NetBSD/lib/libbluetooth/sdp_data.3

.\" $NetBSD: sdp_data.3,v 1.2 2009/05/20 17:22:56 plunky Exp $
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.\" Copyright (c) 2009 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Iain Hibbert.
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.Dd May 7, 2009
.Dt SDP_DATA 3
.Os
.Sh NAME
.Nm sdp_match_uuid16
.Nm sdp_get_data
.Nm sdp_get_attr
.Nm sdp_get_uuid
.Nm sdp_get_bool
.Nm sdp_get_seq
.Nm sdp_get_alt
.Nm sdp_get_uint
.Nm sdp_get_int
.Nm sdp_get_str
.Nm sdp_get_url
.Nm sdp_put_data
.Nm sdp_put_attr
.Nm sdp_put_uuid
.Nm sdp_put_uuid16
.Nm sdp_put_uuid32
.Nm sdp_put_uuid128
.Nm sdp_put_bool
.Nm sdp_put_uint
.Nm sdp_put_uint8
.Nm sdp_put_uint16
.Nm sdp_put_uint32
.Nm sdp_put_uint64
.Nm sdp_put_int
.Nm sdp_put_int8
.Nm sdp_put_int16
.Nm sdp_put_int32
.Nm sdp_put_int64
.Nm sdp_put_seq
.Nm sdp_put_alt
.Nm sdp_put_str
.Nm sdp_put_url
.Nm sdp_set_bool
.Nm sdp_set_uint
.Nm sdp_set_int
.Nm sdp_set_seq
.Nm sdp_set_alt
.Nm sdp_data_size
.Nm sdp_data_type
.Nm sdp_data_valid
.Nm sdp_data_print
.Nd Service Discovery Protocol data manipulation routines
.Sh LIBRARY
.Lb libbluetooth
.Sh SYNOPSIS
.In sdp.h
.Vt extern const uuid_t BLUETOOTH_BASE_UUID ;
.Ft bool
.Fn sdp_match_uuid16 "sdp_data_t *data" "uint16_t uuid"
.Ft bool
.Fn sdp_get_data "sdp_data_t *data" "sdp_data_t *value"
.Ft bool
.Fn sdp_get_attr "sdp_data_t *data" "uint16_t *attr" "sdp_data_t *value"
.Ft bool
.Fn sdp_get_uuid "sdp_data_t *data" "uuid_t *uuid"
.Ft bool
.Fn sdp_get_bool "sdp_data_t *data" "bool *value"
.Ft bool
.Fn sdp_get_seq "sdp_data_t *data" "sdp_data_t *seq"
.Ft bool
.Fn sdp_get_alt "sdp_data_t *data" "sdp_data_t *alt"
.Ft bool
.Fn sdp_get_uint "sdp_data_t *data" "uintmax_t *value"
.Ft bool
.Fn sdp_get_int "sdp_data_t *data" "intmax_t *value"
.Ft bool
.Fn sdp_get_str "sdp_data_t *data" "char **str" "size_t *length"
.Ft bool
.Fn sdp_get_url "sdp_data_t *data" "char **url" "size_t *length"
.Ft bool
.Fn sdp_put_data "sdp_data_t *data" "sdp_data_t *value"
.Ft bool
.Fn sdp_put_attr "sdp_data_t *data" "uint16_t attr" "sdp_data_t *value"
.Ft bool
.Fn sdp_put_uuid "sdp_data_t *data" "const uuid_t *value"
.Ft bool
.Fn sdp_put_uuid16 "sdp_data_t *data" "uint16_t value"
.Ft bool
.Fn sdp_put_uuid32 "sdp_data_t *data" "uint32_t value"
.Ft bool
.Fn sdp_put_uuid128 "sdp_data_t *data" "const uuid_t *value"
.Ft bool
.Fn sdp_put_bool "sdp_data_t *data" "bool value"
.Ft bool
.Fn sdp_put_uint "sdp_data_t *data" "uintmax_t value"
.Ft bool
.Fn sdp_put_uint8 "sdp_data_t *data" "uint8_t value"
.Ft bool
.Fn sdp_put_uint16 "sdp_data_t *data" "uint16_t value"
.Ft bool
.Fn sdp_put_uint32 "sdp_data_t *data" "uint32_t value"
.Ft bool
.Fn sdp_put_int "sdp_data_t *data" "intmax_t value"
.Ft bool
.Fn sdp_put_int8 "sdp_data_t *data" "int8_t value"
.Ft bool
.Fn sdp_put_int16 "sdp_data_t *data" "int16_t value"
.Ft bool
.Fn sdp_put_int32 "sdp_data_t *data" "int32_t value"
.Ft bool
.Fn sdp_put_seq "sdp_data_t *data" "ssize_t length"
.Ft bool
.Fn sdp_put_alt "sdp_data_t *data" "ssize_t length"
.Ft bool
.Fn sdp_put_str "sdp_data_t *data" "const char *str" "ssize_t length"
.Ft bool
.Fn sdp_put_url "sdp_data_t *data" "const char *url" "ssize_t length"
.Ft bool
.Fn sdp_set_bool "const sdp_data_t *data" "bool value"
.Ft bool
.Fn sdp_set_uint "const sdp_data_t *data" "uintmax_t value"
.Ft bool
.Fn sdp_set_int "const sdp_data_t *data" "intmax_t value"
.Ft bool
.Fn sdp_set_seq "const sdp_data_t *data" "ssize_t length"
.Ft ssize_t
.Fn sdp_data_size "const sdp_data_t *data"
.Ft int
.Fn sdp_data_type "const sdp_data_t *data"
.Ft bool
.Fn sdp_data_valid "const sdp_data_t *data"
.Ft void
.Fn sdp_data_print "const sdp_data_t *data" "int indent"
.Sh DESCRIPTION
These routines provide for the manipulation of Service Discovery
Protocol data buffers.
An SDP data buffer type is defined as:
.Bd -literal -offset indent
typedef struct {
	uint8_t *next;
	uint8_t *end;
} sdp_data_t;
.Ed
.Pp
Where
.Fa next
points to the next available byte, and
.Fa end
points to the first address past end of the data area, such that
.Qq end = next + length .
.Pp
The SDP data consists of byte streams describing data elements, where
a data element is a typed data representation consisting of a header
field and a data field.
The header field consists of type and size descriptors, and the data
field is a sequence of bytes whose length is specified in the size
descriptor and whose content is specified by the type descriptor.
For instance, the byte sequence
.Qq 0x09, 0x01, 0x00
describes an 16-bit unsigned integer element (type 0x09) with
value of 0x0100.
.Pp
Data element types including signed and unsigned integers, boolean,
string, sequence and alternative lists are defined in the
.In sdp.h
include file.
See the
.Qq Service Discovery Protocol
chapters of the
.Qq Bluetooth Core Specifications
for more information.
.Pp
To reduce the burden of storing and transferring 128-bit UUID values, a
range of UUID values has been pre-allocated for assignment to often-used,
registered purposes. The first UUID in this pre-allocated range is known
as the
.Qq Bluetooth Base UUID ,
defined in the
.Qq Bluetooth Assigned Numbers
document and declared in
.In sdp.h
as
.Vt const uuid_t BLUETOOTH_BASE_UUID ;
.Pp
The data manipulation routines are arranged into major groups
by function:
.Bl -hang
.It The Fn sdp_match_uuid16
routine examines the next data element in the data buffer for
an element of type UUID that matches the Bluetooth short alias
UUID with 16-bit value given.
If the UUID matches, the function will return
.Dv true
and the
.Fa next
field of the SDP data buffer will be advanced to the next element.
Otherwise
.Dv false
will be returned.
.It The Fn sdp_get_xxxx
routines examine the next data element in the data buffer for an
element of the given type.
If the type matches, the function will extract the typed value to
the address given and advance the
.Fa next
field of the SDP data buffer to the next element then return
.Dv true .
Otherwise
.Dv false
will be returned.
Note, these functions will not modify the
.Fa data
argument unless the correct type was found, and will update the
.Fa data
argument first to allow discarding in the case where a
.Dv sdp_data_t
was being returned.
.It The Fn sdp_put_xxxx
routines will attempt to write a data element of the given type
and value to the data buffer.
If the data buffer is too small to contain the encoded data element,
the function will return
.Dv false ,
otherwise
.Dv true
will be returned and the
.Fa next
field of the SDP data pointer will be advanced.
In the case of
.Fn sdp_put_seq
and
.Fn sdp_put_alt ,
the
.Fa length
argument may be -1, in which case the generated sequence header will
describe all the remaining buffer space.
For
.Fn sdp_put_str
and
.Fn sdp_put_url
the
.Fa length
argument may be -1 in which case the string pointer is treated as
nul terminated.
.It The Fn sdp_set_xxxx
routines examine the SDP data buffer for a data element of the given
type, and replace the content with the passed value.
If the next data element in the buffer is not of the appropriate
type, the function will return
.Dv false ,
otherwise
.Dv true
will be returned and the value updated.
In the case of
.Fn sdp_set_seq
and
.Fn sdp_set_alt ,
the
.Fa length
argument may be -1, in which case the sequence header will be
adjusted to describe the entire data space where possible.
.It The Fn sdp_data_xxxx
routines include various functions to provide information about
the data stream such as
.Fn sdp_data_size
to return the size of the next data element, and
.Fn sdp_data_type
to return the type of the next data element.
.Fn sdp_data_valid
can be used to ensure that the entire data buffer contains
valid SDP data elements and that all of the elements are contained
exactly within the data buffer.
Finally,
.Fn sdp_data_print
will print the data buffer in human readable format.
.El
.Sh EXAMPLES
To parse a ServiceAttribute response obtained from a remote server
using
.Xr sdp_service_attribute 3 ,
examining various attribute values:
.Bd -literal
	sdp_data_t rsp, val;
	uint16_t attr;
	uintmax_t handle;

	/* rsp contains remote response */

	/* discard sequence header */
	if (!sdp_get_seq(\*[Am]rsp, \*[Am]rsp))
		err(EXIT_FAILURE, "response is not a sequence");

	while (sdp_get_attr(\*[Am]rsp, \*[Am]attr, \*[Am]val)) {
		switch(attr) {
		case SDP_ATTR_SERVICE_RECORD_HANDLE:
			sdp_get_uint(\*[Am]val, \*[Am]handle);
			printf("ServiceRecordHandle: 0x%08x\\n", handle);
			break;

		case SDP_ATTR_PROFILE_DESCRIPTOR_LIST:
			printf("ProfileDescriptorList:\\n");
			sdp_data_print(\*[Am]val, 0);
			break;

		default:
			printf("uninteresting attribute 0x%04x\\n", attr);
			break;
		}
	}

.Ed
The following code creates a ProtocolDataList attribute value for a service
using the L2CAP and RFCOMM protocols and illustrates how to construct sequences
of known and unknown length.
.Bd -literal
	uint8_t buf[SIZE];
	sdp_data_t seq;
	uint16_t psm;
	uint8_t channel;

	seq.next = buf;
	seq.end = buf + sizeof(buf);
	sdp_put_seq(\*[Am]seq, -1);

	sdp_put_seq(\*[Am]seq, 6);
	sdp_put_uuid16(\*[Am]seq, SDP_UUID_PROTOCOL_L2CAP);
	sdp_put_uint16(\*[Am]seq, psm);

	sdp_put_seq(\*[Am]seq, 5);
	sdp_put_uuid16(\*[Am]seq, SDP_UUID_PROTOCOL_RFCOMM);
	sdp_put_uint8(\*[Am]seq, channel);

	seq.end = seq.next;
	seq.next = buf;
	sdp_set_seq(\*[Am]seq, -1);
.Ed
.Pp
Note that although
.Dv SIZE
is assumed to be large enough to contain the entire sequence
in this case, the
.Fn sdp_put_xxxx
routines will not overflow the buffer area or write partial data.
.Pp
The encoded data stream will be stored in a space efficient
manner where possible.
In the above example, it is known that the data element sequence
containing the L2CAP UUID will be 8 bytes long overall since the
container length of 6 can be stored in a single byte.
But, because the value of
.Dv SIZE
is unknown, the overall length of the ProtocolDataList may vary
depending if 8, 16 or 32 bits were needed to represent the original
buffer size.
.Fn sdp_seq_seq
will only modify the content, not the size of the header.
.Pp
.Sh SEE ALSO
.Xr sdpquery 1 ,
.Xr bluetooth 3 ,
.Xr sdp 3 ,
.Xr uuid 3 ,
.Xr sdpd 8
.Pp
The
.Qq Service Discovery Protocol
section of the Bluetooth Core specifications, available at
.Qq http://www.bluetooth.com/
.Sh HISTORY
These SDP data parsing and manipulation functions first appeared in
.Nx 6.0 .