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.   Note  that
                                           references  to  the  tablePtr  may  be retained in the
                                           internal representation  of  objPtr,  so  this  should
                                           represent the address of a statically-allocated array.

       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.   Note  that  references   to   the
                                           structTablePtr   may   be  retained  in  the  internal
                                           representation of objPtr, so this should represent 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.
_________________________________________________________________

DESCRIPTION

       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
       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