--- a/ucx/cx/buffer.h Sun Dec 07 20:00:33 2025 +0100
+++ b/ucx/cx/buffer.h Sat Dec 13 15:58:58 2025 +0100
@@ -48,6 +48,7 @@
#include "common.h"
#include "allocator.h"
+#include "string.h"
#ifdef __cplusplus
extern "C" {
@@ -89,6 +90,13 @@
#define CX_BUFFER_COPY_ON_EXTEND 0x08
/**
+ * If this flag is enabled, the buffer will never free its contents regardless of #CX_BUFFER_FREE_CONTENTS.
+ *
+ * This is useful, for example, when you want to keep a pointer to the data after destroying the buffer.
+ */
+#define CX_BUFFER_DO_NOT_FREE 0x10
+
+/**
* Function pointer for cxBufferWrite that is compatible with cx_write_func.
* @see cx_write_func
*/
@@ -99,59 +107,6 @@
*/
#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 the 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. */
struct cx_buffer_s {
@@ -168,16 +123,12 @@
};
/** 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. */
size_t capacity;
+ /** Maximum capacity that this buffer may grow to. */
+ size_t max_capacity;
/** Current size of the buffer content. */
size_t size;
/**
@@ -231,23 +182,6 @@
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_EXPORT int cxBufferEnableFlushing(CxBuffer *buffer, CxBufferFlushConfig config);
-
-/**
* Destroys the buffer contents.
*
* Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
@@ -388,6 +322,20 @@
CX_EXPORT int cxBufferSeek(CxBuffer *buffer, off_t offset, int whence);
/**
+ * Discards items from the end of the buffer.
+ *
+ * When the current position points to a byte that gets discarded,
+ * the position is set to the buffer size.
+ *
+ * @param buffer the buffer
+ * @param size the size of one item
+ * @param nitems the number of items to discard
+ * @return the actual number of discarded items
+ */
+cx_attr_nonnull
+CX_EXPORT size_t cxBufferPop(CxBuffer *buffer, size_t size, size_t nitems);
+
+/**
* Clears the buffer by resetting the position and deleting the data.
*
* The data is deleted by zeroing it with a call to memset().
@@ -425,11 +373,51 @@
cx_attr_nonnull cx_attr_nodiscard
CX_EXPORT bool cxBufferEof(const CxBuffer *buffer);
+/**
+ * Ensures that the buffer has the required capacity.
+ *
+ * If the current capacity is not sufficient, the buffer will be extended.
+ * If the current capacity is larger, the buffer is shrunk and superfluous
+ * content is discarded.
+ *
+ * This function will reserve no more bytes than requested, in contrast to
+ * cxBufferMinimumCapacity(), which may reserve more bytes to improve the
+ * number of future necessary reallocations.
+ *
+ * @param buffer the buffer
+ * @param capacity the required capacity for this buffer
+ * @retval zero on success
+ * @retval non-zero on allocation failure
+ * @see cxBufferShrink()
+ * @see cxBufferMinimumCapacity()
+ */
+cx_attr_nonnull
+CX_EXPORT int cxBufferReserve(CxBuffer *buffer, size_t capacity);
+
+/**
+ * Limits the buffer's capacity.
+ *
+ * If the current capacity is already larger, this function fails and returns
+ * non-zero.
+ *
+ * The capacity limit will affect auto-extension features, as well as future
+ * calls to cxBufferMinimumCapacity() and cxBufferReserve().
+ *
+ * @param buffer the buffer
+ * @param capacity the maximum allowed capacity for this buffer
+ * @retval zero the limit is applied
+ * @retval non-zero the new limit is smaller than the current capacity
+ * @see cxBufferReserve()
+ * @see cxBufferMinimumCapacity()
+ */
+cx_attr_nonnull
+CX_EXPORT int cxBufferMaximumCapacity(CxBuffer *buffer, size_t capacity);
/**
* Ensures that the buffer has a minimum capacity.
*
- * If the current capacity is not sufficient, the buffer will be extended.
+ * If the current capacity is not sufficient, the buffer will be generously
+ * extended.
*
* The new capacity will be a power of two until the system's page size is reached.
* Then, the new capacity will be a multiple of the page size.
@@ -438,6 +426,8 @@
* @param capacity the minimum required capacity for this buffer
* @retval zero the capacity was already sufficient or successfully increased
* @retval non-zero on allocation failure
+ * @see cxBufferMaximumCapacity()
+ * @see cxBufferReserve()
* @see cxBufferShrink()
*/
cx_attr_nonnull
@@ -457,6 +447,7 @@
*
* @param buffer the buffer
* @param reserve the number of bytes that shall remain reserved
+ * @see cxBufferReserve()
* @see cxBufferMinimumCapacity()
*/
cx_attr_nonnull
@@ -465,33 +456,13 @@
/**
* 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 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.
+ * If auto-extension is enabled, the buffer's capacity is automatically
+ * increased when it is not large enough to hold all data.
+ * By default, the capacity grows indefinitely, unless limited with
+ * cxBufferMaximumCapacity().
+ * When auto-extension fails, this function writes no data and returns zero.
*
- * If, after flushing, the number of items that shall be written still exceeds
- * the capacity or flush threshold, this function tries to write all items directly
- * to the flush target, if possible.
- *
- * The number returned by this function is the number of elements from
- * @c ptr that could be written to either the flush target or the buffer.
- * That means it does @em not include the number of items that were already in
- * the buffer and were also 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 misaligned part in the buffer.
- * Afterward, this function only writes as many items as possible to the buffer.
+ * The position of the buffer is moved alongside the written data.
*
* @note The signature is compatible with the fwrite() family of functions.
*
@@ -531,62 +502,6 @@
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 operation 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 makes little 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_EXPORT size_t cxBufferFlush(CxBuffer *buffer);
-
-/**
* Reads data from a CxBuffer.
*
* The position of the buffer is increased by the number of bytes read.
@@ -610,8 +525,9 @@
*
* 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 the buffer extension fails, @c EOF is returned.
+ * the buffer capacity is extended, unless a limit set by
+ * cxBufferMaximumCapacity() is reached.
+ * If the feature is disabled or the buffer extension fails, @c EOF is returned.
*
* On successful writing, the position of the buffer is increased.
*
@@ -620,8 +536,8 @@
*
* @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
- * reached, and automatic extension is not enabled or not possible
+ * @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
@@ -630,28 +546,61 @@
/**
* Writes a terminating zero to a buffer at the current position.
*
- * If successful, sets the size to the current position and advances the position by one.
+ * If successful, also sets the size to the current position and shrinks the buffer.
*
* The purpose of this function is to have the written data ready to be used as
* a C string with the buffer's size being the length of that string.
*
* @param buffer the buffer to write to
* @return zero, if the terminator could be written, non-zero otherwise
+ * @see cxBufferShrink()
*/
cx_attr_nonnull
CX_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>.
+ * Internal function - do not use.
*
* @param buffer the buffer
- * @param str the zero-terminated string
+ * @param str the string
* @return the number of bytes written
+ * @see cxBufferPutString()
+ */
+cx_attr_nonnull
+CX_EXPORT size_t cx_buffer_put_string(CxBuffer *buffer, cxstring str);
+
+/**
+ * Writes a string to a buffer with cxBufferWrite().
+ *
+ * @param buffer (@c CxBuffer*) the buffer
+ * @param str (any string) the zero-terminated string
+ * @return (@c size_t) the number of bytes written
+ * @see cxBufferWrite()
+ * @see cx_strcast()
*/
-cx_attr_nonnull cx_attr_cstr_arg(2)
-CX_EXPORT size_t cxBufferPutString(CxBuffer *buffer, const char *str);
+#define cxBufferPutString(buffer, str) cx_buffer_put_string(buffer, cx_strcast(str))
+
+/**
+ * Internal function - do not use.
+ *
+ * @param buffer the buffer
+ * @param str the string
+ * @return the number of bytes written
+ * @see cxBufferPutString()
+ */
+cx_attr_nonnull
+CX_EXPORT size_t cx_buffer_append_string(CxBuffer *buffer, cxstring str);
+
+/**
+ * Appends a string to a buffer with cxBufferAppend().
+ *
+ * @param buffer (@c CxBuffer*) the buffer
+ * @param str (any string) the zero-terminated string
+ * @return (@c size_t) the number of bytes written
+ * @see cxBufferAppend()
+ * @see cx_strcast()
+ */
+#define cxBufferAppendString(buffer, str) cx_buffer_append_string(buffer, cx_strcast(str))
/**
* Gets a character from a buffer.