65 lines
2.4 KiB
C
65 lines
2.4 KiB
C
#ifndef _BUFFER_H
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#define _BUFFER_H
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/*
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* This file is distributed as part of the SkySQL Gateway. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright SkySQL Ab 2013
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*/
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/*
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* Definitions relating the gateway buffer manipulation facilities.
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* These are used to store all data coming in form or going out to the client and the
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* backend structures.
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*
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* The buffers are designed to be used in linked lists and such that they may be passed
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* from one side of the gateway to another without the need to copy data. It may be the case
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* that not all of the data in the buffer is valid, to this end a start and end pointer are
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* included that point to the first valid byte in the buffer and the first byte after the
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* last valid byte. This allows data to be consumed from either end of the buffer whilst
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* still allowing for the copy free semantics of the buffering system.
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*
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* Revision History
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*
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* Date Who Description
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* 10/06/13 Mark Riddoch Initial implementation
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*
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*/
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typedef struct gwbuf {
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struct gwbuf *next; // Next buffer in a linked chain of buffers
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void *start; // Start of the valid data
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void *end; // First byte after the valid data
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unsigned char *data; // Physical memory that was allocated
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} GWBUF;
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/*
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* Macros to access the data in the buffers
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*/
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#define GWBUF_DATA(b) ((b)->start)
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#define GWBUF_LENGTH(b) ((b)->end - (b)->start)
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#define GWBUF_EMPTY(b) ((b)->start == (b)->end)
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#define GWBUF_CONSUME(b, bytes) (b)->start += bytes
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/*
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* Function prototypes for the API to maniplate the buffers
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*/
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extern GWBUF *gwbuf_alloc(unsigned int size);
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extern void gwbuf_free(GWBUF *buf);
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extern GWBUF *gwbuf_append(GWBUF *head, GWBUF *tail);
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extern GWBUF *gwbuf_consume(GWBUF *head, unsigned int length);
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extern unsigned int gwbuf_length(GWBUF *head);
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#endif
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