linux c curl 乱码

#include <stdio.h>
#include <curl/curl.h>

size_t write_callback(void *ptr, size_t size, size_t nmemb, void *userdata) {
    FILE *stream = (FILE *)userdata;
    if (stream) {
        fwrite(ptr, size, nmemb, stream);
    }
    return size * nmemb;
}

int main(void) {
    CURL *curl;
    FILE *fp;
    CURLcode res;

    curl_global_init(CURL_GLOBAL_DEFAULT);
    curl = curl_easy_init();
    if (curl) {
        fp = fopen("data.txt", "wb");
        curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_callback);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);

        // 设置期望的字符编码为UTF-8
        struct curl_slist *headers = NULL;
        headers = curl_slist_append(headers, "Accept-Charset: UTF-8");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        res = curl_easy_perform(curl);
        if (res != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        }

        curl_easy_cleanup(curl);
        fclose(fp);
    }
    curl_global_cleanup();
    return 0;
}

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

char *convert_encoding(const char *input, size_t input_len, const char *from_encoding, const char *to_encoding) {
    iconv_t cd = iconv_open(to_encoding, from_encoding);
    if (cd == (iconv_t)-1) {
        perror("iconv_open");
        return NULL;
    }

    size_t output_len = input_len * 4; // 足够大的缓冲区
    char *output = malloc(output_len);
    char *outptr = output;

    if (iconv(cd, (char **)&input, &input_len, &outptr, &output_len) == (size_t)-1) {
        perror("iconv");
        free(output);
        iconv_close(cd);
        return NULL;
    }

    iconv_close(cd);
    *outptr = '\0'; // 确保字符串以空字符结尾
    return output;
}

int main(void) {
    // 假设data.txt包含GBK编码的数据
    FILE *fp = fopen("data.txt", "rb");
    if (!fp) {
        perror("fopen");
        return 1;
    }

    fseek(fp, 0, SEEK_END);
    long file_size = ftell(fp);
    fseek(fp, 0, SEEK_SET);

    char *data = malloc(file_size + 1);
    fread(data, 1, file_size, fp);
    fclose(fp);

    char *utf8_data = convert_encoding(data, file_size, "GBK", "UTF-8");
    if (utf8_data) {
        printf("%s\n", utf8_data);
        free(utf8_data);
    }

    free(data);
    return 0;
}