深入剖析NS2的框架代码.docx
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深入剖析NS2的框架代码
1. NS2的主函数main位于tclAppInit.cc文件中
int
main（intargc,char**argv
{
Tcl_Main（argc,argv,Tcl_AppInit;
return0; /*Neededonlytopreventcompilerwarning.*/
}
从这个main函数中我们可以看到：
整个NS2的框架其实完全包含在TCL_Main函数中。
2.Tcl_Main函数位于/generic/TclMain.c文件中，这个函数的代码如下：
（可能比较长）
void
Tcl_Main（argc,argv,appInitProc
intargc; /*Numberofarguments.*/
char**argv; /*Arrayofargumentstrings.*/
Tcl_AppInitProc*appInitProc;
/*Application-specificinitialization
*proceduretocallaftermost
*initializationbutbeforestartingto
*executecommands.*/
{
Tcl_Obj*resultPtr,*argvPtr,*commandPtr=NULL;
PromptTypeprompt=PROMPT_START;
intcode,length,tty,exitCode=0;
Tcl_ChannelinChannel,outChannel,errChannel;
Tcl_Interp*interp;
Tcl_DStringappName;
Tcl_Obj*objPtr;
Tcl_FindExecutable（argv[0]; //寻找可执行文件ns？
作用未知，参数的值为可执行文件ns对应的路径
interp=Tcl_CreateInterp（; //创建OTCL解释器
Tcl_InitMemory（interp; //配置解释器
/*
*Makecommand-lineargumentsavailableintheTclvariables"argc"
*and"argv".Ifthefirstargumentdoesn'tstartwitha"-"then
*stripitoffanduseitasthenameofascriptfiletoprocess.
*/
if（TclGetStartupScriptPath（==NULL{
if（（argc>1&&（argv[1][0]!
='-'{
TclSetStartupScriptFileName（argv[1];
argc--;
argv++;
}
}
if（TclGetStartupScriptPath（==NULL{
Tcl_ExternalToUtfDString（NULL,argv[0],-1,&appName;
}else{
TclSetStartupScriptFileName（Tcl_ExternalToUtfDString（NULL,
TclGetStartupScriptFileName（,-1,&appName;
}
Tcl_SetVar（interp,"argv0",Tcl_DStringValue（&appName,TCL_GLOBAL_ONLY;
Tcl_DStringFree（&appName;
argc--;
argv++;
objPtr=Tcl_NewIntObj（argc;
Tcl_IncrRefCount（objPtr;
Tcl_SetVar2Ex（interp,"argc",NULL,objPtr,TCL_GLOBAL_ONLY;
Tcl_DecrRefCount（objPtr;
argvPtr=Tcl_NewListObj（0,NULL;
while（argc--{
Tcl_DStringds;
Tcl_ExternalToUtfDString（NULL,*argv++,-1,&ds;
Tcl_ListObjAppendElement（NULL,argvPtr,Tcl_NewStringObj（
Tcl_DStringValue（&ds,Tcl_DStringLength（&ds;
Tcl_DStringFree（&ds;
}
Tcl_IncrRefCount（argvPtr;
Tcl_SetVar2Ex（interp,"argv",NULL,argvPtr,TCL_GLOBAL_ONLY;
Tcl_DecrRefCount（argvPtr;
/*
*Setthe"tcl_interactive"variable.
*/
tty=isatty（0;
Tcl_SetVar（interp,"tcl_interactive",
（（TclGetStartupScriptPath（==NULL&&tty?
"1":
"0",
TCL_GLOBAL_ONLY;
/*
*Invokeapplication-specificinitialization.
*/
Tcl_Preserve（（ClientDatainterp;
if（（*appInitProc（interp!
=TCL_OK{ //此处的appInitProc具体实现见于TclAppInit.cc,为了方便，将其代码展示如下：
********************************************************************************************************************************
int
Tcl_AppInit（Tcl_Interp*interp
{
#ifdefMEMDEBUG_SIMULATIONS
externMemTrace*globalMemTrace;
globalMemTrace=newMemTrace;
#endif
setup_floating_point_environment（;
if（Tcl_Init（interp==TCL_ERROR||
Otcl_Init（interp==TCL_ERROR
returnTCL_ERROR;
#ifdefHAVE_LIBTCLDBG
externintTcldbg_Init（Tcl_Interp*; //hackorama
if（Tcldbg_Init（interp==TCL_ERROR{
returnTCL_ERROR;
}
#endif
Tcl_SetVar（interp,"tcl_rcFileName","~/.ns.tcl",TCL_GLOBAL_ONLY;
Tcl:
:
init（interp,"ns";//Tcl:
init会调用到TclClass:
init，而后者完成的任务，主要是将通过调用依次调用所有在main函数前创建的全局TclClass静态实例的bind函数。
而bind函数只在祖先类TclClass中实现了（特殊的是PacketHeaderClass类，它有自己的实现，但也事先调用了TclClass类的实现，其子类亦无实现。
TclClass的bind函数所完成的任务便是根据所有静态实例存储的OTCL类名（定义时拟好的参数，创建相对应的OTCL类，并添加create-shadow和delete-shadow命令。
具体代码见TclClass:
:
bind（
init_misc（;
et_ns_ptypes.load（;
et_ns_lib.load（; //et_ns_lib是一个EmbeddedTcl类，它的私有成员constchar*code_在文件ns_tcl.cc中，被初始化为NS2所需要的所有OTCL类定义串联成的一个巨型字符串（这个字符串是在Makefile中通过将ns-lib.tcl中定义以及用source语句引用的其它tcl文件所对应的源文件全部拷贝并串联起来，生成后导入到ns_tcl.cc中的。
查看ns_tcl.cc的文件中的code_值，我们便可以知道NS2在初始化时建立的所有OTCL对象。
//et_ns_lib.load（其实现为：
/*voidEmbeddedTcl:
:
load（
{
Tcl:
:
instance（.evalc（code_;
}*/
//这个函数所完成的工作，便是将code_存储的所有NS相关的OTCL定义，用新建立起来的tcl环境对其进行解释，并建立相应的OTCL环境。
#ifdefTCL_TEST
if（Tcltest_Init（interp==TCL_ERROR{
returnTCL_ERROR;
}
Tcl_StaticPackage（interp,"Tcltest",Tcltest_Init,
（Tcl_PackageInitProc*NULL;
#endif/*TCL_TEST*/
returnTCL_OK;
}
********************************************************************************************************************************
errChannel=Tcl_GetStdChannel（TCL_STDERR;
if（errChannel{
Tcl_WriteChars（errChannel,
"application-specificinitializationfailed:
",-1;
Tcl_WriteObj（errChannel,Tcl_GetObjResult（interp;
Tcl_WriteChars（errChannel,"\n",1;
}
}
if（Tcl_InterpDeleted（interp{
gotodone;
}
/*
*Ifascriptfilewasspecifiedthenjustsourcethatfile
*andquit.
*/
if（TclGetStartupScriptPath（!
=NULL{
code=Tcl_FSEvalFile（interp,TclGetStartupScriptPath（;
if（code!
=TCL_OK{
errChannel=Tcl_GetStdChannel（TCL_STDERR;
if（errChannel{
/*
*ThefollowingstatementguaranteesthattheerrorInfo
*variableissetproperly.
*/
Tcl_AddErrorInfo（interp,"";
Tcl_WriteObj（errChannel,Tcl_GetVar2Ex（interp,"errorInfo",
NULL,TCL_GLOBAL_ONLY;
Tcl_WriteChars（errChannel,"\n",1;
}
exitCode=1;
}
gotodone;
}
/*
*We'rerunninginteractively.Sourceauser-specificstartup
*fileiftheapplicationspecifiedoneandifthefileexists.
*/
Tcl_SourceRCFile（interp;
/*
*Processcommandsfromstdinuntilthere'sanend-of-file.Note
*thatweneedtofetchthestandardchannelsagainafterevery
*eval,sincetheymayhavebeenchanged.
*/
commandPtr=Tcl_NewObj（;
Tcl_IncrRefCount（commandPtr;
/*
*Getanewvalueforttyifanyonewritesto:
:
tcl_interactive
*/
Tcl_LinkVar（interp,"tcl_interactive",（char*&tty,TCL_LINK_BOOLEAN;
inChannel=Tcl_GetStdChannel（TCL_STDIN;
outChannel=Tcl_GetStdChannel（TCL_STDOUT;
while（（inChannel!
=（Tcl_ChannelNULL&&!
Tcl_InterpDeleted（interp{
if（mainLoopProc==NULL{
if（tty{
Prompt（interp,&prompt;
if（Tcl_InterpDeleted（interp{
break;
}
inChannel=Tcl_GetStdChannel（TCL_STDIN;
if（inChannel==（Tcl_ChannelNULL{
break;
}
}
if（Tcl_IsShared（commandPtr{
Tcl_DecrRefCount（commandPtr;
commandPtr=Tcl_DuplicateObj（commandPtr;
Tcl_IncrRefCount（commandPtr;
}
length=Tcl_GetsObj（inChannel,commandPtr;
if（length<0{
if（Tcl_InputBlocked（inChannel{
/*
*Thiscanonlyhappenifstdinhasbeensetto
*non-blocking.Inthatcasecyclebackandtry
*again.Thissetsupatightpollingloop（since
*wehavenoeventlooprunning.Ifthiscauses
*badCPUhogging,wemighttrytogglingtheblocking
*onstdininstead.
*/
continue;
}
/*
*EitherEOF,oranerroronstdin;we'redone
*/
break;
}
/*
*AddthenewlineremovedbyTcl_GetsObjbacktothestring.
*/
if（Tcl_IsShared（commandPtr{
Tcl_DecrRefCount（commandPtr;
commandPtr=Tcl_DuplicateObj（commandPtr;
Tcl_IncrRefCount（commandPtr;
}
Tcl_AppendToObj（commandPtr,"\n",1;
if（!
TclObjCommandComplete（commandPtr{
prompt=PROMPT_CONTINUE;
continue;
}
prompt=PROMPT_START;
code=Tcl_RecordAndEvalObj（interp,commandPtr,TCL_EVAL_GLOBAL;
inChannel=Tcl_GetStdChannel（TCL_STDIN;
outChannel=Tcl_GetStdChannel（TCL_STDOUT;
errChannel=Tcl_GetStdChannel（TCL_STDERR;
Tcl_DecrRefCount（commandPtr;
commandPtr=Tcl_NewObj（;
Tcl_IncrRefCount（commandPtr;
if（code!
=TCL_OK{
if（errChannel{
Tcl_WriteObj（errChannel,Tcl_GetObjResult（interp;
Tcl_WriteChars（errChannel,"\n",1;
}
}elseif（tty{
resultPtr=Tcl_GetObjResult（interp;
Tcl_IncrRefCount（resultPtr;
Tcl_GetStringFromObj（resultPtr,&length;
if（（length>0&&outChannel{
Tcl_WriteObj（outChannel,resultPtr;
Tcl_WriteChars（outChannel,"\n",1;
}
Tcl_DecrRefCount（resultPtr;
}
}else{ /*（mainLoopProc!
=NULL*/
/*
*Ifamainloophasbeendefinedwhilerunninginteractively,
*wewanttostartafileeventbasedpromptbyestablishinga
*channelhandlerforstdin.
*/
InteractiveState*isPtr=NULL;
if（inChannel{
if（tty{
Prompt（interp,&prompt;
}
isPtr=（InteractiveState*
ckall
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