Append a va_list formatted string to the end of an evbuffer.
@param buf the evbuffer that will be appended to
@param fmt a format string
@param ap a varargs va_list argument array that will be passed to vprintf(3)
@return The number of bytes added if successful, or -1 if an error occurred.
Append a va_list formatted string to the end of an evbuffer.
@param buf the evbuffer that will be appended to @param fmt a format string @param ap a varargs va_list argument array that will be passed to vprintf(3) @return The number of bytes added if successful, or -1 if an error occurred.