C查询字符串解析 [英] C query string parsing

问题描述

我有以下查询字符串

address=1234&port=1234&username=1234&password=1234&gamename=1234&square=1234&LOGIN=LOGIN

我正在尝试将其解析为不同的变量:地址，端口，用户名，密码，游戏名，方块和命令(将保留LOGIN)

I am trying to parse it into different variables: address,port,username,password,gamename,square and command (which would hold LOGIN)

我当时正在考虑使用strtok，但我认为它不会起作用.如何解析字符串以捕获变量?

I was thinking of using strtok but I don't think it would work. How can I parse the string to capture the variables ?

PS-部分字段可能为空-未提供游戏名称或正方形

P.S - some of the fields might be empty - no gamename provided or square

推荐答案

在解析可能在定界符之间包含空字段的字符串时，不能使用strtok，因为strtok将把任意数量的顺序定界符视为一个定界符.

When parsing a sting that may contain an empty-field between delimiters, strtok cannot be used, because strtok will treat any number of sequential delimiters as a single delimiter.

因此，在您的情况下，如果 variable = values 字段在'&'分隔符之间也可能包含空字段，则必须使用strsep或其他功能，例如strcspn ，strpbrk或简单地strchr以及几个指针可以沿着字符串向下移动.

So in your case, if the variable=values fields may also contain an empty-field between the '&' delimiters, you must use strsep, or other functions such as strcspn, strpbrk or simply strchr and a couple of pointers to work your way down the string.

strsep函数是BSD函数，可能不包含在您的C库中. GNU包含了strsep，它被设想为替代strtok，只是因为strtok无法处理空字段.

The strsep function is a BSD function and may not be included with your C library. GNU includes strsep and it was envisioned as a replacement for strtok simply because strtok cannot handle empty-fields.

(如果没有strsep可用，则只需保留 start 和 end 指针，并使用strchr之类的函数来定位每个指针'&'的出现，将 end 指针设置为定界符之前的一个，然后从 start 和<之间的字符获取 var = value 信息. em> end 指针，然后将两者都更新为指向定界符后的一个并重复.)

(If you do not have strsep available, you will simply need to keep a start and end pointer and use a function like strchr to locate each occurrence of '&' setting the end pointer to one before the delimiter and then obtaining the var=value information from the characters between start and end pointer, then updating both to point one past the delimiter and repeating.)

在这里，您可以将strsep与"&\n"分隔符一起使用，以定位每个'&'(假定包含'\n'字符，则假定是从面向 line _ 的文件中读取该行的. >输入功能，例如fgets或POSIX getline).然后，您可以简单地调用strtok，使用"="作为分隔符，从strsep返回的每个令牌中解析 var = value 文本('\n'已从最后一个令牌中删除用strsep解析时)

Here, you can use strsep with a delimiter of "&\n" to locate each '&' (the '\n' char included presuming the line was read from a file with a line-oriented input function such as fgets or POSIX getline). You can then simply call strtok to parse the var=value text from each token returned by strsep using "=" as the delimiter (the '\n' having already been removed from the last token when parsing with strsep)

在"...gamename=1234&&square=1234..."之间插入用于处理的特定空白字段的示例如下:

An example inserting a specific empty-field for handling between "...gamename=1234&&square=1234...", could be as follows:

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

int main (void) {

    char array[] =  "address=1234&port=1234&username=1234&password=1234"
                    "&gamename=1234&&square=1234&LOGIN=LOGIN",
        *query = strdup (array),  /* duplicate array, &array is not char** */
        *tokens = query,
        *p = query;

    while ((p = strsep (&tokens, "&\n"))) {
        char *var = strtok (p, "="),
             *val = NULL;
        if (var && (val = strtok (NULL, "=")))
            printf ("%-8s    %s\n", var, val);
        else
            fputs ("<empty field>\n", stderr);
    }

    free (query);
}

(注意: strsep将char**参数作为其第一个参数，并将修改该参数以使其指向一个超出定界符的位置，因此您必须保留对原始内容开头的引用分配的字符串(上面的query).

(note: strsep takes a char** parameter as its first argument and will modify the argument to point one past the delimiter, so you must preserve a reference to the start of the original allocated string (query above)).

使用/输出示例

$ ./bin/strsep_query
address     1234
port        1234
username    1234
password    1234
gamename    1234
<empty field>
square      1234
LOGIN       LOGIN

(注意:已将"1234"转换为数值)

仔细检查一下，如果还有其他问题，请告诉我.

Look things over and let me know if you have further questions.

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