beginning of this buffer so that the
354 * newly available space can be used to append as much data as possible. This
355 * function only stops writing more elements, when the flush target and this
356 * buffer are both incapable of taking more data or all data has been written.
357 * The number returned by this function is the total number of elements that
358 * could be written during the process. It does not necessarily mean that those
359 * elements are still in this buffer, because some of them could have also be
360 * flushed already.
361 *
362 * If automatic flushing is not enabled, the position of the buffer is increased
363 * by the number of bytes written.
364 *
365 * \note The signature is compatible with the fwrite() family of functions.
366 *
367 * @param ptr a pointer to the memory area containing the bytes to be written
368 * @param size the length of one element
369 * @param nitems the element count
370 * @param buffer the CxBuffer to write to
371 * @return the total count of elements written
372 */
373 __attribute__((__nonnull__))
374 size_t cxBufferWrite(
375 void const *ptr,
376 size_t size,
377 size_t nitems,
378 CxBuffer *buffer
379 );
380
381 /**
382 * Reads data from a CxBuffer.
383 *
384 * The position of the buffer is increased by the number of bytes read.
385 *
386 * \note The signature is compatible with the fread() family of functions.
387 *
388 * @param ptr a pointer to the memory area where to store the read data
389 * @param size the length of one element
390 * @param nitems the element count
391 * @param buffer the CxBuffer to read from
392 * @return the total number of elements read
393 */
394 __attribute__((__nonnull__))
395 size_t cxBufferRead(
396 void *ptr,
397 size_t size,
398 size_t nitems,
399 CxBuffer *buffer
400 );
401
402 /**
403 * Writes a character to a buffer.
404 *
405 * The least significant byte of the argument is written to the buffer. If the
406 * end of the buffer is reached and #CX_BUFFER_AUTO_EXTEND feature is enabled,
407 * the buffer capacity is extended by cxBufferMinimumCapacity(). If the feature is
408 * disabled or buffer extension fails, \c EOF is returned.
409 *
410 * On successful write, the position of the buffer is increased.
411 *
412 * @param buffer the buffer to write to
413 * @param c the character to write
414 * @return the byte that has bean written or \c EOF when the end of the stream is
415 * reached and automatic extension is not enabled or not possible
416 */
417 __attribute__((__nonnull__))
418 int cxBufferPut(
419 CxBuffer *buffer,
420 int c
421 );
422
423 /**
424 * Writes a string to a buffer.
425 *
426 * @param buffer the buffer
427 * @param str the zero-terminated string
428 * @return the number of bytes written
429 */
430 __attribute__((__nonnull__))
431 size_t cxBufferPutString(
432 CxBuffer *buffer,
433 const char *str
434 );
435
436 /**
437 * Gets a character from a buffer.
438 *
439 * The current position of the buffer is increased after a successful read.
440 *
441 * @param buffer the buffer to read from
442 * @return the character or \c EOF, if the end of the buffer is reached
443 */
444 __attribute__((__nonnull__))
445 int cxBufferGet(CxBuffer *buffer);
446
447 #ifdef __cplusplus
448 }
449 #endif
450
451 #endif // UCX_BUFFER_H

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