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32 * \brief Advanced buffer implementation.
34 * Instances of CxBuffer can be used to read from or to write to like one
35 * would do with a stream.
37 * Some features for convenient use of the buffer
38 * can be enabled. See the documentation of the macro constants for more
42 * \author Olaf Wintermann
44 * \copyright 2-Clause BSD License
51 #include "allocator.h"
58 * No buffer features enabled (all flags cleared).
60 #define CX_BUFFER_DEFAULT 0x00
63 * If this flag is enabled, the buffer will automatically free its contents when destroyed.
65 #define CX_BUFFER_FREE_CONTENTS 0x01
68 * If this flag is enabled, the buffer will automatically extends its capacity.
70 #define CX_BUFFER_AUTO_EXTEND 0x02
72 /** Structure for the UCX buffer data. */
74 /** A pointer to the buffer contents. */
77 * Data is interpreted as text.
81 * Data is interpreted as binary.
85 /** The allocator to use for automatic memory management. */
86 CxAllocator const *allocator;
87 /** Current position of the buffer. */
89 /** Current capacity (i.e. maximum size) of the buffer. */
91 /** Current size of the buffer content. */
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).
97 size_t flush_threshold;
99 * The block size for the elements to flush.
100 * Default is 4096 bytes.
102 size_t flush_blksize;
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.
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.
117 * The write function used for flushing.
118 * If NULL, the flushed content gets discarded.
120 cx_write_func flush_func;
123 * The target for \c flush_func.
128 * Flag register for buffer features.
129 * @see #CX_BUFFER_DEFAULT
130 * @see #CX_BUFFER_FREE_CONTENTS
131 * @see #CX_BUFFER_AUTO_EXTEND
139 typedef cx_buffer_s CxBuffer;
142 * Initializes a fresh buffer.
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.
148 * @param buffer the buffer to initialize
149 * @param space pointer to the memory area, or \c NULL to allocate
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
157 __attribute__((__nonnull__(1)))
162 CxAllocator const *allocator,
167 * Allocates and initializes a fresh buffer.
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.
173 * @param space pointer to the memory area, or \c NULL to allocate
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
181 CxBuffer *cxBufferCreate(
184 CxAllocator const *allocator,
189 * Destroys the buffer contents.
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().
194 * @param buffer the buffer which contents shall be destroyed
195 * @see cxBufferInit()
197 __attribute__((__nonnull__))
198 void cxBufferDestroy(CxBuffer *buffer);
201 * Deallocates the buffer.
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().
206 * @param buffer the buffer to deallocate
207 * @see cxBufferCreate()
209 __attribute__((__nonnull__))
210 void cxBufferFree(CxBuffer *buffer);
213 * Shifts the contents of the buffer by the given offset.
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
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).
228 * The buffer position gets shifted alongside with the content but is kept
229 * within the boundaries of the buffer.
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.
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>
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
245 __attribute__((__nonnull__))
252 * Shifts the buffer to the right.
253 * See cxBufferShift() for details.
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()
260 __attribute__((__nonnull__))
261 int cxBufferShiftRight(
267 * Shifts the buffer to the left.
268 * See cxBufferShift() for details.
270 * \note Since a left shift cannot fail due to memory allocation problems, this
271 * function always returns zero.
273 * @param buffer the buffer
274 * @param shift the positive shift offset
275 * @return always zero
276 * @see cxBufferShift()
278 __attribute__((__nonnull__))
279 int cxBufferShiftLeft(
286 * Moves the position of the buffer.
288 * The new position is relative to the \p whence argument.
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.
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).
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
304 __attribute__((__nonnull__))
312 * Clears the buffer by resetting the position and deleting the data.
314 * The data is deleted by zeroing it with a call to memset().
316 * @param buffer the buffer to be cleared
318 __attribute__((__nonnull__))
319 void cxBufferClear(CxBuffer *buffer);
322 * Tests, if the buffer position has exceeded the buffer capacity.
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.
328 __attribute__((__nonnull__))
329 int cxBufferEof(CxBuffer const *buffer);
333 * Ensures that the buffer has a minimum capacity.
335 * If the current capacity is not sufficient, the buffer will be extended.
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
341 __attribute__((__nonnull__))
342 int cxBufferMinimumCapacity(
348 * Writes data to a CxBuffer.
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
362 * If automatic flushing is not enabled, the position of the buffer is increased
363 * by the number of bytes written.
365 * \note The signature is compatible with the fwrite() family of functions.
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
373 __attribute__((__nonnull__))
374 size_t cxBufferWrite(
382 * Reads data from a CxBuffer.
384 * The position of the buffer is increased by the number of bytes read.
386 * \note The signature is compatible with the fread() family of functions.
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
394 __attribute__((__nonnull__))
403 * Writes a character to a buffer.
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.
410 * On successful write, the position of the buffer is increased.
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
417 __attribute__((__nonnull__))
424 * Writes a string to a buffer.
426 * @param buffer the buffer
427 * @param str the zero-terminated string
428 * @return the number of bytes written
430 __attribute__((__nonnull__))
431 size_t cxBufferPutString(
437 * Gets a character from a buffer.
439 * The current position of the buffer is increased after a successful read.
441 * @param buffer the buffer to read from
442 * @return the character or \c EOF, if the end of the buffer is reached
444 __attribute__((__nonnull__))
445 int cxBufferGet(CxBuffer *buffer);
451 #endif // UCX_BUFFER_H