Callback for asynchronous continuation of read(). If |bytes_read| == 0 the
response will be considered complete. If |bytes_read| > 0 then read() will
be called again until the request is complete (based on either the result
or the expected content length). If |bytes_read| < 0 then the request will
fail and the |bytes_read| value will be treated as the error code.
Callback for asynchronous continuation of read(). If |bytes_read| == 0 the response will be considered complete. If |bytes_read| > 0 then read() will be called again until the request is complete (based on either the result or the expected content length). If |bytes_read| < 0 then the request will fail and the |bytes_read| value will be treated as the error code.