This library provides an interface for packing and unpacking (writing
and reading) binary data with template. The functionality is inspired by
Industria's
(weinholt struct pack) library.
template must be a string.
Construct a bytevector with given args according to the given template. Template characters are described below.
template must be a string.
bv must be a bytevector.
offset must a non-negative exact integer.
Converts given args and put it into bv starting from offset. The conversion is done according to the template string.
The template characters are extensible so following description can only cover predefined characters.
x: padding; c: s8; C: u8; s: s16; S: u16; l: s32; L: u32; q: s64; Q: u64; f: ieee-single; d: ieee-double; ! or >: big-endian; <: little-endian; =: native-endian; u: disable natural alignment; a: enable natural alignment. Whitespace is ignored.
(pack "!c" 128)
(pack "s" 100)
(pack "!s" 100)
(pack "!d" 3.14)Fields are by default aligned to their natural alignment and NUL bytes are inserted as necessary to have a field's index to be aligned to its size.
(pack "!xd" 3.14)
(pack "!uxd" 3.14)Digits in front of the syntax characters means repetition. And #\* means
indefinite length repetition.
(pack "3c" 1 2 3)
(pack "*c" 1 2 3 4)When the macro detects the given template is string, then it tries to expand as much as possible. So it might raises the different condition even if the template strings are the same.
(pack "3c" 1 2 3 4)
(pack (car '("3c")) 1 2 3 4)template must be a string.
Unpack the given bytevector according to the given template and returns
the values. The template syntax are the same as pack!.
If the second form is used, then unpacking is done from the given offset.
(unpack "!SS" #vu8(0 1 0 2))
(unpack "!SS" #vu8(0 1 0 2 0 3) 1)
(unpack "!uSS" #vu8(0 1 0 2 0 3) 1)template must be a string.
Utility unpacking macro for binary port.
template must be a string.
Calculate the size of the result bytevector. If the second form is used, then
macro can calculate even if the template contains indefinite length syntax
#\*, otherwise #f is returned.
(format-size "!xd")
(format-size "!uxd")
(format-size "*c")
(format-size "*c" 1 2 3 4)char must character.
pack and unpack are syntactic keywords.
Defines packing extension to given char. This macro can not overwrite the predefined characters. ** can be followings;
s8, u8, s16, u16, s32, u32,
s64, u64, f32, and f64.
;; defining char to u8 converter
(define-u8-packer (#\A v)
(pack (char->integer v))
(unpack (integer->char v)))
(pack "AA" #\a #\b) ;; => #vu8(97 98)
(unpack "AA" #vu8(97 98)) ;; => #\a #\b