- 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
- DESCRIPTION
- REFERENCE COUNT MANAGEMENT
- SEE ALSO
- KEYWORDS
Tcl_GetIndexFromObj, Tcl_GetIndexFromObjStruct — lookup string in table of keywords
#include <tcl.h>
int
Tcl_GetIndexFromObj(interp, objPtr, tablePtr, msg, flags,
indexPtr)
int
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 value is used to search through tablePtr.
If the TCL_INDEX_TEMP_TABLE flag is not specified,
the internal representation is modified to hold the index of the matching
table entry.
- const char *const *tablePtr (in)
-
An array of null-terminated strings. The end of the array is marked
by a NULL string pointer.
Note that, unless the TCL_INDEX_TEMP_TABLE flag is specified,
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, unless the TCL_INDEX_TEMP_TABLE flag is specified,
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 bits that are currently defined are TCL_EXACT
and TCL_INDEX_TEMP_TABLE.
- 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 literal value of
a Tcl value must be chosen from a predefined set.
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 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 the TCL_INDEX_TEMP_TABLE was not specified, when
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. This caching mechanism can be disallowed by specifying
the TCL_INDEX_TEMP_TABLE flag.
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.
Tcl_GetIndexFromObj and Tcl_GetIndexFromObjStruct do not modify
the reference count of their objPtr arguments; they only read. Note
however that these functions may set the interpreter result; if that is the
only place that is holding a reference to the object, it will be deleted.
prefix, Tcl_WrongNumArgs
index, option, value, table lookup
Copyright © 1997 Sun Microsystems, Inc.