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 * Do NOT set this flag together with #CX_BUFFER_COPY_ON_WRITE. It will be automatically
65 * set when the copy-on-write operation is performed.
66 */
67 #define CX_BUFFER_FREE_CONTENTS 0x01
68
69 /**
70 * If this flag is enabled, the buffer will automatically extend its capacity.
71 */
72 #define CX_BUFFER_AUTO_EXTEND 0x02
73
74 /**
75 * If this flag is enabled, the buffer will allocate new memory when written to.
76 *
77 * The current contents of the buffer will be copied to the new memory, and the flag
78 * will be cleared while the #CX_BUFFER_FREE_CONTENTS flag will be set automatically.
79 */
80 #define CX_BUFFER_COPY_ON_WRITE 0x04
81
82 /**
83 * If this flag is enabled, the buffer will copy its contents to a new memory area on reallocation.
84 *
85 * After performing the copy, the flag is automatically cleared.
86 * This flag has no effect on buffers which do not have #CX_BUFFER_AUTO_EXTEND set, which is why
87 * buffers automatically admit the auto-extend flag when initialized with copy-on-extend enabled.
88 */
89 #define CX_BUFFER_COPY_ON_EXTEND 0x08
90
91 /**
92 * Function pointer for cxBufferWrite that is compatible with cx_write_func.
93 * @see cx_write_func
94 */
95 #define cxBufferWriteFunc ((cx_write_func) cxBufferWrite)
96 /**
97 * Function pointer for cxBufferRead that is compatible with cx_read_func.
98 * @see cx_read_func
99 */
100 #define cxBufferReadFunc ((cx_read_func) cxBufferRead)
101
102
103 /** Structure for the UCX buffer data. */
104 struct cx_buffer_s {
105 /** A pointer to the buffer contents. */
106 union {
107 /**
108 * Data is interpreted as text.
109 */
110 char *space;
111 /**
112 * Data is interpreted as binary.
113 */
114 unsigned char *bytes;
115 };
116 /** The allocator to use for automatic memory management. */
117 const CxAllocator *allocator;
118 /** Current position of the buffer. */
119 size_t pos;
120 /** Current capacity (i.e. maximum size) of the buffer. */
121 size_t capacity;
122 /** Maximum capacity that this buffer may grow to. */
123 size_t max_capacity;
124 /** Current size of the buffer content. */
125 size_t size;
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 * @see #CX_BUFFER_COPY_ON_WRITE
132 */
133 int flags;
134 };
135
136 /**
137 * UCX buffer.
138 */
139 typedef struct cx_buffer_s CxBuffer;
140
141 /**
142 * Initializes a fresh buffer.
143 *
144 * You may also provide a read-only @p space, in which case
145 * you will need to cast the pointer, and you should set the
146 * #CX_BUFFER_COPY_ON_WRITE flag.
147 *
148 * You need to set the size manually after initialization if
149 * you provide @p space which already contains data.
150 *
151 * When you specify stack memory as @p space and decide to use
152 * the auto-extension feature, you @em must use the
153 * #CX_BUFFER_COPY_ON_EXTEND flag, instead of the
154 * #CX_BUFFER_AUTO_EXTEND flag.
155 *
156 * @note You may provide @c NULL as the argument for @p space.
157 * Then this function will allocate the space and enforce
158 * the #CX_BUFFER_FREE_CONTENTS flag. In that case, specifying
159 * copy-on-write should be avoided, because the allocated
160 * space will be leaking after the copy-on-write operation.
161 *
162 * @param buffer the buffer to initialize
163 * @param space pointer to the memory area, or @c NULL to allocate
164 * new memory
165 * @param capacity the capacity of the buffer
166 * @param allocator the allocator this buffer shall use for automatic
167 * memory management
168 * (if @c NULL, the cxDefaultAllocator will be used)
169 * @param flags buffer features (see cx_buffer_s.flags)
170 * @return zero on success, non-zero if a required allocation failed
171 */
172 cx_attr_nonnull_arg(1)
173 CX_EXPORT int cxBufferInit(CxBuffer *buffer, void *space, size_t capacity,
174 const CxAllocator *allocator, int flags);
175
176 /**
177 * Destroys the buffer contents.
178 *
179 * Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
180 * If you want to free the memory of the entire buffer, use cxBufferFree().
181 *
182 * @param buffer the buffer which contents shall be destroyed
183 * @see cxBufferInit()
184 */
185 cx_attr_nonnull
186 CX_EXPORT void cxBufferDestroy(CxBuffer *buffer);
187
188 /**
189 * Deallocates the buffer.
190 *
191 * If the #CX_BUFFER_FREE_CONTENTS feature is enabled, this function also destroys
192 * the contents. If you @em only want to destroy the contents, use cxBufferDestroy().
193 *
194 * @param buffer the buffer to deallocate
195 * @see cxBufferCreate()
196 */
197 CX_EXPORT void cxBufferFree(CxBuffer *buffer);
198
199 /**
200 * Allocates and initializes a fresh buffer.
201 *
202 * You may also provide a read-only @p space, in which case
203 * you will need to cast the pointer, and you should set the
204 * #CX_BUFFER_COPY_ON_WRITE flag.
205 * When you specify stack memory as @p space and decide to use
206 * the auto-extension feature, you @em must use the
207 * #CX_BUFFER_COPY_ON_EXTEND flag, instead of the
208 * #CX_BUFFER_AUTO_EXTEND flag.
209 *
210 * @note You may provide @c NULL as the argument for @p space.
211 * Then this function will allocate the space and enforce
212 * the #CX_BUFFER_FREE_CONTENTS flag.
213 *
214 * @param space pointer to the memory area, or @c NULL to allocate
215 * new memory
216 * @param capacity the capacity of the buffer
217 * @param allocator the allocator to use for allocating the structure and the automatic
218 * memory management within the buffer
219 * (if @c NULL, the cxDefaultAllocator will be used)
220 * @param flags buffer features (see cx_buffer_s.flags)
221 * @return a pointer to the buffer on success, @c NULL if a required allocation failed
222 */
223 cx_attr_malloc cx_attr_dealloc(cxBufferFree, 1) cx_attr_nodiscard
224 CX_EXPORT CxBuffer *cxBufferCreate(void *space, size_t capacity,
225 const CxAllocator *allocator, int flags);
226
227 /**
228 * Shifts the contents of the buffer by the given offset.
229 *
230 * If the offset is positive, the contents are shifted to the right.
231 * If auto extension is enabled, the buffer grows, if necessary.
232 * In case the auto extension fails, this function returns a non-zero value and
233 * no contents are changed.
234 * When the auto extension is disabled, the contents that do not fit into the
235 * buffer are discarded.
236 *
237 * If the offset is negative, the contents are shifted to the left where the
238 * first @p shift bytes are discarded.
239 * The new size of the buffer is the old size minus the absolute shift value.
240 * If this value is larger than the buffer size, the buffer is emptied (but
241 * not cleared, see the security note below).
242 *
243 * The buffer position gets shifted alongside the content but is kept
244 * within the boundaries of the buffer.
245 *
246 * @note For situations where @c off_t is not large enough, there are specialized cxBufferShiftLeft() and
247 * cxBufferShiftRight() functions using a @c size_t as the parameter type.
248 *
249 * @attention
250 * Security Note: The shifting operation does @em not erase the previously occupied memory cells.
251 * But you can do that manually by calling
252 * <code>memset(buffer->bytes, 0, shift)</code> for a right shift or
253 * <code>memset(buffer->bytes + buffer->size, 0, buffer->capacity - buffer->size)</code>
254 * for a left shift.
255 *
256 * @param buffer the buffer
257 * @param shift the shift offset (negative means left shift)
258 * @retval zero success
259 * @retval non-zero if a required auto-extension or copy-on-write fails
260 * @see cxBufferShiftLeft()
261 * @see cxBufferShiftRight()
262 */
263 cx_attr_nonnull
264 CX_EXPORT int cxBufferShift(CxBuffer *buffer, off_t shift);
265
266 /**
267 * Shifts the buffer to the right.
268 * See cxBufferShift() for details.
269 *
270 * @param buffer the buffer
271 * @param shift the shift offset
272 * @retval zero success
273 * @retval non-zero if a required auto-extension or copy-on-write fails
274 * @see cxBufferShift()
275 */
276 cx_attr_nonnull
277 CX_EXPORT int cxBufferShiftRight(CxBuffer *buffer, size_t shift);
278
279 /**
280 * Shifts the buffer to the left.
281 * See cxBufferShift() for details.
282 *
283 * @param buffer the buffer
284 * @param shift the positive shift offset
285 * @retval zero success
286 * @retval non-zero if the buffer uses copy-on-write and the allocation fails
287 * @see cxBufferShift()
288 */
289 cx_attr_nonnull
290 CX_EXPORT int cxBufferShiftLeft(CxBuffer *buffer, size_t shift);
291
292
293 /**
294 * Moves the position of the buffer.
295 *
296 * The new position is relative to the @p whence argument.
297 *
298 * @li @c SEEK_SET marks the start of the buffer.
299 * @li @c SEEK_CUR marks the current position.
300 * @li @c SEEK_END marks the end of the buffer.
301 *
302 * With an offset of zero, this function sets the buffer position to zero
303 * (@c SEEK_SET), the buffer size (@c SEEK_END) or leaves the buffer position
304 * unchanged (@c SEEK_CUR).
305 *
306 * @param buffer the buffer
307 * @param offset position offset relative to @p whence
308 * @param whence one of @c SEEK_SET, @c SEEK_CUR or @c SEEK_END
309 * @retval zero success
310 * @retval non-zero if the position is invalid
311 *
312 */
313 cx_attr_nonnull
314 CX_EXPORT int cxBufferSeek(CxBuffer *buffer, off_t offset, int whence);
315
316 /**
317 * Discards items from the end of the buffer.
318 *
319 * When the current position points to a byte that gets discarded,
320 * the position is set to the buffer size.
321 *
322 * @param buffer the buffer
323 * @param size the size of one item
324 * @param nitems the number of items to discard
325 * @return the actual number of discarded items
326 */
327 cx_attr_nonnull
328 CX_EXPORT size_t cxBufferPop(CxBuffer *buffer, size_t size, size_t nitems);
329
330 /**
331 * Clears the buffer by resetting the position and deleting the data.
332 *
333 * The data is deleted by zeroing it with a call to memset().
334 * If you do not need that, you can use the faster cxBufferReset().
335 *
336 * @note If the #CX_BUFFER_COPY_ON_WRITE flag is set, this function
337 * will not erase the data and behave exactly as cxBufferReset().
338 *
339 * @param buffer the buffer to be cleared
340 * @see cxBufferReset()
341 */
342 cx_attr_nonnull
343 CX_EXPORT void cxBufferClear(CxBuffer *buffer);
344
345 /**
346 * Resets the buffer by resetting the position and size to zero.
347 *
348 * The data in the buffer is not deleted. If you need a safe
349 * reset of the buffer, use cxBufferClear().
350 *
351 * @param buffer the buffer to be cleared
352 * @see cxBufferClear()
353 */
354 cx_attr_nonnull
355 CX_EXPORT void cxBufferReset(CxBuffer *buffer);
356
357 /**
358 * Tests, if the buffer position has exceeded the buffer size.
359 *
360 * @param buffer the buffer to test
361 * @retval true if the current buffer position has exceeded the last
362 * byte of the buffer's contents
363 * @retval false otherwise
364 */
365 cx_attr_nonnull cx_attr_nodiscard
366 CX_EXPORT bool cxBufferEof(const CxBuffer *buffer);
367
368 /**
369 * Ensures that the buffer has the required capacity.
370 *
371 * If the current capacity is not sufficient, the buffer will be extended.
372 * If the current capacity is larger, the buffer is shrunk and superfluous
373 * content is discarded.
374 *
375 * This function will reserve no more bytes than requested, in contrast to
376 * cxBufferMinimumCapacity(), which may reserve more bytes to improve the
377 * number of future necessary reallocations.
378 *
379 * @param buffer the buffer
380 * @param capacity the required capacity for this buffer
381 * @retval zero on success
382 * @retval non-zero on allocation failure
383 * @see cxBufferShrink()
384 * @see cxBufferMinimumCapacity()
385 */
386 cx_attr_nonnull
387 CX_EXPORT int cxBufferReserve(CxBuffer *buffer, size_t capacity);
388
389 /**
390 * Limits the buffer's capacity.
391 *
392 * If the current capacity is already larger, this function fails and returns
393 * non-zero.
394 *
395 * The capacity limit will affect auto-extension features, as well as future
396 * calls to cxBufferMinimumCapacity() and cxBufferReserve().
397 *
398 * @param buffer the buffer
399 * @param capacity the maximum allowed capacity for this buffer
400 * @retval zero the limit is applied
401 * @retval non-zero the new limit is smaller than the current capacity
402 * @see cxBufferReserve()
403 * @see cxBufferMinimumCapacity()
404 */
405 cx_attr_nonnull
406 CX_EXPORT int cxBufferMaximumCapacity(CxBuffer *buffer, size_t capacity);
407
408 /**
409 * Ensures that the buffer has a minimum capacity.
410 *
411 * If the current capacity is not sufficient, the buffer will be generously
412 * extended.
413 *
414 * The new capacity will be a power of two until the system's page size is reached.
415 * Then, the new capacity will be a multiple of the page size.
416 *
417 * @param buffer the buffer
418 * @param capacity the minimum required capacity for this buffer
419 * @retval zero the capacity was already sufficient or successfully increased
420 * @retval non-zero on allocation failure
421 * @see cxBufferMaximumCapacity()
422 * @see cxBufferReserve()
423 * @see cxBufferShrink()
424 */
425 cx_attr_nonnull
426 CX_EXPORT int cxBufferMinimumCapacity(CxBuffer *buffer, size_t capacity);
427
428 /**
429 * Shrinks the capacity of the buffer to fit its current size.
430 *
431 * If @p reserve is larger than zero, the buffer is shrunk to its size plus
432 * the number of reserved bytes.
433 *
434 * If the current capacity is not larger than the size plus the reserved bytes,
435 * nothing happens.
436 *
437 * If the #CX_BUFFER_COPY_ON_WRITE or #CX_BUFFER_COPY_ON_EXTEND flag is set,
438 * this function does nothing.
439 *
440 * @param buffer the buffer
441 * @param reserve the number of bytes that shall remain reserved
442 * @see cxBufferReserve()
443 * @see cxBufferMinimumCapacity()
444 */
445 cx_attr_nonnull
446 CX_EXPORT void cxBufferShrink(CxBuffer *buffer, size_t reserve);
447
448 /**
449 * Writes data to a CxBuffer.
450 *
451 * If auto-extension is enabled, the buffer's capacity is automatically
452 * increased when it is not large enough to hold all data.
453 * By default, the capacity grows indefinitely, unless limited with
454 * cxBufferMaximumCapacity().
455 * When auto-extension fails, this function writes no data and returns zero.
456 *
457 * The position of the buffer is moved alongside the written data.
458 *
459 * @note The signature is compatible with the fwrite() family of functions.
460 *
461 * @param ptr a pointer to the memory area containing the bytes to be written
462 * @param size the length of one element
463 * @param nitems the element count
464 * @param buffer the CxBuffer to write to
465 * @return the total count of elements written
466 * @see cxBufferAppend()
467 * @see cxBufferRead()
468 */
469 cx_attr_nonnull
470 CX_EXPORT size_t cxBufferWrite(const void *ptr, size_t size,
471 size_t nitems, CxBuffer *buffer);
472
473 /**
474 * Appends data to a CxBuffer.
475 *
476 * The data is always appended to current data within the buffer,
477 * regardless of the current position.
478 * This is especially useful when the buffer is primarily meant for reading
479 * while additional data is added to the buffer occasionally.
480 * Consequently, the position of the buffer is unchanged after this operation.
481 *
482 * @note The signature is compatible with the fwrite() family of functions.
483 *
484 * @param ptr a pointer to the memory area containing the bytes to be written
485 * @param size the length of one element
486 * @param nitems the element count
487 * @param buffer the CxBuffer to write to
488 * @return the total count of elements written
489 * @see cxBufferWrite()
490 * @see cxBufferRead()
491 */
492 cx_attr_nonnull
493 CX_EXPORT size_t cxBufferAppend(const void *ptr, size_t size,
494 size_t nitems, CxBuffer *buffer);
495
496 /**
497 * Reads data from a CxBuffer.
498 *
499 * The position of the buffer is increased by the number of bytes read.
500 *
501 * @note The signature is compatible with the fread() family of functions.
502 *
503 * @param ptr a pointer to the memory area where to store the read data
504 * @param size the length of one element
505 * @param nitems the element count
506 * @param buffer the CxBuffer to read from
507 * @return the total number of elements read
508 * @see cxBufferWrite()
509 * @see cxBufferAppend()
510 */
511 cx_attr_nonnull
512 CX_EXPORT size_t cxBufferRead(void *ptr, size_t size,
513 size_t nitems, CxBuffer *buffer);
514
515 /**
516 * Writes a character to a buffer.
517 *
518 * The least significant byte of the argument is written to the buffer. If the
519 * end of the buffer is reached and #CX_BUFFER_AUTO_EXTEND feature is enabled,
520 * the buffer capacity is extended, unless a limit set by
521 * cxBufferMaximumCapacity() is reached.
522 * If the feature is disabled or the buffer extension fails, @c EOF is returned.
523 *
524 * On successful writing, the position of the buffer is increased.
525 *
526 * If you just want to write a null-terminator at the current position, you
527 * should use cxBufferTerminate() instead.
528 *
529 * @param buffer the buffer to write to
530 * @param c the character to write
531 * @return the byte that has been written or @c EOF when the end of the
532 * stream is reached, and automatic extension is not enabled or not possible
533 * @see cxBufferTerminate()
534 */
535 cx_attr_nonnull
536 CX_EXPORT int cxBufferPut(CxBuffer *buffer, int c);
537
538 /**
539 * Writes a terminating zero to a buffer at the current position.
540 *
541 * If successful, sets the size to the current position and advances
542 * the position by one.
543 *
544 * The purpose of this function is to have the written data ready to be used as
545 * a C string with the buffer's size being the length of that string.
546 *
547 * @param buffer the buffer to write to
548 * @return zero, if the terminator could be written, non-zero otherwise
549 */
550 cx_attr_nonnull
551 CX_EXPORT int cxBufferTerminate(CxBuffer *buffer);
552
553 /**
554 * Writes a string to a buffer.
555 *
556 * This is a convenience function for <code>cxBufferWrite(str, 1, strlen(str), buffer)</code>.
557 *
558 * @param buffer the buffer
559 * @param str the zero-terminated string
560 * @return the number of bytes written
561 */
562 cx_attr_nonnull cx_attr_cstr_arg(2)
563 CX_EXPORT size_t cxBufferPutString(CxBuffer *buffer, const char *str);
564
565 /**
566 * Gets a character from a buffer.
567 *
568 * The current position of the buffer is increased after a successful read.
569 *
570 * @param buffer the buffer to read from
571 * @return the character or @c EOF, if the end of the buffer is reached
572 */
573 cx_attr_nonnull
574 CX_EXPORT int cxBufferGet(CxBuffer *buffer);
575
576 #ifdef __cplusplus
577 }
578 #endif
579
580 #endif // UCX_BUFFER_H
581