c++ - "Failed writing body"CURLOPT_WRITEDATA

Question

下面的代码是使用 wsdl 从服务器获取响应，这里的问题是 curl 返回响应但无法打印它。

错误:

写入正文失败写入数据失败

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

size_t write_data(void *ptr, size_t size, size_t count, void *stream)
{
      /* ptr - your string variable.
      stream - data chuck you received */

     printf("%.*s", size, (char*)stream);
}


int main()
{
    int res=0,i=0;
    char buffer[4098]="",buff[128]="",buf[256]="",buf7[30]="",buf6[30]="",buf5[30]="";
    char machineid[]="SUBANI";
    char filename1[50]="";
    int refno=0,paymode=0,taxtype=0;
    FILE *fbc;

    memset(filename1,0,sizeof(filename1));
    sprintf(filename1,"/mnt/jffs2/Response_Details1.xml");
    lk_dispclr();
    lk_disptext(1,0,(unsigned char *)"Sending Request",0);
    lk_disptext(2,0,(unsigned char *)"Please Wait",0);
    memset(buffer,0,sizeof(buffer));

    sprintf(buffer,"<?xml version=\"1.0\" encoding=\"utf-8\"?>\
                        <soap:Envelope xmlns:soap=\"http://www.w3.org/2003/05/soap-envelope\" xmlns:log=\"http://wsdlclassess.application.sims.test.com\">\
                        <soap:Header>\
                        </soap:Header>\
                        <soap:Body>\
                        <log:loginMethod>\
                        <log:loginid>%s</log:loginid>\
                        <log:password>%s</log:password>\
                        </log:loginMethod>\
                        </soap:Body>\
                        </soap:Envelope>","raja","test");


    res=GET_FILE1(buffer,filename1);


    return 0;
}


int GET_FILE1(char *buffer,char *filename)
{
    CURL *curl;
    CURLcode res;
    struct curl_slist *headers = NULL;
    FILE *out_fd = (FILE *) 0;
    char errorbuf[300] = "",tmpbuff[128]="";
    char errmsg[256];
    int Timeout=120;   //Default timeout is = 2 mins
    int buffer_size = 0;
    char urlbuff[256]="";
    char mstr[10240];

    memset(urlbuff,0,sizeof(urlbuff));
        memset(tmpbuff,0,sizeof(tmpbuff));
    buffer_size = strlen(buffer);
         strcpy(tmpbuff,"http://10.10.1.111:8081/test_server/services/application?wsdl");
             tmpbuff[strlen(tmpbuff)]='\0';
    curl = curl_easy_init();
    if(curl)
    {
        out_fd = fopen (filename, "w");
        curl_easy_setopt(curl, CURLOPT_FILE, out_fd);
        printf("%s:Sign-In Request\n", __func__);
        headers = curl_slist_append(headers, "Content-type:application/soap+xml; charset=utf-8; action=\"http://wsdlclassess.application.sims.test.com/loginMethod\"");

        curl_easy_setopt(curl, CURLOPT_URL, tmpbuff);
        curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0);
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);

        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);

    curl_easy_setopt(curl, CURLOPT_WRITEDATA, mstr);


        curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, buffer_size);
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, buffer);

        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
        curl_easy_setopt(curl, CURLOPT_TIMEOUT, Timeout);
        curl_easy_setopt(curl, CURLOPT_ERRORBUFFER,errmsg);

        printf("The Server%s:Performing Transaction.....\n",__func__);
        res = curl_easy_perform(curl);
        printf("res=after culreasey perform%d\n",res);
        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
        printf("\nerrorbuf:%s\n",errmsg);
        fclose(out_fd);
        if(CURLE_OK != res)
        {
            puts("error occured is\n" );
            //ppp_close();
            return -1;
        }
    }

    return 0;
}

Answer 1

错误是您没有从函数返回正确的值，实际上您没有返回任何东西。

此外，提供给函数的数据实际上是第一个 ptr 参数。

---

我同意 documentation不是很清楚，但它说:

The size of the data pointed to by ptr is size multiplied with nmemb, it will not be zero terminated.

上面一行(强调我的)告诉您数据在 ptr 中，这是文档中提供的函数声明中的第一个参数。

文档还指出:

Return the number of bytes actually taken care of. If that amount differs from the amount passed to your function, it'll signal an error to the library. This will abort the transfer and return CURLE_WRITE_ERROR.

您没有从函数返回值，因此您有未定义的行为，返回一个看似随机的值导致整个操作失败。要解决此问题，您应该返回 size * count。

您还使用 size 来打印字符串，这是所用基础类型的大小(可能是 1)，您的 count 变量是 CURL 读取的字符数。要完全工作，而不调用更多未定义的行为(因为数据未终止)，您应该像这样调用 printf:

printf("%*.*s", size * count, size * count, ptr);