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(python2.1-lib.info)binascii

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Convert between binary and ASCII
================================

Tools for converting between binary and various ASCII-encoded binary
representations.

The `binascii' module contains a number of methods to convert between
binary and various ASCII-encoded binary representations. Normally, you
will not use these functions directly but use wrapper modules like `uu'
or `binhex'  instead, this module solely exists because
bit-manipulation of large amounts of data is slow in Python.

The `binascii' module defines the following functions:

`a2b_uu(string)'
     Convert a single line of uuencoded data back to binary and return
     the binary data. Lines normally contain 45 (binary) bytes, except
     for the last line. Line data may be followed by whitespace.

`b2a_uu(data)'
     Convert binary data to a line of ASCII characters, the return value
     is the converted line, including a newline char. The length of
     DATA should be at most 45.

`a2b_base64(string)'
     Convert a block of base64 data back to binary and return the
     binary data. More than one line may be passed at a time.

`b2a_base64(data)'
     Convert binary data to a line of ASCII characters in base64 coding.
     The return value is the converted line, including a newline char.
     The length of DATA should be at most 57 to adhere to the base64
     standard.

`a2b_hqx(string)'
     Convert binhex4 formatted ASCII data to binary, without doing
     RLE-decompression. The string should contain a complete number of
     binary bytes, or (in case of the last portion of the binhex4 data)
     have the remaining bits zero.

`rledecode_hqx(data)'
     Perform RLE-decompression on the data, as per the binhex4
     standard. The algorithm uses `0x90' after a byte as a repeat
     indicator, followed by a count. A count of `0' specifies a byte
     value of `0x90'. The routine returns the decompressed data, unless
     data input data ends in an orphaned repeat indicator, in which
     case the `Incomplete' exception is raised.

`rlecode_hqx(data)'
     Perform binhex4 style RLE-compression on DATA and return the
     result.

`b2a_hqx(data)'
     Perform hexbin4 binary-to-ASCII translation and return the
     resulting string. The argument should already be RLE-coded, and
     have a length divisible by 3 (except possibly the last fragment).

`crc_hqx(data, crc)'
     Compute the binhex4 crc value of DATA, starting with an initial
     CRC and returning the result.

`crc32(data[, crc])'
     Compute CRC-32, the 32-bit checksum of data, starting with an
     initial crc.  This is consistent with the ZIP file checksum.  Use
     as follows:
              print binascii.crc32("hello world")
              # Or, in two pieces:
              crc = binascii.crc32("hello")
              crc = binascii.crc32(" world", crc)
              print crc

`b2a_hex(data)'

`hexlify data'
     Return the hexadecimal representation of the binary DATA.  Every
     byte of DATA is converted into the corresponding 2-digit hex
     representation.  The resulting string is therefore twice as long as
     the length of DATA.

`a2b_hex(hexstr)'

`unhexlify hexstr'
     Return the binary data represented by the hexadecimal string
     HEXSTR.  This function is the inverse of `b2a_hex()'.  HEXSTR must
     contain an even number of hexadecimal digits (which can be upper
     or lower case), otherwise a `TypeError' is raised.

`Error'
     Exception raised on errors. These are usually programming errors.

`Incomplete'
     Exception raised on incomplete data. These are usually not
     programming errors, but may be handled by reading a little more
     data and trying again.

See also:
     Note: base64 Support for base64 encoding used in MIME email
     messages.

     Note: binhex Support for the binhex format used on the Macintosh.

     Note: uu Support for UU encoding used on UNIX.