Tcl_LinkVar(3tcl)
Tcl_LinkVar(3) Tcl Library Procedures Tcl_LinkVar(3)
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NAME
Tcl_LinkVar, Tcl_UnlinkVar, Tcl_UpdateLinkedVar - link Tcl
variable to C variable
SYNOPSIS
#include <tcl.h>
int
Tcl_LinkVar(interp, varName, addr, type)
Tcl_UnlinkVar(interp, varName)
Tcl_UpdateLinkedVar(interp, varName)
ARGUMENTS
Tcl_Interp *interp (in) Interpreter that contains
varName. Also used by
Tcl_LinkVar to return
error messages.
const char *varName (in) Name of global variable.
char *addr (in) Address of C variable that
is to be linked to var-
Name.
int type (in) Type of C variable. Must
be one of TCL_LINK_INT, |
TCL_LINK_UINT, |
TCL_LINK_CHAR, |
TCL_LINK_UCHAR, |
TCL_LINK_SHORT, |
TCL_LINK_USHORT, |
TCL_LINK_LONG, |
TCL_LINK_ULONG,
TCL_LINK_WIDE_INT, |
TCL_LINK_WIDE_UINT, |
TCL_LINK_FLOAT,
TCL_LINK_DOUBLE,
TCL_LINK_BOOLEAN, or
TCL_LINK_STRING, option-
ally OR'ed with
TCL_LINK_READ_ONLY to make
Tcl variable read-only.
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DESCRIPTION
Tcl_LinkVar uses variable traces to keep the Tcl variable
named by varName in sync with the C variable at the address
Tcl Last change: 7.5 1
Tcl_LinkVar(3) Tcl Library Procedures Tcl_LinkVar(3)
given by addr. Whenever the Tcl variable is read the value
of the C variable will be returned, and whenever the Tcl
variable is written the C variable will be updated to have
the same value. Tcl_LinkVar normally returns TCL_OK; if an
error occurs while setting up the link (e.g. because varName
is the name of array) then TCL_ERROR is returned and the
interpreter's result contains an error message.
The type argument specifies the type of the C variable, and
must have one of the following values, optionally OR'ed with
TCL_LINK_READ_ONLY:
TCL_LINK_INT
The C variable is of type int. Any value written into
the Tcl variable must have a proper integer form
acceptable to Tcl_GetIntFromObj; attempts to write
non-integer values into varName will be rejected with
Tcl errors. |
TCL_LINK_UINT ||
The C variable is of type unsigned int. Any value |
written into the Tcl variable must have a proper |
unsigned integer form acceptable to |
Tcl_GetWideIntFromObj and in the platform's defined |
range for the unsigned int type; attempts to write |
non-integer values (or values outside the range) into |
varName will be rejected with Tcl errors. |
TCL_LINK_CHAR ||
The C variable is of type char. Any value written into |
the Tcl variable must have a proper integer form |
acceptable to Tcl_GetIntFromObj and be in the range of |
the char datatype; attempts to write non-integer or |
out-of-range values into varName will be rejected with |
Tcl errors. |
TCL_LINK_UCHAR ||
The C variable is of type unsigned char. Any value |
written into the Tcl variable must have a proper |
unsigned integer form acceptable to Tcl_GetIntFromObj |
and in the platform's defined range for the unsigned |
char type; attempts to write non-integer values (or |
values outside the range) into varName will be rejected |
with Tcl errors. |
TCL_LINK_SHORT ||
The C variable is of type short. Any value written |
into the Tcl variable must have a proper integer form |
acceptable to Tcl_GetIntFromObj and be in the range of |
the short datatype; attempts to write non-integer or |
out-of-range values into varName will be rejected with |
Tcl errors. |
Tcl Last change: 7.5 2
Tcl_LinkVar(3) Tcl Library Procedures Tcl_LinkVar(3)
TCL_LINK_USHORT ||
The C variable is of type unsigned short. Any value |
written into the Tcl variable must have a proper |
unsigned integer form acceptable to Tcl_GetIntFromObj |
and in the platform's defined range for the unsigned |
short type; attempts to write non-integer values (or |
values outside the range) into varName will be rejected |
with Tcl errors. |
TCL_LINK_LONG ||
The C variable is of type long. Any value written into |
the Tcl variable must have a proper integer form |
acceptable to Tcl_GetLongFromObj; attempts to write |
non-integer or out-of-range values into varName will be |
rejected with Tcl errors. |
TCL_LINK_ULONG ||
The C variable is of type unsigned long. Any value |
written into the Tcl variable must have a proper |
unsigned integer form acceptable to |
Tcl_GetWideIntFromObj and in the platform's defined |
range for the unsigned long type; attempts to write |
non-integer values (or values outside the range) into |
varName will be rejected with Tcl errors.
TCL_LINK_DOUBLE
The C variable is of type double. Any value written
into the Tcl variable must have a proper real form
acceptable to Tcl_GetDoubleFromObj; attempts to write
non-real values into varName will be rejected with Tcl
errors. |
TCL_LINK_FLOAT ||
The C variable is of type float. Any value written |
into the Tcl variable must have a proper real form |
acceptable to Tcl_GetDoubleFromObj and must be within |
the range acceptable for a float; attempts to write |
non-real values (or values outside the range) into var- |
Name will be rejected with Tcl errors.
TCL_LINK_WIDE_INT
The C variable is of type Tcl_WideInt (which is an
integer type at least 64-bits wide on all platforms
that can support it.) Any value written into the Tcl
variable must have a proper integer form acceptable to
Tcl_GetWideIntFromObj; attempts to write non-integer
values into varName will be rejected with Tcl errors. |
TCL_LINK_WIDE_UINT ||
The C variable is of type Tcl_WideUInt (which is an |
unsigned integer type at least 64-bits wide on all |
platforms that can support it.) Any value written into |
Tcl Last change: 7.5 3
Tcl_LinkVar(3) Tcl Library Procedures Tcl_LinkVar(3)
the Tcl variable must have a proper unsigned integer |
form acceptable to Tcl_GetWideIntFromObj (it will be |
cast to unsigned); attempts to write non-integer values |
into varName will be rejected with Tcl errors.
TCL_LINK_BOOLEAN
The C variable is of type int. If its value is zero
then it will read from Tcl as "0"; otherwise it will
read from Tcl as "1". Whenever varName is modified,
the C variable will be set to a 0 or 1 value. Any
value written into the Tcl variable must have a proper
boolean form acceptable to Tcl_GetBooleanFromObj;
attempts to write non-boolean values into varName will
be rejected with Tcl errors.
TCL_LINK_STRING
The C variable is of type char *. If its value is not
NULL then it must be a pointer to a string allocated
with Tcl_Alloc or ckalloc. Whenever the Tcl variable
is modified the current C string will be freed and new
memory will be allocated to hold a copy of the
variable's new value. If the C variable contains a
NULL pointer then the Tcl variable will read as "NULL".
If the TCL_LINK_READ_ONLY flag is present in type then the
variable will be read-only from Tcl, so that its value can
only be changed by modifying the C variable. Attempts to
write the variable from Tcl will be rejected with errors.
Tcl_UnlinkVar removes the link previously set up for the
variable given by varName. If there does not exist a link
for varName then the procedure has no effect.
Tcl_UpdateLinkedVar may be invoked after the C variable has
changed to force the Tcl variable to be updated immediately.
In many cases this procedure is not needed, since any
attempt to read the Tcl variable will return the latest
value of the C variable. However, if a trace has been set
on the Tcl variable (such as a Tk widget that wishes to
display the value of the variable), the trace will not
trigger when the C variable has changed.
Tcl_UpdateLinkedVar ensures that any traces on the Tcl vari-
able are invoked.
KEYWORDS
boolean, integer, link, read-only, real, string, traces,
variable
Tcl Last change: 7.5 4
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