Package cds.savot.binary

Class Base64InputStream

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable
    public final class Base64InputStream
extends java.io.FilterInputStream

    A Base64InputStream decodes Base64-encoded bytes read from the given InputStream.

    The Base 64 decoding

    • The length of Base64-encoded data MUST be a multiple of 4 and MAY end by 1 or 2 padding characters (=).
    • Encoded data MAY be splitted in lines of 76 characters.
    • Valid Base64 characters are: A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,0,1,2,3,4,5,6,7,8,9,+,/.
    • Invalid Base64 characters are ignored but a warning message is displayed in the standard error output.

    Buffer

    This stream is buffered. That means that several bytes have already been read and decoded from the inner input stream. By default the buffer size is: 8192.

    Warning ! To fill the buffer of a Base64InputStream with N bytes, (N/3)*4 bytes must be fetched from the inner input stream. Indeed, with the Base64 encoding, the number of encoded bytes is always greater than the number of the corresponding decoded bytes: 3 bytes will be encoded by 4 characters encoded on 6 bits (which allows an alphabet of 2^6=64 characters, hence base64). Consequently: for a buffer of 8192 bytes, 10924 bytes are needed.

    However the number of bytes stored in the buffer may be less than the size given at the initialization. That is to say: the buffer can contain AT MOST 8192 decoded bytes. Indeed some bytes coming from the inner input stream may correspond to invalid Base64 characters. In this case, they are ignored and so they are not stored in the buffer.

    Warning & Errors

    A Base64InputStream writes a warning in the standard error output when:

    • invalid Base64 characters are encountered before the end of the encoded data

    A Base64InputStream throws an exception when:

    • the inner stream ends whereas a group of 4 valid characters/bytes is not complete
    • valid Base64 characters are encountered after padding characters
    • more than 2 padding characters are encountered

    Mark & Reset

    The mark(int) and reset() methods are not supported in a Base64InputStream.

    Since:
    09/2011
    Author:
    Gregory Mantelet
    See Also:
    Base64

    • Field Summary

      • Fields inherited from class java.io.FilterInputStream

        in

    • Constructor Summary

      Constructors 
      Constructor Description
      Base64InputStream​(java.io.InputStream encodedStream)  
      Base64InputStream​(java.io.InputStream encodedStream, int bufferSize)  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int available()  
      void close()  
      void mark​(int readlimit)  
      boolean markSupported()  
      int read()  
      int read​(byte[] b)  
      int read​(byte[] b, int off, int len)  
      void reset()  
      long skip​(long n)  

      • Methods inherited from class java.io.InputStream

        nullInputStream, readAllBytes, readNBytes, readNBytes, transferTo

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • Base64InputStream

        public Base64InputStream​(java.io.InputStream encodedStream)

      • Base64InputStream

        public Base64InputStream​(java.io.InputStream encodedStream,
                         int bufferSize)
        Parameters:
        encodedStream -
        bufferSize -

    • Method Detail

      • available

        public int available()
              throws java.io.IOException
        Overrides:
        available in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • read

        public int read()
         throws java.io.IOException
        Overrides:
        read in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • read

        public int read​(byte[] b)
         throws java.io.IOException
        Overrides:
        read in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • read

        public int read​(byte[] b,
                int off,
                int len)
         throws java.io.IOException
        Overrides:
        read in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • skip

        public long skip​(long n)
          throws java.io.IOException
        Overrides:
        skip in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • close

        public void close()
           throws java.io.IOException
        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class java.io.FilterInputStream
        Throws:
        java.io.IOException

      • markSupported

        public boolean markSupported()
        Overrides:
        markSupported in class java.io.FilterInputStream

      • mark

        public void mark​(int readlimit)
        Overrides:
        mark in class java.io.FilterInputStream

      • reset

        public void reset()
           throws java.io.IOException
        Overrides:
        reset in class java.io.FilterInputStream
        Throws:
        java.io.IOException