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/*
Copyright (C) 2012 Carl Hetherington <cth@carlh.net>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stdint.h>
#include <cstring>
#include <algorithm>
#include <iostream>
#include "delay_line.h"
using namespace std;
/** Construct a DelayLine delaying by some number of bytes.
* @param d Number of bytes to delay by; +ve moves data later.
*/
DelayLine::DelayLine (int d)
: _delay (d)
, _buffer (0)
, _negative_delay_remaining (0)
{
if (d > 0) {
/* We need a buffer to keep some data in */
_buffer = new uint8_t[d];
memset (_buffer, 0, d);
} else if (d < 0) {
/* We can do -ve delays just by chopping off
the start, so no buffer needed.
*/
_negative_delay_remaining = -d;
}
}
DelayLine::~DelayLine ()
{
delete[] _buffer;
}
int
DelayLine::feed (uint8_t* data, int size)
{
int available = size;
if (_delay > 0) {
/* Copy the input data */
uint8_t input[size];
memcpy (input, data, size);
int to_do = size;
/* Write some of our buffer to the output */
int const from_buffer = min (to_do, _delay);
memcpy (data, _buffer, from_buffer);
to_do -= from_buffer;
/* Write some of the input to the output */
int const from_input = min (to_do, size);
memcpy (data + from_buffer, input, from_input);
int const left_in_buffer = _delay - from_buffer;
/* Shuffle our buffer down */
memmove (_buffer, _buffer + from_buffer, left_in_buffer);
/* Copy remaining input data to our buffer */
memcpy (_buffer + left_in_buffer, input + from_input, size - from_input);
} else if (_delay < 0) {
/* Chop the initial data off until _negative_delay_remaining
is zero, then just pass data.
*/
int const to_do = min (size, _negative_delay_remaining);
available = size - to_do;
memmove (data, data + to_do, available);
_negative_delay_remaining -= to_do;
}
return available;
}
/** With -ve delays, the DelayLine will have data to give after
* all input data has been passed to ::feed().
* Call this method after passing all input data.
*
* @param buffer Pointer to buffer of _delay bytes in length,
* which will be filled with remaining data.
*/
void
DelayLine::get_remaining (uint8_t* buffer)
{
memset (buffer, 0, -_delay);
}
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