From 630d94c1eea1a8379aaa76c2ddcae862710a4061 Mon Sep 17 00:00:00 2001
From: Valentin Ochs <a@0au.de>
Date: Wed, 30 Dec 2020 08:15:28 +0100
Subject: [PATCH] Comments and stuff

---
 02_preamble.ksy |  5 +++++
 03_sections.ksy |  3 +++
 05_data.ksy     |  3 +++
 08_enums.ksy    | 33 +++++++++++++++++++--------------
 4 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/02_preamble.ksy b/02_preamble.ksy
index cc697bc..af21f6f 100644
--- a/02_preamble.ksy
+++ b/02_preamble.ksy
@@ -7,11 +7,16 @@ seq:
   - id: magic
     type: str
     size: 4
+    # We don't actually handle invalid files here.
+    # If we wanted, we could also use this key:
+    # contents: "RIFF"
+    # But then we could not use the type key...
   - id: size
     type: u4
   - id: wave_str
     type: str
     size: 4
+    # Same as with the magic field
 instances: {}
 types: {}
 enums: {}
diff --git a/03_sections.ksy b/03_sections.ksy
index a00a422..dbd8fac 100644
--- a/03_sections.ksy
+++ b/03_sections.ksy
@@ -14,6 +14,7 @@ seq:
     size: 4
   - id: sections
     type: section
+    # Repeat until the end of the stream
     repeat: eos
 instances: {}
 types:
@@ -26,6 +27,8 @@ types:
         type: u4
       - id: content
         size: size
+        # No type yet - just read in a byte array of the given
+        # size, which refers to the size field just before
 enums: {}
 doc: Hello, world
 doc-ref: https://example.com
diff --git a/05_data.ksy b/05_data.ksy
index a778444..f02ce95 100644
--- a/05_data.ksy
+++ b/05_data.ksy
@@ -59,6 +59,9 @@ types:
         seq:
           - id: data
             type: 
+              # I don't mention this in the video, but you
+              # can use arithmetic expressions here as well
+              # I just did this to show value instances :)
               switch-on: _root.sections[0].content.\
                 as<fmt>.combined_type
               cases:
diff --git a/08_enums.ksy b/08_enums.ksy
index e3f9186..a448c93 100644
--- a/08_enums.ksy
+++ b/08_enums.ksy
@@ -8,24 +8,32 @@ seq:
     # Could assert using contents here, but 
     # just make sections conditional later
     #contents: "RIFF"
+    
+    # Not using contents means we can give this a type
+    # Big endian, because we store the 4-character string
+    # 'RIFF' (0x52 0x49 0x46 0x46) as enum value 0x52494646
     type: u4be
+    
+    # Integers can have an optional enum key
     enum: fourcc
   - id: size
     type: u4
   - id: wave_str
+    # Same as the magic field
     #contents: "WAVE"
     type: u4be
     enum: fourcc
   - id: sections
     type: section
     repeat: eos
+    # Only try to decode this if this looks like a wave file
     if: 'magic == fourcc::riff and wave_str == fourcc::wave'
 instances: {}
 types:
   section:
     seq:
       - id: name
-        type: u4be # Big endian!
+        type: u4be # Big endian, same reason as above
         enum: fourcc
       - id: size
         type: u4
@@ -43,7 +51,7 @@ types:
     seq:
       - id: type
         type: u2
-        enum: encoding_type_enum
+        enum: encoding
       - id: channels
         type: u2
       - id: samplerate
@@ -61,24 +69,21 @@ types:
         type:
           switch-on: _root.sections[0].name
           cases:
-            'fourcc::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>)
             _: u1
         repeat: eos
     types:
       sample:
         params:
-          - id: encoding_type
-            type: u2
-            enum: encoding_type_enum
-          - id: encoding_size
-            type: u2
+          - id: fmt
+            type: fmt
         seq:
           - id: data
             type: 
-              switch-on: encoding_type
+              switch-on: fmt.type
               cases:
-                'encoding_type_enum::float': float_type
-                'encoding_type_enum::int': int_type
+                'encoding::float': float_type
+                'encoding::int': int_type 
             repeat: expr
             repeat-expr: _root.sections[0].content.\
               as<fmt>.channels
@@ -87,7 +92,7 @@ types:
             seq:
               - id: data
                 type:
-                  switch-on: _parent.encoding_size
+                  switch-on: _parent.fmt.bits_per_unit
                   cases:
                     32: f4
                     64: f8
@@ -95,7 +100,7 @@ types:
             seq:
               - id: data
                 type:
-                  switch-on: _parent.encoding_size
+                  switch-on: _parent.fmt.bits_per_unit
                   cases:
                     8: u1
                     16: s2
@@ -142,7 +147,7 @@ enums:
     0x5045414b: 'peak'
     0x64617461: 'data'
     0x4c495354: 'list'
-  encoding_type_enum:
+  encoding:
     1: 'int'
     3: 'float'
 doc: Hello, world