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 #include "string.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 * Do NOT set this flag together with #CX_BUFFER_COPY_ON_WRITE. It will be automatically
66 * set when the copy-on-write operation is performed.
67 */
68 #define CX_BUFFER_FREE_CONTENTS 0x01
69
70 /**
71 * If this flag is enabled, the buffer will automatically extend its capacity.
72 */
73 #define CX_BUFFER_AUTO_EXTEND 0x02
74
75 /**
76 * If this flag is enabled, the buffer will allocate new memory when written to.
77 *
78 * The current contents of the buffer will be copied to the new memory, and the flag
79 * will be cleared while the #CX_BUFFER_FREE_CONTENTS flag will be set automatically.
80 */
81 #define CX_BUFFER_COPY_ON_WRITE 0x04
82
83 /**
84 * If this flag is enabled, the buffer will copy its contents to a new memory area on reallocation.
85 *
86 * After performing the copy, the flag is automatically cleared.
87 * This flag has no effect on buffers which do not have #CX_BUFFER_AUTO_EXTEND set, which is why
88 * buffers automatically admit the auto-extend flag when initialized with copy-on-extend enabled.
89 */
90 #define CX_BUFFER_COPY_ON_EXTEND 0x08
91
92 /**
93 * If this flag is enabled, the buffer will never free its contents regardless of #CX_BUFFER_FREE_CONTENTS.
94 *
95 * This is useful, for example, when you want to keep a pointer to the data after destroying the buffer.
96 */
97 #define CX_BUFFER_DO_NOT_FREE 0x10
98
99 /**
100 * Function pointer for cxBufferWrite that is compatible with cx_write_func.
101 * @see cx_write_func
102 */
103 #define cxBufferWriteFunc ((cx_write_func) cxBufferWrite)
104 /**
105 * Function pointer for cxBufferRead that is compatible with cx_read_func.
106 * @see cx_read_func
107 */
108 #define cxBufferReadFunc ((cx_read_func) cxBufferRead)
109
110
111 /** Structure for the UCX buffer data. */
112 struct cx_buffer_s {
113 /** A pointer to the buffer contents. */
114 union {
115 /**
116 * Data is interpreted as text.
117 */
118 char *space;
119 /**
120 * Data is interpreted as binary.
121 */
122 unsigned char *bytes;
123 };
124 /** The allocator to use for automatic memory management. */
125 const CxAllocator *allocator;
126 /** Current position of the buffer. */
127 size_t pos;
128 /** Current capacity (i.e. maximum size) of the buffer. */
129 size_t capacity;
130 /** Maximum capacity that this buffer may grow to. */
131 size_t max_capacity;
132 /** Current size of the buffer content. */
133 size_t size;
134 /**
135 * Flag register for buffer features.
136 * @see #CX_BUFFER_DEFAULT
137 * @see #CX_BUFFER_FREE_CONTENTS
138 * @see #CX_BUFFER_AUTO_EXTEND
139 * @see #CX_BUFFER_COPY_ON_WRITE
140 */
141 int flags;
142 };
143
144 /**
145 * UCX buffer.
146 */
147 typedef struct cx_buffer_s CxBuffer;
148
149 /**
150 * Initializes a fresh buffer.
151 *
152 * You may also provide a read-only @p space, in which case
153 * you will need to cast the pointer, and you should set the
154 * #CX_BUFFER_COPY_ON_WRITE flag.
155 *
156 * You need to set the size manually after initialization if
157 * you provide @p space which already contains data.
158 *
159 * When you specify stack memory as @p space and decide to use
160 * the auto-extension feature, you @em must use the
161 * #CX_BUFFER_COPY_ON_EXTEND flag, instead of the
162 * #CX_BUFFER_AUTO_EXTEND flag.
163 *
164 * @note You may provide @c NULL as the argument for @p space.
165 * Then this function will allocate the space and enforce
166 * the #CX_BUFFER_FREE_CONTENTS flag. In that case, specifying
167 * copy-on-write should be avoided, because the allocated
168 * space will be leaking after the copy-on-write operation.
169 *
170 * @param buffer the buffer to initialize
171 * @param space pointer to the memory area, or @c NULL to allocate
172 * new memory
173 * @param capacity the capacity of the buffer
174 * @param allocator the allocator this buffer shall use for automatic
175 * memory management
176 * (if @c NULL, the cxDefaultAllocator will be used)
177 * @param flags buffer features (see cx_buffer_s.flags)
178 * @return zero on success, non-zero if a required allocation failed
179 */
180 cx_attr_nonnull_arg(1)
181 CX_EXPORT int cxBufferInit(CxBuffer *buffer, void *space, size_t capacity,
182 const CxAllocator *allocator, int flags);
183
184 /**
185 * Destroys the buffer contents.
186 *
187 * Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
188 * If you want to free the memory of the entire buffer, use cxBufferFree().
189 *
190 * @param buffer the buffer which contents shall be destroyed
191 * @see cxBufferInit()
192 */
193 cx_attr_nonnull
194 CX_EXPORT void cxBufferDestroy(CxBuffer *buffer);
195
196 /**
197 * Deallocates the buffer.
198 *
199 * If the #CX_BUFFER_FREE_CONTENTS feature is enabled, this function also destroys
200 * the contents. If you @em only want to destroy the contents, use cxBufferDestroy().
201 *
202 * @param buffer the buffer to deallocate
203 * @see cxBufferCreate()
204 */
205 CX_EXPORT void cxBufferFree(CxBuffer *buffer);
206
207 /**
208 * Allocates and initializes a fresh buffer.
209 *
210 * You may also provide a read-only @p space, in which case
211 * you will need to cast the pointer, and you should set the
212 * #CX_BUFFER_COPY_ON_WRITE flag.
213 * When you specify stack memory as @p space and decide to use
214 * the auto-extension feature, you @em must use the
215 * #CX_BUFFER_COPY_ON_EXTEND flag, instead of the
216 * #CX_BUFFER_AUTO_EXTEND flag.
217 *
218 * @note You may provide @c NULL as the argument for @p space.
219 * Then this function will allocate the space and enforce
220 * the #CX_BUFFER_FREE_CONTENTS flag.
221 *
222 * @param space pointer to the memory area, or @c NULL to allocate
223 * new memory
224 * @param capacity the capacity of the buffer
225 * @param allocator the allocator to use for allocating the structure and the automatic
226 * memory management within the buffer
227 * (if @c NULL, the cxDefaultAllocator will be used)
228 * @param flags buffer features (see cx_buffer_s.flags)
229 * @return a pointer to the buffer on success, @c NULL if a required allocation failed
230 */
231 cx_attr_malloc cx_attr_dealloc(cxBufferFree, 1) cx_attr_nodiscard
232 CX_EXPORT CxBuffer *cxBufferCreate(void *space, size_t capacity,
233 const CxAllocator *allocator, int flags);
234
235 /**
236 * Shifts the contents of the buffer by the given offset.
237 *
238 * If the offset is positive, the contents are shifted to the right.
239 * If auto extension is enabled, the buffer grows, if necessary.
240 * In case the auto extension fails, this function returns a non-zero value and
241 * no contents are changed.
242 * When the auto extension is disabled, the contents that do not fit into the
243 * buffer are discarded.
244 *
245 * If the offset is negative, the contents are shifted to the left where the
246 * first @p shift bytes are discarded.
247 * The new size of the buffer is the old size minus the absolute shift value.
248 * If this value is larger than the buffer size, the buffer is emptied (but
249 * not cleared, see the security note below).
250 *
251 * The buffer position gets shifted alongside the content but is kept
252 * within the boundaries of the buffer.
253 *
254 * @note For situations where @c off_t is not large enough, there are specialized cxBufferShiftLeft() and
255 * cxBufferShiftRight() functions using a @c size_t as the parameter type.
256 *
257 * @attention
258 * Security Note: The shifting operation does @em not erase the previously occupied memory cells.
259 * But you can do that manually by calling
260 * <code>memset(buffer->bytes, 0, shift)</code> for a right shift or
261 * <code>memset(buffer->bytes + buffer->size, 0, buffer->capacity - buffer->size)</code>
262 * for a left shift.
263 *
264 * @param buffer the buffer
265 * @param shift the shift offset (negative means left shift)
266 * @retval zero success
267 * @retval non-zero if a required auto-extension or copy-on-write fails
268 * @see cxBufferShiftLeft()
269 * @see cxBufferShiftRight()
270 */
271 cx_attr_nonnull
272 CX_EXPORT int cxBufferShift(CxBuffer *buffer, off_t shift);
273
274 /**
275 * Shifts the buffer to the right.
276 * See cxBufferShift() for details.
277 *
278 * @param buffer the buffer
279 * @param shift the shift offset
280 * @retval zero success
281 * @retval non-zero if a required auto-extension or copy-on-write fails
282 * @see cxBufferShift()
283 */
284 cx_attr_nonnull
285 CX_EXPORT int cxBufferShiftRight(CxBuffer *buffer, size_t shift);
286
287 /**
288 * Shifts the buffer to the left.
289 * See cxBufferShift() for details.
290 *
291 * @param buffer the buffer
292 * @param shift the positive shift offset
293 * @retval zero success
294 * @retval non-zero if the buffer uses copy-on-write and the allocation fails
295 * @see cxBufferShift()
296 */
297 cx_attr_nonnull
298 CX_EXPORT int cxBufferShiftLeft(CxBuffer *buffer, size_t shift);
299
300
301 /**
302 * Moves the position of the buffer.
303 *
304 * The new position is relative to the @p whence argument.
305 *
306 * @li @c SEEK_SET marks the start of the buffer.
307 * @li @c SEEK_CUR marks the current position.
308 * @li @c SEEK_END marks the end of the buffer.
309 *
310 * With an offset of zero, this function sets the buffer position to zero
311 * (@c SEEK_SET), the buffer size (@c SEEK_END) or leaves the buffer position
312 * unchanged (@c SEEK_CUR).
313 *
314 * @param buffer the buffer
315 * @param offset position offset relative to @p whence
316 * @param whence one of @c SEEK_SET, @c SEEK_CUR or @c SEEK_END
317 * @retval zero success
318 * @retval non-zero if the position is invalid
319 *
320 */
321 cx_attr_nonnull
322 CX_EXPORT int cxBufferSeek(CxBuffer *buffer, off_t offset, int whence);
323
324 /**
325 * Discards items from the end of the buffer.
326 *
327 * When the current position points to a byte that gets discarded,
328 * the position is set to the buffer size.
329 *
330 * @param buffer the buffer
331 * @param size the size of one item
332 * @param nitems the number of items to discard
333 * @return the actual number of discarded items
334 */
335 cx_attr_nonnull
336 CX_EXPORT size_t cxBufferPop(CxBuffer *buffer, size_t size, size_t nitems);
337
338 /**
339 * Clears the buffer by resetting the position and deleting the data.
340 *
341 * The data is deleted by zeroing it with a call to memset().
342 * If you do not need that, you can use the faster cxBufferReset().
343 *
344 * @note If the #CX_BUFFER_COPY_ON_WRITE flag is set, this function
345 * will not erase the data and behave exactly as cxBufferReset().
346 *
347 * @param buffer the buffer to be cleared
348 * @see cxBufferReset()
349 */
350 cx_attr_nonnull
351 CX_EXPORT void cxBufferClear(CxBuffer *buffer);
352
353 /**
354 * Resets the buffer by resetting the position and size to zero.
355 *
356 * The data in the buffer is not deleted. If you need a safe
357 * reset of the buffer, use cxBufferClear().
358 *
359 * @param buffer the buffer to be cleared
360 * @see cxBufferClear()
361 */
362 cx_attr_nonnull
363 CX_EXPORT void cxBufferReset(CxBuffer *buffer);
364
365 /**
366 * Tests, if the buffer position has exceeded the buffer size.
367 *
368 * @param buffer the buffer to test
369 * @retval true if the current buffer position has exceeded the last
370 * byte of the buffer's contents
371 * @retval false otherwise
372 */
373 cx_attr_nonnull cx_attr_nodiscard
374 CX_EXPORT bool cxBufferEof(const CxBuffer *buffer);
375
376 /**
377 * Ensures that the buffer has the required capacity.
378 *
379 * If the current capacity is not sufficient, the buffer will be extended.
380 * If the current capacity is larger, the buffer is shrunk and superfluous
381 * content is discarded.
382 *
383 * This function will reserve no more bytes than requested, in contrast to
384 * cxBufferMinimumCapacity(), which may reserve more bytes to improve the
385 * number of future necessary reallocations.
386 *
387 * @param buffer the buffer
388 * @param capacity the required capacity for this buffer
389 * @retval zero on success
390 * @retval non-zero on allocation failure
391 * @see cxBufferShrink()
392 * @see cxBufferMinimumCapacity()
393 */
394 cx_attr_nonnull
395 CX_EXPORT int cxBufferReserve(CxBuffer *buffer, size_t capacity);
396
397 /**
398 * Limits the buffer's capacity.
399 *
400 * If the current capacity is already larger, this function fails and returns
401 * non-zero.
402 *
403 * The capacity limit will affect auto-extension features, as well as future
404 * calls to cxBufferMinimumCapacity() and cxBufferReserve().
405 *
406 * @param buffer the buffer
407 * @param capacity the maximum allowed capacity for this buffer
408 * @retval zero the limit is applied
409 * @retval non-zero the new limit is smaller than the current capacity
410 * @see cxBufferReserve()
411 * @see cxBufferMinimumCapacity()
412 */
413 cx_attr_nonnull
414 CX_EXPORT int cxBufferMaximumCapacity(CxBuffer *buffer, size_t capacity);
415
416 /**
417 * Ensures that the buffer has a minimum capacity.
418 *
419 * If the current capacity is not sufficient, the buffer will be generously
420 * extended.
421 *
422 * The new capacity will be a power of two until the system's page size is reached.
423 * Then, the new capacity will be a multiple of the page size.
424 *
425 * @param buffer the buffer
426 * @param capacity the minimum required capacity for this buffer
427 * @retval zero the capacity was already sufficient or successfully increased
428 * @retval non-zero on allocation failure
429 * @see cxBufferMaximumCapacity()
430 * @see cxBufferReserve()
431 * @see cxBufferShrink()
432 */
433 cx_attr_nonnull
434 CX_EXPORT int cxBufferMinimumCapacity(CxBuffer *buffer, size_t capacity);
435
436 /**
437 * Shrinks the capacity of the buffer to fit its current size.
438 *
439 * If @p reserve is larger than zero, the buffer is shrunk to its size plus
440 * the number of reserved bytes.
441 *
442 * If the current capacity is not larger than the size plus the reserved bytes,
443 * nothing happens.
444 *
445 * If the #CX_BUFFER_COPY_ON_WRITE or #CX_BUFFER_COPY_ON_EXTEND flag is set,
446 * this function does nothing.
447 *
448 * @param buffer the buffer
449 * @param reserve the number of bytes that shall remain reserved
450 * @see cxBufferReserve()
451 * @see cxBufferMinimumCapacity()
452 */
453 cx_attr_nonnull
454 CX_EXPORT void cxBufferShrink(CxBuffer *buffer, size_t reserve);
455
456 /**
457 * Writes data to a CxBuffer.
458 *
459 * If auto-extension is enabled, the buffer's capacity is automatically
460 * increased when it is not large enough to hold all data.
461 * By default, the capacity grows indefinitely, unless limited with
462 * cxBufferMaximumCapacity().
463 * When auto-extension fails, this function writes no data and returns zero.
464 *
465 * The position of the buffer is moved alongside the written data.
466 *
467 * @note The signature is compatible with the fwrite() family of functions.
468 *
469 * @param ptr a pointer to the memory area containing the bytes to be written
470 * @param size the length of one element
471 * @param nitems the element count
472 * @param buffer the CxBuffer to write to
473 * @return the total count of elements written
474 * @see cxBufferAppend()
475 * @see cxBufferRead()
476 */
477 cx_attr_nonnull
478 CX_EXPORT size_t cxBufferWrite(const void *ptr, size_t size,
479 size_t nitems, CxBuffer *buffer);
480
481 /**
482 * Appends data to a CxBuffer.
483 *
484 * The data is always appended to current data within the buffer,
485 * regardless of the current position.
486 * This is especially useful when the buffer is primarily meant for reading
487 * while additional data is added to the buffer occasionally.
488 * Consequently, the position of the buffer is unchanged after this operation.
489 *
490 * @note The signature is compatible with the fwrite() family of functions.
491 *
492 * @param ptr a pointer to the memory area containing the bytes to be written
493 * @param size the length of one element
494 * @param nitems the element count
495 * @param buffer the CxBuffer to write to
496 * @return the total count of elements written
497 * @see cxBufferWrite()
498 * @see cxBufferRead()
499 */
500 cx_attr_nonnull
501 CX_EXPORT size_t cxBufferAppend(const void *ptr, size_t size,
502 size_t nitems, CxBuffer *buffer);
503
504 /**
505 * Reads data from a CxBuffer.
506 *
507 * The position of the buffer is increased by the number of bytes read.
508 *
509 * @note The signature is compatible with the fread() family of functions.
510 *
511 * @param ptr a pointer to the memory area where to store the read data
512 * @param size the length of one element
513 * @param nitems the element count
514 * @param buffer the CxBuffer to read from
515 * @return the total number of elements read
516 * @see cxBufferWrite()
517 * @see cxBufferAppend()
518 */
519 cx_attr_nonnull
520 CX_EXPORT size_t cxBufferRead(void *ptr, size_t size,
521 size_t nitems, CxBuffer *buffer);
522
523 /**
524 * Writes a character to a buffer.
525 *
526 * The least significant byte of the argument is written to the buffer. If the
527 * end of the buffer is reached and #CX_BUFFER_AUTO_EXTEND feature is enabled,
528 * the buffer capacity is extended, unless a limit set by
529 * cxBufferMaximumCapacity() is reached.
530 * If the feature is disabled or the buffer extension fails, @c EOF is returned.
531 *
532 * On successful writing, the position of the buffer is increased.
533 *
534 * If you just want to write a null-terminator at the current position, you
535 * should use cxBufferTerminate() instead.
536 *
537 * @param buffer the buffer to write to
538 * @param c the character to write
539 * @return the byte that has been written or @c EOF when the end of the
540 * stream is reached, and automatic extension is not enabled or not possible
541 * @see cxBufferTerminate()
542 */
543 cx_attr_nonnull
544 CX_EXPORT int cxBufferPut(CxBuffer *buffer, int c);
545
546 /**
547 * Writes a terminating zero to a buffer at the current position.
548 *
549 * If successful, also sets the size to the current position and shrinks the buffer.
550 *
551 * The purpose of this function is to have the written data ready to be used as
552 * a C string with the buffer's size being the length of that string.
553 *
554 * @param buffer the buffer to write to
555 * @return zero, if the terminator could be written, non-zero otherwise
556 * @see cxBufferShrink()
557 */
558 cx_attr_nonnull
559 CX_EXPORT int cxBufferTerminate(CxBuffer *buffer);
560
561 /**
562 * Internal function - do not use.
563 *
564 * @param buffer the buffer
565 * @param str the string
566 * @return the number of bytes written
567 * @see cxBufferPutString()
568 */
569 cx_attr_nonnull
570 CX_EXPORT size_t cx_buffer_put_string(CxBuffer *buffer, cxstring str);
571
572 /**
573 * Writes a string to a buffer with cxBufferWrite().
574 *
575 * @param buffer (@c CxBuffer*) the buffer
576 * @param str (any string) the zero-terminated string
577 * @return (@c size_t) the number of bytes written
578 * @see cxBufferWrite()
579 * @see cx_strcast()
580 */
581 #define cxBufferPutString(buffer, str) cx_buffer_put_string(buffer, cx_strcast(str))
582
583 /**
584 * Internal function - do not use.
585 *
586 * @param buffer the buffer
587 * @param str the string
588 * @return the number of bytes written
589 * @see cxBufferPutString()
590 */
591 cx_attr_nonnull
592 CX_EXPORT size_t cx_buffer_append_string(CxBuffer *buffer, cxstring str);
593
594 /**
595 * Appends a string to a buffer with cxBufferAppend().
596 *
597 * @param buffer (@c CxBuffer*) the buffer
598 * @param str (any string) the zero-terminated string
599 * @return (@c size_t) the number of bytes written
600 * @see cxBufferAppend()
601 * @see cx_strcast()
602 */
603 #define cxBufferAppendString(buffer, str) cx_buffer_append_string(buffer, cx_strcast(str))
604
605 /**
606 * Gets a character from a buffer.
607 *
608 * The current position of the buffer is increased after a successful read.
609 *
610 * @param buffer the buffer to read from
611 * @return the character or @c EOF, if the end of the buffer is reached
612 */
613 cx_attr_nonnull
614 CX_EXPORT int cxBufferGet(CxBuffer *buffer);
615
616 #ifdef __cplusplus
617 }
618 #endif
619
620 #endif // UCX_BUFFER_H
621