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NAME
Tcl_GetIndexFromObj - lookup string in table of keywords
SYNOPSIS
#include <tcl.h>
int
Tcl_GetIndexFromObj(interp, objPtr, tablePtr, msg, flags,
indexPtr)
int |
Tcl_GetIndexFromObjStruct(interp, objPtr, tablePtr, offset, |
msg, flags, indexPtr) |
ARGUMENTS
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 entry.
char **tablePtr (in) An array of null-
terminated strings. The
end of the array is
marked by a NULL string
pointer. |
int offset (in) ||
The offset to add to |
tablePtr to get to the |
next string in the list. |
The end of the array is |
marked by a NULL string |
pointer.
char *msg (in) Null-terminated string
describing what is being
looked up, such as
option. This string is
included in error mes-
sages.
int flags (in) OR-ed combination of
bits providing addi-
tional 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.
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DESCRIPTION
This procedure provides an efficient way for looking up key-
words, 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 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.
If there is no matching entry, TCL_ERROR is returned and an
error message is left in interp's result if interp isn't
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 the |
first in a series of string ptrs that are spaced apart by |
offset bytes. This is particularly useful when processing |
things like Tk_ConfigurationSpec, whose string keys are in |
the same place in each of several array elements.
SEE ALSO
Tcl_WrongNumArgs
KEYWORDS
index, object, table lookup
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