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1480
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1 package goodjava.io;
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2 import java.io.InputStream;
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3 import java.io.FilterInputStream;
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4 import java.io.IOException;
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5
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6
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7 public final class LimitedInputStream extends FilterInputStream {
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8 private final long limit;
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9 private long pos = 0;
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10
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11 public LimitedInputStream(InputStream in, long limit) {
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12 super(in);
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13 this.limit = limit;
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14 }
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15
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16 public synchronized int read() throws IOException {
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17 if( pos >= limit )
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18 return -1;
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19 int n = super.read();
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20 if( n != -1 )
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21 pos++;
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22 return n;
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23 }
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24
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25 public synchronized int read(byte[] b, int off, int len) throws IOException {
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26 long avail = limit - pos;
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27 if( avail <= 0 )
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28 return -1;
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29 if( len > avail )
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30 len = (int)avail;
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31 int n = super.read(b,off,len);
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32 if( n > 0 )
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33 pos += n;
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34 return n;
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35 }
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36
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37 public synchronized long skip(long n) throws IOException {
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38 long avail = limit - pos;
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39 if( avail <= 0 )
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40 return 0;
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41 if( n > avail )
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42 n = (int)avail;
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43 n = super.skip(n);
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44 pos += n;
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45 return n;
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46 }
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47
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48 public synchronized int available() throws IOException {
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49 long avail = limit - pos;
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50 if( avail <= 0 )
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51 return 0;
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52 int n = super.available();
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53 if( n > avail )
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54 n = (int)avail;
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55 return n;
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56 }
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57
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58 }
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