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105 lines
3.7 KiB
TeX
105 lines
3.7 KiB
TeX
\section{\module{binascii} ---
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Convert between binary and \ASCII{}}
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\declaremodule{builtin}{binascii}
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\modulesynopsis{Tools for converting between binary and various
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\ASCII{}-encoded binary representations.}
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The \module{binascii} module contains a number of methods to convert
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between binary and various \ASCII{}-encoded binary
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representations. Normally, you will not use these functions directly
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but use wrapper modules like \refmodule{uu}\refstmodindex{uu} or
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\refmodule{binhex}\refstmodindex{binhex} instead, this module solely
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exists because bit-manipuation of large amounts of data is slow in
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Python.
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The \module{binascii} module defines the following functions:
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\begin{funcdesc}{a2b_uu}{string}
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Convert a single line of uuencoded data back to binary and return the
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binary data. Lines normally contain 45 (binary) bytes, except for the
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last line. Line data may be followed by whitespace.
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\end{funcdesc}
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\begin{funcdesc}{b2a_uu}{data}
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Convert binary data to a line of \ASCII{} characters, the return value
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is the converted line, including a newline char. The length of
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\var{data} should be at most 45.
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\end{funcdesc}
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\begin{funcdesc}{a2b_base64}{string}
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Convert a block of base64 data back to binary and return the
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binary data. More than one line may be passed at a time.
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\end{funcdesc}
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\begin{funcdesc}{b2a_base64}{data}
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Convert binary data to a line of \ASCII{} characters in base64 coding.
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The return value is the converted line, including a newline char.
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The length of \var{data} should be at most 57 to adhere to the base64
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standard.
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\end{funcdesc}
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\begin{funcdesc}{a2b_hqx}{string}
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Convert binhex4 formatted \ASCII{} data to binary, without doing
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RLE-decompression. The string should contain a complete number of
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binary bytes, or (in case of the last portion of the binhex4 data)
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have the remaining bits zero.
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\end{funcdesc}
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\begin{funcdesc}{rledecode_hqx}{data}
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Perform RLE-decompression on the data, as per the binhex4
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standard. The algorithm uses \code{0x90} after a byte as a repeat
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indicator, followed by a count. A count of \code{0} specifies a byte
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value of \code{0x90}. The routine returns the decompressed data,
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unless data input data ends in an orphaned repeat indicator, in which
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case the \exception{Incomplete} exception is raised.
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\end{funcdesc}
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\begin{funcdesc}{rlecode_hqx}{data}
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Perform binhex4 style RLE-compression on \var{data} and return the
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result.
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\end{funcdesc}
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\begin{funcdesc}{b2a_hqx}{data}
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Perform hexbin4 binary-to-\ASCII{} translation and return the
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resulting string. The argument should already be RLE-coded, and have a
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length divisible by 3 (except possibly the last fragment).
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\end{funcdesc}
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\begin{funcdesc}{crc_hqx}{data, crc}
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Compute the binhex4 crc value of \var{data}, starting with an initial
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\var{crc} and returning the result.
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\end{funcdesc}
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\begin{funcdesc}{crc32}{data\optional{, crc}}
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Compute CRC-32, the 32-bit checksum of data, starting with an initial
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crc. This is consistent with the ZIP file checksum. Use as follows:
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\begin{verbatim}
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print binascii.crc32("hello world")
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# Or, in two pieces:
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crc = binascii.crc32("hello")
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crc = binascii.crc32(" world", crc)
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print crc
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\end{verbatim}
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\end{funcdesc}
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\begin{excdesc}{Error}
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Exception raised on errors. These are usually programming errors.
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\end{excdesc}
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\begin{excdesc}{Incomplete}
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Exception raised on incomplete data. These are usually not programming
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errors, but may be handled by reading a little more data and trying
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again.
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\end{excdesc}
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\begin{seealso}
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\seemodule{base64}{support for base64 encoding used in MIME email messages}
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\seemodule{binhex}{support for the binhex format used on the Macintosh}
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\seemodule{uu}{support for UU encoding used on \UNIX{}}
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\end{seealso}
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