--- a/ucx/cx/buffer.h Thu Dec 12 20:01:43 2024 +0100
+++ b/ucx/cx/buffer.h Mon Jan 06 22:22:55 2025 +0100
@@ -27,9 +27,9 @@
*/
/**
- * \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.
@@ -38,9 +38,9 @@
* can be enabled. See the documentation of the macro constants for more
* information.
*
- * \author Mike Becker
- * \author Olaf Wintermann
- * \copyright 2-Clause BSD License
+ * @author Mike Becker
+ * @author Olaf Wintermann
+ * @copyright 2-Clause BSD License
*/
#ifndef UCX_BUFFER_H
@@ -49,7 +49,7 @@
#include "common.h"
#include "allocator.h"
-#ifdef __cplusplus
+#ifdef __cplusplus
extern "C" {
#endif
@@ -60,16 +60,90 @@
/**
* If this flag is enabled, the buffer will automatically free its contents when destroyed.
+ *
+ * Do NOT set this flag together with #CX_BUFFER_COPY_ON_WRITE. It will be automatically
+ * set when the copy-on-write operations is performed.
*/
#define CX_BUFFER_FREE_CONTENTS 0x01
/**
- * If this flag is enabled, the buffer will automatically extends its capacity.
+ * If this flag is enabled, the buffer will automatically extend its capacity.
*/
#define CX_BUFFER_AUTO_EXTEND 0x02
+/**
+ * If this flag is enabled, the buffer will allocate new memory when written to.
+ *
+ * The current contents of the buffer will be copied to the new memory and the flag
+ * will be cleared while the #CX_BUFFER_FREE_CONTENTS flag will be set automatically.
+ */
+#define CX_BUFFER_COPY_ON_WRITE 0x04
+
+/**
+ * If this flag is enabled, the buffer will copy its contents to a new memory area on reallocation.
+ *
+ * After performing the copy, the flag is automatically cleared.
+ * 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
+
+/**
+ * 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. */
-typedef struct {
+struct cx_buffer_s {
/** A pointer to the buffer contents. */
union {
/**
@@ -83,6 +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. */
@@ -90,70 +170,52 @@
/** 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.
*
- * \note You may provide \c NULL as argument for \p space.
+ * 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.
+ *
+ * When you specify stack memory as @p space and decide to use
+ * 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.
* Then this function will allocate the space and enforce
- * the #CX_BUFFER_FREE_CONTENTS flag.
+ * 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, the default heap allocator will be used.
+ * memory management
+ * (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
*/
-__attribute__((__nonnull__(1)))
+cx_attr_nonnull_arg(1)
int cxBufferInit(
CxBuffer *buffer,
void *space,
@@ -163,25 +225,23 @@
);
/**
- * Allocates and initializes a fresh buffer.
+ * Configures the buffer for flushing.
*
- * \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.
+ * Flushing can happen automatically when data is written
+ * to the buffer (see cxBufferWrite()) or manually when
+ * cxBufferFlush() is called.
*
- * @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, the default heap 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
+ * @param buffer the buffer
+ * @param config the flush configuration
+ * @retval zero success
+ * @retval non-zero failure
+ * @see cxBufferFlush()
+ * @see cxBufferWrite()
*/
-CxBuffer *cxBufferCreate(
- void *space,
- size_t capacity,
- const CxAllocator *allocator,
- int flags
+cx_attr_nonnull
+int cxBufferEnableFlushing(
+ CxBuffer *buffer,
+ CxBufferFlushConfig config
);
/**
@@ -193,22 +253,58 @@
* @param buffer the buffer which contents shall be destroyed
* @see cxBufferInit()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
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
+ * case it does nothing.
*
* @param buffer the buffer to deallocate
* @see cxBufferCreate()
*/
-__attribute__((__nonnull__))
void cxBufferFree(CxBuffer *buffer);
/**
+ * Allocates and initializes a fresh buffer.
+ *
+ * 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
+ * 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.
+ * 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
+ * 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)
+ * @param flags buffer features (see cx_buffer_s.flags)
+ * @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
+CxBuffer *cxBufferCreate(
+ void *space,
+ size_t capacity,
+ const CxAllocator *allocator,
+ int flags
+);
+
+/**
* Shifts the contents of the buffer by the given offset.
*
* If the offset is positive, the contents are shifted to the right.
@@ -219,7 +315,7 @@
* 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).
@@ -227,11 +323,11 @@
* 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
- * cxBufferShiftRight() functions using a \c size_t as parameter type.
+ * @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.
*
- * \attention
- * Security Note: The shifting operation does \em not erase the previously occupied memory cells.
+ * @attention
+ * 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>
@@ -239,9 +335,12 @@
*
* @param buffer the buffer
* @param shift the shift offset (negative means left shift)
- * @return 0 on success, non-zero if a required auto-extension fails
+ * @retval zero success
+ * @retval non-zero if a required auto-extension or copy-on-write fails
+ * @see cxBufferShiftLeft()
+ * @see cxBufferShiftRight()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
int cxBufferShift(
CxBuffer *buffer,
off_t shift
@@ -253,10 +352,11 @@
*
* @param buffer the buffer
* @param shift the shift offset
- * @return 0 on success, non-zero if a required auto-extension fails
+ * @retval zero success
+ * @retval non-zero if a required auto-extension or copy-on-write fails
* @see cxBufferShift()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
int cxBufferShiftRight(
CxBuffer *buffer,
size_t shift
@@ -266,15 +366,13 @@
* Shifts the buffer to the left.
* See cxBufferShift() for details.
*
- * \note Since a left shift cannot fail due to memory allocation problems, this
- * function always returns zero.
- *
* @param buffer the buffer
* @param shift the positive shift offset
- * @return always zero
+ * @retval zero success
+ * @retval non-zero if the buffer uses copy-on-write and the allocation fails
* @see cxBufferShift()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
int cxBufferShiftLeft(
CxBuffer *buffer,
size_t shift
@@ -284,23 +382,24 @@
/**
* 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_CUR marks the current position.
- * \li \c SEEK_END marks the end of the buffer.
+ * @li @c SEEK_SET marks the start of the buffer.
+ * @li @c SEEK_CUR marks the current position.
+ * @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
- * unchanged (\c SEEK_CUR).
+ * (@c SEEK_SET), the buffer size (@c SEEK_END) or leaves the buffer position
+ * unchanged (@c SEEK_CUR).
*
* @param buffer the buffer
- * @param offset position offset relative to \p whence
- * @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
+ * @param offset position offset relative to @p whence
+ * @param whence one of @c SEEK_SET, @c SEEK_CUR or @c SEEK_END
+ * @retval zero success
+ * @retval non-zero if the position is invalid
*
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
int cxBufferSeek(
CxBuffer *buffer,
off_t offset,
@@ -313,10 +412,13 @@
* 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
+ * will not erase the data and behave exactly as cxBufferReset().
+ *
* @param buffer the buffer to be cleared
* @see cxBufferReset()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
void cxBufferClear(CxBuffer *buffer);
/**
@@ -328,18 +430,20 @@
* @param buffer the buffer to be cleared
* @see cxBufferClear()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
void cxBufferReset(CxBuffer *buffer);
/**
* Tests, if the buffer position has exceeded the buffer size.
*
* @param buffer the buffer to test
- * @return non-zero, if the current buffer position has exceeded the last
- * byte of the buffer's contents.
+ * @retval true if the current buffer position has exceeded the last
+ * byte of the buffer's contents
+ * @retval false otherwise
*/
-__attribute__((__nonnull__))
-int cxBufferEof(const CxBuffer *buffer);
+cx_attr_nonnull
+cx_attr_nodiscard
+bool cxBufferEof(const CxBuffer *buffer);
/**
@@ -349,9 +453,10 @@
*
* @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
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
int cxBufferMinimumCapacity(
CxBuffer *buffer,
size_t capacity
@@ -360,6 +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
@@ -367,23 +476,23 @@
* 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 be
- * flushed already.
+ * 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.
*
- * If automatic flushing is not enabled, the position of the buffer is increased
- * by the number of bytes written.
- *
- * \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 cxBufferAppend()
+ * @see cxBufferRead()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
size_t cxBufferWrite(
const void *ptr,
size_t size,
@@ -392,19 +501,104 @@
);
/**
+ * Appends data to a CxBuffer.
+ *
+ * The data is always appended to current data within the 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.
+ *
+ * @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
+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
+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()
+ * @see cxBufferAppend()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
size_t cxBufferRead(
void *ptr,
size_t size,
@@ -417,30 +611,52 @@
*
* 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.
+ * the buffer capacity is extended by cxBufferMinimumCapacity(). If the feature
+ * 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 bean 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()
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
int cxBufferPut(
CxBuffer *buffer,
int c
);
/**
+ * 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
+ * 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
+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
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
+cx_attr_cstr_arg(2)
size_t cxBufferPutString(
CxBuffer *buffer,
const char *str
@@ -452,9 +668,9 @@
* 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
*/
-__attribute__((__nonnull__))
+cx_attr_nonnull
int cxBufferGet(CxBuffer *buffer);
#ifdef __cplusplus