If you have used the Python struct module then this will look
familiar. Otherwise, check out
Attached are three files: * struct.scm: the source code * struct.texi:
documentation * struct.test: test code
Struct Module =============
The '(potluck struct)' module provides procedures for packing and
unpacking scheme data to and from bytevectors based on a format
string.
(use-modules (potluck struct))
;; pack two unsigned shorts and a double float in big endian
order (define data (pack ">2Hd" 3 22 34.0)) (write data)
(newline) ==> #vu8(0 3 0 22 64 65 0 0 0 0 0 0)
;; verify using unpack (write (unpack ">2Hd" data)) (newline) ==>
(3 22 34.0)
-- Scheme Procedure: pack format vals ... Return a bytevector that
contains encoded data from VALS, based on the string FORMAT.
-- Scheme Procedure: unpack format bvec Return a list of scheme
objects decoded from the bytevector BVEC, based on the string
FORMAT.
-- Scheme Procedure: packed-size format Return the number of bytes
represented by the string FORMAT.
The _format_ string used for PACK and UNPACK is constructed as a
sequence of digits, representing a repeat count, and codes,
representing the binary content.
The string may optionally begin with a special character that
represents the endianness: = native endianness < little-endian >
big-endian ! network order -- i.e., big-endian
Type codes used in the format string are interpreted as follows: x
blank byte c 8-bit character ? boolean b signed 8-bit integer B
unsigned 8-bit integer h signed 16-bit integer H unsigned 16-bit
integer i signed 32-bit integer I unsigned 32-bit integer l signed
32-bit integer L unsigned 32-bit integer q signed 64-bit integer Q
unsigned 64-bit integer f 32-bit IEEE floating point d 64-bit IEEE
floating point s string
The following issues remain to be addressed: string padding 'pack'
assumes that the string length in the format is the same as in the
passed string. Non-conformance is not trapped as an error.