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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 input_event;
     39 
     40 InputEventCircularReader::InputEventCircularReader(size_t numEvents)
     41     : mBuffer(new input_event[numEvents]),
     42       mBufferEnd(mBuffer + numEvents),
     43       mHead(mBuffer),
     44       mCurr(mBuffer),
     45       mEvents(numEvents),
     46       mFreeSpace(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 (mFreeSpace) {
     59         struct iovec iov[2];
     60 
     61         const size_t numFirst = min(mFreeSpace, (size_t)(mBufferEnd - mHead));
     62         const size_t numSecond = mFreeSpace - numFirst;
     63 
     64         int iovcnt = 1;
     65         iov[0].iov_base = mHead;
     66         iov[0].iov_len = numFirst * sizeof(input_event);
     67 
     68         if (numSecond > 0)
     69         {
     70             iovcnt++;
     71             iov[1].iov_base = mBuffer;
     72             iov[1].iov_len = numSecond * sizeof(input_event);
     73         }
     74 
     75         const ssize_t nread = readv(fd, iov, iovcnt);
     76         if (nread < 0 || nread % sizeof(input_event)) {
     77             // we got a partial event!!
     78             return nread < 0 ? -errno : -EINVAL;
     79         }
     80 
     81         numEventsRead = nread / sizeof(input_event);
     82         if (numEventsRead) {
     83             mHead += numEventsRead;
     84             mFreeSpace -= numEventsRead;
     85             if (mHead >= mBufferEnd)
     86                 mHead -= mBufferEnd - mBuffer;
     87         }
     88     }
     89 
     90     return numEventsRead;
     91 }
     92 
     93 bool InputEventCircularReader::readEvent(int fd, input_event const** events)
     94 {
     95     if (mFreeSpace >= mEvents) {
     96         ssize_t eventCount = fill(fd);
     97         if (eventCount <= 0)
     98             return false;
     99     }
    100     *events = mCurr;
    101     return true;
    102 }
    103 
    104 void InputEventCircularReader::next()
    105 {
    106     mCurr++;
    107     mFreeSpace++;
    108     if (mCurr >= mBufferEnd) {
    109         mCurr = mBuffer;
    110     }
    111 }
    112