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/**
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* Copyright (c) 2011, Willem-Hendrik Thiart
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE.bipbuffer file.
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*
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* @file
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* @author Willem Thiart himself@willemthiart.com
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*/
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#include "stdio.h"
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#include <stdlib.h>
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/* for memcpy */
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#include <string.h>
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#include "bipbuffer.h"
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static size_t bipbuf_sizeof(const unsigned int size)
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{
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return sizeof(bipbuf_t) + size;
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}
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int bipbuf_unused(const bipbuf_t* me)
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{
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if (1 == me->b_inuse)
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/* distance between region B and region A */
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return me->a_start - me->b_end;
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else
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return me->size - me->a_end;
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}
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int bipbuf_size(const bipbuf_t* me)
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{
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return me->size;
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}
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int bipbuf_used(const bipbuf_t* me)
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{
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return (me->a_end - me->a_start) + me->b_end;
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}
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void bipbuf_init(bipbuf_t* me, const unsigned int size)
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{
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me->a_start = me->a_end = me->b_end = 0;
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me->size = size;
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me->b_inuse = 0;
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}
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bipbuf_t *bipbuf_new(const unsigned int size)
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{
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bipbuf_t *me = malloc(bipbuf_sizeof(size));
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if (!me)
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return NULL;
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bipbuf_init(me, size);
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return me;
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}
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void bipbuf_free(bipbuf_t* me)
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{
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free(me);
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}
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int bipbuf_is_empty(const bipbuf_t* me)
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{
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return me->a_start == me->a_end;
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}
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/* find out if we should turn on region B
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* ie. is the distance from A to buffer's end less than B to A? */
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static void __check_for_switch_to_b(bipbuf_t* me)
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{
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if (me->size - me->a_end < me->a_start - me->b_end)
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me->b_inuse = 1;
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}
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/* TODO: DOCUMENT THESE TWO FUNCTIONS */
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unsigned char *bipbuf_request(bipbuf_t* me, const int size)
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{
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if (bipbuf_unused(me) < size)
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return 0;
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if (1 == me->b_inuse)
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{
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return (unsigned char *)me->data + me->b_end;
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}
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else
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{
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return (unsigned char *)me->data + me->a_end;
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}
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}
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int bipbuf_push(bipbuf_t* me, const int size)
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{
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if (bipbuf_unused(me) < size)
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return 0;
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if (1 == me->b_inuse)
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{
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me->b_end += size;
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}
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else
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{
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me->a_end += size;
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}
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__check_for_switch_to_b(me);
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return size;
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}
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int bipbuf_offer(bipbuf_t* me, const unsigned char *data, const int size)
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{
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/* not enough space */
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if (bipbuf_unused(me) < size)
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return 0;
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if (1 == me->b_inuse)
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{
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memcpy(me->data + me->b_end, data, size);
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me->b_end += size;
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}
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else
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{
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memcpy(me->data + me->a_end, data, size);
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me->a_end += size;
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}
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__check_for_switch_to_b(me);
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return size;
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}
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unsigned char *bipbuf_peek(const bipbuf_t* me, const unsigned int size)
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{
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/* make sure we can actually peek at this data */
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if (me->size < me->a_start + size)
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return NULL;
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if (bipbuf_is_empty(me))
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return NULL;
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return (unsigned char *)me->data + me->a_start;
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}
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unsigned char *bipbuf_peek_all(const bipbuf_t* me, unsigned int *size)
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{
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if (bipbuf_is_empty(me))
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return NULL;
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*size = me->a_end - me->a_start;
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return (unsigned char*)me->data + me->a_start;
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}
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unsigned char *bipbuf_poll(bipbuf_t* me, const unsigned int size)
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{
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if (bipbuf_is_empty(me))
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return NULL;
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/* make sure we can actually poll this data */
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if (me->size < me->a_start + size)
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return NULL;
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void *end = me->data + me->a_start;
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me->a_start += size;
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/* we seem to be empty.. */
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if (me->a_start == me->a_end)
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{
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/* replace a with region b */
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if (1 == me->b_inuse)
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{
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me->a_start = 0;
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me->a_end = me->b_end;
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me->b_end = me->b_inuse = 0;
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}
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else
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/* safely move cursor back to the start because we are empty */
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me->a_start = me->a_end = 0;
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}
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__check_for_switch_to_b(me);
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return end;
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}
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