本文介绍了如何使tokinezer检测空白空间，同时使用strtok（）的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在设计一个c ++程序，在程序中的某个地方，我需要检测是否有一个空白（空令牌）使用的令牌使用知道例如。
I am designing a c++ program, somewhere in the program i need to detect if there is a blank(empty token) next to the token used know eg.
if(token1==start)
{
token2=strtok(NULL," ");
if(token2==NULL)
{LCCTR=0;}
else
{LCCTR=atoi(token2);}
所以在以前的peice token1指向开始，我想检查是否有开始旁边的数字，所以我使用 token2 = strtok（NULL，）指向下一个令牌，但不幸的是strtok函数不能检测空格，所以它在运行时给我一个错误INVALID NULL POINTER修复它或有另一个函数用于检测空格。
so in the previous peice token1 is pointing to start , and i want to check if there is anumber next to the start , so I used token2=strtok(NULL," ") to point to the next token but unfortunattly the strtok function cannot detect empty spaces so it gives me an error at run time"INVALID NULL POINTER" how can i fix it or is there another function to use to detect empty spaces
#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;
}
推荐答案
很难说什么确切的问题是。一个通用的答案如下。
Without seeing your actual code it's hard to say what the exact problem is. A generic answer follows.
strtok 你不能只是在 NULL 上调用它。
strtok is stateful internally. You're can't just willy-nilly call it on on NULL.
您可以有一个传递，将您的字符串标记化，并将返回的标记收集到数组或向量中。首先调用 start ，后续调用（直到 strtok 返回 NULL ）on NULL 。你可以很容易地弄清楚什么是什么。
You could have a pass that tokenizes your string and gathers the returned tokens into an array or vector. First call on start, subsequent calls (until strtok returns NULL) on NULL. You can then easily figure out what's what.
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