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 value is used to search through tablePtr.
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 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 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
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.
SEE ALSO¶
prefix(3tcl), Tcl_WrongNumArgs(3tcl)
KEYWORDS¶
index, option, value, table lookup