dbutils: comparison ucx/cx/buffer.h

-:862ab606ee06
+:04c9f8d8f03b
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
 /**
-* \file buffer.h
+* @file buffer.h
 *
-* \brief Advanced buffer implementation.
+* @brief Advanced buffer implementation.
 *
 * Instances of CxBuffer can be used to read from or to write to like one
 * would do with a stream.
 *
 * Some features for convenient use of the buffer
 * can be enabled. See the documentation of the macro constants for more
 * information.
 *
-* \author Mike Becker
+* @author Mike Becker
-* \author Olaf Wintermann
+* @author Olaf Wintermann
-* \copyright 2-Clause BSD License
+* @copyright 2-Clause BSD License
 */
 #ifndef UCX_BUFFER_H
 #define UCX_BUFFER_H
 * This flag has no effect on buffers which do not have #CX_BUFFER_AUTO_EXTEND set, which is why
 * buffers automatically admit the auto-extend flag when initialized with copy-on-extend enabled.
 */
 #define CX_BUFFER_COPY_ON_EXTEND 0x08
+/**
+* Function pointer for cxBufferWrite that is compatible with cx_write_func.
+* @see cx_write_func
+*/
+#define cxBufferWriteFunc  ((cx_write_func) cxBufferWrite)
+/**
+* Function pointer for cxBufferRead that is compatible with cx_read_func.
+* @see cx_read_func
+*/
+#define cxBufferReadFunc  ((cx_read_func) cxBufferRead)
+/**
+* Configuration for automatic flushing.
+*/
+struct cx_buffer_flush_config_s {
+/**
+* The buffer may not extend beyond this threshold before starting to flush.
+*
+* Only used when the buffer uses #CX_BUFFER_AUTO_EXTEND.
+* The threshold will be the maximum capacity the buffer is extended to
+* before flushing.
+*/
+size_t threshold;
+/**
+* The block size for the elements to flush.
+*/
+size_t blksize;
+/**
+* The maximum number of blocks to flush in one cycle.
+*
+* @attention while it is guaranteed that cxBufferFlush() will not flush
+* more blocks, this is not necessarily the case for cxBufferWrite().
+* After performing a flush cycle, cxBufferWrite() will retry the write
+* operation and potentially trigger another flush cycle, until the
+* flush target accepts no more data.
+*/
+size_t blkmax;
+/**
+* The target for write function.
+*/
+void *target;
+/**
+* The write-function used for flushing.
+* If NULL, the flushed content gets discarded.
+*/
+cx_write_func wfunc;
+};
+/**
+* Type alias for the flush configuration struct.
+*
+* @code
+* struct cx_buffer_flush_config_s {
+*     size_t threshold;
+*     size_t blksize;
+*     size_t blkmax;
+*     void *target;
+*     cx_write_func wfunc;
+* };
+* @endcode
+*/
+typedef struct cx_buffer_flush_config_s CxBufferFlushConfig;
 /** Structure for the UCX buffer data. */
-typedef struct {
+struct cx_buffer_s {
 /** A pointer to the buffer contents. */
 union {
 /**
 * Data is interpreted as text.
 */
 */
 unsigned char *bytes;
 };
 /** The allocator to use for automatic memory management. */
 const CxAllocator *allocator;
+/**
+* Optional flush configuration
+*
+* @see cxBufferEnableFlushing()
+*/
+CxBufferFlushConfig *flush;
 /** Current position of the buffer. */
 size_t pos;
 /** Current capacity (i.e. maximum size) of the buffer. */
 size_t capacity;
 /** Current size of the buffer content. */
 size_t size;
-/**
-* The buffer may not extend beyond this threshold before starting to flush.
-* Default is \c SIZE_MAX (flushing disabled when auto extension is enabled).
-*/
-size_t flush_threshold;
-/**
-* The block size for the elements to flush.
-* Default is 4096 bytes.
-*/
-size_t flush_blksize;
-/**
-* The maximum number of blocks to flush in one cycle.
-* Zero disables flushing entirely (this is the default).
-* Set this to \c SIZE_MAX to flush the entire buffer.
-*
-* @attention if the maximum number of blocks multiplied with the block size
-* is smaller than the expected contents written to this buffer within one write
-* operation, multiple flush cycles are performed after that write.
-* That means the total number of blocks flushed after one write to this buffer may
-* be larger than \c flush_blkmax.
-*/
-size_t flush_blkmax;
-/**
-* The write function used for flushing.
-* If NULL, the flushed content gets discarded.
-*/
-cx_write_func flush_func;
-/**
-* The target for \c flush_func.
-*/
-void *flush_target;
 /**
 * Flag register for buffer features.
 * @see #CX_BUFFER_DEFAULT
 * @see #CX_BUFFER_FREE_CONTENTS
 * @see #CX_BUFFER_AUTO_EXTEND
 * @see #CX_BUFFER_COPY_ON_WRITE
 */
 int flags;
-} cx_buffer_s;
+};
 /**
 * UCX buffer.
 */
-typedef cx_buffer_s CxBuffer;
+typedef struct cx_buffer_s CxBuffer;
 /**
 * Initializes a fresh buffer.
 *
-* You may also provide a read-only \p space, in which case
+* You may also provide a read-only @p space, in which case
 * you will need to cast the pointer, and you should set the
 * #CX_BUFFER_COPY_ON_WRITE flag.
 *
 * You need to set the size manually after initialization, if
-* you provide \p space which already contains data.
+* you provide @p space which already contains data.
 *
-* When you specify stack memory as \p space and decide to use
+* When you specify stack memory as @p space and decide to use
-* the auto-extension feature, you \em must use the
+* the auto-extension feature, you @em must use the
 * #CX_BUFFER_COPY_ON_EXTEND flag, instead of the
 * #CX_BUFFER_AUTO_EXTEND flag.
 *
-* \note You may provide \c NULL as argument for \p space.
+* @note You may provide @c NULL as argument for @p space.
 * Then this function will allocate the space and enforce
 * the #CX_BUFFER_FREE_CONTENTS flag. In that case, specifying
 * copy-on-write should be avoided, because the allocated
 * space will be leaking after the copy-on-write operation.
 *
 * @param buffer the buffer to initialize
-* @param space pointer to the memory area, or \c NULL to allocate
+* @param space pointer to the memory area, or @c NULL to allocate
 * new memory
 * @param capacity the capacity of the buffer
 * @param allocator the allocator this buffer shall use for automatic
 * memory management
-* (if \c NULL, a default stdlib allocator will be used)
+* (if @c NULL, a default stdlib allocator will be used)
 * @param flags buffer features (see cx_buffer_s.flags)
 * @return zero on success, non-zero if a required allocation failed
 */
 cx_attr_nonnull_arg(1)
+cx_attr_export
 int cxBufferInit(
 CxBuffer *buffer,
 void *space,
 size_t capacity,
 const CxAllocator *allocator,
 int flags
 );
 /**
+* Configures the buffer for flushing.
+*
+* Flushing can happen automatically when data is written
+* to the buffer (see cxBufferWrite()) or manually when
+* cxBufferFlush() is called.
+*
+* @param buffer the buffer
+* @param config the flush configuration
+* @retval zero success
+* @retval non-zero failure
+* @see cxBufferFlush()
+* @see cxBufferWrite()
+*/
+cx_attr_nonnull
+cx_attr_export
+int cxBufferEnableFlushing(
+CxBuffer *buffer,
+CxBufferFlushConfig config
+);
+/**
 * Destroys the buffer contents.
 *
 * Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
 * If you want to free the memory of the entire buffer, use cxBufferFree().
 *
 * @param buffer the buffer which contents shall be destroyed
 * @see cxBufferInit()
 */
 cx_attr_nonnull
+cx_attr_export
 void cxBufferDestroy(CxBuffer *buffer);
 /**
 * Deallocates the buffer.
 *
 * If the #CX_BUFFER_FREE_CONTENTS feature is enabled, this function also destroys
-* the contents. If you \em only want to destroy the contents, use cxBufferDestroy().
+* the contents. If you @em only want to destroy the contents, use cxBufferDestroy().
 *
-* \remark As with all free() functions, this accepts \c NULL arguments in which
+* @remark As with all free() functions, this accepts @c NULL arguments in which
 * case it does nothing.
 *
 * @param buffer the buffer to deallocate
 * @see cxBufferCreate()
 */
+cx_attr_export
 void cxBufferFree(CxBuffer *buffer);
 /**
 * Allocates and initializes a fresh buffer.
 *
-* You may also provide a read-only \p space, in which case
+* You may also provide a read-only @p space, in which case
 * you will need to cast the pointer, and you should set the
 * #CX_BUFFER_COPY_ON_WRITE flag.
-* When you specify stack memory as \p space and decide to use
+* When you specify stack memory as @p space and decide to use
-* the auto-extension feature, you \em must use the
+* the auto-extension feature, you @em must use the
 * #CX_BUFFER_COPY_ON_EXTEND flag, instead of the
 * #CX_BUFFER_AUTO_EXTEND flag.
 *
-* \note You may provide \c NULL as argument for \p space.
+* @note You may provide @c NULL as argument for @p space.
 * Then this function will allocate the space and enforce
 * the #CX_BUFFER_FREE_CONTENTS flag.
 *
-* @param space pointer to the memory area, or \c NULL to allocate
+* @param space pointer to the memory area, or @c NULL to allocate
 * new memory
 * @param capacity the capacity of the buffer
 * @param allocator the allocator to use for allocating the structure and the automatic
 * memory management within the buffer
-* (if \c NULL, a default stdlib allocator will be used)
+* (if @c NULL, a default stdlib allocator will be used)
 * @param flags buffer features (see cx_buffer_s.flags)
-* @return a pointer to the buffer on success, \c NULL if a required allocation failed
+* @return a pointer to the buffer on success, @c NULL if a required allocation failed
 */
 cx_attr_malloc
 cx_attr_dealloc(cxBufferFree, 1)
 cx_attr_nodiscard
+cx_attr_export
 CxBuffer *cxBufferCreate(
 void *space,
 size_t capacity,
 const CxAllocator *allocator,
 int flags
 * no contents are changed.
 * If auto extension is disabled, the contents that do not fit into the buffer
 * are discarded.
 *
 * If the offset is negative, the contents are shifted to the left where the
-* first \p shift bytes are discarded.
+* first @p shift bytes are discarded.
 * The new size of the buffer is the old size minus the absolute shift value.
 * If this value is larger than the buffer size, the buffer is emptied (but
 * not cleared, see the security note below).
 *
 * The buffer position gets shifted alongside with the content but is kept
 * within the boundaries of the buffer.
 *
-* \note For situations where \c off_t is not large enough, there are specialized cxBufferShiftLeft() and
+* @note For situations where @c off_t is not large enough, there are specialized cxBufferShiftLeft() and
-* cxBufferShiftRight() functions using a \c size_t as parameter type.
+* cxBufferShiftRight() functions using a @c size_t as parameter type.
 *
-* \attention
+* @attention
-* Security Note: The shifting operation does \em not erase the previously occupied memory cells.
+* Security Note: The shifting operation does @em not erase the previously occupied memory cells.
 * But you can easily do that manually, e.g. by calling
 * <code>memset(buffer->bytes, 0, shift)</code> for a right shift or
 * <code>memset(buffer->bytes + buffer->size, 0, buffer->capacity - buffer->size)</code>
 * for a left shift.
 *
 * @param buffer the buffer
 * @param shift the shift offset (negative means left shift)
-* @return 0 on success, non-zero if a required auto-extension or copy-on-write fails
+* @retval zero success
-*/
+* @retval non-zero if a required auto-extension or copy-on-write fails
-cx_attr_nonnull
+* @see cxBufferShiftLeft()
+* @see cxBufferShiftRight()
+*/
+cx_attr_nonnull
+cx_attr_export
 int cxBufferShift(
 CxBuffer *buffer,
 off_t shift
 );
 * Shifts the buffer to the right.
 * See cxBufferShift() for details.
 *
 * @param buffer the buffer
 * @param shift the shift offset
-* @return 0 on success, non-zero if a required auto-extension or copy-on-write fails
+* @retval zero success
+* @retval non-zero if a required auto-extension or copy-on-write fails
 * @see cxBufferShift()
 */
 cx_attr_nonnull
+cx_attr_export
 int cxBufferShiftRight(
 CxBuffer *buffer,
 size_t shift
 );
 * Shifts the buffer to the left.
 * See cxBufferShift() for details.
 *
 * @param buffer the buffer
 * @param shift the positive shift offset
-* @return usually zero, except the buffer uses copy-on-write and the allocation fails
+* @retval zero success
+* @retval non-zero if the buffer uses copy-on-write and the allocation fails
 * @see cxBufferShift()
 */
 cx_attr_nonnull
+cx_attr_export
 int cxBufferShiftLeft(
 CxBuffer *buffer,
 size_t shift
 );
 /**
 * Moves the position of the buffer.
 *
-* The new position is relative to the \p whence argument.
+* The new position is relative to the @p whence argument.
 *
-* \li \c SEEK_SET marks the start of the buffer.
+* @li @c SEEK_SET marks the start of the buffer.
-* \li \c SEEK_CUR marks the current position.
+* @li @c SEEK_CUR marks the current position.
-* \li \c SEEK_END marks the end of the buffer.
+* @li @c SEEK_END marks the end of the buffer.
 *
 * With an offset of zero, this function sets the buffer position to zero
-* (\c SEEK_SET), the buffer size (\c SEEK_END) or leaves the buffer position
+* (@c SEEK_SET), the buffer size (@c SEEK_END) or leaves the buffer position
-* unchanged (\c SEEK_CUR).
+* unchanged (@c SEEK_CUR).
 *
 * @param buffer the buffer
-* @param offset position offset relative to \p whence
+* @param offset position offset relative to @p whence
-* @param whence one of \c SEEK_SET, \c SEEK_CUR or \c SEEK_END
+* @param whence one of @c SEEK_SET, @c SEEK_CUR or @c SEEK_END
-* @return 0 on success, non-zero if the position is invalid
+* @retval zero success
-*
+* @retval non-zero if the position is invalid
-*/
+*
-cx_attr_nonnull
+*/
+cx_attr_nonnull
+cx_attr_export
 int cxBufferSeek(
 CxBuffer *buffer,
 off_t offset,
 int whence
 );
 * Clears the buffer by resetting the position and deleting the data.
 *
 * The data is deleted by zeroing it with a call to memset().
 * If you do not need that, you can use the faster cxBufferReset().
 *
-* \note If the #CX_BUFFER_COPY_ON_WRITE flag is set, this function
+* @note If the #CX_BUFFER_COPY_ON_WRITE flag is set, this function
 * will not erase the data and behave exactly as cxBufferReset().
 *
 * @param buffer the buffer to be cleared
 * @see cxBufferReset()
 */
 cx_attr_nonnull
+cx_attr_export
 void cxBufferClear(CxBuffer *buffer);
 /**
 * Resets the buffer by resetting the position and size to zero.
 *
 *
 * @param buffer the buffer to be cleared
 * @see cxBufferClear()
 */
 cx_attr_nonnull
+cx_attr_export
 void cxBufferReset(CxBuffer *buffer);
 /**
 * Tests, if the buffer position has exceeded the buffer size.
 *
 * @param buffer the buffer to test
-* @return true, if the current buffer position has exceeded the last
+* @retval true if the current buffer position has exceeded the last
-* byte of the buffer's contents.
+* byte of the buffer's contents
+* @retval false otherwise
 */
 cx_attr_nonnull
 cx_attr_nodiscard
+cx_attr_export
 bool cxBufferEof(const CxBuffer *buffer);
 /**
 * Ensures that the buffer has a minimum capacity.
 *
 * If the current capacity is not sufficient, the buffer will be extended.
 *
 * @param buffer the buffer
 * @param capacity the minimum required capacity for this buffer
-* @return 0 on success or a non-zero value on failure
+* @retval zero the capacity was already sufficient or successfully increased
-*/
+* @retval non-zero on allocation failure
-cx_attr_nonnull
+*/
+cx_attr_nonnull
+cx_attr_export
 int cxBufferMinimumCapacity(
 CxBuffer *buffer,
 size_t capacity
 );
 /**
 * Writes data to a CxBuffer.
+*
+* If automatic flushing is not enabled, the data is simply written into the
+* buffer at the current position and the position of the buffer is increased
+* by the number of bytes written.
 *
 * If flushing is enabled and the buffer needs to flush, the data is flushed to
 * the target until the target signals that it cannot take more data by
 * returning zero via the respective write function. In that case, the remaining
 * data in this buffer is shifted to the beginning of this buffer so that the
-* newly available space can be used to append as much data as possible. This
+* newly available space can be used to append as much data as possible.
-* function only stops writing more elements, when the flush target and this
+*
+* This function only stops writing more elements, when the flush target and this
 * buffer are both incapable of taking more data or all data has been written.
-* The number returned by this function is the total number of elements that
+*
-* could be written during the process. It does not necessarily mean that those
+* If, after flushing, the number of items that shall be written still exceeds
-* elements are still in this buffer, because some of them could have also be
+* the capacity or flush threshold, this function tries to write all items directly
-* flushed already.
+* to the flush target, if possible.
 *
-* If automatic flushing is not enabled, the position of the buffer is increased
+* The number returned by this function is the number of elements from
-* by the number of bytes written.
+* @c ptr that could be written to either the flush target or the buffer
-*
+* (so it does not include the number of items that had been already in the buffer
-* \note The signature is compatible with the fwrite() family of functions.
+* in were flushed during the process).
+*
+* @attention
+* When @p size is larger than one and the contents of the buffer are not aligned
+* with @p size, flushing stops after all complete items have been flushed, leaving
+* the mis-aligned part in the buffer.
+* Afterward, this function only writes as many items as possible to the buffer.
+*
+* @note The signature is compatible with the fwrite() family of functions.
 *
 * @param ptr a pointer to the memory area containing the bytes to be written
 * @param size the length of one element
 * @param nitems the element count
 * @param buffer the CxBuffer to write to
 * @return the total count of elements written
-*/
+* @see cxBufferAppend()
-cx_attr_nonnull
+* @see cxBufferRead()
+*/
+cx_attr_nonnull
+cx_attr_export
 size_t cxBufferWrite(
 const void *ptr,
 size_t size,
 size_t nitems,
 CxBuffer *buffer
 * regardless of the current position.
 * This is especially useful when the buffer is primarily meant for reading
 * while additional data is added to the buffer occasionally.
 * Consequently, the position of the buffer is unchanged after this operation.
 *
-* \note The signature is compatible with the fwrite() family of functions.
+* @note The signature is compatible with the fwrite() family of functions.
 *
 * @param ptr a pointer to the memory area containing the bytes to be written
 * @param size the length of one element
 * @param nitems the element count
 * @param buffer the CxBuffer to write to
 * @return the total count of elements written
 * @see cxBufferWrite()
-*/
+* @see cxBufferRead()
-cx_attr_nonnull
+*/
+cx_attr_nonnull
+cx_attr_export
 size_t cxBufferAppend(
 const void *ptr,
 size_t size,
 size_t nitems,
 CxBuffer *buffer
 );
 /**
+* Performs a single flush-run on the specified buffer.
+*
+* Does nothing when the position in the buffer is zero.
+* Otherwise, the data until the current position minus
+* one is considered for flushing.
+* Note carefully that flushing will never exceed the
+* current @em position, even when the size of the
+* buffer is larger than the current position.
+*
+* One flush run will try to flush @c blkmax many
+* blocks of size @c blksize until either the @p buffer
+* has no more data to flush or the write function
+* used for flushing returns zero.
+*
+* The buffer is shifted left for that many bytes
+* the flush operation has successfully flushed.
+*
+* @par Example 1
+* Assume you have a buffer with size 340 and you are
+* at position 200. The flush configuration is
+* @c blkmax=4 and @c blksize=64 .
+* Assume that the entire flush operation is successful.
+* All 200 bytes on the left hand-side from the current
+* position are written.
+* That means, the size of the buffer is now 140 and the
+* position is zero.
+*
+* @par Example 2
+* Same as Example 1, but now the @c blkmax is 1.
+* The size of the buffer is now 276 and the position is 136.
+*
+* @par Example 3
+* Same as Example 1, but now assume the flush target
+* only accepts 100 bytes before returning zero.
+* That means, the flush operations manages to flush
+* one complete block and one partial block, ending
+* up with a buffer with size 240 and position 100.
+*
+* @remark Just returns zero when flushing was not enabled with
+* cxBufferEnableFlushing().
+*
+* @remark When the buffer uses copy-on-write, the memory
+* is copied first, before attempting any flush.
+* This is, however, considered an erroneous use of the
+* buffer, because it does not make much sense to put
+* readonly data into an UCX buffer for flushing, instead
+* of writing it directly to the target.
+*
+* @param buffer the buffer
+* @return the number of successfully flushed bytes
+* @see cxBufferEnableFlushing()
+*/
+cx_attr_nonnull
+cx_attr_export
+size_t cxBufferFlush(CxBuffer *buffer);
+/**
 * Reads data from a CxBuffer.
 *
 * The position of the buffer is increased by the number of bytes read.
 *
-* \note The signature is compatible with the fread() family of functions.
+* @note The signature is compatible with the fread() family of functions.
 *
 * @param ptr a pointer to the memory area where to store the read data
 * @param size the length of one element
 * @param nitems the element count
 * @param buffer the CxBuffer to read from
 * @return the total number of elements read
-*/
+* @see cxBufferWrite()
-cx_attr_nonnull
+* @see cxBufferAppend()
+*/
+cx_attr_nonnull
+cx_attr_export
 size_t cxBufferRead(
 void *ptr,
 size_t size,
 size_t nitems,
 CxBuffer *buffer
 * Writes a character to a buffer.
 *
 * The least significant byte of the argument is written to the buffer. If the
 * end of the buffer is reached and #CX_BUFFER_AUTO_EXTEND feature is enabled,
 * the buffer capacity is extended by cxBufferMinimumCapacity(). If the feature
-* is disabled or buffer extension fails, \c EOF is returned.
+* is disabled or buffer extension fails, @c EOF is returned.
 *
 * On successful write, the position of the buffer is increased.
+*
+* If you just want to write a null-terminator at the current position, you
+* should use cxBufferTerminate() instead.
 *
 * @param buffer the buffer to write to
 * @param c the character to write
-* @return the byte that has been written or \c EOF when the end of the stream is
+* @return the byte that has been written or @c EOF when the end of the stream is
 * reached and automatic extension is not enabled or not possible
-*/
+* @see cxBufferTerminate()
-cx_attr_nonnull
+*/
+cx_attr_nonnull
+cx_attr_export
 int cxBufferPut(
 CxBuffer *buffer,
 int c
 );
 /**
-* Writes a terminating zero to a buffer.
+* Writes a terminating zero to a buffer at the current position.
 *
-* On successful write, \em neither the position \em nor the size of the buffer is
+* On successful write, @em neither the position @em nor the size of the buffer is
 * increased.
 *
 * The purpose of this function is to have the written data ready to be used as
 * a C string.
 *
 * @param buffer the buffer to write to
 * @return zero, if the terminator could be written, non-zero otherwise
 */
 cx_attr_nonnull
+cx_attr_export
 int cxBufferTerminate(CxBuffer *buffer);
 /**
 * Writes a string to a buffer.
+*
+* This is a convenience function for <code>cxBufferWrite(str, 1, strlen(str), buffer)</code>.
 *
 * @param buffer the buffer
 * @param str the zero-terminated string
 * @return the number of bytes written
 */
 cx_attr_nonnull
 cx_attr_cstr_arg(2)
+cx_attr_export
 size_t cxBufferPutString(
 CxBuffer *buffer,
 const char *str
 );
 * Gets a character from a buffer.
 *
 * The current position of the buffer is increased after a successful read.
 *
 * @param buffer the buffer to read from
-* @return the character or \c EOF, if the end of the buffer is reached
+* @return the character or @c EOF, if the end of the buffer is reached
 */
 cx_attr_nonnull
+cx_attr_export
 int cxBufferGet(CxBuffer *buffer);
 #ifdef __cplusplus
 }
 #endif

Mercurial > hg > dbutils / file comparison

comparison: ucx/cx/buffer.h

ucx/cx/buffer.h