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author | Bob Ippolito <bob@redivi.com> | 2006-05-23 19:12:41 (GMT) |
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committer | Bob Ippolito <bob@redivi.com> | 2006-05-23 19:12:41 (GMT) |
commit | 232f3c91f90655b10f3a6ec6d5b00eab37850de9 (patch) | |
tree | 032f4c6292f6bf46a59ed6c4e3cb686925717090 /Lib | |
parent | 7ccc95a315315568dd0660b5fb915f9e2e38f9da (diff) | |
download | cpython-232f3c91f90655b10f3a6ec6d5b00eab37850de9.zip cpython-232f3c91f90655b10f3a6ec6d5b00eab37850de9.tar.gz cpython-232f3c91f90655b10f3a6ec6d5b00eab37850de9.tar.bz2 |
patch #1493701: performance enhancements for struct module
Diffstat (limited to 'Lib')
-rw-r--r-- | Lib/struct.py | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/Lib/struct.py b/Lib/struct.py new file mode 100644 index 0000000..aa7af71 --- /dev/null +++ b/Lib/struct.py @@ -0,0 +1,76 @@ +""" +Functions to convert between Python values and C structs. +Python strings are used to hold the data representing the C struct +and 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 long +Whitespace 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 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) + |