Chunked responses in libevent2
- by Sri
Hi
I am trying to do a chunked response (of large files) in libevent this way::
evhttp_send_reply_start(request, HTTP_OK, "OK");
int fd = open("filename", O_RDONLY);
size_t fileSize = <get_file_size>;
struct evbuffer *databuff = NULL;
for (off_t offset = 0;offset < fileSize;)
{
databuff = evbuffer_new();
size_t bytesLeft = fileSize - offset;
size_t bytesToRead = bytesLeft > MAX_READ_SIZE ? MAX_READ_SIZE : bytesLeft;
evbuffer_add_file(databuff, fd, offset, bytesToRead);
offset += bytesToRead;
evhttp_send_reply_chunk(request, databuff); // send it
evbuffer_free(databuff); // destroy it
}
evhttp_send_reply_end(request);
fclose(fptr);
Problem is with this I have a feeling the add_file is asynchronous so the 3rd or so evhttp_send_reply_chunk gives me an error (or something similar):
[warn] evhttp_send_chain Closed(45): Bad file descriptor
I set MAX_READ_SIZE to be 8 to actually test out chunked transfer encoding.
I noticed there was a evhttp_request_set_chunked_cb (struct evhttp_request *, void(*cb)(struct evhttp_request *, void *)) method I could use but could not find any examples on how to use.
For instance, how could I pass an argument to the callback? The argument seems to be the same argument that was passed to the request handler which is not what I want, because I want to create an object that holds the file descriptor and the file offset I am sending out.
Appreciate all help.
Thanks in advance
Sri
