[potluck dish] the module (potluck struct)

[Matt Wette]

If you have used the Python struct module then this will look

familiar.  Otherwise, check out

https://docs.python.org/2/library/struct.html

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.

struct.scm
Description: Binary data

struct.test
Description: Binary data

struct.texi
Description: Binary data