如何在流字符数组编辑元素 [英] How to edit an element in a streaming char array

问题描述

我有（用popen（），而不是文件的网络数据）都在为const char从与fgets进来记录*阵列格式。

I have records coming in from fgets (web data using popen(), not a file) that are in const char * array format.

const char * cstr = buff;

第3项是字符串，并且需要被移除或被改变到零。
我如何进入第3个元素一个const char *数组流增量为5？

The 3rd item is a string and needs to either be removed or changed to a zero. How do I access the 3rd element in a const char * array stream in increments of 5?

1
2
string
4
5
1
2
string
4
5

code：

while(fgets(buff, sizeof buff, fp) != NULL)
{
        const char * cstr2 = buff;
        for(int i = 0; i < 5; ++i){
                if(i == 3){
                        if (!strcmp(cstr2, "Buy\n")) {
                                printf("Found One!\n");
                                cstr2[2] = 0;
                        }
                        if (!strcmp(cstr2, "Sell\n")) {
                                printf("Found Two!\n");
                                cstr2[2] = 0;
                        }
                }
        }
}

期望的输出：

1
2
0
4
5
1
2
0
4
5

错误：
没有匹配和：
错误：只读位置'*（cstr2 + 2U）

error: no match and : error: assignment of read-only location '*(cstr2 + 2u)'

你如何正确地访问3元素在字符流字符数组？

How do you correctly access the 3rd element in a char streaming char array?

推荐答案

此溶液previously发表匿名：

This solution was previously posted by anonymous:

char* getmyData()
{
    char buff[BUFSIZ];
    FILE *fp = popen("php getMyorders.php 155", "r");
    if (fp == NULL) perror ("Error opening file");
    size_t size = 1000;
    char* data = (char*)malloc(size);
    char* ptr = data;
    std::string::size_type sz;
    int i=0;
    while(fgets(buff, sizeof(buff), fp) != NULL)
    {
            const char * cstr2 = buff;
            const char* test = ptr;
            //for(int i = 0; i < 5; ++i)
            {
                    if(i == 2){
                            if (!strcmp(cstr2, "Buy\n")) {
                                    printf("Found One!\n");
                                    strcpy(ptr,"0\n");
                                    //ptr+=2;
                            }
                            else
                            if (!strcmp(cstr2, "Sell\n")) {
                                    printf("Found Two!\n");
                                    strcpy(ptr,"0\n");
                                    //ptr+=2;
                            }
                            else
                            {
                                strcpy(ptr,cstr2);
                                ptr+=strlen(cstr2);
                            }
                    }
                    else
                    {
                        strcpy(ptr,cstr2);
                        ptr+=strlen(cstr2);
                    }

                    try
                    {
                        int nc = std::stod (test,&sz);
                        std::cout << "Test: " << 1+nc << "\n";
                    }
                    catch(...)
                    {
                    }

                    i++;
                    if (i==5)
                        i=0;


            }

            if (ptr-data+100>=size)
            {
                int ofs = ptr-data;
                size*=2;
                data = (char*)realloc(data,size);
                ptr = data+ofs;
            }
        }
    return data; // DONT FORGET TO call free() on it
}

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