doc: Add demo.ksy

Author: heinrich5991

doc/demo.ksy

@@ -0,0 +1,118 @@
+meta:
+  id: tw_demo_v3_v4_v5_v6
+  file-extension: demo
+  endian: be
+  license: MIT/Apache-2.0
+doc-ref: https://github.com/heinrich5991/libtw2/blob/0085b3eb76ff1ffc7136f874129c79fce0f955ee/doc/demo.md
+seq:
+  - id: header
+    type: header
+  - id: timeline_markers
+    type: timeline_markers
+    if: header.version >= 4
+  - id: map_sha256
+    type: map_sha256
+    if: header.version >= 6
+  - id: map
+    size: header.map_size
+  - id: chunks
+    type: chunk
+    repeat: eos
+enums:
+  chunk_type:
+    1: snapshot
+    2: message
+    3: snapshot_delta
+types:
+  header:
+    seq:
+      - id: magic
+        contents: ['TWDEMO', 0]
+      - id: version
+        type: u1
+      - id: net_version
+        type: strz
+        encoding: utf8
+        size: 64
+      - id: map_name
+        type: strz
+        encoding: utf8
+        size: 64
+      - id: map_size
+        type: s4
+      - id: map_crc
+        type: u4
+      - id: type
+        type: strz
+        encoding: utf8
+        size: 8
+      - id: length
+        type: s4
+      - id: timestamp
+        type: strz
+        encoding: utf8
+        size: 20
+  timeline_markers:
+    seq:
+      - id: num_timeline_markers
+        type: s4
+      - id: timeline_marker
+        type: s4
+        repeat: expr
+        repeat-expr: 64
+  map_sha256:
+    seq:
+      - id: magic
+        contents: [0x6b, 0xe6, 0xda, 0x4a, 0xce, 0xbd, 0x38, 0x0c, 0x9b, 0x5b, 0x12, 0x89, 0xc8, 0x42, 0xd7, 0x80]
+      - id: map_sha256
+        size: 32
+  chunk:
+    seq:
+      - id: is_tick
+        type: b1
+
+      # tick
+      - id: keyframe
+        type: b1
+        if: is_tick
+      - id: inline_tick_delta
+        type: b1
+        if: _root.header.version >= 5 and is_tick
+      - id: tick_delta_v5
+        type: b5
+        if: _root.header.version >= 5 and is_tick
+      - id: tick_delta_v3
+        type: b6
+        if: _root.header.version < 5 and is_tick
+
+      # non-tick
+      - id: type
+        type: b2
+        enum: chunk_type
+        if: not is_tick
+      - id: size_inline
+        type: b5
+        if: not is_tick
+
+      # tick
+      - id: tick_absolute
+        type: s4
+        if: is_tick and (_root.header.version >= 5 ? not inline_tick_delta : tick_delta_v3 == 0)
+
+      # non-tick
+      - id: size_extern_8
+        type: u1
+        if: not is_tick and size_inline == 30
+      - id: size_extern_16
+        type: u2le
+        if: not is_tick and size_inline == 31
+      - id: compressed_data
+        size: size
+
+    instances:
+      tick_delta:
+        value: _root.header.version >= 5 ? tick_delta_v5 : tick_delta_v3
+        if: is_tick and (_root.header.version >= 5 ? inline_tick_delta : tick_delta_v3 != 0)
+      size:
+        value: size_inline == 31 ? size_extern_16 : size_inline == 30 ? size_extern_8 : size_inline
+        if: not is_tick