sensor_hub/libsensors/InputEventReader.cpp

/*
 * Copyright (C) 2008-2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <errno.h>
#include <poll.h>
#include <stdint.h>
#include <string.h>
#include <sys/cdefs.h>
#include <sys/types.h>
#include <unistd.h>

#include <cutils/log.h>

#include "InputEventReader.h"

/*****************************************************************************/

struct cw_event;

InputEventCircularReader::InputEventCircularReader(size_t numEvents)
    : mBuffer(new cw_event[numEvents * 2])
    , mBufferEnd(mBuffer + numEvents)
    , mHead(mBuffer)
    , mCurr(mBuffer)
    , mFreeSpace(numEvents)
{
}

InputEventCircularReader::~InputEventCircularReader()
{
    delete [] mBuffer;
}

ssize_t InputEventCircularReader::fill(int fd)
{
    size_t numEventsRead = 0;
    if (mFreeSpace) {
        const ssize_t nread = read(fd, mHead, mFreeSpace * sizeof(cw_event));
        if (nread<0 || nread % sizeof(cw_event)) {
            // we got a partial event!!
            return nread<0 ? -errno : -EINVAL;
        }

        numEventsRead = nread / sizeof(cw_event);
        if (numEventsRead) {
            mHead += numEventsRead;
            mFreeSpace -= numEventsRead;
            if (mHead > mBufferEnd) {
                size_t s = mHead - mBufferEnd;
                memcpy(mBuffer, mBufferEnd, s * sizeof(cw_event));
                mHead = mBuffer + s;
            }
        }
    }

    return numEventsRead;
}

ssize_t InputEventCircularReader::readEvent(cw_event const** events)
{
    *events = mCurr;
    ssize_t available = (mBufferEnd - mBuffer) - mFreeSpace;
    return available ? 1 : 0;
}

void InputEventCircularReader::next()
{
    mCurr++;
    mFreeSpace++;
    if (mCurr >= mBufferEnd) {
        mCurr = mBuffer;
    }
}