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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 * \copyright 2-Clause BSD License
44 */
45
46 #ifndef UCX_BUFFER_H
47 #define UCX_BUFFER_H
48
49 #include "common.h"
50 #include "allocator.h"
51
52 #ifdef __cplusplus
53 extern "C" {
54 #endif
55
56 /**
57 * No buffer features enabled (all flags cleared).
58 */
59 #define CX_BUFFER_DEFAULT 0x00
60
61 /**
62 * If this flag is enabled, the buffer will automatically free its contents when destroyed.
63 */
64 #define CX_BUFFER_FREE_CONTENTS 0x01
65
66 /**
67 * If this flag is enabled, the buffer will automatically extends its capacity.
68 */
69 #define CX_BUFFER_AUTO_EXTEND 0x02
70
71 /** Structure for the UCX buffer data. */
72 typedef struct {
73 /** A pointer to the buffer contents. */
74 union {
75 /**
76 * Data is interpreted as text.
77 */
78 char *space;
79 /**
80 * Data is interpreted as binary.
81 */
82 unsigned char *bytes;
83 };
84 /** The allocator to use for automatic memory management. */
85 CxAllocator const *allocator;
86 /** Current position of the buffer. */
87 size_t pos;
88 /** Current capacity (i.e. maximum size) of the buffer. */
89 size_t capacity;
90 /** Current size of the buffer content. */
91 size_t size;
92 /**
93 * The buffer may not extend beyond this threshold before starting to flush.
94 * Default is \c SIZE_MAX (flushing disabled when auto extension is enabled).
95 */
96 size_t flush_threshold;
97 /**
98 * The block size for the elements to flush.
99 * Default is 4096 bytes.
100 */
101 size_t flush_blksize;
102 /**
103 * The maximum number of blocks to flush in one cycle.
104 * Zero disables flushing entirely (this is the default).
105 * Set this to \c SIZE_MAX to flush the entire buffer.
106 *
107 * @attention if the maximum number of blocks multiplied with the block size
108 * is smaller than the expected contents written to this buffer within one write
109 * operation, multiple flush cycles are performed after that write.
110 * That means the total number of blocks flushed after one write to this buffer may
111 * be larger than \c flush_blkmax.
112 */
113 size_t flush_blkmax;
114
115 /**
116 * The write function used for flushing.
117 * If NULL, the flushed content gets discarded.
118 */
119 cx_write_func flush_func;
120
121 /**
122 * The target for \c flush_func.
123 */
124 void *flush_target;
125
126 /**
127 * Flag register for buffer features.
128 * @see #CX_BUFFER_DEFAULT
129 * @see #CX_BUFFER_FREE_CONTENTS
130 * @see #CX_BUFFER_AUTO_EXTEND
131 */
132 int flags;
133 } cx_buffer_s;
134
135 /**
136 * UCX buffer.
137 */
138 typedef cx_buffer_s CxBuffer;
139
140 /**
141 * Initializes a fresh buffer.
142 *
143 * \note You may provide \c NULL as argument for \p space.
144 * Then this function will allocate the space and enforce
145 * the #CX_BUFFER_FREE_CONTENTS flag.
146 *
147 * @param buffer the buffer to initialize
148 * @param space pointer to the memory area, or \c NULL to allocate
149 * new memory
150 * @param capacity the capacity of the buffer
151 * @param allocator the allocator this buffer shall use for automatic
152 * memory management. If \c NULL, the default heap allocator will be used.
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)))
157 int cxBufferInit(
158 CxBuffer *buffer,
159 void *space,
160 size_t capacity,
161 CxAllocator const *allocator,
162 int flags
163 );
164
165 /**
166 * Allocates and initializes a fresh buffer.
167 *
168 * \note You may provide \c NULL as argument for \p space.
169 * Then this function will allocate the space and enforce
170 * the #CX_BUFFER_FREE_CONTENTS flag.
171 *
172 * @param space pointer to the memory area, or \c NULL to allocate
173 * new memory
174 * @param capacity the capacity of the buffer
175 * @param allocator the allocator to use for allocating the structure and the automatic
176 * memory management within the buffer. If \c NULL, the default heap allocator will be used.
177 * @param flags buffer features (see cx_buffer_s.flags)
178 * @return a pointer to the buffer on success, \c NULL if a required allocation failed
179 */
180 CxBuffer *cxBufferCreate(
181 void *space,
182 size_t capacity,
183 CxAllocator const *allocator,
184 int flags
185 );
186
187 /**
188 * Destroys the buffer contents.
189 *
190 * Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
191 * If you want to free the memory of the entire buffer, use cxBufferFree().
192 *
193 * @param buffer the buffer which contents shall be destroyed
194 * @see cxBufferInit()
195 */
196 __attribute__((__nonnull__))
197 void cxBufferDestroy(CxBuffer *buffer);
198
199 /**
200 * Deallocates the buffer.
201 *
202 * If the #CX_BUFFER_FREE_CONTENTS feature is enabled, this function also destroys
203 * the contents. If you \em only want to destroy the contents, use cxBufferDestroy().
204 *
205 * @param buffer the buffer to deallocate
206 * @see cxBufferCreate()
207 */
208 __attribute__((__nonnull__))
209 void cxBufferFree(CxBuffer *buffer);
210
211 /**
212 * Shifts the contents of the buffer by the given offset.
213 *
214 * If the offset is positive, the contents are shifted to the right.
215 * If auto extension is enabled, the buffer grows, if necessary.
216 * In case the auto extension fails, this function returns a non-zero value and
217 * no contents are changed.
218 * If auto extension is disabled, the contents that do not fit into the buffer
219 * are discarded.
220 *
221 * If the offset is negative, the contents are shifted to the left where the
222 * first \p shift bytes are discarded.
223 * The new size of the buffer is the old size minus the absolute shift value.
224 * If this value is larger than the buffer size, the buffer is emptied (but
225 * not cleared, see the security note below).
226 *
227 * The buffer position gets shifted alongside with the content but is kept
228 * within the boundaries of the buffer.
229 *
230 * \note For situations where \c off_t is not large enough, there are specialized cxBufferShiftLeft() and
231 * cxBufferShiftRight() functions using a \c size_t as parameter type.
232 *
233 * \attention
234 * Security Note: The shifting operation does \em not erase the previously occupied memory cells.
235 * But you can easily do that manually, e.g. by calling
236 * <code>memset(buffer->bytes, 0, shift)</code> for a right shift or
237 * <code>memset(buffer->bytes + buffer->size, 0, buffer->capacity - buffer->size)</code>
238 * for a left shift.
239 *
240 * @param buffer the buffer
241 * @param shift the shift offset (negative means left shift)
242 * @return 0 on success, non-zero if a required auto-extension fails
243 */
244 __attribute__((__nonnull__))
245 int cxBufferShift(
246 CxBuffer *buffer,
247 off_t shift
248 );
249
250 /**
251 * Shifts the buffer to the right.
252 * See cxBufferShift() for details.
253 *
254 * @param buffer the buffer
255 * @param shift the shift offset
256 * @return 0 on success, non-zero if a required auto-extension fails
257 * @see cxBufferShift()
258 */
259 __attribute__((__nonnull__))
260 int cxBufferShiftRight(
261 CxBuffer *buffer,
262 size_t shift
263 );
264
265 /**
266 * Shifts the buffer to the left.
267 * See cxBufferShift() for details.
268 *
269 * \note Since a left shift cannot fail due to memory allocation problems, this
270 * function always returns zero.
271 *
272 * @param buffer the buffer
273 * @param shift the positive shift offset
274 * @return always zero
275 * @see cxBufferShift()
276 */
277 __attribute__((__nonnull__))
278 int cxBufferShiftLeft(
279 CxBuffer *buffer,
280 size_t shift
281 );
282
283
284 /**
285 * Moves the position of the buffer.
286 *
287 * The new position is relative to the \p whence argument.
288 *
289 * \li \c SEEK_SET marks the start of the buffer.
290 * \li \c SEEK_CUR marks the current position.
291 * \li \c SEEK_END marks the end of the buffer.
292 *
293 * With an offset of zero, this function sets the buffer position to zero
294 * (\c SEEK_SET), the buffer size (\c SEEK_END) or leaves the buffer position
295 * unchanged (\c SEEK_CUR).
296 *
297 * @param buffer the buffer
298 * @param offset position offset relative to \p whence
299 * @param whence one of \c SEEK_SET, \c SEEK_CUR or \c SEEK_END
300 * @return 0 on success, non-zero if the position is invalid
301 *
302 */
303 __attribute__((__nonnull__))
304 int cxBufferSeek(
305 CxBuffer *buffer,
306 off_t offset,
307 int whence
308 );
309
310 /**
311 * Clears the buffer by resetting the position and deleting the data.
312 *
313 * The data is deleted by zeroing it with a call to memset().
314 * If you do not need that, you can use the faster cxBufferReset().
315 *
316 * @param buffer the buffer to be cleared
317 * @see cxBufferReset()
318 */
319 __attribute__((__nonnull__))
320 void cxBufferClear(CxBuffer *buffer);
321
322 /**
323 * Resets the buffer by resetting the position and size to zero.
324 *
325 * The data in the buffer is not deleted. If you need a safe
326 * reset of the buffer, use cxBufferClear().
327 *
328 * @param buffer the buffer to be cleared
329 * @see cxBufferClear()
330 */
331 __attribute__((__nonnull__))
332 void cxBufferReset(CxBuffer *buffer);
333
334 /**
335 * Tests, if the buffer position has exceeded the buffer size.
336 *
337 * @param buffer the buffer to test
338 * @return non-zero, if the current buffer position has exceeded the last
339 * byte of the buffer's contents.
340 */
341 __attribute__((__nonnull__))
342 int cxBufferEof(CxBuffer const *buffer);
343
344
345 /**
346 * Ensures that the buffer has a minimum capacity.
347 *
348 * If the current capacity is not sufficient, the buffer will be extended.
349 *
350 * @param buffer the buffer
351 * @param capacity the minimum required capacity for this buffer
352 * @return 0 on success or a non-zero value on failure
353 */
354 __attribute__((__nonnull__))
355 int cxBufferMinimumCapacity(
356 CxBuffer *buffer,
357 size_t capacity
358 );
359
360 /**
361 * Writes data to a CxBuffer.
362 *
363 * If flushing is enabled and the buffer needs to flush, the data is flushed to
364 * the target until the target signals that it cannot take more data by
365 * returning zero via the respective write function. In that case, the remaining
366 * data in this buffer is shifted to the beginning of this buffer so that the
367 * newly available space can be used to append as much data as possible. This
368 * function only stops writing more elements, when the flush target and this
369 * buffer are both incapable of taking more data or all data has been written.
370 * The number returned by this function is the total number of elements that
371 * could be written during the process. It does not necessarily mean that those
372 * elements are still in this buffer, because some of them could have also be
373 * flushed already.
374 *
375 * If automatic flushing is not enabled, the position of the buffer is increased
376 * by the number of bytes written.
377 *
378 * \note The signature is compatible with the fwrite() family of functions.
379 *
380 * @param ptr a pointer to the memory area containing the bytes to be written
381 * @param size the length of one element
382 * @param nitems the element count
383 * @param buffer the CxBuffer to write to
384 * @return the total count of elements written
385 */
386 __attribute__((__nonnull__))
387 size_t cxBufferWrite(
388 void const *ptr,
389 size_t size,
390 size_t nitems,
391 CxBuffer *buffer
392 );
393
394 /**
395 * Reads data from a CxBuffer.
396 *
397 * The position of the buffer is increased by the number of bytes read.
398 *
399 * \note The signature is compatible with the fread() family of functions.
400 *
401 * @param ptr a pointer to the memory area where to store the read data
402 * @param size the length of one element
403 * @param nitems the element count
404 * @param buffer the CxBuffer to read from
405 * @return the total number of elements read
406 */
407 __attribute__((__nonnull__))
408 size_t cxBufferRead(
409 void *ptr,
410 size_t size,
411 size_t nitems,
412 CxBuffer *buffer
413 );
414
415 /**
416 * Writes a character to a buffer.
417 *
418 * The least significant byte of the argument is written to the buffer. If the
419 * end of the buffer is reached and #CX_BUFFER_AUTO_EXTEND feature is enabled,
420 * the buffer capacity is extended by cxBufferMinimumCapacity(). If the feature is
421 * disabled or buffer extension fails, \c EOF is returned.
422 *
423 * On successful write, the position of the buffer is increased.
424 *
425 * @param buffer the buffer to write to
426 * @param c the character to write
427 * @return the byte that has bean written or \c EOF when the end of the stream is
428 * reached and automatic extension is not enabled or not possible
429 */
430 __attribute__((__nonnull__))
431 int cxBufferPut(
432 CxBuffer *buffer,
433 int c
434 );
435
436 /**
437 * Writes a string to a buffer.
438 *
439 * @param buffer the buffer
440 * @param str the zero-terminated string
441 * @return the number of bytes written
442 */
443 __attribute__((__nonnull__))
444 size_t cxBufferPutString(
445 CxBuffer *buffer,
446 const char *str
447 );
448
449 /**
450 * Gets a character from a buffer.
451 *
452 * The current position of the buffer is increased after a successful read.
453 *
454 * @param buffer the buffer to read from
455 * @return the character or \c EOF, if the end of the buffer is reached
456 */
457 __attribute__((__nonnull__))
458 int cxBufferGet(CxBuffer *buffer);
459
460 #ifdef __cplusplus
461 }
462 #endif
463
464 #endif // UCX_BUFFER_H

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