Question

I have an output evbuffer that I want to populate with the following data:

HTTP/1.1 200 OK
Date: Tue, 06 Dec 2011 10:35:08 GMT
Server: Apache/2.2.14 (Ubuntu)
X-Powered-By: PHP/5.3.2-1ubuntu4.9
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 48
Content-Type: text/html

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                          �4�@�

I was using evbuffer_add_printf(...),

I have the following C callback function:

static void echo_read_cb(struct bufferevent *bev, void *ctx){
    /* This callback is invoked when there is data to read on bev. */
    struct evbuffer *input = bufferevent_get_input(bev);
    struct evbuffer *output = bufferevent_get_output(bev);

    ...
    char* response=NULL;
    response=applyGetReq(url,data,len);

    int contLen=0;
    contLen=getContentLength(response);

    char* binData=strstr(response,"\r\n\r\n");
    binData=binData+strlen("\r\n\r\n");
    fwrite(binData,sizeof(char),contLen,stdout);
    printf("\n");

    evbuffer_add_printf(output,"%s",binData);   //I want to print binData as binary, not printf!!!
}

So I have the binary data pointer (binData) and I have a length (contLen), how do I print this to the output buffer?

Many thanks in advance

Answer 1

You can’t add binary data in safe way using evbuffer_add_printf. Try evbuffer_add function:

int
evbuffer_add(struct evbuffer *buf, const void *data, size_t datlen)
{
    size_t need = buf->misalign + buf->off + datlen;
    size_t oldoff = buf->off;

    if (buf->totallen < need) {
            if (evbuffer_expand(buf, datlen) == -1)
                    return (-1);
    }

    memcpy(buf->buffer + buf->off, data, datlen);
    buf->off += datlen;

    if (datlen && buf->cb != NULL)
            (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);

    return (0);
}

Can’t find good documentation, the best I’ve seen except for source code is:

http://transmission.sourcearchive.com/documentation/1.75/event_8h_b652a2f82d23509713258a6e44697164.html#b652a2f82d23509713258a6e44697164

 int evbuffer_add   (   struct evbuffer *   ,
    const void *    ,
    size_t           
)           

Append data to the end of an evbuffer.

Parameters:

    buf     the event buffer to be appended to
    data    pointer to the beginning of the data buffer
    datlen  the number of bytes to be copied from the data buffer