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Member "stud-0.3/ringbuffer.c" (2 Nov 2011, 3604 Bytes) of package /linux/privat/old/stud-0.3.tar.gz:


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    1 /**
    2   * Copyright 2011 Bump Technologies, Inc. All rights reserved.
    3   *
    4   * Redistribution and use in source and binary forms, with or without modification, are
    5   * permitted provided that the following conditions are met:
    6   *
    7   *    1. Redistributions of source code must retain the above copyright notice, this list of
    8   *       conditions and the following disclaimer.
    9   *
   10   *    2. Redistributions in binary form must reproduce the above copyright notice, this list
   11   *       of conditions and the following disclaimer in the documentation and/or other materials
   12   *       provided with the distribution.
   13   *
   14   * THIS SOFTWARE IS PROVIDED BY BUMP TECHNOLOGIES, INC. ``AS IS'' AND ANY EXPRESS OR IMPLIED
   15   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   16   * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BUMP TECHNOLOGIES, INC. OR
   17   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   18   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   19   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
   20   * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   21   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   22   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   23   *
   24   * The views and conclusions contained in the software and documentation are those of the
   25   * authors and should not be interpreted as representing official policies, either expressed
   26   * or implied, of Bump Technologies, Inc.
   27   *
   28   **/
   29 
   30 #include "ringbuffer.h"
   31 #include <assert.h>
   32 
   33 /* Initialize a ringbuffer structure to empty */
   34 
   35 void ringbuffer_init(ringbuffer *rb) {
   36     rb->head = &rb->slots[0];
   37     rb->tail = &rb->slots[0];
   38     rb->used = 0;
   39     int x;
   40     for (x=0; x<RING_SLOTS; x++)
   41         rb->slots[x].next = &(rb->slots[(x + 1) % RING_SLOTS]);
   42 }
   43 
   44 /** READ FUNCTIONS **/
   45 
   46 /* Return a char * that represents the current unconsumed buffer */
   47 char * ringbuffer_read_next(ringbuffer *rb, int * length) {
   48     assert(rb->used);
   49     *length = rb->head->left;
   50     return rb->head->ptr;
   51 }
   52 
   53 /* Mark consumption of only part of the read head buffer */
   54 void ringbuffer_read_skip(ringbuffer *rb, int length) {
   55     assert(rb->used);
   56     rb->head->ptr += length;
   57     rb->head->left -= length;
   58 }
   59 
   60 /* Pop a consumed (fully read) head from the buffer */
   61 void ringbuffer_read_pop(ringbuffer *rb) {
   62     assert(rb->used);
   63     rb->head = rb->head->next;
   64     rb->used--;
   65 }
   66 
   67 
   68 /** WRITE FUNCTIONS **/
   69 
   70 /* Return the tail ptr (current target of new writes) */
   71 char * ringbuffer_write_ptr(ringbuffer *rb) {
   72     assert(rb->used < RING_SLOTS);
   73     return rb->tail->data;
   74 }
   75 
   76 /* Mark the tail appended for `length` bytes, and move the cursor
   77  * to the next slot */
   78 void ringbuffer_write_append(ringbuffer *rb, int length) {
   79     assert(rb->used < RING_SLOTS);
   80 
   81     rb->used++;
   82 
   83     rb->tail->ptr = rb->tail->data;
   84     rb->tail->left = length;
   85     rb->tail = rb->tail->next;
   86 }
   87 
   88 /** RING STATE FUNCTIONS **/
   89 
   90 /* Used size of the ringbuffer */
   91 int ringbuffer_size(ringbuffer *rb) {
   92     return rb->used;
   93 }
   94 
   95 /* Used size of the ringbuffer */
   96 int ringbuffer_capacity(ringbuffer *rb) {
   97     (void) rb;
   98     return RING_SLOTS;
   99 }
  100 
  101 /* Is the ringbuffer completely empty (implies: no data to be written) */
  102 int ringbuffer_is_empty(ringbuffer *rb) {
  103     return rb->used == 0;
  104 }
  105 
  106 /* Is the ringbuffer completely full (implies: no more data should be read) */
  107 int ringbuffer_is_full(ringbuffer *rb) {
  108     return rb->used == RING_SLOTS;
  109 }
  110