152 lines
3.3 KiB
C
152 lines
3.3 KiB
C
/*
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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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* buffer.h - The Gateway buffer management functions
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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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#include <stdlib.h>
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#include <buffer.h>
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/*
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* Allocate a new gateway buffer structure of size bytes.
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*
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* For now we allocate memory directly from malloc for buffer the management
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* structure and the actual data buffer itself. We may swap at a future date
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* to a more effecient mechanism.
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*
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* @param size The size in bytes of the data area required
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* @return Pointer to the buffer structure or NULL if memory could not
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* be allocated.
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*/
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GWBUF *
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gwbuf_alloc(unsigned int size)
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{
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GWBUF *rval;
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// Allocate the buffer header
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if ((rval = (GWBUF *)malloc(sizeof(GWBUF))) == NULL)
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{
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return NULL;
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}
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// Allocate the space for the actual data
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if ((rval->data = (unsigned char *)malloc(size)) == NULL)
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{
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free(rval);
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return NULL;
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}
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rval->start = rval->data;
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rval->end = rval->start + size;
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rval->next = NULL;
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return rval;
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}
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/*
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* Free a gateway buffer
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*
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* @param buf The buffer to free
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*/
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void
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gwbuf_free(GWBUF *buf)
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{
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free(buf->data);
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free(buf);
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}
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/*
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* Append a buffer onto a linked list of buffer structures.
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*
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* This call should be made with the caller holding the lock for the linked
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* list.
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*
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* @param head The current head of the linked list
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* @param tail The new buffer to make the tail of the linked list
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* @return The new head of the linked list
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*/
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GWBUF *
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gwbuf_append(GWBUF *head, GWBUF *tail)
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{
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GWBUF *ptr = head;
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if (!head)
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return tail;
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while (ptr->next)
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{
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ptr = ptr->next;
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}
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ptr->next = tail;
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return head;
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}
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/*
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* Consume data from a buffer in the linked list. The assumption is to consume
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* n bytes from the buffer chain.
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*
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* If after consuming the bytes from the first buffer that buffer becomes
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* empty it will be freed and the linked list updated.
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*
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* The return value is the new head of the linked list.
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*
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* This call should be made with the caller holding the lock for the linked
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* list.
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*
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* @param head The head of the linked list
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* @param length The amount of data to consume
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* @return The head of the linked list
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*/
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GWBUF *
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gwbuf_consume(GWBUF *head, unsigned int length)
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{
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GWBUF *rval = head;
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GWBUF_CONSUME(head, length);
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if (GWBUF_EMPTY(head))
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{
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rval = head->next;
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gwbuf_free(head);
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}
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return rval;
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}
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/*
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* Return the number of bytes of data in the linked list.
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*
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* @param head The current head of the linked list
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* @return The number of bytes of data in the linked list
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*/
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unsigned int
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gwbuf_length(GWBUF *head)
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{
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int rval = 0;
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while (head)
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{
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rval += GWBUF_LENGTH(head);
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head = head->next;
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}
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return rval;
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}
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