feat: allow extracting to the end by omitting length parameter for extract op code

Author: boblat

src/impl/pure.ts

@@ -103,30 +103,29 @@ export const expw = (a: internal.primitives.StubUint64Compat, b: internal.primit
   return toUint128(base ** exponent)
 }
 
-export const extract = (
+type ExtractType = ((a: internal.primitives.StubBytesCompat, b: internal.primitives.StubUint64Compat) => bytes) &
+  ((a: internal.primitives.StubBytesCompat, b: internal.primitives.StubUint64Compat, c: internal.primitives.StubUint64Compat) => bytes)
+export const extract = ((
   a: internal.primitives.StubBytesCompat,
   b: internal.primitives.StubUint64Compat,
-  c: internal.primitives.StubUint64Compat,
+  c?: internal.primitives.StubUint64Compat,
 ): bytes => {
   const bytesValue = internal.primitives.BytesCls.fromCompat(a)
   const bytesLength = bytesValue.length.asBigInt()
 
   const start = internal.primitives.Uint64Cls.fromCompat(b).asBigInt()
-  const length = internal.primitives.Uint64Cls.fromCompat(c).asBigInt()
-  let end = start + length
-  if ((typeof b === 'number' || typeof b === 'bigint') && (typeof c === 'number' || typeof c === 'bigint') && length === 0n) {
-    end = bytesLength
-  }
+  const length = c !== undefined ? internal.primitives.Uint64Cls.fromCompat(c).asBigInt() : undefined
+  const end = length !== undefined ? start + length : undefined
 
   if (start > bytesLength) {
     internal.errors.codeError(`extraction start ${start} is beyond length`)
   }
-  if (end > bytesLength) {
+  if (end !== undefined && end > bytesLength) {
     internal.errors.codeError(`extraction end ${end} is beyond length`)
   }
 
   return bytesValue.slice(start, end).asAlgoTs()
-}
+}) as ExtractType
 
 export const extractUint16 = (a: internal.primitives.StubBytesCompat, b: internal.primitives.StubUint64Compat): uint64 => {
   const result = extract(a, b, 2)

tests/artifacts/miscellaneous-ops/contract.algo.ts

@@ -95,10 +95,9 @@ export class MiscellaneousOpsContract extends arc4.Contract {
     return result
   }
 
-  // TODO: recompile to check if this results in correct TEAL code
   @arc4.abimethod()
   public verify_extract_from_2(a: bytes): bytes {
-    const result = op.extract(a, 2, 0)
+    const result = op.extract(a, 2)
     return result
   }