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      1 /*
      2 Copyright (c) 2011 Stanislav Vitvitskiy
      3 
      4 Permission is hereby granted, free of charge, to any person obtaining a copy of this
      5 software and associated documentation files (the "Software"), to deal in the Software
      6 without restriction, including without limitation the rights to use, copy, modify,
      7 merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
      8 permit persons to whom the Software is furnished to do so, subject to the following
      9 conditions:
     10 
     11 The above copyright notice and this permission notice shall be included in all copies or
     12 substantial portions of the Software.
     13 
     14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
     15 INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
     16 PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
     17 FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
     18 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
     19 OR OTHER DEALINGS IN THE SOFTWARE.
     20 */
     21 package com.googlecode.mp4parser.h264.read;
     22 
     23 import com.googlecode.mp4parser.h264.CharCache;
     24 
     25 import java.io.IOException;
     26 import java.io.InputStream;
     27 
     28 /**
     29  * A dummy implementation of H264 RBSP reading
     30  *
     31  * @author Stanislav Vitvitskiy
     32  */
     33 public class BitstreamReader {
     34     private InputStream is;
     35     private int curByte;
     36     private int nextByte;
     37     int nBit;
     38     protected static int bitsRead;
     39 
     40     protected CharCache debugBits = new CharCache(50);
     41 
     42     public BitstreamReader(InputStream is) throws IOException {
     43         this.is = is;
     44         curByte = is.read();
     45         nextByte = is.read();
     46     }
     47 
     48     /*
     49       * (non-Javadoc)
     50       *
     51       * @see ua.org.jplayer.javcodec.h264.RBSPInputStream#read1Bit()
     52       */
     53     public int read1Bit() throws IOException {
     54         if (nBit == 8) {
     55             advance();
     56             if (curByte == -1) {
     57                 return -1;
     58             }
     59         }
     60         int res = (curByte >> (7 - nBit)) & 1;
     61         nBit++;
     62 
     63         debugBits.append(res == 0 ? '0' : '1');
     64         ++bitsRead;
     65 
     66         return res;
     67     }
     68 
     69     /*
     70       * (non-Javadoc)
     71       *
     72       * @see ua.org.jplayer.javcodec.h264.RBSPInputStream#readNBit(int)
     73       */
     74     public long readNBit(int n) throws IOException {
     75         if (n > 64)
     76             throw new IllegalArgumentException("Can not readByte more then 64 bit");
     77 
     78         long val = 0;
     79 
     80         for (int i = 0; i < n; i++) {
     81             val <<= 1;
     82             val |= read1Bit();
     83         }
     84 
     85         return val;
     86     }
     87 
     88     private void advance() throws IOException {
     89         curByte = nextByte;
     90         nextByte = is.read();
     91         nBit = 0;
     92     }
     93 
     94     /*
     95       * (non-Javadoc)
     96       *
     97       * @see ua.org.jplayer.javcodec.h264.RBSPInputStream#readByte()
     98       */
     99     public int readByte() throws IOException {
    100         if (nBit > 0) {
    101             advance();
    102         }
    103 
    104         int res = curByte;
    105 
    106         advance();
    107 
    108         return res;
    109     }
    110 
    111     /*
    112       * (non-Javadoc)
    113       *
    114       * @see ua.org.jplayer.javcodec.h264.RBSPInputStream#moreRBSPData()
    115       */
    116     public boolean moreRBSPData() throws IOException {
    117         if (nBit == 8) {
    118             advance();
    119         }
    120         int tail = 1 << (8 - nBit - 1);
    121         int mask = ((tail << 1) - 1);
    122         boolean hasTail = (curByte & mask) == tail;
    123 
    124         return !(curByte == -1 || (nextByte == -1 && hasTail));
    125     }
    126 
    127     public long getBitPosition() {
    128         return (bitsRead * 8 + (nBit % 8));
    129     }
    130 
    131     /*
    132       * (non-Javadoc)
    133       *
    134       * @see ua.org.jplayer.javcodec.h264.RBSPInputStream#readRemainingByte()
    135       */
    136     public long readRemainingByte() throws IOException {
    137         return readNBit(8 - nBit);
    138     }
    139 
    140     /*
    141       * (non-Javadoc)
    142       *
    143       * @see ua.org.jplayer.javcodec.h264.RBSPInputStream#next_bits(int)
    144       */
    145     public int peakNextBits(int n) throws IOException {
    146         if (n > 8)
    147             throw new IllegalArgumentException("N should be less then 8");
    148         if (nBit == 8) {
    149             advance();
    150             if (curByte == -1) {
    151                 return -1;
    152             }
    153         }
    154         int[] bits = new int[16 - nBit];
    155 
    156         int cnt = 0;
    157         for (int i = nBit; i < 8; i++) {
    158             bits[cnt++] = (curByte >> (7 - i)) & 0x1;
    159         }
    160 
    161         for (int i = 0; i < 8; i++) {
    162             bits[cnt++] = (nextByte >> (7 - i)) & 0x1;
    163         }
    164 
    165         int result = 0;
    166         for (int i = 0; i < n; i++) {
    167             result <<= 1;
    168             result |= bits[i];
    169         }
    170 
    171         return result;
    172     }
    173 
    174     /*
    175       * (non-Javadoc)
    176       *
    177       * @see ua.org.jplayer.javcodec.h264.RBSPInputStream#byte_aligned()
    178       */
    179     public boolean isByteAligned() {
    180         return (nBit % 8) == 0;
    181     }
    182 
    183     /*
    184       * (non-Javadoc)
    185       *
    186       * @see ua.org.jplayer.javcodec.h264.RBSPInputStream#close()
    187       */
    188     public void close() throws IOException {
    189     }
    190 
    191     public int getCurBit() {
    192         return nBit;
    193     }
    194 }