From 17c6b07367ba85ce9153a8dc376e56d2ff927e03 Mon Sep 17 00:00:00 2001
From: Robin Chappatte <robin.chappatte@gmail.com>
Date: Sat, 25 Apr 2026 05:35:01 +0200
Subject: [PATCH] add automatic padding in build script

(cherry picked from commit aad1fa45f776d9e6ec86902272b3c3b0c54dc075)
---
 build.ts               | 49 ++++++++++++++++++++++++++----------------
 src/reserved_space.asm |  2 ++
 2 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/build.ts b/build.ts
index 4902471..e60928f 100755
--- a/build.ts
+++ b/build.ts
@@ -27,25 +27,26 @@ const asmFilePaths = [
 ];
 const reservedSpacePath = 'src/reserved_space.asm';
 
+const instructionLength = 4; // in bytes
 const mapWidth = 15;
 const spriteWidth = 5;
 
 const mapMatchingStrings = {
-  0x00_00_00: 'U8 0', // Empty
-  0xFF_00_00: 'U8 1', // Wall
-  0xFF_FF_00: 'U8 2', // Coin
+  0x00_00_00: '0', // Empty
+  0xFF_00_00: '1', // Wall
+  0xFF_FF_00: '2', // Coin
 };
 
 const spritesMatchingStrings = {
-  0x00_00_00: 'U8 0b000_000_00',
-  0x00_00_FF: 'U8 0b000_000_11',
-  0x00_FF_00: 'U8 0b000_111_00',
-  0x77_77_77: 'U8 0b010_011_10',
-  0xFF_00_00: 'U8 0b111_000_00',
-  0xFF_00_FF: 'U8 0b111_000_11',
-  0xFF_80_00: 'U8 0b111_100_00',
-  0xFF_FF_00: 'U8 0b111_110_00',
-  0xFF_FF_FF: 'U8 0b111_111_11',
+  0x00_00_00: '0b000_000_00',
+  0x00_00_FF: '0b000_000_11',
+  0x00_FF_00: '0b000_111_00',
+  0x77_77_77: '0b010_011_10',
+  0xFF_00_00: '0b111_000_00',
+  0xFF_00_FF: '0b111_000_11',
+  0xFF_80_00: '0b111_100_00',
+  0xFF_FF_00: '0b111_110_00',
+  0xFF_FF_FF: '0b111_111_11',
 };
 
 const mapPath = 'assets/map.ppm';
@@ -86,11 +87,11 @@ for (const path of asmFilePaths) {
 const asmRawRepresentations = [];
 
 const mapBytes = await getDataFromPPM(mapPath);
-asmRawRepresentations.push(byteToAsmRawData('map', mapBytes, mapMatchingStrings, mapWidth));
+asmRawRepresentations.push(bytesToAsmConstU8('map', mapBytes, mapMatchingStrings, mapWidth));
 
 for (const [label, path] of Object.entries(spritesPath)) {
   const bytes = await getDataFromPPM(path);
-  asmRawRepresentations.push(byteToAsmRawData(label, bytes, spritesMatchingStrings, spriteWidth));
+  asmRawRepresentations.push(bytesToAsmConstU8(label, bytes, spritesMatchingStrings, spriteWidth));
 }
 
 console.log(asmRawRepresentations.join("\n\n"));
@@ -104,7 +105,9 @@ console.log(`
 console.log(await Deno.readTextFile(reservedSpacePath))
 
 /**
- * Return an ASM representation of the given data
+ * Return an ASM constant (U8) representation of the given data
+ * 
+ * If needed, the representation will be padded to ensure the following code stays aligned on the instruction's length
  * 
  * @param label The label to write before the first raw data
  * @param data An array of bytes to interprete as 24 bits values
@@ -113,14 +116,18 @@ console.log(await Deno.readTextFile(reservedSpacePath))
  * 
  * @returns The ASM representation of that raw data, pre- and post-fixed by the given label
  */
-function byteToAsmRawData(label: string, data: Uint8Array, matchingStrings: Record<number, string>, lineLength = 0): string {
+function bytesToAsmConstU8(label: string, data: Uint8Array, matchingStrings: Record<number, string>, lineLength = 0): string {
   lineLength ??= Infinity;
 
   const stringValues = [];
   for (let i = 0; i < data.length - 2; i += 3) {
     const pixelValue = (data[i] << 16) + (data[i+1] << 8) + (data[i+2])
+    if (!Object.hasOwn(matchingStrings, pixelValue)) {
+      console.error(`No matching value defined for "${pixelValue.toString(2)}" (which is ${label}'s ${i} pixel)`);
+      Deno.exit(1);
+    }
     
-    stringValues.push(matchingStrings[pixelValue]);
+    stringValues.push(`U8 ${matchingStrings[pixelValue]}`);
   }
 
   const lines = [];
@@ -131,10 +138,16 @@ function byteToAsmRawData(label: string, data: Uint8Array, matchingStrings: Reco
       lines.push(stringValues.slice(i, i+lineLength).join("\t"));
     }
   }
+
+  const paddingBytes = [];
+  for (let i = 0; i < stringValues.length % instructionLength; i++) {
+    paddingBytes.push('U8 0');
+  }
+  const paddingString = paddingBytes.length === 0 ? '' : `\n${paddingBytes.join('\t')} ; padding to preserve ${8 * instructionLength} bits alignment`
   
   return `${label}:
 ${lines.join("\n")}
-${label}_end:`
+${label}_end:${paddingString}`
 }
 
 /**
diff --git a/src/reserved_space.asm b/src/reserved_space.asm
index 41ea207..f513191 100644
--- a/src/reserved_space.asm
+++ b/src/reserved_space.asm
@@ -24,10 +24,12 @@ pub ptr.state_robot:
 U8 0 ; x coord
 U8 0 ; y coord
 U8 0 ; direction
+U8 0 ; [padding]
 
 pub ptr.state_ghost:
 U8 0 ; x coord
 U8 0 ; y coord
 U8 0 ; direction
+U8 0 ; [padding]
 
 pub ptr.screen:
\ No newline at end of file