c语言url编码怎么解码

c 语言 url 解码

问题：如何用 C 语言解码 URL 编码的字符串？

详细解答：

URL 编码是一种将特定字符转换为其 ASCII 代码的格式，以便通过网络安全传输。要解码 URL 编码的字符串，可以使用以下步骤：

1. 分配内存：为解码后的字符串分配足够的内存空间。
2. 逐个字符遍历：遍历 URL 编码的字符串，逐个字符处理。
3. 检查字符：对于每个字符，检查它是否为百分号 (%)。
4. 解码百分号编码：如果是百分号，则提取后面的两个字符并将其转换为十六进制数字。
5. 还原字符：将十六进制数字转换为 ASCII 字符，并将其添加到解码后的字符串中。
6. 忽略非 URL 编码的字符：对于非 URL 编码的字符（例如字母、数字和下划线），直接将其添加到解码后的字符串中。
7. 终止字符串：解码完成后，用 ‘\0’ 结尾符终止解码后的字符串。

示例代码：

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

char *url_decode(char *encoded_string) {
    char *decoded_string;
    int decoded_length = 0;

    for (int i = 0; encoded_string[i] != '
#include <stdio.h>
#include <stdlib.h>
char *url_decode(char *encoded_string) {
char *decoded_string;
int decoded_length = 0;
for (int i = 0; encoded_string[i] != '\0'; i++) {
if (encoded_string[i] == '%') {
char hex_di<a style="color:#f60; text-decoration:underline;" href="https://www.php.cn/zt/15841.html" target="_blank">git</a>s[3] = { encoded_string[i+1], encoded_string[i+2], '\0' };
int hex_value = strtol(hex_digits, NULL, 16);
decoded_string[decoded_length++] = hex_value;
i += 2;
} else {
decoded_string[decoded_length++] = encoded_string[i];
}
}
decoded_string[decoded_length] = '\0';
return decoded_string;
}
int main() {
char encoded_string[] = "%20This%20is%20a%20URL%20encoded%20string";
char *decoded_string = url_decode(encoded_string);
printf("Decoded string: %s\n", decoded_string);
free(decoded_string);
return 0;
}</stdlib.h></stdio.h>
'; i++) {
        if (encoded_string[i] == '%') {
            char hex_di<a style="color:#f60; text-decoration:underline;" href="https://www.php.cn/zt/15841.html" target="_blank">git</a>s[3] = { encoded_string[i+1], encoded_string[i+2], '
#include <stdio.h>
#include <stdlib.h>
char *url_decode(char *encoded_string) {
char *decoded_string;
int decoded_length = 0;
for (int i = 0; encoded_string[i] != '\0'; i++) {
if (encoded_string[i] == '%') {
char hex_di<a style="color:#f60; text-decoration:underline;" href="https://www.php.cn/zt/15841.html" target="_blank">git</a>s[3] = { encoded_string[i+1], encoded_string[i+2], '\0' };
int hex_value = strtol(hex_digits, NULL, 16);
decoded_string[decoded_length++] = hex_value;
i += 2;
} else {
decoded_string[decoded_length++] = encoded_string[i];
}
}
decoded_string[decoded_length] = '\0';
return decoded_string;
}
int main() {
char encoded_string[] = "%20This%20is%20a%20URL%20encoded%20string";
char *decoded_string = url_decode(encoded_string);
printf("Decoded string: %s\n", decoded_string);
free(decoded_string);
return 0;
}</stdlib.h></stdio.h>
' };
            int hex_value = strtol(hex_digits, NULL, 16);
            decoded_string[decoded_length++] = hex_value;
            i += 2;
        } else {
            decoded_string[decoded_length++] = encoded_string[i];
        }
    }

    decoded_string[decoded_length] = '
#include <stdio.h>
#include <stdlib.h>
char *url_decode(char *encoded_string) {
char *decoded_string;
int decoded_length = 0;
for (int i = 0; encoded_string[i] != '\0'; i++) {
if (encoded_string[i] == '%') {
char hex_di<a style="color:#f60; text-decoration:underline;" href="https://www.php.cn/zt/15841.html" target="_blank">git</a>s[3] = { encoded_string[i+1], encoded_string[i+2], '\0' };
int hex_value = strtol(hex_digits, NULL, 16);
decoded_string[decoded_length++] = hex_value;
i += 2;
} else {
decoded_string[decoded_length++] = encoded_string[i];
}
}
decoded_string[decoded_length] = '\0';
return decoded_string;
}
int main() {
char encoded_string[] = "%20This%20is%20a%20URL%20encoded%20string";
char *decoded_string = url_decode(encoded_string);
printf("Decoded string: %s\n", decoded_string);
free(decoded_string);
return 0;
}</stdlib.h></stdio.h>
';
    return decoded_string;
}

int main() {
    char encoded_string[] = "%20This%20is%20a%20URL%20encoded%20string";
    char *decoded_string = url_decode(encoded_string);
    printf("Decoded string: %s\n", decoded_string);
    free(decoded_string);
    return 0;
}</stdlib.h></stdio.h>

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