Transceiver52M/device/smpl_buf.cpp

/*
 * Sample Buffer - Allows reading and writing of timed samples
 *
 * Copyright 2010,2011 Free Software Foundation, Inc.
 * Copyright (C) 2015 Ettus Research LLC
 * Copyright 2019 sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
 *
 * Author: Tom Tsou <tom.tsou@ettus.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * See the COPYING file in the main directory for details.
 */

#include "smpl_buf.h"
#include <inttypes.h>

smpl_buf::smpl_buf(size_t len)
	: buf_len(len), time_start(0), time_end(0),
	  data_start(0), data_end(0)
{
	data = new uint32_t[len];
}

smpl_buf::~smpl_buf()
{
	delete[] data;
}

ssize_t smpl_buf::avail_smpls(TIMESTAMP timestamp) const
{
	if (timestamp < time_start)
		return ERROR_TIMESTAMP;
	else if (timestamp >= time_end)
		return 0;
	else
		return time_end - timestamp;
}

ssize_t smpl_buf::read(void *buf, size_t len, TIMESTAMP timestamp)
{
	int type_sz = 2 * sizeof(short);

	// Check for valid read
	if (timestamp < time_start)
		return ERROR_TIMESTAMP;
	if (timestamp >= time_end)
		return 0;
	if (len >= buf_len)
		return ERROR_READ;

	// How many samples should be copied
	size_t num_smpls = time_end - timestamp;
	if (num_smpls > len)
		num_smpls = len;

	// Starting index
	size_t read_start = (data_start + (timestamp - time_start)) % buf_len;

	// Read it
	if (read_start + num_smpls < buf_len) {
		size_t numBytes = len * type_sz;
		memcpy(buf, data + read_start, numBytes);
	} else {
		size_t first_cp = (buf_len - read_start) * type_sz;
		size_t second_cp = len * type_sz - first_cp;

		memcpy(buf, data + read_start, first_cp);
		memcpy((char*) buf + first_cp, data, second_cp);
	}

	data_start = (read_start + len) % buf_len;
	time_start = timestamp + len;

	if (time_start > time_end)
		return ERROR_READ;
	else
		return num_smpls;
}

ssize_t smpl_buf::write(void *buf, size_t len, TIMESTAMP timestamp)
{
	int type_sz = 2 * sizeof(short);

	// Check for valid write
	if ((len == 0) || (len >= buf_len))
		return ERROR_WRITE;
	if ((timestamp + len) <= time_end)
		return ERROR_TIMESTAMP;

	if (timestamp < time_end) {
		LOGC(DDEV, ERR) << "Overwriting old buffer data: timestamp="
				<< timestamp << " time_end=" << time_end;
		// Do not return error here, because it's a rounding error and is not fatal
	}
	if (timestamp > time_end && time_end != 0) {
		LOGC(DDEV, ERR) << "Skipping buffer data: timestamp="
				<< timestamp << " time_end=" << time_end;
		// Do not return error here, because it's a rounding error and is not fatal
	}

	// Starting index
	size_t write_start = (data_start + (timestamp - time_start)) % buf_len;

	// Write it
	if ((write_start + len) < buf_len) {
		size_t numBytes = len * type_sz;
		memcpy(data + write_start, buf, numBytes);
	} else {
		size_t first_cp = (buf_len - write_start) * type_sz;
		size_t second_cp = len * type_sz - first_cp;

		memcpy(data + write_start, buf, first_cp);
		memcpy(data, (char*) buf + first_cp, second_cp);
	}

	data_end = (write_start + len) % buf_len;
	time_end = timestamp + len;

	if (!data_start)
		data_start = write_start;

	if (((write_start + len) > buf_len) && (data_end > data_start))
		return ERROR_OVERFLOW;
	else if (time_end <= time_start)
		return ERROR_WRITE;
	else
		return len;
}

std::string smpl_buf::str_status(TIMESTAMP timestamp) const
{
	std::ostringstream ost("Sample buffer: ");

	ost << "timestamp = " << timestamp;
	ost << ", length = " << buf_len;
	ost << ", time_start = " << time_start;
	ost << ", time_end = " << time_end;
	ost << ", data_start = " << data_start;
	ost << ", data_end = " << data_end;

	return ost.str();
}

std::string smpl_buf::str_code(ssize_t code)
{
	switch (code) {
	case ERROR_TIMESTAMP:
		return "Sample buffer: Requested timestamp is not valid";
	case ERROR_READ:
		return "Sample buffer: Read error";
	case ERROR_WRITE:
		return "Sample buffer: Write error";
	case ERROR_OVERFLOW:
		return "Sample buffer: Overrun";
	default:
		return "Sample buffer: Unknown error";
	}
}