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Document the 'p' format character.

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Clean up some of the markup.
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Fred Drake 1998-07-23 21:18:25 +00:00
parent c457ca7ede
commit cf0fb8bfee
1 changed files with 16 additions and 7 deletions
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Doc/lib/libstruct.tex
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@ -55,6 +55,7 @@ and Python values should be obvious given their types:
\lineiii{f}{float}{float} \lineiii{f}{float}{float}
\lineiii{d}{double}{float} \lineiii{d}{double}{float}
\lineiii{s}{char[]}{string} \lineiii{s}{char[]}{string}
\lineiii{p}{char[]}{string}
\end{tableiii} \end{tableiii}
A format character may be preceded by an integral repeat count; e.g.\ A format character may be preceded by an integral repeat count; e.g.\
@ -63,7 +64,7 @@ the format string \code{'4h'} means exactly the same as \code{'hhhh'}.
Whitespace characters between formats are ignored; a count and its Whitespace characters between formats are ignored; a count and its
format must not contain whitespace though. format must not contain whitespace though.
For the \code{'s'} format character, the count is interpreted as the For the \character{s} format character, the count is interpreted as the
size of the string, not a repeat count like for the other format size of the string, not a repeat count like for the other format
characters; e.g. \code{'10s'} means a single 10-byte string, while characters; e.g. \code{'10s'} means a single 10-byte string, while
\code{'10c'} means 10 characters. For packing, the string is \code{'10c'} means 10 characters. For packing, the string is
@ -72,7 +73,15 @@ For unpacking, the resulting string always has exactly the specified
number of bytes. As a special case, \code{'0s'} means a single, empty number of bytes. As a special case, \code{'0s'} means a single, empty
string (while \code{'0c'} means 0 characters). string (while \code{'0c'} means 0 characters).
For the \code{'I'} and \code{'L'} format characters, the return The \character{p} format character can be used to encode a Pascal
string. The first byte is the length of the stored string, with the
bytes of the string following. If count is given, it is used as the
total number of bytes used, including the length byte. If the string
passed in to \function{pack()} is too long, the stored representation
is truncated. If the string is too short, padding is used to ensure
that exactly enough bytes are used to satisfy the count.
For the \character{I} and \character{L} format characters, the return
value is a Python long integer. value is a Python long integer.
By default, C numbers are represented in the machine's native format By default, C numbers are represented in the machine's native format
@ -91,7 +100,7 @@ according to the following table:
\lineiii{!}{network (= big-endian)}{standard} \lineiii{!}{network (= big-endian)}{standard}
\end{tableiii} \end{tableiii}
If the first character is not one of these, \code{'@'} is assumed. If the first character is not one of these, \character{@} is assumed.
Native byte order is big-endian or little-endian, depending on the Native byte order is big-endian or little-endian, depending on the
host system (e.g. Motorola and Sun are big-endian; Intel and DEC are host system (e.g. Motorola and Sun are big-endian; Intel and DEC are
@ -105,16 +114,16 @@ for any type (so you have to use pad bytes); short is 2 bytes; int and
long are 4 bytes. Float and double are 32-bit and 64-bit IEEE floating long are 4 bytes. Float and double are 32-bit and 64-bit IEEE floating
point numbers, respectively. point numbers, respectively.
Note the difference between \code{'@'} and \code{'='}: both use native Note the difference between \character{@} and \character{=}: both use native
byte order, but the size and alignment of the latter is standardized. byte order, but the size and alignment of the latter is standardized.
The form \code{'!'} is available for those poor souls who claim they The form \character{!} is available for those poor souls who claim they
can't remember whether network byte order is big-endian or can't remember whether network byte order is big-endian or
little-endian. little-endian.
There is no way to indicate non-native byte order (i.e. force There is no way to indicate non-native byte order (i.e. force
byte-swapping); use the appropriate choice of \code{'<'} or byte-swapping); use the appropriate choice of \character{<} or
\code{'>'}. \character{>}.
Examples (all using native byte order, size and alignment, on a Examples (all using native byte order, size and alignment, on a
big-endian machine): big-endian machine):