Tcl_GetIndexFromObj, Tcl_GetIndexFromObjStruct - lookup string in table of keywords
- Tcl_GetIndexFromObj, Tcl_GetIndexFromObjStruct - lookup string in table of keywords
- #include <tcl.h>
- Tcl_GetIndexFromObj(interp, objPtr, tablePtr, msg, flags,
- Tcl_GetIndexFromObjStruct(interp, objPtr, structTablePtr, offset,
- msg, flags, indexPtr)
- SEE ALSO
Tcl_GetIndexFromObj(interp, objPtr, tablePtr, msg, flags,
Tcl_GetIndexFromObjStruct(interp, objPtr, structTablePtr, offset,
msg, flags, indexPtr)
This procedure provides 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.
ObjPtr is compared 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 matching entry is stored at *indexPtr
and TCL_OK is returned.
- 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
- const char **tablePtr (in)
An array of null-terminated strings. The end of the array is marked
by a NULL string pointer.
- 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 structure is given by offset.
- 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.
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_ERROR.
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 several array elements.
index, object, table lookup
Copyright © 1995-1997 Roger E. Critchlow Jr.
Copyright © 1997 Sun Microsystems, Inc.