Jxck

OpenSSL DTLS API

The API used for DTLS is mostly the same as for TLS, because of the mapping of generic functions to protocol specifc ones. Some additional functions are still necessary, because of the new BIO objects and the timer handling for handshake messages. The generic concept of the API is described in the following sections. Examples of applications using DTLS are available at [9].

DTLS の API は TLS とほぼ同じ。 BIO オブジェクトの生成とタイマのために追加でいくつか必要。

fenbf

// SFINAE, enable_if example
// based on http://stackoverflow.com/questions/257288/is-it-possible-to-write-a-c-template-to-check-for-a-functions-existence


#include <iostream>
#include <type_traits>

class ClassWithToString
{
public:

hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD