--- a/src/cx/buffer.h Sun Jan 05 14:03:30 2025 +0100
+++ b/src/cx/buffer.h Sun Jan 05 18:19:42 2025 +0100
@@ -88,6 +88,60 @@
*/
#define CX_BUFFER_COPY_ON_EXTEND 0x08
+/**
+ * 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 alais 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. */
struct cx_buffer_s {
/** A pointer to the buffer contents. */
@@ -103,6 +157,12 @@
};
/** 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. */
@@ -110,40 +170,6 @@
/** 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
@@ -199,6 +225,26 @@
);
/**
+ * 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
+int cxBufferEnableFlushing(
+ CxBuffer *buffer,
+ CxBufferFlushConfig config
+);
+
+/**
* Destroys the buffer contents.
*
* Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
@@ -419,6 +465,10 @@
/**
* 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
@@ -426,16 +476,11 @@
* newly available space can be used to append as much data as possible. 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
- * elements are still in this buffer, because some of them could have also been
- * flushed already.
- *
- * 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.
- * Use cxBufferAppend() if you want to add data to this buffer regardless of
- * the position.
+ * If number of items that shall be written is larger than the buffer can hold,
+ * the first items from @c ptr are directly relayed to the flush target, if
+ * possible.
+ * The number returned by this function is only the number of elements from
+ * @c ptr that could be written to either the flush target or the buffer.
*
* @note The signature is compatible with the fwrite() family of functions.
*
@@ -483,6 +528,62 @@
);
/**
+ * 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
+size_t cxBufferFlush(CxBuffer *buffer);
+
+/**
* Reads data from a CxBuffer.
*
* The position of the buffer is increased by the number of bytes read.