More enums, and conditional evaluation

08_enums.ksy

@@ -5,23 +5,28 @@ meta:
   endian: le
 seq:
   - id: magic
-    contents: "RIFF"
-    size: 4
+    # Could assert using contents here, but 
+    # just make sections conditional later
+    #contents: "RIFF"
+    type: u4be
+    enum: fourcc
   - id: size
     type: u4
   - id: wave_str
-    contents: "WAVE"
-    size: 4
+    #contents: "WAVE"
+    type: u4be
+    enum: fourcc
   - id: sections
     type: section
     repeat: eos
+    if: 'magic == fourcc::riff and wave_str == fourcc::wave'
 instances: {}
 types:
   section:
     seq:
       - id: name
-        type: str
-        size: 4
+        type: u4be # Big endian!
+        enum: fourcc
       - id: size
         type: u4
       - id: content
@@ -29,11 +34,11 @@ types:
         type:
           switch-on: name
           cases:
-            '"fmt "': fmt
-            '"data"': data
-            '"fact"': fact
-            '"PEAK"': peak
-            '"LIST"': list
+            'fourcc::fmt': fmt
+            'fourcc::data': data
+            'fourcc::fact': fact
+            'fourcc::peak': peak
+            'fourcc::list': list
   fmt:
     seq:
       - id: type
@@ -56,7 +61,7 @@ types:
         type:
           switch-on: _root.sections[0].name
           cases:
-            '"fmt "': sample(_root.sections[0].content.as<fmt>.type, _root.sections[0].content.as<fmt>.bits_per_unit)
+            'fourcc::fmt': sample(_root.sections[0].content.as<fmt>.type, _root.sections[0].content.as<fmt>.bits_per_unit)
             _: u1
         repeat: eos
     types:
@@ -129,6 +134,14 @@ types:
             type: strz
             size: size
 enums:
+  fourcc:
+    0x52494646: 'riff'
+    0x57415645: 'wave'
+    0x666d7420: 'fmt'
+    0x66616374: 'fact'
+    0x5045414b: 'peak'
+    0x64617461: 'data'
+    0x4c495354: 'list'
   encoding_type_enum:
     1: 'int'
     3: 'float'