cbuf.cpp

/* 
 cbuf.cpp - Circular buffer implementation
 Copyright (c) 2014 Ivan Grokhotkov. All rights reserved.
 This file is part of the esp8266 core for Arduino environment.
 
 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.

 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "cbuf.h"
#include "Arduino.h"

cbuf::cbuf(size_t size) :
    _size(size), _buf(new char[size]), _bufend(_buf + size), _begin(_buf), _end(_begin) {
}

cbuf::~cbuf() {
    delete[] _buf;
}

size_t cbuf::getSize() const {
    if(_end >= _begin) {
        return _end - _begin;
    }
    return _size - (_begin - _end);
}

size_t cbuf::room() const {
    if(_end >= _begin) {
        return _size - (_end - _begin) - 1;
    }
    return _begin - _end - 1;
}

bool cbuf::empty() const {
    return _begin == _end;
}

bool cbuf::full() const {
    return wrap_if_bufend(_end + 1) == _begin;
}

int cbuf::peek() {
    if(empty()) return -1;

    return static_cast<int>(*_begin);
}

size_t cbuf::read(char* dst, size_t size) {
    size_t bytes_available = getSize();
    size_t size_to_read = (size < bytes_available) ? size : bytes_available;
    size_t size_read = size_to_read;
    if(_end < _begin && size_to_read > (size_t)(_bufend - _begin)) {
        size_t top_size = _bufend - _begin;
        memcpy(dst, _begin, top_size);
        _begin = _buf;
        size_to_read -= top_size;
        dst += top_size;
    }
    memcpy(dst, _begin, size_to_read);
    _begin = wrap_if_bufend(_begin + size_to_read);
    return size_read;
}

int cbuf::read() {
    if(empty()) return -1;

    char result = *_begin;
    _begin = wrap_if_bufend(_begin + 1);
    return static_cast<int>(result);
}

size_t cbuf::write(const char* src, size_t size) {
    size_t bytes_available = room();
    size_t size_to_write = (size < bytes_available) ? size : bytes_available;
    size_t size_written = size_to_write;
    if(_end >= _begin && size_to_write > (size_t)(_bufend - _end)) {
        size_t top_size = _bufend - _end;
        memcpy(_end, src, top_size);
        _end = _buf;
        size_to_write -= top_size;
        src += top_size;
    }
    memcpy(_end, src, size_to_write);
    _end = wrap_if_bufend(_end + size_to_write);
    return size_written;
}

size_t cbuf::write(char c) {
     if(full()) return 0;

     *_end = c;
     _end = wrap_if_bufend(_end + 1);
     return 1;
}

void cbuf::flush() {
    _begin = _buf;
    _end = _buf;
}

char* cbuf::wrap_if_bufend(char* ptr) const {
    return (ptr == _bufend) ? _buf : ptr;
}