我正在设计一个c ++程序，在程序的某个地方，我需要检测所用的令牌旁边是否有空白（空标记），例如。
if(token1==start)
{
token2=strtok(NULL," ");
if(token2==NULL)
{LCCTR=0;}
else
{LCCTR=atoi(token2);}
所以在之前的peice中，token1指向start，我想检查开头旁边是否有数字，所以我使用token2=strtok(NULL," ")指向下一个令牌，但不幸的是strtok函数无法检测到空空格所以它在运行时给出了一个错误“INVALID NULL POINTER”我该如何修复它还是有另一个函数用来检测空格
#include <iostream>
#include<string>
#include<map>
#include<iomanip>
#include<fstream>
#include<ctype.h>
using namespace std;
const int MAX=300;
int LCCTR;
int START(char* token1);
char* PASS1(char*token1);
void tokinizer()
{
ifstream in;
ofstream out;
char oneline[MAX];
in.open("infile.txt");
out.open("outfile.txt");
if(in.is_open())
{
char *token1;
in.getline(oneline,MAX);
token1 = strtok(oneline," \t");
START (token1);
//cout<<'\t';
while(token1!=NULL)
{
//PASS1(token1);
//cout<<token1<<" ";
token1=strtok(NULL," \t");
if(NULL==token1)
{//cout<<endl;
//cout<<LCCTR<<'\t';
in.getline(oneline,MAX);
token1 = strtok(oneline," \t");
}
}
}
in.close();
out.close();
}
int START(char* token1)
{
string start("START");
char*token2;
if(token1 != start)
{LCCTR=0;}
else if(token1==start)
{
token2=strchr(token1+2,' ');
cout<<token2;
if(token2==NULL)
{LCCTR=0;}
else
{LCCTR=atoi(token2);
if(atoi(token2)>9999||atoi(token2)<0){cout<<"IVALID STARTING ADDRESS"<<endl;exit(1);}
}
}
return LCCTR;
}
char* PASS1 (char*token1)
{
map<string,int> operations;
map<string,int>symtable;
map<string,int>::iterator it;
pair<map<string,int>::iterator,bool> ret;
char*token3=NULL;
char*token2=NULL;
string test;
string comp(" ");
string start("START");
string word("WORD");
string byte("BYTE");
string resb("RESB");
string resw("RESW");
string end("END");
operations["ADD"] = 18;
operations["AND"] = 40;
operations["COMP"] = 28;
operations["DIV"] = 24;
operations["J"] = 0X3c;
operations["JEQ"] =30;
operations["JGT"] =34;
operations["JLT"] =38;
operations["JSUB"] =48;
operations["LDA"] =00;
operations["LDCH"] =50;
operations["LDL"] =55;
operations["LDX"] =04;
operations["MUL"] =20;
operations["OR"] =44;
operations["RD"] =0xd8;
operations["RSUB"] =0x4c;
operations["STA"] =0x0c;
operations["STCH"] =54;
operations["STL"] =14;
operations["STSW"] =0xe8;
operations["STX"] =10;
operations["SUB"] =0x1c;
operations["TD"] =0xe0;
operations["TIX"] =0x2c;
operations["WD"] =0xdc;
if(operations.find("ADD")->first==token1)
{ token2=strtok(NULL," ");
//test=token2;
cout<<token2;
//if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
//else{LCCTR=LCCTR+3;}
}
/*else if(operations.find("AND")->first==token1)
{ token2=strtok(NULL," ");
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("COMP")->first==token1)
{ token2=token1+5;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("DIV")->first==token1)
{ token2=token1+4;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("J")->first==token1)
{ token2=token1+2;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("JEQ")->first==token1)
{ token2=token1+5;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("JGT")->first==token1)
{ token2=strtok(NULL," ");
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("JLT")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("JSUB")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("LDA")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("LDCH")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("LDL")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("LDX")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("MUL")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("OR")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("RD")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("RSUB")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("STA")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("STCH")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("STL")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("STSW")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("STX")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("SUB")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("TD")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("TIX")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}
else if(operations.find("WD")->first==token1)
{ token2=token1+6;
test=token2;
if(test.empty()){cout<<"MISSING OPERAND"<<endl;exit(1);}
else{LCCTR=LCCTR+3;}
}*/
//else if(
if(word==token1)
{LCCTR=LCCTR+3;}
else if(byte==token1)
{string test;
token2=token1+7;
test=token2;
if(test[0]=='C')
{token3=token1+10;
test=token3;
if(test.length()>15)
{cout<<"ERROR"<<endl;
exit(1);}
}
else if(test[0]=='X')
{token3=token1+10;
test=token3;
if(test.length()>14)
{cout<<"ERROR"<<endl;
exit(1);}
}
LCCTR=LCCTR+test.length();
}
else if(resb==token1)
{token3=token1+5;
LCCTR=LCCTR+atoi(token3);}
else if(resw==token1)
{token3=token1+5;
LCCTR=LCCTR+3*atoi(token3);}
else if(end==token1)
{exit(1);}
/*else
{
test=token1;
int last=test.length();
if(token1==start||test[0]=='C'||test[0]=='X'||ispunct(test[last])||isdigit(test[0])||isdigit(test[1])||isdigit(test[2])||isdigit(test[3])){}
else {
token2=strtok(NULL," ");
//test=token2;
cout<<token2;
if(token2!=NULL)
{
symtable.insert( pair<string,int>(token1,LCCTR));
for(it=symtable.begin() ;it!=symtable.end() ;++it)
{/*cout<<"symbol: "<<it->first<<" LCCTR: "<<it->second<<endl;}
}
else{}
}
}*/
return token3;
}
int main()
{
tokinizer();
return 0;
}
答案 0 :(得分：1)
如果没有看到您的实际代码，很难说出确切的问题是什么。通用答案如下。
strtok内部是有状态的。你不能随便在NULL上打电话给它。
你可以有一个标记你的字符串的传递，并将返回的标记收集到一个数组或向量中。首先致电start，strtok后续电话（直到NULL返回NULL）。然后，您可以轻松找出什么是什么。