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authorGeorg Brandl <georg@python.org>2007-08-15 14:28:01 (GMT)
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+
+:mod:`binascii` --- Convert between binary and ASCII
+====================================================
+
+.. module:: binascii
+ :synopsis: Tools for converting between binary and various ASCII-encoded binary
+ representations.
+
+
+.. index::
+ module: uu
+ module: base64
+ module: binhex
+
+The :mod:`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 :mod:`uu`,
+:mod:`base64`, or :mod:`binhex` instead. The :mod:`binascii` module contains
+low-level functions written in C for greater speed that are used by the
+higher-level modules.
+
+The :mod:`binascii` module defines the following functions:
+
+
+.. function:: 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.
+
+
+.. function:: 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.
+
+
+.. function:: 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.
+
+
+.. function:: 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.
+
+
+.. function:: a2b_qp(string[, header])
+
+ Convert a block of quoted-printable data back to binary and return the binary
+ data. More than one line may be passed at a time. If the optional argument
+ *header* is present and true, underscores will be decoded as spaces.
+
+
+.. function:: b2a_qp(data[, quotetabs, istext, header])
+
+ Convert binary data to a line(s) of ASCII characters in quoted-printable
+ encoding. The return value is the converted line(s). If the optional argument
+ *quotetabs* is present and true, all tabs and spaces will be encoded. If the
+ optional argument *istext* is present and true, newlines are not encoded but
+ trailing whitespace will be encoded. If the optional argument *header* is
+ present and true, spaces will be encoded as underscores per RFC1522. If the
+ optional argument *header* is present and false, newline characters will be
+ encoded as well; otherwise linefeed conversion might corrupt the binary data
+ stream.
+
+
+.. function:: 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.
+
+
+.. function:: 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 :exc:`Incomplete` exception is raised.
+
+
+.. function:: rlecode_hqx(data)
+
+ Perform binhex4 style RLE-compression on *data* and return the result.
+
+
+.. function:: 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).
+
+
+.. function:: crc_hqx(data, crc)
+
+ Compute the binhex4 crc value of *data*, starting with an initial *crc* and
+ returning the result.
+
+
+.. function:: 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. Since the algorithm is designed for
+ use as a checksum algorithm, it is not suitable for use as a general hash
+ algorithm. Use as follows::
+
+ print binascii.crc32("hello world")
+ # Or, in two pieces:
+ crc = binascii.crc32("hello")
+ crc = binascii.crc32(" world", crc)
+ print crc
+
+
+.. function:: 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*.
+
+
+.. function:: a2b_hex(hexstr)
+ unhexlify(hexstr)
+
+ Return the binary data represented by the hexadecimal string *hexstr*. This
+ function is the inverse of :func:`b2a_hex`. *hexstr* must contain an even number
+ of hexadecimal digits (which can be upper or lower case), otherwise a
+ :exc:`TypeError` is raised.
+
+
+.. exception:: Error
+
+ Exception raised on errors. These are usually programming errors.
+
+
+.. exception:: 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.
+
+
+.. seealso::
+
+ Module :mod:`base64`
+ Support for base64 encoding used in MIME email messages.
+
+ Module :mod:`binhex`
+ Support for the binhex format used on the Macintosh.
+
+ Module :mod:`uu`
+ Support for UU encoding used on Unix.
+
+ Module :mod:`quopri`
+ Support for quoted-printable encoding used in MIME email messages.
+