1.7.10 (5) multiprotocol support (#64)

Adds 1.7.10 protocol version 5 support, a major update with significant changes.
Expands https://github.com/iceiix/steven/issues/18 Enhance protocol support

* Add v1_7_10 protocol packet structures and IDs

* EncryptionRequest/Response i16 variant in login protocol

* 1.7.10 slot NBT data parsing

* Support both 1.7/1.8+ item::Stack in read_from, using if protocol_verson

* 1.7.10 chunk format support, ChunkDataBulk_17 and ChunkData_17 

* Extract dirty_chunks_by_bitmask from load_chunks17/18/19

* Implement keepalive i32 handler

* Send PlayerPositionLook_HeadY

* Send PlayerBlockPlacement_u8_Item_u8y

* Handle JoinGame_i8_NoDebug

* Handle SpawnPlayer_i32_HeldItem_String

* BlockChange_u8, MultiBlockChange_i16, UpdateBlockEntity_Data, EntityMove_i8_i32_NoGround, EntityLook_i32_NoGround, EntityLookAndMove_i8_i32_NoGround

* UpdateSign_u16, PlayerInfo_String, EntityDestroy_u8, EntityTeleport_i32_i32_NoGround

* Send feet_y = head_y - 1.62, fixes Illegal stance

https://wiki.vg/index.php?title=Protocol&oldid=6003#Player_Position

> Updates the players XYZ position on the server. If HeadY - FeetY is less than 0.1 or greater than 1.65, the stance is illegal and the client will be kicked with the message “Illegal Stance”.

> Absolute feet position, normally HeadY - 1.62. Used to modify the players bounding box when going up stairs, crouching, etc…

* Set on_ground = true in entity teleport, fixes bouncing

* Implement block change, fix metadata/id packing, bounce _u8 through on_block_change

* Implement on_multi_block_change_u16, used with explosions

src/item.rs

@@ -43,11 +43,32 @@ impl Serializable for Option<Stack> {
         if id == -1 {
             return Ok(None);
         }
+        let count = buf.read_u8()? as isize;
+        let damage = buf.read_i16::<BigEndian>()? as isize;
+
+        let protocol_version = unsafe { protocol::CURRENT_PROTOCOL_VERSION };
+
+        let tag: Option<nbt::NamedTag> = if protocol_version >= 47 {
+            Serializable::read_from(buf)?
+        } else {
+            // 1.7 uses a different slot data format described on https://wiki.vg/index.php?title=Slot_Data&diff=6056&oldid=4753
+            let tag_size = buf.read_i16::<BigEndian>()?;
+            if tag_size != -1 {
+                for _ in 0..tag_size {
+                    let _ = buf.read_u8()?;
+                }
+                // TODO: decompress zlib NBT for 1.7
+                None
+            } else {
+                None
+            }
+        };
+
         Ok(Some(Stack {
             id: id as isize,
-            count: buf.read_u8()? as isize,
-            damage: buf.read_i16::<BigEndian>()? as isize,
-            tag: Serializable::read_from(buf)?,
+            count,
+            damage,
+            tag,
         }))
     }
     fn write_to<W: io::Write>(&self, buf: &mut W) -> Result<(), protocol::Error> {
@@ -56,6 +77,7 @@ impl Serializable for Option<Stack> {
                 buf.write_i16::<BigEndian>(val.id as i16)?;
                 buf.write_u8(val.count as u8)?;
                 buf.write_i16::<BigEndian>(val.damage as i16)?;
+                // TODO: compress zlib NBT if 1.7
                 val.tag.write_to(buf)?;
             }
             None => buf.write_i16::<BigEndian>(-1)?,

src/protocol/mod.rs

@@ -37,7 +37,7 @@ use flate2::Compression;
 use std::time::{Instant, Duration};
 use crate::shared::Position;
 
-pub const SUPPORTED_PROTOCOLS: [i32; 8] = [340, 316, 315, 210, 109, 107, 74, 47];
+pub const SUPPORTED_PROTOCOLS: [i32; 9] = [340, 316, 315, 210, 109, 107, 74, 47, 5];
 
 // TODO: switch to using thread_local storage?, see https://doc.rust-lang.org/std/macro.thread_local.html
 pub static mut CURRENT_PROTOCOL_VERSION: i32 = SUPPORTED_PROTOCOLS[0];
@@ -553,6 +553,16 @@ impl <L: Lengthable> fmt::Debug for LenPrefixedBytes<L> {
     }
 }
 
+impl Lengthable for u8 {
+    fn into(self) -> usize {
+        self as usize
+    }
+
+    fn from(u: usize) -> u8 {
+        u as u8
+    }
+}
+
 impl Lengthable for i16 {
     fn into(self) -> usize {
         self as usize