99 lines
3.6 KiB
C
99 lines
3.6 KiB
C
#ifndef _BUFFER_H
|
|
#define _BUFFER_H
|
|
/*
|
|
* This file is distributed as part of the SkySQL Gateway. It is free
|
|
* software: you can redistribute it and/or modify it under the terms of the
|
|
* GNU General Public License as published by the Free Software Foundation,
|
|
* version 2.
|
|
*
|
|
* This program is distributed in the hope that it will be useful, but WITHOUT
|
|
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
|
|
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
|
|
* details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License along with
|
|
* this program; if not, write to the Free Software Foundation, Inc., 51
|
|
* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
|
|
*
|
|
* Copyright SkySQL Ab 2013
|
|
*/
|
|
|
|
/**
|
|
* @file buffer.h Definitions relating the gateway buffer manipulation facilities.
|
|
*
|
|
* These are used to store all data coming in form or going out to the client and the
|
|
* backend structures.
|
|
*
|
|
* The buffers are designed to be used in linked lists and such that they may be passed
|
|
* from one side of the gateway to another without the need to copy data. It may be the case
|
|
* that not all of the data in the buffer is valid, to this end a start and end pointer are
|
|
* included that point to the first valid byte in the buffer and the first byte after the
|
|
* last valid byte. This allows data to be consumed from either end of the buffer whilst
|
|
* still allowing for the copy free semantics of the buffering system.
|
|
*
|
|
* @verbatim
|
|
* Revision History
|
|
*
|
|
* Date Who Description
|
|
* 10/06/2013 Mark Riddoch Initial implementation
|
|
* 11/07/2013 Mark Riddoch Addition of reference count in the gwbuf
|
|
* 16/07/2013 Massimiliano Pinto Added command type for the queue
|
|
*
|
|
* @endverbatim
|
|
*/
|
|
|
|
/**
|
|
* A structure to encapsualte the data in a form that the data itself can be
|
|
* shared between multiple GWBUF's without the need to make multiple copies
|
|
* but still maintain separate data pointers.
|
|
*/
|
|
typedef struct {
|
|
unsigned char *data; /**< Physical memory that was allocated */
|
|
int refcount; /**< Reference count on the buffer */
|
|
} SHARED_BUF;
|
|
|
|
/**
|
|
* The buffer structure used by the descriptor control blocks.
|
|
*
|
|
* Linked lists of buffers are created as data is read from a descriptor
|
|
* or written to a descriptor. The use of linked lists of buffers with
|
|
* flexible data pointers is designed to minimise the need for data to
|
|
* be copied within the gateway.
|
|
*/
|
|
typedef struct gwbuf {
|
|
struct gwbuf *next; /**< Next buffer in a linked chain of buffers */
|
|
void *start; /**< Start of the valid data */
|
|
void *end; /**< First byte after the valid data */
|
|
SHARED_BUF *sbuf; /**< The shared buffer with the real data */
|
|
int command; /**< The command type for the queue */
|
|
} GWBUF;
|
|
|
|
/*
|
|
* Macros to access the data in the buffers
|
|
*/
|
|
#define GWBUF_DATA(b) ((b)->start) /**< First valid, uncomsumed
|
|
* byte in the buffer
|
|
*/
|
|
#define GWBUF_LENGTH(b) ((b)->end - (b)->start) /**< Number of bytes in the
|
|
* individual buffer
|
|
*/
|
|
#define GWBUF_EMPTY(b) ((b)->start == (b)->end) /**< True if all bytes in the
|
|
* buffer have been consumed
|
|
*/
|
|
#define GWBUF_CONSUME(b, bytes) (b)->start += bytes /**< Consume a number of bytes
|
|
* in the buffer
|
|
*/
|
|
|
|
/*
|
|
* Function prototypes for the API to maniplate the buffers
|
|
*/
|
|
extern GWBUF *gwbuf_alloc(unsigned int size);
|
|
extern void gwbuf_free(GWBUF *buf);
|
|
extern GWBUF *gwbuf_clone(GWBUF *buf);
|
|
extern GWBUF *gwbuf_append(GWBUF *head, GWBUF *tail);
|
|
extern GWBUF *gwbuf_consume(GWBUF *head, unsigned int length);
|
|
extern unsigned int gwbuf_length(GWBUF *head);
|
|
|
|
|
|
#endif
|