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add description of proto_tree_add_bitmask() 

svn path=/trunk/; revision=20011
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Ronnie Sahlberg 2006-11-28 09:09:58 +00:00
parent 612c85a7af
commit 3ea6b058d9
1 changed files with 52 additions and 0 deletions
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doc/README.developer
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@ -1940,6 +1940,10 @@ protocol or field labels to the proto_tree:
proto_tree_add_oid_format_value(tree, id, tvb, start, length,
value_ptr, format, ...);
proto_item *
proto_tree_add_bitmask(tree, tvb, start, header, ett, **fields,
little_endian);
The 'tree' argument is the tree to which the item is to be added. The
'tvb' argument is the tvbuff from which the item's value is being
extracted; the 'start' argument is the offset from the beginning of that
@ -2292,6 +2296,54 @@ This is like proto_tree_add_text(), but takes, as the last argument, a
variable-length list of arguments to add a text item to the protocol
tree.
proto_tree_add_bitmask()
---------------------
This function provides an easy to use and convenient helper function
to manage many types of common bitmasks that occur in protocols.
This function will dissect a 1/2/3/4 byte large bitmask into its individual
fields.
header is an integer type and must be of type FT_[U]INT{8|16|24|32} and
represents the entire width of the bitmask.
'header' and 'ett' are the hf fields and ett field respectively to create an
expansion that covers the 1-4 bytes of the bitmask.
'**fields' is a NULL terminated a array of pointers to hf fields representing
the individual subfields of the bitmask. These fields must either be integers
of the same byte width as 'header' or of the type FT_BOOLEAN.
Each of the entries in '**fields' will be dissected as an item under the
'header' expansion and also IF the field is a booelan and IF it is set to 1,
then the name of that boolean field will be printed on the 'header' expansion
line. For integer type subfields that have a value_string defined, the
matched string from that value_string will be printed on the expansion line as well.
Example: (from the scsi dissector)
static int hf_scsi_inq_peripheral = -1;
static int hf_scsi_inq_qualifier = -1;
static gint ett_scsi_inq_peripheral = -1;
...
static const int *peripheal_fields[] = {
&hf_scsi_inq_qualifier,
&hf_scsi_inq_devtype,
NULL
};
...
/* Qualifier and DeviceType */
proto_tree_add_bitmask(tree, tvb, offset, hf_scsi_inq_peripheral, ett_scsi_inq_peripheral, peripheal_fields, FALSE);
offset+=1;
...
{ &hf_scsi_inq_peripheral,
{"Peripheral", "scsi.inquiry.preipheral", FT_UINT8, BASE_HEX,
NULL, 0, "", HFILL}},
{ &hf_scsi_inq_qualifier,
{"Qualifier", "scsi.inquiry.qualifier", FT_UINT8, BASE_HEX,
VALS (scsi_qualifier_val), 0xE0, "", HFILL}},
...
Which provides very pretty dissection of this one byte bitmask.
1.7 Utility routines.
1.7.1 match_strval and val_to_str.