"""Functions to convert between Python values and C structs.Python strings are used to hold the data representing the C structand also as format strings to describe the layout of data in the C struct. The optional first format char indicates byte order, size and alignment: @: native order, size & alignment (default) =: native order, std. size & alignment <: little-endian, std. size & alignment >: big-endian, std. size & alignment !: same as > The remaining chars indicate types of args and must match exactly;these can be preceded by a decimal repeat count: x: pad byte (no data); c:char; b:signed byte; B:unsigned byte; h:short; H:unsigned short; i:int; I:unsigned int; l:long; L:unsigned long; f:float; d:double.Special cases (preceding decimal count indicates length): s:string (array of char); p: pascal string (with count byte).Special case (only available in native format): P:an integer type that is wide enough to hold a pointer.Special case (not in native mode unless 'long long' in platform C): q:long long; Q:unsigned long longWhitespace between formats is ignored. The variable struct.error is an exception raised on errors."""__version__ = '0.1' from _struct import Struct, error _MAXCACHE = 100_cache = {} def _compile(fmt):    # Internal: compile struct pattern    if len(_cache) >= _MAXCACHE:        _cache.clear()    s = Struct(fmt)    _cache[fmt] = s    return s def calcsize(fmt):    """    Return size of C struct described by format string fmt.    See struct.__doc__ for more on format strings.    """    try:        o = _cache[fmt]    except KeyError:        o = _compile(fmt)    return o.size def pack(fmt, *args):    """    Return string containing values v1, v2, ... packed according to fmt.    See struct.__doc__ for more on format strings.    """    try:        o = _cache[fmt]    except KeyError:        o = _compile(fmt)    return o.pack(*args) def pack_into(fmt, buf, offset, *args):    """    Pack the values v1, v2, ... according to fmt, write    the packed bytes into the writable buffer buf starting at offset.    See struct.__doc__ for more on format strings.    """    try:        o = _cache[fmt]    except KeyError:        o = _compile(fmt)    return o.pack_into(buf, offset, *args) def unpack(fmt, s):    """    Unpack the string, containing packed C structure data, according    to fmt.  Requires len(string)==calcsize(fmt).    See struct.__doc__ for more on format strings.    """    try:        o = _cache[fmt]    except KeyError:        o = _compile(fmt)    return o.unpack(s) def unpack_from(fmt, buf, offset=0):    """    Unpack the buffer, containing packed C structure data, according to    fmt starting at offset. Requires len(buffer[offset:]) >= calcsize(fmt).    See struct.__doc__ for more on format strings.    """    try:        o = _cache[fmt]    except KeyError:        o = _compile(fmt)    return o.unpack_from(buf, offset)