MHVLib  20111011
An efficiency oriented runtime library for AVR microcontrollers
A:/eclipse/mhvlib/MHV_RingBuffer.cpp
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00001 /*
00002  * Copyright (c) 2011, Make, Hack, Void Inc
00003  * All rights reserved.
00004  *
00005  * Redistribution and use in source and binary forms, with or without
00006  * modification, are permitted provided that the following conditions are met:
00007  *  * Redistributions of source code must retain the above copyright
00008  *    notice, this list of conditions and the following disclaimer.
00009  *  * Redistributions in binary form must reproduce the above copyright
00010  *    notice, this list of conditions and the following disclaimer in the
00011  *    documentation and/or other materials provided with the distribution.
00012  *  * Neither the name of the Make, Hack, Void nor the
00013  *    names of its contributors may be used to endorse or promote products
00014  *    derived from this software without specific prior written permission.
00015  *
00016  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
00017  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
00018  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
00019  * DISCLAIMED. IN NO EVENT SHALL MAKE, HACK, VOID BE LIABLE FOR ANY
00020  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
00021  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00022  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
00023  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
00024  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00025  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00026  */
00027 
00028 
00029 #include "MHV_RingBuffer.h"
00030 
00036 MHV_RingBuffer::MHV_RingBuffer(char *buffer, uint8_t size) {
00037         _buffer = buffer;
00038         _size = size;
00039         _head = 0; // Where we are about to write to
00040         _tail = 0; // Where we will start reading from
00041 }
00042 
00048 inline uint8_t MHV_RingBuffer::increment (uint8_t index) {
00049         uint8_t next = index + 1;
00050         if (next == _size) {
00051                 next = 0;
00052         }
00053 
00054         return next;
00055 }
00056 
00061 bool MHV_RingBuffer::append(char c) {
00062         uint8_t next = increment(_head);
00063 
00064         // Don't overwrite valid data in the buffer
00065         if (next == _tail) {
00066                 return true;
00067         }
00068 
00069         _buffer[_head] = c;
00070         _head = next;
00071 
00072         return false;
00073 }
00074 
00081 bool MHV_RingBuffer::append(const void *p, uint8_t pLength) {
00082         if (full(pLength)) {
00083                 return true;
00084         }
00085 
00086         uint8_t i;
00087 
00088         char *c = (char *)p;
00089         for (i = 0; i < pLength; i++) {
00090                 append(*c++);
00091         }
00092 
00093         return false;
00094 }
00095 
00099 int MHV_RingBuffer::consume() {
00100         if (_head == _tail) {
00101                 return -1;
00102         }
00103 
00104         unsigned char c = _buffer[_tail];
00105         _tail = increment(_tail);
00106         return c;
00107 }
00108 
00115 bool MHV_RingBuffer::consume(void *p, uint8_t pLength) {
00116         if (length() < pLength) {
00117                 return true;
00118         }
00119 
00120         uint8_t i;
00121         char *c = (char *)p;
00122 
00123         for (i = 0; i < pLength; i++) {
00124                 *c++ = (char)consume();
00125         }
00126 
00127         return false;
00128 }
00129 
00130 
00134 void MHV_RingBuffer::flush() {
00135         _head = _tail = 0;
00136 }
00137 
00142 uint8_t MHV_RingBuffer::size() {
00143         return _size;
00144 }
00145 
00150 uint8_t MHV_RingBuffer::length() {
00151         int16_t length = _head - _tail;
00152         if (length < 0) {
00153 // The pointers have wrapped
00154                 length = (_size - _tail) + _head + 1;
00155         }
00156 
00157         return (uint8_t) length;
00158 }
00159 
00164 bool MHV_RingBuffer::full() {
00165         return length() == _size - 1;
00166 }
00167 
00173 bool MHV_RingBuffer::full(uint8_t blockLength) {
00174         return length() > (_size - 1 - blockLength);
00175 }
00176 
00177 
00182 int MHV_RingBuffer::peekHead() {
00183         if (_head == _tail) {
00184                 return -1;
00185         }
00186 
00187         // We want the character just before head
00188         int offset;
00189         if (0 == _head) {
00190                 offset = _size - 1;
00191         } else {
00192                 offset = _head - 1;
00193         }
00194         return (int) _buffer[offset];
00195 }