Tcl_GetIndexFromObj(3) Tcl Library Procedures Tcl_GetIndexFromObj(3)
____________________________________________________________________________________________________________
NAME
Tcl_GetIndexFromObj, Tcl_GetIndexFromObjStruct - lookup string in table of keywords
SYNOPSIS
#include <tcl.h>
int
Tcl_GetIndexFromObj(interp, objPtr, tablePtr, msg, flags,
indexPtr)
int |
Tcl_GetIndexFromObjStruct(interp, objPtr, structTablePtr, 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.
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 off- |
set (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.
____________________________________________________________________________________________________________
DESCRIPTION
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 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 nonmatching
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_Configu- |
rationSpec, whose string keys are in the same place in each of several array elements.
SEE ALSO
Tcl_WrongNumArgs
KEYWORDS
index, object, table lookup
Tcl 8.1 Tcl_GetIndexFromObj(3)
|