Add bswap/bswap16 post MVP polyfills (#34)

std/assembly.d.ts

@@ -175,6 +175,11 @@ declare function free_memory(ptr: usize): void;
 /** Emits an unreachable operation that results in a runtime error when executed. Both a statement and an expression of any type. */
 declare function unreachable(): any; // sic
 
+/** [Polyfill] Performs the sign-agnostic reverse bytes **/
+declare function bswap<T = i8 | u8 | i16 | u16 | i32 | u32 | i64 | u64 | isize | usize>(value: T): T;
+/** [Polyfill] Performs the sign-agnostic reverse bytes only for last 16-bit **/
+declare function bswap16<T = i8 | u8 | i16 | u16 | i32 | u32>(value: T): T;
+
 /** NaN (not a number) as a 32-bit or 64-bit float depending on context. */
 declare const NaN: f32 | f64;
 /** Positive infinity as a 32-bit or 64-bit float depending on context. */

std/assembly/error.ts

@@ -12,3 +12,7 @@ export class Error {
 export class RangeError extends Error {
   name: string = "RangeError";
 }
+
+export class TypeError extends Error {
+  name: string = "TypeError";
+}

std/assembly/polyfills.ts

@@ -0,0 +1,31 @@
+export function bswap<T>(value: T): T {
+  assert(sizeof<T>() == 1 || sizeof<T>() == 2 || sizeof<T>() == 4 || sizeof<T>() == 8);
+
+  if (sizeof<T>() == 2) {
+    return bswap16<T>(value);
+  } else if (sizeof<T>() == 4) {
+    return <T>(
+      rotl<u32>(<u32>value & 0xFF00FF00, 8) |
+      rotr<u32>(<u32>value & 0x00FF00FF, 8)
+    );
+  } else if (sizeof<T>() == 8) {
+    var a: u64 = (<u64>value >> 8) & 0x00FF00FF00FF00FF;
+    var b: u64 = (<u64>value & 0x00FF00FF00FF00FF) << 8;
+    var v: u64 = a | b;
+
+    a = (v >> 16) & 0x0000FFFF0000FFFF;
+    b = (v & 0x0000FFFF0000FFFF) << 16;
+
+    return <T>rotr<u64>(a | b, 32);
+  }
+  return value;
+}
+
+export function bswap16<T>(value: T): T {
+  assert(sizeof<T>() == 1 || sizeof<T>() == 2 || sizeof<T>() == 4);
+
+  if (sizeof<T>() == 2 || sizeof<T>() == 4) {
+    return <T>(((value << 8) & <T>0xFF00) | ((value >> 8) & <T>0x00FF) | (value & <T>0xFFFF0000));
+  }
+  return value;
+}

std/portable.d.ts

@@ -129,6 +129,11 @@ declare function store<T = u8>(ptr: usize, value: T, constantOffset?: usize): vo
 /** Emits an unreachable operation that results in a runtime error when executed. */
 declare function unreachable(): any; // sic
 
+/** [Polyfill] Performs the sign-agnostic reverse bytes **/
+declare function bswap<T = i32 | u32 | isize | usize>(value: T): T;
+/** [Polyfill] Performs the sign-agnostic reverse bytes only for last 16-bit **/
+declare function bswap16<T = i16 | u16 | i32 | u32>(value: T): T;
+
 /** Changes the type of any value of `usize` kind to another one of `usize` kind. Useful for casting class instances to their pointer values and vice-versa. Beware that this is unsafe.*/
 declare function changetype<T>(value: any): T;
 /** Traps if the specified value is not true-ish, otherwise returns the value. */

std/portable.js

@@ -71,6 +71,19 @@ globalScope["select"] = function select(ifTrue, ifFalse, condition) { return con
 globalScope["sqrt"] = Math.sqrt;
 globalScope["trunc"] = Math.trunc;
 
+globalScope["bswap"] = function bswap(value) {
+  var a = value >> 8 & 0x00FF00FF;
+  var b = (value & 0x00FF00FF) << 8;
+  value = a | b;
+  a = value >> 16 & 0x0000FFFF;
+  b = (value & 0x0000FFFF) << 16;
+  return a | b;
+}
+
+globalScope["bswap16"] = function bswap16(value) {
+  return ((value << 8) & 0xFF00) | ((value >> 8) & 0x00FF) | (value & 0xFFFF0000);
+}
+
 function UnreachableError() {
   if (Error.captureStackTrace)
     Error.captureStackTrace(this, UnreachableError);