From 8f9f6a2a1711e1e976243069a558fa11cf47209f Mon Sep 17 00:00:00 2001 From: patthoyts Date: Mon, 15 Dec 2008 23:42:01 +0000 Subject: Fix line endings damaged by last commit --- doc/NRE.3 | 606 +++++++++++++++++++++++++++++++------------------------------- 1 file changed, 303 insertions(+), 303 deletions(-) diff --git a/doc/NRE.3 b/doc/NRE.3 index edddd7b..a453219 100644 --- a/doc/NRE.3 +++ b/doc/NRE.3 @@ -1,303 +1,303 @@ -.\" -.\" Copyright (c) 2008 by Kevin B. Eknny. -.\" - -'\" See the file "license.terms" for information on usage and redistribution -'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. -'\" -'\" RCS: @(#) $Id: NRE.3,v 1.1 2008/12/12 04:38:12 kennykb Exp $ -'\" -.so man.macros -.TH NRE 3 8.6 Tcl "Tcl Library Procedures" -.BS -.SH NAME -Tcl_NRCreateCommand, Tcl_NRCallObjProc, Tcl_NREvalObj, Tcl_NREvalObjv, Tcl_NRCmdSwap, Tcl_NRAddCallback \- Non-Recursive (stackless) evaluation of Tcl scripts. -.SH SYNOPSIS -.nf -\fB#include \fR -.sp -Tcl_Command -\fBTcl_NRCreateCommand\fR(\fIinterp, cmdName, proc, nreProc, clientData, deleteProc\fR) -.sp -int -\fBTcl_NRCallObjProc\fR(\fIinterp, nreProc, clientData, objc, objv\fR) -.sp -int -\fBTcl_NREvalObj\fR(\fIinterp, objPtr, flags\fR) -.sp -int -\fBTcl_NREvalObjv\fR(\fIinterp, objc, objv, flags\fR) -.sp -int -\fBTcl_NRCmdSwap\fR(\fIinterp, cmd, objc, objv, flags\fR) -.sp -void -\fBTcl_NRAddCallback\fR(\fIinterp, postProcPtr, data0, data1, data2, data3\fR) -.fi -.SH ARGUMENTS -.AS Tcl_CmdDeleteProc *postProcPtr in -.AP Tcl_Interp *interp in -Interpreter in which to create or evaluate a command. -.AP char *cmdName in -Name of a new command to create. -.AP Tcl_ObjCmdProc *proc in -Implementation of a command that will be called whenever \fIcmdName\fR -is invoked as a command in the unoptimized way. -.AP Tcl_ObjCmdProc *nreProc in -Implementation of a command that will be called whenever \fIcmdName\fR -is invoked and requested to conserve the C stack. -.AP ClientData clientData in -Arbitrary one-word value that will be passed to \fIproc\fR, \fInreProc\fR, -\fIdeleteProc\fR and \fIobjProc\fR. -.AP Tcl_CmdDeleteProc *deleteProc in/out -Procedure to call before \fIcmdName\fR is deleted from the interpreter. -This procedure allows for command-specific cleanup. If \fIdeletProc\fR -is \fBNULL\fR, then no procedure is called before the command is deleted. -.AP int objc in -Count of parameters provided to the implementation of a command. -.AP Tcl_Obj **objv in -Pointer to an array of Tcl objects. Each object holds the value of a -single word in the command to execute. -.AP Tcl_Obj *objPtr in -Pointer to a Tcl_Obj whose value is a script to execute. -.AP int flags in -ORed combination of flag bits that specify additional options. -\fBTCL_EVAL_GLOBAL\fR is the only flag that is currently supported. -.\" TODO: This is a lie. But kbk didn't grasp TCL_EVAL_INVOKE and -.\" TCL_EVAL_NOERR well enough to document them. -.AP Tcl_Command cmd in -.AP Tcl_NRPostProc *postProcPtr in -Pointer to a function that will be invoked when the command currently -executing in the interpreter designated by \fIinterp\fR completes. -.AP ClientData data0 in -.AP ClientData data1 in -.AP ClientData data2 in -.AP ClientData data3 in -\fIdata0\fR through \fIdata3\fR are four one-word values that will be passed -to the function designated by \fIpostProcPtr\fR when it is invoked. -.BE -.SH DESCRIPTION -.PP -This series of C functions provides an interface whereby commands that -are implemented in C can be evaluated, and invoke Tcl commands scripts -and scripts, without consuming space on the C stack. The non-recursive -evaluation is done by installing a \fItrampoline\fR, a small piece of -code that invokes a command or script, and then executes a series of -callbacks when the command or script returns. -.PP -The \fBTcl_NRCreateCommand\fR function creates a Tcl command in the -interpreter designated by \fIinterp\fR that is prepared to handle -nonrecursive evaluation with a trampoline. The \fIcmdName\fR argument -gives the name of the new command. If \fIcmdName\fR contains any -namespace qualifiers, then the new command is added to the specified -namespace; otherwise, it is added to the global namespace. \fIproc\fR -gives the procedure that will be called when the interpreter wishes to -evaluate the command in an unoptimized manner, and \fInreProc\fR is -the procedure that will be called when the interpreter wishes to -evaluate the command using a trampoline. \fIdeleteProc\fR is a -function that will be called before the command is deleted from the -interpreter. When any of the three functions is invoked, it is passed -the \fIclientData\fR parameter. -.PP -\fBTcl_NRCreateCommand\fR deletes any existing command -\fIname\fR already associated with the interpreter -(however see below for an exception where the existing command -is not deleted). -It returns a token that may be used to refer -to the command in subsequent calls to \fBTcl_GetCommandName\fR. -If \fBTcl_NRCreateCommand\fR is called for an interpreter that is in -the process of being deleted, then it does not create a new command, -does not delete any existing command of the same name, and returns NULL. -.PP -The \fIproc\fR and \fInreProc\fR function are expected to conform to -all the rules set forth for the \fIproc\fR argument to -\fBTcl_CreateObjCommand\fR(3) (\Iq.v.\fR). -.PP -When a command that is written to cope with evaluation via trampoline -is invoked without a trampoline on the stack, it will usually respond -to the invocation by creating a trampoline and calling the -trampoline-enabled implementation of the same command. This call is done by -means of \fBTcl_NRCallObjProc\fR. In the call to -\fBTcl_NRCallObjProc\fR, the \fIinterp\fR, \fIclientData\fR, -\fIobjc\fR and \fIobjv\fR parameters should be the same ones that were -passed to \fIproc\fR. The \fInreProc\fR parameter should designate the -trampoline-enabled implementation of the command. -.PP -\fBTcl_NREvalObj\fR arranges for the script contained in \fIobjPtr\fR -to be evaluated in the interpreter designated by \fIinterp\fR after -the current command (which must be trampoline-enabled) returns. It is -the method by which a command may invoke a script without consuming -space on the C stack. Similarly, \fBTcl_NREvalObjv\fR arranges to -invoke a single Tcl command whose words have already been separated -and substituted. The \fIobjc\fR and \fIobjv\fR parameters give the -words of the command to be evaluated when execution reaches the -trampoline. -.PP -\fBTcl_NRCmdSwap allows for trampoline evaluation of a command whose -resolution is already known. The \fIcmd\fR parameter gives a -\fBTcl_Command\fR object (returned from \fBTcl_CreateObjCmd\fR or -\fBTcl_GetCommandFromObj\fR) identifying the command to be invoked in -the trampoline; this command must match the word in \fIobjv[0]\fR. -The remaining arguments are as for \fBTcl_NREvalObj\fR. -.PP -\fBTcl_NREvalObj\fR, \fBTcl_NREvalObjv\fR and \fBTcl_NRCmdSwap\fR -all accept a \fIflags\fR parameter, which is an OR-ed-together set of -bits to control evaluation. At the present time, the only flag -available to callers is \fBTCL_EVAL_GLOBAL\fR. -.\" TODO: Again, this is a lie. Do we want to explain TCL_EVAL_INVOKE -.\" and TCL_EVAL_NOERR? -If the \fBTCL_EVAL_GLOBAL\fR flag is set, the script or command is -evaluated in the global namespace. If it is not set, it is evaluated -in the current namespace. -.PP -All three of the routines return \fBTCL_OK\fR if command invocation -has been scheduled successfully. If for any reason command invocation -cannot be scheduled (for example, if the interpreter is unable to find -the requested command), they return \fBTCL_ERROR\fR with an -appropriate message left in the interpreter's result. -.PP -\fBTcl_NRAddCallback\fR arranges to have a C function called when the -current trampoline-enabled command in the Tcl interpreter designated -by \fIinterp\fR returns. The \fIpostProcPtr\fR argument is a pointer -to the callback function, which must have arguments and return value -consistent with the \fBTcl_NRPostProc\fR data type: -.PP -.CS -typedef int -\fBTcl_NRPostProc\fR( - \fBClientData\fR \fIdata\fR[], - \fBTcl_Interp\fR *\fIinterp\fR, - int \fIresult\fR); -.CE -.PP -When the trampoline invokes the callback function, the \fIdata\fR -parameter will point to an array containing the four one-word -quantities that were passed to \fBTcl_NRAddCallback\fR in the -\fIdata0\fR through \fIdata3\fR parameters. The Tcl interpreter will -be designated by the \fIinterp\fR parameter, and the \fIresult\fR -parameter will contain the result (\fBTCL_OK\fR, \fBTCL_ERROR\fR, -\fBTCL_RETURN\fR, \fBTCL_BREAK\fR or \fBTCL_CONTINUE\fR) that was -returned by the command evaluation. The callback function is expected, -in turn, either to return a \fIresult\fR to control further evaluation. -.PP -Multiple \fBTcl_NRAddCallback\fR invocations may request multiple -callbacks, which may be to the same or different callback -functions. If multiple callbacks are requested, they are executed in -last-in, first-out order, that is, the most recently requested -callback is executed first. -.SH EXAMPLE -.PP -The usual pattern for Tcl commands that invoke other Tcl commands -is something like: -.PP -.CS -int \fITheCmdObjProc\fR( - \fBClientData\fR \fIclientData\fR, - \fBTcl_Interp\fR *\fIinterp\fR, - int \fIobjc\fR, - \fBTcl_Obj\fR *const \fIobjv\fR[]) -{ - int \fIresult\fR; - \fBTcl_Obj\fR *\fIobjPtr\fR; - \fI... preparation ...\fR - \fIresult\fR = \fBTcl_EvalObjEx\fR(\fIinterp\fR, \fIobjPtr\fR, 0); - \fI... postprocessing ...\fR - return \fIresult\fR; -} -\fBTcl_CreateObjCommand\fR(\fIinterp\fR, "theCommand", - \fITheCmdObjProc\fR, \fIclientData\fR, - \fITheCmdDeleteProc\fR); -.CE -.PP -To enable a command like this one for trampoline-based evaluation, -it must be split into three pieces: -.IP \(bu -A non-trampoline implementation, \fITheCmdNewObjProc\fR, -which will simply create a trampoline -and invoke the trampoline-based implementation. -.IP \(bu -A trampoline-enabled implementation, \fITheCmdNRObjProc\fR. This -function will perform the initialization, request that the trampoline -call the postprocessing routine after command evaluation, and finally, -request that the trampoline call the inner command. -.IP \(bu -A postprocessing routine, \fITheCmdPostProc\fR. This function will -perform the postprocessing formerly done after the return from the -inner command in \fITheCmdObjProc\fR. -.PP -The non-trampoline implementation is simple and stylized, containing -a single statement: -.PP -.CS -int -TheCmdNewObjProc - \fBClientData\fR \fIclientData\fR, - \fBTcl_Interp\fR *\fIinterp\fR, - int \fIobjc\fR, - \fBTcl_Obj\fR *const \fIobjv\fR[]) -{ - return \fBTcl_NRCallObjProc\fR(\fIinterp, name,\fR - \fITheCmdNRObjProc, clientData, objc, objv\fR); -} -.CE -.PP -The trampoline-enabled implementation requests postprocessing, -and returns to the trampoline requesting command evaluation. -.PP -.CS -int -TheCmdNRObjProc - \fBClientData\fR \fIclientData\fR, - \fBTcl_Interp\fR *\fIinterp\fR, - int \fIobjc\fR, - \fBTcl_Obj\fR *const \fIobjv\fR[]) -{ - \fI... preparation ...\fR - \fBTcl_NRAddCallback\fR(\fIinterp, TheCmdPostProc,\fR - \fIdata0, data1, data2, data3\fR); - /* \fIdata0 .. data3\fR are up to four one-word items - * to pass to the postprocessing procedure */ - return \fBTcl_NREvalObj\fR(\fIinterp, objPtr, 0\fR); -} -.CE -.PP -The postprocessing procedure does whatever the original command did -upon return from the inner evaluation. -.PP -.CS -int -TheCmdNRPostProc - \fBClientData\fR \fIdata\fR[], - \fBTcl_Interp\fR *\fIinterp\fR, - int \fRresult\fR -{ - /* \fIdata[0] .. data[4]\fR are the four words of data - * passed to \fBTcl_NREvalObj\fR */ - \fI... postprocessing ...\fR - return result; -} -.CE -.PP -If \fItheCommand\fR is a command that results in multiple commands or -scripts being evaluated, its postprocessing routine may schedule -additional postprocessing and then request another command evaluation -by means of \fBTcl_NREvalObj\fR or one of the other evaluation -routines. Looping and sequencing constructs may be implemented in this way. -.PP -Finally, to install a trampoline-enabled command in the interpreter, -\fBTcl_NRCreateCommand\fR is used in place of -\fBTcl_CreateObjCommand\fR. It accepts two command procedures instead -of one. The first is for use when no trampoline is yet on the stack, -and the second is for use when there is already a trampoline in place. -.PP -.CS -\fBTcl_NRCreateCommand\fR(\fIinterp\fR, "theCommand", - \fITheCmdObjProc\fR, \fITheCmdNRObjProc\fR, \fIclientData\fR, - \fITheCmdDeleteProc\fR); -.CE -.SH "SEE ALSO" -Tcl_CreateCommand(3), Tcl_CreateObjCommand(3), Tcl_EvalObjEx(3), Tcl_GetCommandFromObj(3) -.SH KEYWORDS -stackless, nonrecursive, execute, command, global, object, result, script -.SH COPYRIGHT -Copyright (c) 2008 by Kevin B. Kenny \ No newline at end of file +.\" +.\" Copyright (c) 2008 by Kevin B. Eknny. +.\" + +'\" See the file "license.terms" for information on usage and redistribution +'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. +'\" +'\" RCS: @(#) $Id: NRE.3,v 1.2 2008/12/15 23:42:01 patthoyts Exp $ +'\" +.so man.macros +.TH NRE 3 8.6 Tcl "Tcl Library Procedures" +.BS +.SH NAME +Tcl_NRCreateCommand, Tcl_NRCallObjProc, Tcl_NREvalObj, Tcl_NREvalObjv, Tcl_NRCmdSwap, Tcl_NRAddCallback \- Non-Recursive (stackless) evaluation of Tcl scripts. +.SH SYNOPSIS +.nf +\fB#include \fR +.sp +Tcl_Command +\fBTcl_NRCreateCommand\fR(\fIinterp, cmdName, proc, nreProc, clientData, deleteProc\fR) +.sp +int +\fBTcl_NRCallObjProc\fR(\fIinterp, nreProc, clientData, objc, objv\fR) +.sp +int +\fBTcl_NREvalObj\fR(\fIinterp, objPtr, flags\fR) +.sp +int +\fBTcl_NREvalObjv\fR(\fIinterp, objc, objv, flags\fR) +.sp +int +\fBTcl_NRCmdSwap\fR(\fIinterp, cmd, objc, objv, flags\fR) +.sp +void +\fBTcl_NRAddCallback\fR(\fIinterp, postProcPtr, data0, data1, data2, data3\fR) +.fi +.SH ARGUMENTS +.AS Tcl_CmdDeleteProc *postProcPtr in +.AP Tcl_Interp *interp in +Interpreter in which to create or evaluate a command. +.AP char *cmdName in +Name of a new command to create. +.AP Tcl_ObjCmdProc *proc in +Implementation of a command that will be called whenever \fIcmdName\fR +is invoked as a command in the unoptimized way. +.AP Tcl_ObjCmdProc *nreProc in +Implementation of a command that will be called whenever \fIcmdName\fR +is invoked and requested to conserve the C stack. +.AP ClientData clientData in +Arbitrary one-word value that will be passed to \fIproc\fR, \fInreProc\fR, +\fIdeleteProc\fR and \fIobjProc\fR. +.AP Tcl_CmdDeleteProc *deleteProc in/out +Procedure to call before \fIcmdName\fR is deleted from the interpreter. +This procedure allows for command-specific cleanup. If \fIdeletProc\fR +is \fBNULL\fR, then no procedure is called before the command is deleted. +.AP int objc in +Count of parameters provided to the implementation of a command. +.AP Tcl_Obj **objv in +Pointer to an array of Tcl objects. Each object holds the value of a +single word in the command to execute. +.AP Tcl_Obj *objPtr in +Pointer to a Tcl_Obj whose value is a script to execute. +.AP int flags in +ORed combination of flag bits that specify additional options. +\fBTCL_EVAL_GLOBAL\fR is the only flag that is currently supported. +.\" TODO: This is a lie. But kbk didn't grasp TCL_EVAL_INVOKE and +.\" TCL_EVAL_NOERR well enough to document them. +.AP Tcl_Command cmd in +.AP Tcl_NRPostProc *postProcPtr in +Pointer to a function that will be invoked when the command currently +executing in the interpreter designated by \fIinterp\fR completes. +.AP ClientData data0 in +.AP ClientData data1 in +.AP ClientData data2 in +.AP ClientData data3 in +\fIdata0\fR through \fIdata3\fR are four one-word values that will be passed +to the function designated by \fIpostProcPtr\fR when it is invoked. +.BE +.SH DESCRIPTION +.PP +This series of C functions provides an interface whereby commands that +are implemented in C can be evaluated, and invoke Tcl commands scripts +and scripts, without consuming space on the C stack. The non-recursive +evaluation is done by installing a \fItrampoline\fR, a small piece of +code that invokes a command or script, and then executes a series of +callbacks when the command or script returns. +.PP +The \fBTcl_NRCreateCommand\fR function creates a Tcl command in the +interpreter designated by \fIinterp\fR that is prepared to handle +nonrecursive evaluation with a trampoline. The \fIcmdName\fR argument +gives the name of the new command. If \fIcmdName\fR contains any +namespace qualifiers, then the new command is added to the specified +namespace; otherwise, it is added to the global namespace. \fIproc\fR +gives the procedure that will be called when the interpreter wishes to +evaluate the command in an unoptimized manner, and \fInreProc\fR is +the procedure that will be called when the interpreter wishes to +evaluate the command using a trampoline. \fIdeleteProc\fR is a +function that will be called before the command is deleted from the +interpreter. When any of the three functions is invoked, it is passed +the \fIclientData\fR parameter. +.PP +\fBTcl_NRCreateCommand\fR deletes any existing command +\fIname\fR already associated with the interpreter +(however see below for an exception where the existing command +is not deleted). +It returns a token that may be used to refer +to the command in subsequent calls to \fBTcl_GetCommandName\fR. +If \fBTcl_NRCreateCommand\fR is called for an interpreter that is in +the process of being deleted, then it does not create a new command, +does not delete any existing command of the same name, and returns NULL. +.PP +The \fIproc\fR and \fInreProc\fR function are expected to conform to +all the rules set forth for the \fIproc\fR argument to +\fBTcl_CreateObjCommand\fR(3) (\Iq.v.\fR). +.PP +When a command that is written to cope with evaluation via trampoline +is invoked without a trampoline on the stack, it will usually respond +to the invocation by creating a trampoline and calling the +trampoline-enabled implementation of the same command. This call is done by +means of \fBTcl_NRCallObjProc\fR. In the call to +\fBTcl_NRCallObjProc\fR, the \fIinterp\fR, \fIclientData\fR, +\fIobjc\fR and \fIobjv\fR parameters should be the same ones that were +passed to \fIproc\fR. The \fInreProc\fR parameter should designate the +trampoline-enabled implementation of the command. +.PP +\fBTcl_NREvalObj\fR arranges for the script contained in \fIobjPtr\fR +to be evaluated in the interpreter designated by \fIinterp\fR after +the current command (which must be trampoline-enabled) returns. It is +the method by which a command may invoke a script without consuming +space on the C stack. Similarly, \fBTcl_NREvalObjv\fR arranges to +invoke a single Tcl command whose words have already been separated +and substituted. The \fIobjc\fR and \fIobjv\fR parameters give the +words of the command to be evaluated when execution reaches the +trampoline. +.PP +\fBTcl_NRCmdSwap allows for trampoline evaluation of a command whose +resolution is already known. The \fIcmd\fR parameter gives a +\fBTcl_Command\fR object (returned from \fBTcl_CreateObjCmd\fR or +\fBTcl_GetCommandFromObj\fR) identifying the command to be invoked in +the trampoline; this command must match the word in \fIobjv[0]\fR. +The remaining arguments are as for \fBTcl_NREvalObj\fR. +.PP +\fBTcl_NREvalObj\fR, \fBTcl_NREvalObjv\fR and \fBTcl_NRCmdSwap\fR +all accept a \fIflags\fR parameter, which is an OR-ed-together set of +bits to control evaluation. At the present time, the only flag +available to callers is \fBTCL_EVAL_GLOBAL\fR. +.\" TODO: Again, this is a lie. Do we want to explain TCL_EVAL_INVOKE +.\" and TCL_EVAL_NOERR? +If the \fBTCL_EVAL_GLOBAL\fR flag is set, the script or command is +evaluated in the global namespace. If it is not set, it is evaluated +in the current namespace. +.PP +All three of the routines return \fBTCL_OK\fR if command invocation +has been scheduled successfully. If for any reason command invocation +cannot be scheduled (for example, if the interpreter is unable to find +the requested command), they return \fBTCL_ERROR\fR with an +appropriate message left in the interpreter's result. +.PP +\fBTcl_NRAddCallback\fR arranges to have a C function called when the +current trampoline-enabled command in the Tcl interpreter designated +by \fIinterp\fR returns. The \fIpostProcPtr\fR argument is a pointer +to the callback function, which must have arguments and return value +consistent with the \fBTcl_NRPostProc\fR data type: +.PP +.CS +typedef int +\fBTcl_NRPostProc\fR( + \fBClientData\fR \fIdata\fR[], + \fBTcl_Interp\fR *\fIinterp\fR, + int \fIresult\fR); +.CE +.PP +When the trampoline invokes the callback function, the \fIdata\fR +parameter will point to an array containing the four one-word +quantities that were passed to \fBTcl_NRAddCallback\fR in the +\fIdata0\fR through \fIdata3\fR parameters. The Tcl interpreter will +be designated by the \fIinterp\fR parameter, and the \fIresult\fR +parameter will contain the result (\fBTCL_OK\fR, \fBTCL_ERROR\fR, +\fBTCL_RETURN\fR, \fBTCL_BREAK\fR or \fBTCL_CONTINUE\fR) that was +returned by the command evaluation. The callback function is expected, +in turn, either to return a \fIresult\fR to control further evaluation. +.PP +Multiple \fBTcl_NRAddCallback\fR invocations may request multiple +callbacks, which may be to the same or different callback +functions. If multiple callbacks are requested, they are executed in +last-in, first-out order, that is, the most recently requested +callback is executed first. +.SH EXAMPLE +.PP +The usual pattern for Tcl commands that invoke other Tcl commands +is something like: +.PP +.CS +int \fITheCmdObjProc\fR( + \fBClientData\fR \fIclientData\fR, + \fBTcl_Interp\fR *\fIinterp\fR, + int \fIobjc\fR, + \fBTcl_Obj\fR *const \fIobjv\fR[]) +{ + int \fIresult\fR; + \fBTcl_Obj\fR *\fIobjPtr\fR; + \fI... preparation ...\fR + \fIresult\fR = \fBTcl_EvalObjEx\fR(\fIinterp\fR, \fIobjPtr\fR, 0); + \fI... postprocessing ...\fR + return \fIresult\fR; +} +\fBTcl_CreateObjCommand\fR(\fIinterp\fR, "theCommand", + \fITheCmdObjProc\fR, \fIclientData\fR, + \fITheCmdDeleteProc\fR); +.CE +.PP +To enable a command like this one for trampoline-based evaluation, +it must be split into three pieces: +.IP \(bu +A non-trampoline implementation, \fITheCmdNewObjProc\fR, +which will simply create a trampoline +and invoke the trampoline-based implementation. +.IP \(bu +A trampoline-enabled implementation, \fITheCmdNRObjProc\fR. This +function will perform the initialization, request that the trampoline +call the postprocessing routine after command evaluation, and finally, +request that the trampoline call the inner command. +.IP \(bu +A postprocessing routine, \fITheCmdPostProc\fR. This function will +perform the postprocessing formerly done after the return from the +inner command in \fITheCmdObjProc\fR. +.PP +The non-trampoline implementation is simple and stylized, containing +a single statement: +.PP +.CS +int +TheCmdNewObjProc + \fBClientData\fR \fIclientData\fR, + \fBTcl_Interp\fR *\fIinterp\fR, + int \fIobjc\fR, + \fBTcl_Obj\fR *const \fIobjv\fR[]) +{ + return \fBTcl_NRCallObjProc\fR(\fIinterp, name,\fR + \fITheCmdNRObjProc, clientData, objc, objv\fR); +} +.CE +.PP +The trampoline-enabled implementation requests postprocessing, +and returns to the trampoline requesting command evaluation. +.PP +.CS +int +TheCmdNRObjProc + \fBClientData\fR \fIclientData\fR, + \fBTcl_Interp\fR *\fIinterp\fR, + int \fIobjc\fR, + \fBTcl_Obj\fR *const \fIobjv\fR[]) +{ + \fI... preparation ...\fR + \fBTcl_NRAddCallback\fR(\fIinterp, TheCmdPostProc,\fR + \fIdata0, data1, data2, data3\fR); + /* \fIdata0 .. data3\fR are up to four one-word items + * to pass to the postprocessing procedure */ + return \fBTcl_NREvalObj\fR(\fIinterp, objPtr, 0\fR); +} +.CE +.PP +The postprocessing procedure does whatever the original command did +upon return from the inner evaluation. +.PP +.CS +int +TheCmdNRPostProc + \fBClientData\fR \fIdata\fR[], + \fBTcl_Interp\fR *\fIinterp\fR, + int \fRresult\fR +{ + /* \fIdata[0] .. data[4]\fR are the four words of data + * passed to \fBTcl_NREvalObj\fR */ + \fI... postprocessing ...\fR + return result; +} +.CE +.PP +If \fItheCommand\fR is a command that results in multiple commands or +scripts being evaluated, its postprocessing routine may schedule +additional postprocessing and then request another command evaluation +by means of \fBTcl_NREvalObj\fR or one of the other evaluation +routines. Looping and sequencing constructs may be implemented in this way. +.PP +Finally, to install a trampoline-enabled command in the interpreter, +\fBTcl_NRCreateCommand\fR is used in place of +\fBTcl_CreateObjCommand\fR. It accepts two command procedures instead +of one. The first is for use when no trampoline is yet on the stack, +and the second is for use when there is already a trampoline in place. +.PP +.CS +\fBTcl_NRCreateCommand\fR(\fIinterp\fR, "theCommand", + \fITheCmdObjProc\fR, \fITheCmdNRObjProc\fR, \fIclientData\fR, + \fITheCmdDeleteProc\fR); +.CE +.SH "SEE ALSO" +Tcl_CreateCommand(3), Tcl_CreateObjCommand(3), Tcl_EvalObjEx(3), Tcl_GetCommandFromObj(3) +.SH KEYWORDS +stackless, nonrecursive, execute, command, global, object, result, script +.SH COPYRIGHT +Copyright (c) 2008 by Kevin B. Kenny -- cgit v0.12