strtok（）在以后的调用中返回NULL，即使有更多的令牌要读取

Question

我的程序在调用strtok（NULL，“ \ r \ n”）;时遇到问题；即使仍有更多标记，在我进行函数调用后仍返回NULL。我已经研究了很长一段时间，无法弄清楚此函数调用会改变随后的strtok（）调用的行为。我将非常感谢任何能提供帮助的人。干杯。

主要功能：

int main() 
{ 
    char raw[] = "0 4 96 30\r\n3 4 64 60\r\n3 5 64 20\r\n3 2 32 40\r\n5 1 100 20\r\n20 3 4 30\r\n"; 

    char* line = strtok(raw, "\r\n");            //line == "0 4 96 30" OK
    line = strtok(NULL, "\r\n");                 //line == "3 4 64 60" OK
    line = strtok(NULL, "\r\n");                 //line == "3 5 64 20" OK
    struct Process current = parseProcess(line); //Now strtok calls after this will return NULL...
    line = strtok(NULL, "\r\n");                 //line == NULL (supposed to be "3 2 32 40")
    line = strtok(NULL, "\r\n");                 //line == NULL

    return 0; 
}   

使用的结构和功能：

#include <stdio.h> 
#include <stdlib.h>
#include <string.h> 

struct Process {
    long timeArrived;
    long processId;
    long memorySizeReq;
    long jobTime;
    long remainingTime;
};

//Rips values from the input and puts it into a struct
struct Process parseProcess(char* input){
    struct Process output;

    //Makes a back up as to not mutate input
    char* temp = malloc(strlen(input) * sizeof(char));
    strcpy(temp, input);
    char* token = strtok(temp, " ");

    //Fills out the fields of the parsed output
    for(int i=0; i<4; i++){
        switch(i){
            case 0:
                output.timeArrived = atoi(token);
                token = strtok(NULL, " ");
                break;
            case 1:
                output.processId = atoi(token);
                token = strtok(NULL, " ");
                break;
            case 2:
                output.memorySizeReq = atoi(token);
                token = strtok(NULL, " ");
                break;
            case 3:
                output.jobTime = atoi(token);
                output.remainingTime = atoi(token);
                token = strtok(NULL, " ");
                break;
        }
    }
    return output;
}

Answer 1

它可以，但是POSIX strtok_r在Windows中不起作用，但是您可以使用strtok_s来解决您的问题：

strtok_s

输出：

#include <stdio.h> 
#include <stdlib.h>
#include <string.h> 

struct Process {
    long timeArrived;
    long processId;
    long memorySizeReq;
    long jobTime;
    long remainingTime;
};

//Rips values from the input and puts it into a struct
struct Process parseProcess(char* input){
    struct Process output;
    char* strmax;
    //Makes a back up as to not mutate input
    char* temp = malloc(strlen(input) * sizeof(char));
    strcpy(temp, input);
    char* token = strtok_s(temp, " ", &strmax);

    //Fills out the fields of the parsed output
    for(int i=0; i<4; i++){
        switch(i){
            case 0:
                output.timeArrived = atoi(token);
                token = strtok_s(NULL, " ", &strmax);
                break;
            case 1:
                output.processId = atoi(token);
                token = strtok_s(NULL, " ", &strmax);
                break;
            case 2:
                output.memorySizeReq = atoi(token);
                token = strtok_s(NULL, " ", &strmax);
                break;
            case 3:
                output.jobTime = atoi(token);
                output.remainingTime = atoi(token);
                token = strtok_s(NULL, " ", &strmax);
                break;
        }
    }
    return output;
}

int main() 
{ 
    char raw[] = "0 4 96 30\r\n3 4 64 60\r\n3 5 64 20\r\n3 2 32 40\r\n5 1 100 20\r\n20 3 4 30\r\n"; 
    char* strmax;
    char* line = strtok_s(raw, "\r\n", &strmax);            //line == "0 4 96 30" OK
    printf("%s\n", raw); //test prints
    line = strtok_s(NULL, "\r\n", &strmax);                 //line == "3 4 64 60" OK
    printf("%s\n", line);
    line = strtok_s(NULL, "\r\n", &strmax);
    printf("%s\n", line);                 //line == "3 5 64 20" OK
    struct Process current = parseProcess(line); //Now strtok_s calls after, &strmax this will return NULL...
    line = strtok_s(NULL, "\r\n", &strmax);
    printf("%s\n", line);                 //line == NULL (supposed to be "3 2 32 40")
    line = strtok_s(NULL, "\r\n", &strmax);                 //line == NULL
    printf("%s\n", line);

    return 0; 
}