libcurl下载到内存(String方法)

libcurl的文档中有getinmemory.c这个例子，把下载的网页写入自己定义的一个memorystruct中，看了这个例子的做法，它需要自己照顾内存的开辟，特别是需要在curl_easy_perform的调用函数中释放已开辟的内存，很不利于函数的封装，而且应用于multihandle的时候，运行时会出莫名其妙的assert错误。因此改写了一下，将下载的内容放入stl的string中，这样根本不需要自己照顾内存的开辟和释放。源代码如下：

#include "curl.h"

using namespace std;
static char errorBuffer[CURL_ERROR_SIZE];
static int writer(char *, size_t, size_t, string *);
static bool init(CURL *&, char *,string *);

int main()
{
    CURL *conn = NULL;
    CURLcode code;
 string buffer;
 
    curl_global_init(CURL_GLOBAL_DEFAULT);
    char* url="http://cool.haxx.se/";
 if (!init(conn,url,&buffer ))
    {
        fprintf(stderr, "Connection initializion failed\n");
        exit(EXIT_FAILURE);
    }
    code = curl_easy_perform(conn);
   
    if (code != CURLE_OK)
    {
        fprintf(stderr, "Failed to get '%s' [%s]\n", url, errorBuffer);
        exit(EXIT_FAILURE);
    }
 curl_easy_cleanup(conn);
 printf("%s\n",buffer.c_str());
    return 0;
    
}

static bool init(CURL *&conn, char *url,string *p_buffer)
{
    CURLcode code;
    conn = curl_easy_init();
    if (conn == NULL)
    {
        fprintf(stderr, "Failed to create CURL connection\n");
        exit(EXIT_FAILURE);
    }
    code = curl_easy_setopt(conn, CURLOPT_ERRORBUFFER, errorBuffer);
    if (code != CURLE_OK)
    {
        fprintf(stderr, "Failed to set error buffer [%d]\n", code);
        return false;
    }
    code = curl_easy_setopt(conn, CURLOPT_URL, url);
    if (code != CURLE_OK)
    {
        fprintf(stderr, "Failed to set URL [%s]\n", errorBuffer);
        return false;
    }
    code = curl_easy_setopt(conn, CURLOPT_FOLLOWLOCATION, 1);
    if (code != CURLE_OK)
    {
        fprintf(stderr, "Failed to set redirect option [%s]\n", errorBuffer);
        return false;
    }
    code = curl_easy_setopt(conn, CURLOPT_WRITEFUNCTION, writer);
    if (code != CURLE_OK)
    {
        fprintf(stderr, "Failed to set writer [%s]\n", errorBuffer);
        return false;
    }
    code = curl_easy_setopt(conn, CURLOPT_WRITEDATA, p_buffer);
    if (code != CURLE_OK)
    {
        fprintf(stderr, "Failed to set write data [%s]\n", errorBuffer);
        return false;
    }
    return true;
}

static int writer(char *data, size_t size, size_t nmemb, string *writerData)
{
    unsigned long sizes = size * nmemb;
    if (writerData == NULL) return 0;
    writerData->append(data, sizes);
    return sizes;
}