/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/**
* \file buffer.h
*
* \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 Olaf Wintermann
* \copyright 2-Clause BSD License
*/
#ifndef UCX_BUFFER_H
#define UCX_BUFFER_H
#include "common.h"
#include "allocator.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* No buffer features enabled (all flags cleared).
*/
#define CX_BUFFER_DEFAULT 0x00
/**
* If this flag is enabled, the buffer will automatically free its contents when destroyed.
*/
#define CX_BUFFER_FREE_CONTENTS 0x01
/**
* If this flag is enabled, the buffer will automatically extends its capacity.
*/
#define CX_BUFFER_AUTO_EXTEND 0x02
/** Structure for the UCX buffer data. */
typedef struct {
/** A pointer to the buffer contents. */
union {
/**
* Data is interpreted as text.
*/
char *space;
/**
* Data is interpreted as binary.
*/
unsigned char *bytes;
};
/** The allocator to use for automatic memory management. */
const CxAllocator *allocator;
/** 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
*/
int flags;
} cx_buffer_s;
/**
* UCX buffer.
*/
typedef cx_buffer_s CxBuffer;
/**
* Initializes a fresh buffer.
*
* \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 buffer the buffer to initialize
* @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.
* @param flags buffer features (see cx_buffer_s.flags)
* @return zero on success, non-zero if a required allocation failed
*/
__attribute__((__nonnull__(1)))
int cxBufferInit(
CxBuffer *buffer,
void *space,
size_t capacity,
const CxAllocator *allocator,
int flags
);
/**
* Allocates and initializes a fresh buffer.
*
* \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, 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
*/
CxBuffer *cxBufferCreate(
void *space,
size_t capacity,
const CxAllocator *allocator,
int flags
);
/**
* 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()
*/
__attribute__((__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().
*
* @param buffer the buffer to deallocate
* @see cxBufferCreate()
*/
__attribute__((__nonnull__))
void cxBufferFree(CxBuffer *buffer);
/**
* Shifts the contents of the buffer by the given offset.
*
* If the offset is positive, the contents are shifted to the right.
* If auto extension is enabled, the buffer grows, if necessary.
* In case the auto extension fails, this function returns a non-zero value and
* 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.
* 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
* 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.
* 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 fails
*/
__attribute__((__nonnull__))
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 fails
* @see cxBufferShift()
*/
__attribute__((__nonnull__))
int cxBufferShiftRight(
CxBuffer *buffer,
size_t shift
);
/**
* 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
* @see cxBufferShift()
*/
__attribute__((__nonnull__))
int cxBufferShiftLeft(
CxBuffer *buffer,
size_t shift
);
/**
* Moves the position of the buffer.
*
* 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.
*
* 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).
*
* @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
*
*/
__attribute__((__nonnull__))
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().
*
* @param buffer the buffer to be cleared
* @see cxBufferReset()
*/
__attribute__((__nonnull__))
void cxBufferClear(CxBuffer *buffer);
/**
* Resets the buffer by resetting the position and size to zero.
*
* The data in the buffer is not deleted. If you need a safe
* reset of the buffer, use cxBufferClear().
*
* @param buffer the buffer to be cleared
* @see cxBufferClear()
*/
__attribute__((__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.
*/
__attribute__((__nonnull__))
int 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
*/
__attribute__((__nonnull__))
int cxBufferMinimumCapacity(
CxBuffer *buffer,
size_t capacity
);
/**
* Writes data to a CxBuffer.
*
* 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.
* 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 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.
*
* @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
*/
__attribute__((__nonnull__))
size_t cxBufferWrite(
const void *ptr,
size_t size,
size_t nitems,
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.
*
* @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
*/
__attribute__((__nonnull__))
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.
*
* On successful write, the position of the buffer is increased.
*
* @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
* reached and automatic extension is not enabled or not possible
*/
__attribute__((__nonnull__))
int cxBufferPut(
CxBuffer *buffer,
int c
);
/**
* Writes a string to a buffer.
*
* @param buffer the buffer
* @param str the zero-terminated string
* @return the number of bytes written
*/
__attribute__((__nonnull__))
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
*/
__attribute__((__nonnull__))
int cxBufferGet(CxBuffer *buffer);
#ifdef __cplusplus
}
#endif
#endif // UCX_BUFFER_H