Add string conversion error modes (AssemblyScript#1902)

Author: dcodeIO

lib/loader/index.js

@@ -37,17 +37,24 @@ const ARRAY_SIZE = 16;
 const BIGINT = typeof BigUint64Array !== "undefined";
 const THIS = Symbol();
 
-const STRING_DECODE_THRESHOLD = 32;
-const decoder = new TextDecoder("utf-16le");
+const STRING_SMALLSIZE = 192; // break-even point in V8
+const STRING_CHUNKSIZE = 1024; // mitigate stack overflow
+const utf16 = new TextDecoder("utf-16le", { fatal: true }); // != wtf16
 
-/** Gets a string from an U32 and an U16 view on a memory. */
+/** Gets a string from memory. */
 function getStringImpl(buffer, ptr) {
-  const len = new Uint32Array(buffer)[ptr + SIZE_OFFSET >>> 2] >>> 1;
-  const arr = new Uint16Array(buffer, ptr, len);
-  if (len <= STRING_DECODE_THRESHOLD) {
-    return String.fromCharCode.apply(String, arr);
+  let len = new Uint32Array(buffer)[ptr + SIZE_OFFSET >>> 2] >>> 1;
+  const wtf16 = new Uint16Array(buffer, ptr, len);
+  if (len <= STRING_SMALLSIZE) return String.fromCharCode(...wtf16);
+  try {
+    return utf16.decode(wtf16);
+  } catch {
+    let str = "", off = 0;
+    while (len - off > STRING_CHUNKSIZE) {
+      str += String.fromCharCode(...wtf16.subarray(off, off += STRING_CHUNKSIZE));
+    }
+    return str + String.fromCharCode(...wtf16.subarray(off));
   }
-  return decoder.decode(arr);
 }
 
 /** Prepares the base module prior to instantiation. */

lib/loader/package.json

@@ -43,5 +43,8 @@
     "umd/index.js",
     "umd/package.json",
     "README.md"
-  ]
-}
+  ],
+  "devDependencies": {
+    "esm2umd": "^0.1.2"
+  }
+}

lib/loader/tests/build/default.wasm

@@ -44,19 +44,33 @@ var loader = (function(exports) {
   const ARRAY_SIZE = 16;
   const BIGINT = typeof BigUint64Array !== "undefined";
   const THIS = Symbol();
-  const STRING_DECODE_THRESHOLD = 32;
-  const decoder = new TextDecoder("utf-16le");
-  /** Gets a string from an U32 and an U16 view on a memory. */
+  const STRING_SMALLSIZE = 192; // break-even point in V8
+  
+  const STRING_CHUNKSIZE = 1024; // mitigate stack overflow
+  
+  const utf16 = new TextDecoder("utf-16le", {
+    fatal: true
+  }); // != wtf16
+  
+  /** Gets a string from memory. */
 
   function getStringImpl(buffer, ptr) {
-    const len = new Uint32Array(buffer)[ptr + SIZE_OFFSET >>> 2] >>> 1;
-    const arr = new Uint16Array(buffer, ptr, len);
+    let len = new Uint32Array(buffer)[ptr + SIZE_OFFSET >>> 2] >>> 1;
+    const wtf16 = new Uint16Array(buffer, ptr, len);
+    if (len <= STRING_SMALLSIZE) return String.fromCharCode(...wtf16);
+  
+    try {
+      return utf16.decode(wtf16);
+    } catch {
+      let str = "",
+          off = 0;
+  
+      while (len - off > STRING_CHUNKSIZE) {
+        str += String.fromCharCode(...wtf16.subarray(off, off += STRING_CHUNKSIZE));
+      }
 
-    if (len <= STRING_DECODE_THRESHOLD) {
-      return String.fromCharCode.apply(String, arr);
+      return str + String.fromCharCode(...wtf16.subarray(off));
     }
-  
-    return decoder.decode(arr);
   }
   /** Prepares the base module prior to instantiation. */
 
@@ -110,9 +124,10 @@ var loader = (function(exports) {
 
     const __collect = exports.__collect || F_NOEXPORTRUNTIME;
 
-    const __rtti_base = exports.__rtti_base || ~0; // oob if not present
-  
-  
+    const __rtti_base = exports.__rtti_base;
+    const getRttiCount = __rtti_base ? function (arr) {
+      return arr[__rtti_base >>> 2];
+    } : F_NOEXPORTRUNTIME;
     extendedExports.__new = __new;
     extendedExports.__pin = __pin;
     extendedExports.__unpin = __unpin;
@@ -121,7 +136,7 @@ var loader = (function(exports) {
 
     function getInfo(id) {
       const U32 = new Uint32Array(memory.buffer);
-      const count = U32[__rtti_base >>> 2];
+      const count = getRttiCount(U32);
       if ((id >>>= 0) >= count) throw Error(`invalid id: ${id}`);
       return U32[(__rtti_base + 4 >>> 2) + id * 2];
     }
@@ -138,7 +153,7 @@ var loader = (function(exports) {
 
     function getBase(id) {
       const U32 = new Uint32Array(memory.buffer);
-      const count = U32[__rtti_base >>> 2];
+      const count = getRttiCount(U32);
       if ((id >>>= 0) >= count) throw Error(`invalid id: ${id}`);
       return U32[(__rtti_base + 4 >>> 2) + id * 2 + 1];
     }
@@ -330,7 +345,7 @@ var loader = (function(exports) {
       const U32 = new Uint32Array(memory.buffer);
       let id = U32[ptr + ID_OFFSET >>> 2];
 
-      if (id <= U32[__rtti_base >>> 2]) {
+      if (id <= getRttiCount(U32)) {
         do {
           if (id == baseId) return true;
           id = getBase(id);

lib/loader/tests/build/legacy.wasm

@@ -1773,12 +1773,21 @@ declare class String {
 declare namespace String {
   /** Encoding helpers for UTF-8. */
   export namespace UTF8 {
+    /** UTF-8 encoding error modes. */
+    export const enum ErrorMode {
+      /** Keeps unpaired surrogates as of WTF-8. This is the default. */
+      WTF8,
+      /** Replaces unpaired surrogates with the replacement character (U+FFFD). */
+      REPLACE,
+      /** Throws an error on unpaired surrogates. */
+      ERROR
+    }
     /** Calculates the byte length of the specified string when encoded as UTF-8, optionally null terminated. */
     export function byteLength(str: string, nullTerminated?: bool): i32;
-    /** Encodes the specified string to UTF-8 bytes, optionally null terminated. */
-    export function encode(str: string, nullTerminated?: bool): ArrayBuffer;
-    /** Encodes the specified raw string to UTF-8 bytes, opionally null terminated. Returns the number of bytes written. */
-    export function encodeUnsafe(str: usize, len: i32, buf: usize, nullTerminated?: bool): usize;
+    /** Encodes the specified string to UTF-8 bytes, optionally null terminated. ErrorMode defaults to WTF-8. */
+    export function encode(str: string, nullTerminated?: bool, errorMode?: ErrorMode): ArrayBuffer;
+    /** Encodes the specified raw string to UTF-8 bytes, opionally null terminated. ErrorMode defaults to WTF-8. Returns the number of bytes written. */
+    export function encodeUnsafe(str: usize, len: i32, buf: usize, nullTerminated?: bool, errorMode?: ErrorMode): usize;
     /** Decodes the specified buffer from UTF-8 bytes to a string, optionally null terminated. */
     export function decode(buf: ArrayBuffer, nullTerminated?: bool): string;
     /** Decodes raw UTF-8 bytes to a string, optionally null terminated. */

lib/loader/umd/index.js

@@ -3,7 +3,7 @@
 import { OBJECT, BLOCK_MAXSIZE, TOTAL_OVERHEAD } from "./rt/common";
 import { compareImpl, strtol, strtod, isSpace, isAscii, isFinalSigma, toLower8, toUpper8 } from "./util/string";
 import { SPECIALS_UPPER, casemap, bsearch } from "./util/casemap";
-import { E_INDEXOUTOFRANGE, E_INVALIDLENGTH } from "./util/error";
+import { E_INDEXOUTOFRANGE, E_INVALIDLENGTH, E_UNPAIRED_SURROGATE } from "./util/error";
 import { idof } from "./builtins";
 import { Array } from "./array";
 
@@ -661,6 +661,12 @@ export namespace String {
 
   export namespace UTF8 {
 
+    export const enum ErrorMode {
+      WTF8,
+      REPLACE,
+      ERROR
+    }
+
     export function byteLength(str: string, nullTerminated: bool = false): i32 {
       var strOff = changetype<usize>(str);
       var strEnd = strOff + <usize>changetype<OBJECT>(changetype<usize>(str) - TOTAL_OVERHEAD).rtSize;
@@ -687,15 +693,15 @@ export namespace String {
       return bufLen;
     }
 
-    export function encode(str: string, nullTerminated: bool = false): ArrayBuffer {
+    export function encode(str: string, nullTerminated: bool = false, errorMode: ErrorMode = ErrorMode.WTF8): ArrayBuffer {
       var buf = changetype<ArrayBuffer>(__new(<usize>byteLength(str, nullTerminated), idof<ArrayBuffer>()));
-      encodeUnsafe(changetype<usize>(str), str.length, changetype<usize>(buf), nullTerminated);
+      encodeUnsafe(changetype<usize>(str), str.length, changetype<usize>(buf), nullTerminated, errorMode);
       return buf;
     }
 
     // @ts-ignore: decorator
     @unsafe
-    export function encodeUnsafe(str: usize, len: i32, buf: usize, nullTerminated: bool = false): usize {
+    export function encodeUnsafe(str: usize, len: i32, buf: usize, nullTerminated: bool = false, errorMode: ErrorMode = ErrorMode.WTF8): usize {
       var strEnd = str + (<usize>len << 1);
       var bufOff = buf;
       while (str < strEnd) {
@@ -709,17 +715,29 @@ export namespace String {
           store<u16>(bufOff, b1 << 8 | b0);
           bufOff += 2;
         } else {
-          if ((c1 & 0xFC00) == 0xD800 && str + 2 < strEnd) {
-            let c2 = <u32>load<u16>(str, 2);
-            if ((c2 & 0xFC00) == 0xDC00) {
-              c1 = 0x10000 + ((c1 & 0x03FF) << 10) | (c2 & 0x03FF);
-              let b0 = c1 >> 18 | 240;
-              let b1 = c1 >> 12 & 63 | 128;
-              let b2 = c1 >> 6  & 63 | 128;
-              let b3 = c1       & 63 | 128;
-              store<u32>(bufOff, b3 << 24 | b2 << 16 | b1 << 8 | b0);
-              bufOff += 4; str += 4;
-              continue;
+          // D800: 11011 0 0000000000 Lead
+          // DBFF: 11011 0 1111111111
+          // DC00: 11011 1 0000000000 Trail
+          // DFFF: 11011 1 1111111111
+          // F800: 11111 0 0000000000 Mask
+          // FC00: 11111 1 0000000000
+          if ((c1 & 0xF800) == 0xD800) {
+            if (c1 < 0xDC00 && str + 2 < strEnd) {
+              let c2 = <u32>load<u16>(str, 2);
+              if ((c2 & 0xFC00) == 0xDC00) {
+                c1 = 0x10000 + ((c1 & 0x03FF) << 10) | (c2 & 0x03FF);
+                let b0 = c1 >> 18 | 240;
+                let b1 = c1 >> 12 & 63 | 128;
+                let b2 = c1 >> 6  & 63 | 128;
+                let b3 = c1       & 63 | 128;
+                store<u32>(bufOff, b3 << 24 | b2 << 16 | b1 << 8 | b0);
+                bufOff += 4; str += 4;
+                continue;
+              }
+            }
+            if (errorMode != ErrorMode.WTF8) { // unlikely
+              if (errorMode == ErrorMode.ERROR) throw new Error(E_UNPAIRED_SURROGATE);
+              c1 = 0xFFFD;
             }
           }
           let b0 = c1 >> 12 | 224;

std/assembly/index.d.ts

@@ -52,3 +52,7 @@ export const E_URI_MALFORMED: string = "URI malformed";
 // @ts-ignore: decorator
 @lazy @inline
 export const E_INVALIDDATE: string = "Invalid Date";
+
+// @ts-ignore: decorator
+@lazy @inline
+export const E_UNPAIRED_SURROGATE: string = "Unpaired surrogate";