static int
ChanTruncateObjCmd(
ClientData dummy, /* Not used. */
Tcl_Interp *interp, /* Current interpreter. */
int objc, /* Number of arguments. */
Tcl_Obj *const objv[]) /* Argument objects. */
{
Tcl_Channel chan;
Tcl_WideInt length;
if ((objc < 2) || (objc > 3)) {
Tcl_WrongNumArgs(interp, 1, objv, "channelId ?length?");
return TCL_ERROR;
}
if (TclGetChannelFromObj(interp, objv[1], &chan, NULL, 0) != TCL_OK) {
return TCL_ERROR;
}
if (objc == 3) {
/*
* User is supplying an explicit length.
*/
if (Tcl_GetWideIntFromObj(interp, objv[2], &length) != TCL_OK) {
return TCL_ERROR;
}
if (length < 0) {
Tcl_AppendResult(interp,
"cannot truncate to negative length of file", NULL);
return TCL_ERROR;
}
} else {
/*
* User wants to truncate to the current file position.
*/
length = Tcl_Tell(chan);
if (length == Tcl_WideAsLong(-1)) {
Tcl_AppendResult(interp,
"could not determine current location in \"",
TclGetString(objv[1]), "\": ",
Tcl_PosixError(interp), NULL);
return TCL_ERROR;
}
}
if (Tcl_TruncateChannel(chan, length) != TCL_OK) {
Tcl_AppendResult(interp, "error during truncate on \"",
TclGetString(objv[1]), "\": ",
Tcl_PosixError(interp), NULL);
return TCL_ERROR;
}
return TCL_OK;
}
static int
FileSeekProc(
ClientData instanceData, /* File state. */
long offset, /* Offset to seek to. */
int mode, /* Relative to where should we seek? Can be
* one of SEEK_START, SEEK_SET or SEEK_END. */
int *errorCodePtr) /* To store error code. */
{
FileState *fsPtr = instanceData;
Tcl_WideInt oldLoc, newLoc;
/*
* Save our current place in case we need to roll-back the seek.
*/
oldLoc = TclOSseek(fsPtr->fd, (Tcl_SeekOffset) 0, SEEK_CUR);
if (oldLoc == Tcl_LongAsWide(-1)) {
/*
* Bad things are happening. Error out...
*/
*errorCodePtr = errno;
return -1;
}
newLoc = TclOSseek(fsPtr->fd, (Tcl_SeekOffset) offset, mode);
/*
* Check for expressability in our return type, and roll-back otherwise.
*/
if (newLoc > Tcl_LongAsWide(INT_MAX)) {
*errorCodePtr = EOVERFLOW;
TclOSseek(fsPtr->fd, (Tcl_SeekOffset) oldLoc, SEEK_SET);
return -1;
} else {
*errorCodePtr = (newLoc == Tcl_LongAsWide(-1)) ? errno : 0;
}
return (int) Tcl_WideAsLong(newLoc);
}
static Tcl_WideInt
TransformWideSeekProc(
ClientData instanceData, /* The channel to manipulate. */
Tcl_WideInt offset, /* Size of movement. */
int mode, /* How to move. */
int *errorCodePtr) /* Location of error flag. */
{
TransformChannelData *dataPtr = instanceData;
Tcl_Channel parent = Tcl_GetStackedChannel(dataPtr->self);
const Tcl_ChannelType *parentType = Tcl_GetChannelType(parent);
Tcl_DriverSeekProc *parentSeekProc = Tcl_ChannelSeekProc(parentType);
Tcl_DriverWideSeekProc *parentWideSeekProc =
Tcl_ChannelWideSeekProc(parentType);
ClientData parentData = Tcl_GetChannelInstanceData(parent);
if ((offset == Tcl_LongAsWide(0)) && (mode == SEEK_CUR)) {
/*
* This is no seek but a request to tell the caller the current
* location. Simply pass the request down.
*/
if (parentWideSeekProc != NULL) {
return parentWideSeekProc(parentData, offset, mode, errorCodePtr);
}
return Tcl_LongAsWide(parentSeekProc(parentData, 0, mode,
errorCodePtr));
}
/*
* It is a real request to change the position. Flush all data waiting for
* output and discard everything in the input buffers. Then pass the
* request down, unchanged.
*/
PreserveData(dataPtr);
if (dataPtr->mode & TCL_WRITABLE) {
ExecuteCallback(dataPtr, NULL, A_FLUSH_WRITE, NULL, 0, TRANSMIT_DOWN,
P_NO_PRESERVE);
}
if (dataPtr->mode & TCL_READABLE) {
ExecuteCallback(dataPtr, NULL, A_CLEAR_READ, NULL, 0, TRANSMIT_DONT,
P_NO_PRESERVE);
ResultClear(&dataPtr->result);
dataPtr->readIsFlushed = 0;
dataPtr->eofPending = 0;
}
ReleaseData(dataPtr);
/*
* If we have a wide seek capability, we should stick with that.
*/
if (parentWideSeekProc != NULL) {
return parentWideSeekProc(parentData, offset, mode, errorCodePtr);
}
/*
* We're transferring to narrow seeks at this point; this is a bit complex
* because we have to check whether the seek is possible first (i.e.
* whether we are losing information in truncating the bits of the
* offset). Luckily, there's a defined error for what happens when trying
* to go out of the representable range.
*/
if (offset<Tcl_LongAsWide(LONG_MIN) || offset>Tcl_LongAsWide(LONG_MAX)) {
*errorCodePtr = EOVERFLOW;
return Tcl_LongAsWide(-1);
}
return Tcl_LongAsWide(parentSeekProc(parentData, Tcl_WideAsLong(offset),
mode, errorCodePtr));
}
