Tcl_GetIndexFromObj(3) Tcl Library Procedures Tcl_GetIndexFromObj(3)
Tcl_GetIndexFromObj, Tcl_GetIndexFromObjStruct - lookup string in table of keywords
Tcl_GetIndexFromObj(interp, objPtr, tablePtr, msg, flags,
Tcl_GetIndexFromObjStruct(interp, objPtr, structTablePtr, offset,
msg, flags, indexPtr)
Tcl_Interp *interp (in) Interpreter to use for error reporting; if NULL,
then no message is provided on errors.
Tcl_Obj *objPtr (in/out) The string value of this object is used to search
through tablePtr. The internal representation is
modified to hold the index of the matching table
const char **tablePtr (in) An array of null-terminated strings. The end of
the array is marked by a NULL string pointer.
Note that references to the tablePtr may be
retained in the internal representation of
objPtr, so this should represent the address of a
const void *structTablePtr (in) An array of arbitrary type, typically some struct
type. The first member of the structure must be
a null-terminated string. The size of the struc-
ture is given by offset. Note that references to
the structTablePtr may be retained in the inter-
nal representation of objPtr, so this should rep-
resent the address of a statically-allocated
array of structures.
int offset (in) The offset to add to structTablePtr to get to the
next entry. The end of the array is marked by a
NULL string pointer.
const char *msg (in) Null-terminated string describing what is being
looked up, such as option. This string is
included in error messages.
int flags (in) OR-ed combination of bits providing additional
information for operation. The only bit that is
currently defined is TCL_EXACT.
int *indexPtr (out) The index of the string in tablePtr that matches
the value of objPtr is returned here.
These procedures provide an efficient way for looking up keywords, switch names, option
names, and similar things where the value of an object must be one of a predefined set of
values. Tcl_GetIndexFromObj compares objPtr against each of the strings in tablePtr to
find a match. A match occurs if objPtr's string value is identical to one of the strings
in tablePtr, or if it is a non-empty unique abbreviation for exactly one of the strings in
tablePtr and the TCL_EXACT flag was not specified; in either case the index of the match-
ing entry is stored at *indexPtr and TCL_OK is returned.
If there is no matching entry, TCL_ERROR is returned and an error message is left in
interp's result if interp is not NULL. Msg is included in the error message to indicate
what was being looked up. For example, if msg is option the error message will have a
form like "bad option "firt": must be first, second, or third".
If Tcl_GetIndexFromObj completes successfully it modifies the internal representation of
objPtr to hold the address of the table and the index of the matching entry. If
Tcl_GetIndexFromObj is invoked again with the same objPtr and tablePtr arguments (e.g.
during a reinvocation of a Tcl command), it returns the matching index immediately without
having to redo the lookup operation. Note: Tcl_GetIndexFromObj assumes that the entries
in tablePtr are static: they must not change between invocations. If the value of objPtr
is the empty string, Tcl_GetIndexFromObj will treat it as a non-matching value and return
Tcl_GetIndexFromObjStruct works just like Tcl_GetIndexFromObj, except that instead of
treating tablePtr as an array of string pointers, it treats it as a pointer to the first
string in a series of strings that have offset bytes between them (i.e. that there is a
pointer to the first array of characters at tablePtr, a pointer to the second array of
characters at tablePtr+offset bytes, etc.) This is particularly useful when processing
things like Tk_ConfigurationSpec, whose string keys are in the same place in each of sev-
eral array elements.
index, object, table lookup
Tcl 8.1 Tcl_GetIndexFromObj(3)