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.\" Author: Archie Cobbs <archie@freebsd.org>
.\"
.\" $Id: structs_type_struct.3,v 1.1.1.1 2012/02/21 23:25:53 misho Exp $
.\"
.Dd April 22, 2002
.Dt STRUCTS_TYPE_STRUCT 3
.Os
.Sh NAME
.Nm structs_type_struct
.Nd structs types for C structures
.Sh LIBRARY
PDEL Library (libpdel, \-lpdel)
.Sh SYNOPSIS
.In sys/types.h
.In stddef.h
.In pdel/structs/structs.h
.In pdel/structs/type/struct.h
.Fn STRUCTS_STRUCT_TYPE struct_name field_list
.Fn STRUCTS_STRUCT_FIELD struct_name field_name field_type
.Fn STRUCTS_STRUCT_FIELD2 struct_name field_name display_name field_type
.Sh DESCRIPTION
The
.Fn STRUCTS_STRUCT_TYPE
macro defines a
.Xr structs 3
type (i.e., a
.Dv "struct structs_type" )
for describing the C structure
.Li struct
.Fa struct_name .
The
.Fa field_list
parameter must point to an array of
.Li "struct structs_field"
structures describing the fields:
.Pp
.Bd -literal -compact -offset 3n
/* This structure describes one field in a structure */
struct structs_field {
    const char                  *name;      /* field name */
    const struct structs_type   *type;      /* field type */
    u_int16_t                   size;       /* field size */
    u_int16_t                   offset;     /* field offset */
};
.Ed
.Pp
The fields need not be listed in the array in the same order as they
are declared in the C structure.
However, the array must be terminated with
.Dv STRUCTS_STRUCT_FIELD_END ,
which is defined as follows:
.Pp
.Dl #define STRUCTS_STRUCT_FIELD_END { NULL, NULL, 0, 0 }
.Pp
The
.Fn STRUCTS_STRUCT_FIELD
macro should be used to define an entry in the field array:
.Fa field_name
is the name of the field and
.Fa field_type
is a pointer to the
.Xr structs 3
type describing the field.
.Pp
To define a field and give it a different
.Xr structs 3
name than its name in the C structure, use
.Fn STRUCTS_STRUCT_FIELD2
with the desired
.Fa display_name
in double quotes.
.Sh SEE ALSO
.Xr libpdel 3 ,
.Xr structs 3 ,
.Xr structs_type 3 ,
.Xr structs_type_union 3
.Sh EXAMPLES
The program below prints out the contents (as an ASCII string)
of the field specified on the command line:
.Pp
.Bd -literal -compact -offset 3n
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdio.h>
#include <stdlib.h>
#include <err.h>

#include <pdel/structs/structs.h>
#include <pdel/structs/type/struct.h>
#include <pdel/structs/type/string.h>
#include <pdel/structs/type/ip4.h>
#include <pdel/util/typed_mem.h>

/* My structure */
struct foobar {
        char            *name;
        u_int16_t       index;
        struct in_addr  ipaddr;
};

/* Structs type describing a 'struct foobar' */
static const struct structs_field foobar_fields = {
        STRUCTS_STRUCT_FIELD(foobar, name, &structs_type_string),
        STRUCTS_STRUCT_FIELD(foobar, index, &structs_type_uint16),
        STRUCTS_STRUCT_FIELD(foobar, ipaddr, &structs_type_ip4),
        STRUCTS_STRUCT_FIELD_END
};
static const struct structs_type foobar_type =
        STRUCTS_STRUCT_TYPE(foobar, &foobar_fields);

int
main(int argc, char **argv)
{
	struct foobar f;
	const char *fieldname;
	char *fieldvalue;

	/* Initialize our structure with some contents */
	if (structs_init(&foobar_type, NULL, &f) == -1)
		err(1, "structs_init");
	f.index = 123;
	(void)inet_aton("12.34.56.78", &f.ipaddr);
	if (structs_set_string(&foobar_type, "name",
	    "this is a string", &f, NULL, 0) == -1)
		err(1, "structs_set_string");

	/* Get the requested field's name from the command line */
	if (argc != 2)
		err(1, "usage: getfield <fieldname>");
	fieldname = argv[1];

	/* Display the requested field's value */
	if ((fieldvalue = structs_get_string(&foobar_type,
	    fieldname, &f, TYPED_MEM_TEMP)) == NULL)
		err(1, "%s", fieldname);
	printf("The value of field \\"%s\\" is: %s\\n",
	    fieldname, fieldvalue);

	/* Done, clean up */
	FREE(TYPED_MEM_TEMP, fieldvalue);
	structs_free(&foobar_type, NULL, &f);
	return (0);
}
.Ed
.Sh HISTORY
The PDEL library was developed at Packet Design, LLC.
.Dv "http://www.packetdesign.com/"
.Sh AUTHORS
.An Archie Cobbs Aq archie@freebsd.org