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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include <stdint.h>
     18 #include <errno.h>
     19 #include <unistd.h>
     20 #include <poll.h>
     21 
     22 #include <sys/cdefs.h>
     23 #include <sys/types.h>
     24 
     25 #include <linux/input.h>
     26 
     27 #include <cutils/log.h>
     28 
     29 #include "InputEventReader.h"
     30 
     31 /*****************************************************************************/
     32 
     33 template <typename T>
     34 static inline T min(T a, T b) {
     35     return a<b ? a : b;
     36 }
     37 
     38 struct iio_event_data;
     39 
     40 InputEventCircularReader::InputEventCircularReader(size_t numEvents)
     41     : mBuffer(new iio_event_data[numEvents]),
     42       mBufferEnd(mBuffer + numEvents),
     43       mHead(mBuffer),
     44       mCurr(mBuffer),
     45       mMaxEvents(numEvents),
     46       mFreeEvents(numEvents)
     47 {
     48 }
     49 
     50 InputEventCircularReader::~InputEventCircularReader()
     51 {
     52     delete [] mBuffer;
     53 }
     54 
     55 ssize_t InputEventCircularReader::fill(int fd)
     56 {
     57     size_t numEventsRead = 0;
     58     if (mFreeEvents) {
     59         struct iovec iov[2];
     60 
     61         const size_t numFirst = min(mFreeEvents, (size_t)(mBufferEnd - mHead));
     62         const ssize_t numSecond = mFreeEvents - numFirst;
     63 
     64         int iovcnt = 1;
     65         iov[0].iov_base = mHead;
     66         iov[0].iov_len = numFirst * sizeof(iio_event_data);
     67 
     68         if (numSecond > 0) {
     69             iovcnt++;
     70             iov[1].iov_base = mBuffer;
     71             iov[1].iov_len = numSecond * sizeof(iio_event_data);
     72         }
     73 
     74         const ssize_t nread = readv(fd, iov, iovcnt);
     75         if (nread < 0 || nread % sizeof(iio_event_data)) {
     76             // we got a partial event!!
     77             return nread < 0 ? -errno : -EINVAL;
     78         }
     79 
     80         numEventsRead = nread / sizeof(iio_event_data);
     81         if (numEventsRead) {
     82             mHead += numEventsRead;
     83             mFreeEvents -= numEventsRead;
     84             if (mHead >= mBufferEnd)
     85                 mHead -= mMaxEvents;
     86         }
     87     }
     88 
     89     return numEventsRead;
     90 }
     91 
     92 bool InputEventCircularReader::readEvent(int fd, iio_event_data const** events)
     93 {
     94     if (mFreeEvents >= mMaxEvents) {
     95         ssize_t eventCount = fill(fd);
     96         if (eventCount <= 0)
     97             return false;
     98     }
     99     *events = mCurr;
    100     return true;
    101 }
    102 
    103 void InputEventCircularReader::next()
    104 {
    105     mCurr++;
    106     if (mCurr >= mBufferEnd) {
    107         mCurr = mBuffer;
    108     }
    109     if (mFreeEvents < mMaxEvents) {
    110        mFreeEvents++;
    111     }
    112 }
    113