SizeLimitedInputStream


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17  
18  package org.apache.james.smtpserver;
19  
20  import java.io.IOException  ;
21  import java.io.InputStream  ;
22  
23  /** 
24    * Wraps an underlying input stream, limiting the allowable size
25    * of incoming data. The size limit is configured in the conf file,
26    * and when the limit is reached, a MessageSizeException is thrown.
27    */
28  public class SizeLimitedInputStream extends InputStream   {
29      /**
30       * Maximum number of bytes to read.
31       */
32      private long maxmessagesize = 0;
33      /**
34       * Running total of bytes read from wrapped stream.
35       */
36      private long bytesread = 0;
37  
38      /**
39       * InputStream that will be wrapped.
40       */
41      private InputStream   in = null;
42  
43      /**
44       * Constructor for the stream. Wraps an underlying stream.
45       * @param in InputStream to use as basis for new Stream.
46       * @param maxmessagesize Message size limit, in Kilobytes
47       */
48      public SizeLimitedInputStream(InputStream   in, long maxmessagesize) {
49          this.in = in;
50          this.maxmessagesize = maxmessagesize;
51      }
52  
53      /**
54       * Overrides the read method of InputStream to call the read() method of the
55       * wrapped input stream.
56       * @throws IOException Throws a MessageSizeException, which is a sub-type of IOException
57       * @return Returns the number of bytes read.
58       */
59      public int read(byte[] b, int off, int len) throws IOException   {
60          int l = in.read(b, off, len);
61  
62          bytesread += l;
63  
64          if (maxmessagesize > 0 && bytesread > maxmessagesize) {
65              throw new MessageSizeException();
66          }
67  
68          return l;
69      }
70  
71      /**
72       * Overrides the read method of InputStream to call the read() method of the
73       * wrapped input stream.
74       * @throws IOException Throws a MessageSizeException, which is a sub-type of IOException.
75       * @return Returns the int character value of the byte read.
76       */
77      public int read() throws IOException   {
78          if (maxmessagesize > 0 && bytesread <= maxmessagesize) {
79              bytesread++;
80              return in.read();
81          } else {
82              throw new MessageSizeException();
83          }
84      }
85  }
86
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