compilers support that. Variables should be declared outside a
function, or at the beginning of a function or compound statement.
-Don't use anonymous unions; not all compilers support it.
+Don't use anonymous unions; not all compilers support them.
Example:
-typedef struct foo {
- guint32 foo;
- union {
- guint32 foo_l;
- guint16 foo_s;
- } u; /* have a name here */
-} foo_t;
+
+ typedef struct foo {
+ guint32 foo;
+ union {
+ guint32 foo_l;
+ guint16 foo_s;
+ } u; /* have a name here */
+ } foo_t;
Don't use "uchar", "u_char", "ushort", "u_short", "uint", "u_int",
"ulong", "u_long" or "boolean"; they aren't defined on all platforms.
call_routine2(xxx, format, ap);
va_end(ap);
-rather
+rather
va_start(ap, format);
call_routine1(xxx, format, ap);
call_routine2(xxx, format, ap);
*/
PROTOABBREV_handle = new_create_dissector_handle(dissect_PROTOABBREV,
proto_PROTOABBREV);
- dissector_add("PARENT_SUBFIELD", ID_VALUE, PROTOABBREV_handle);
-
initialized = TRUE;
} else {
strings
-------
+-- value_string
Some integer fields, of type FT_UINT*, need labels to represent the true
value of a field. You could think of those fields as having an
enumerated data type, rather than an integral data type.
If the field has a numeric rather than an enumerated type, the 'strings'
field would be set to NULL.
+-- Extended value strings
You can also use an extended version of the value_string for faster lookups.
It requires a value_string as input.
-It will use the value as a pointer to the string if all values from 0 to max
-are present in the array; otherwise if the values are in assending order
-a binary search will be used. The init macro will perform a check on the value string
+If all of a contiguous range of values from min to max are present in the array
+the value will be used as as a direct index into a value_string array.
+
+If the values in the array are not contiguous (ie: there are "gaps"), but are in assending order
+a binary search will be used.
+
+Note: "gaps" in a value_string array can be filled with "empty" entries eg: {value, "Unknown"} so that
+direct access to the array is is possible.
+
+The init macro (see below) will perform a check on the value string
the first time it is used to determine which search algorithm fits and fall back to a linear search
if the value_string does not meet the criteria above.
-Use this macro to initialise the extended value_string:
+Use this macro to initialise the extended value_string at comile time:
static value_string_ext valstringname_ext = VALUE_STRING_EXT_INIT(valstringname);
-For FT_(U)INT* fields that need a 'valstringname_ext' struct, the 'strings' field
+Extended value strings can be created at runtime by calling
+ value_string_ext_new(<ptr to value_string array>,
+ <total number of entries in the value_string_array>, /* include {0, NULL} entry */
+ <value_string_name>);
+
+For hf[] array FT_(U)INT* fields that need a 'valstringname_ext' struct, the 'strings' field
would be set to '&valstringname_ext)'. Furthermore, 'display' field must be
ORed with 'BASE_EXT_STRING' (e.g. BASE_DEC|BASE_EXT_STRING).
+-- Ranges
If the field has a numeric type that might logically fit in ranges of values
one can use a range_string struct.
would be set to 'RVALS(rvalstringname)'. Furthermore, 'display' field must be
ORed with 'BASE_RANGE_STRING' (e.g. BASE_DEC|BASE_RANGE_STRING).
+-- Booleans
FT_BOOLEANs have a default map of 0 = "False", 1 (or anything else) = "True".
Sometimes it is useful to change the labels for boolean values (e.g.,
to "Yes"/"No", "Fast"/"Slow", etc.). For these mappings, a struct called
1.7 Utility routines.
-1.7.1 match_strval and val_to_str.
+1.7.1 match_strval, match_strval_ext, val_to_str and val_to_str_ext.
A dissector may need to convert a value to a string, using a
'value_string' structure, by hand, rather than by declaring a field with
col_add_fstr(COL_INFO, ", %s", val_to_str(val, table, "Unknown %d"));
+The match_strval_ext and val_to_str_ext functions are "extended" versions
+of match_strval and val_to_str. They should be used for large value-string
+arrays which contain many entries. They implement value to string conversions
+which will do either a direct access or a binary search of the
+value string array if possible. See "Extended Value Strings" under
+section 1.6 "Constructing the protocol tree" for more information.
+
+See epan/value_string.h for detailed information on the various value_string
+functions.
+
+
1.7.2 match_strrval and rval_to_str.
A dissector may need to convert a range of values to a string, using a
description - Comments added to the preference file above the
preference value
var - pointer to the storage location that is updated when the
- field is changed in the preference dialog box
+ field is changed in the preference dialog box. Note that
+ with string preferences the given pointer is overwritten
+ with a pointer to a new copy of the string during the
+ preference registration. The passed-in string may be
+ freed, but you must keep another pointer to the string
+ in order to free it.
base - Base that the unsigned integer is expected to be in,
see strtoul(3).
enumvals - an array of enum_val_t structures. This must be
git.samba.org / obnox / wireshark / wip.git / blobdiff