Its the buttons of the last frame (although i prefer to get them on my own in server_frame because I have a bad experience with this).
When you have the current and the last buttons, you can easily get what buttons were pressed / released between this frame and the frame before.
Code:
g_PlayerKeysPressed[i] = (g_PlayerKeys[i] ^ g_PlayerOldKeys[i]) & g_PlayerKeys[i]; // (new xor old) and new
g_PlayerKeysReleased[i] = (g_PlayerKeys[i] ^ g_PlayerOldKeys[i]) & g_PlayerOldKeys[i]; // (new xor old) and old
That is how i do it in my superkeeper plugin.
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