diff options
| -rw-r--r-- | Doc/lib/libstruct.tex | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/Doc/lib/libstruct.tex b/Doc/lib/libstruct.tex index 22595cb..08b930c 100644 --- a/Doc/lib/libstruct.tex +++ b/Doc/lib/libstruct.tex @@ -55,6 +55,7 @@ and Python values should be obvious given their types: \lineiii{f}{float}{float} \lineiii{d}{double}{float} \lineiii{s}{char[]}{string} + \lineiii{p}{char[]}{string} \end{tableiii} 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 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 characters; e.g. \code{'10s'} means a single 10-byte string, while \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 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. 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} \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 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 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. -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 little-endian. There is no way to indicate non-native byte order (i.e. force -byte-swapping); use the appropriate choice of \code{'<'} or -\code{'>'}. +byte-swapping); use the appropriate choice of \character{<} or +\character{>}. Examples (all using native byte order, size and alignment, on a big-endian machine): |