Fix args decoder.

tomusdrw · Jan 2, 2025 · 9b51ecf · 9b51ecf
1 parent ec25c5d
commit 9b51ecf
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Showing 3 changed files with 17 additions and 26 deletions.
diff --git a/assembly/api-generic.ts b/assembly/api-generic.ts
@@ -53,16 +53,10 @@ export function getAssembly(p: Program): string {
     v += changetype<string>(iData.namePtr);
     v += `(${instruction})`;
 
-    const argsLen = p.mask.argsLen(i);
+    const argsLen = p.mask.argsLen(i, len);
     const end = i + 1 + argsLen;
-    if (end > len) {
-      const name = changetype<string>(iData.namePtr);
-      const intro = "Invalid program - code is not long enough";
-      throw new Error(`${intro} Expected: ${argsLen} for ${name} at ${i} (${end} > ${len})`);
-    }
-
     const args = decodeArguments(iData.kind, p.code.subarray(i + 1, end));
-    const argsArray = args === null ? [0, 0, 0, 0] : [args.a, args.b, args.c, args.d];
+    const argsArray = [args.a, args.b, args.c, args.d];
     const relevantArgs = RELEVANT_ARGS[iData.kind];
     for (let i = 0; i < relevantArgs; i++) {
       v += ` ${argsArray[i]}, `;

diff --git a/assembly/interpreter.ts b/assembly/interpreter.ts
@@ -80,18 +80,9 @@ export class Interpreter {
     }
 
     // get args and invoke instruction
-    const argsLen = this.program.mask.argsLen(pc);
+    const argsLen = this.program.mask.argsLen(pc, this.program.code.length);
     const end = pc + 1 + argsLen;
-    if (end > <u32>this.program.code.length) {
-      this.status = Status.PANIC;
-      return false;
-    }
-
     const args = decodeArguments(iData.kind, this.program.code.subarray(pc + 1, end));
-    if (args === null) {
-      this.status = Status.PANIC;
-      return false;
-    }
 
     // additional gas cost of sbrk
     if (iData === SBRK) {

diff --git a/assembly/program.ts b/assembly/program.ts
@@ -64,11 +64,11 @@ export function decodeProgram(program: Uint8Array): Program {
 
 export class Mask {
   // NOTE: might be longer than code (bit-alignment)
-  readonly bytesToSkip: StaticArray<u8>;
+  readonly bytesToSkip: StaticArray<u32>;
 
   constructor(packedMask: Uint8Array, codeLength: i32) {
-    this.bytesToSkip = new StaticArray<u8>(codeLength);
-    let lastInstructionOffset: u8 = 0;
+    this.bytesToSkip = new StaticArray<u32>(codeLength);
+    let lastInstructionOffset: u32 = 0;
     for (let i: i32 = packedMask.length - 1; i >= 0; i -= 1) {
       let bits = packedMask[i];
       const index = i * 8;
@@ -91,11 +91,12 @@ export class Mask {
     return this.bytesToSkip[index] === 0;
   }
 
-  argsLen(i: u32): u8 {
-    if (i + 1 < <u32>this.bytesToSkip.length) {
+  argsLen(i: u32, maxLen: u32): u32 {
+    if (i + 1 < this.bytesToSkip.length) {
       return this.bytesToSkip[i + 1];
     }
-    return 0;
+
+    return maxLen - i - 1;
   }
 
   toString(): string {
@@ -198,9 +199,14 @@ export class Program {
   }
 }
 
-export function decodeArguments(kind: Arguments, data: Uint8Array): Args | null {
+export function decodeArguments(kind: Arguments, data: Uint8Array): Args {
   if (data.length < REQUIRED_BYTES[kind]) {
-    return null;
+    // in case we have less data than needed we extend the data with zeros.
+    const extended = new Uint8Array(REQUIRED_BYTES[kind]);
+    for (let i = 0; i < data.length; i++) {
+      extended[i] = data[i];
+    }
+    return DECODERS[kind](extended);
   }
   return DECODERS[kind](data);
 }