1 files changed, 232 insertions, 0 deletions
diff --git a/js/src/vm/ToSource.cpp b/js/src/vm/ToSource.cpp
new file mode 100644
index 0000000000..2e76b37b25
--- /dev/null
+++ b/js/src/vm/ToSource.cpp
@@ -0,0 +1,232 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "vm/ToSource.h"
+
+#include "mozilla/Assertions.h"     // MOZ_ASSERT
+#include "mozilla/FloatingPoint.h"  // mozilla::IsNegativeZero
+
+#include <iterator>  // std::size
+#include <stdint.h>  // uint32_t
+
+#include "jsfriendapi.h"  // CheckRecursionLimit
+
+#include "builtin/Array.h"          // ArrayToSource
+#include "builtin/Boolean.h"        // BooleanToString
+#include "builtin/Object.h"         // ObjectToSource
+#include "gc/Allocator.h"           // CanGC
+#include "js/Class.h"               // ESClass
+#include "js/friend/StackLimits.h"  // js::CheckRecursionLimit
+#include "js/Object.h"              // JS::GetBuiltinClass
+#include "js/Symbol.h"              // SymbolCode, JS::WellKnownSymbolLimit
+#include "js/TypeDecls.h"  // Rooted{Function, Object, String, Value}, HandleValue, Latin1Char
+#include "js/Utility.h"         // UniqueChars
+#include "js/Value.h"           // JS::Value
+#include "util/StringBuffer.h"  // JSStringBuilder
+#include "vm/ArrayObject.h"     // ArrayObject
+#include "vm/ErrorObject.h"     // ErrorObject, ErrorToSource
+#include "vm/Interpreter.h"     // Call
+#include "vm/JSContext.h"       // JSContext
+#include "vm/JSFunction.h"      // JSFunction, fun_toStringHelper
+#include "vm/Printer.h"         // QuoteString
+#include "vm/SelfHosting.h"     // CallSelfHostedFunction
+#include "vm/Stack.h"           // FixedInvokeArgs
+#include "vm/StringType.h"      // NewStringCopy{N,Z}, ToString
+#include "vm/SymbolType.h"      // Symbol
+
+#include "vm/JSContext-inl.h"         // JSContext::check
+#include "vm/JSObject-inl.h"          // IsCallable
+#include "vm/ObjectOperations-inl.h"  // GetProperty
+
+using namespace js;
+
+using mozilla::IsNegativeZero;
+
+using JS::GetBuiltinClass;
+
+/*
+ * Convert a JSString to its source expression; returns null after reporting an
+ * error, otherwise returns a new string reference. No Handle needed since the
+ * input is dead after the GC.
+ */
+static JSString* StringToSource(JSContext* cx, JSString* str) {
+  UniqueChars chars = QuoteString(cx, str, '"');
+  if (!chars) {
+    return nullptr;
+  }
+  return NewStringCopyZ<CanGC>(cx, chars.get());
+}
+
+static JSString* SymbolToSource(JSContext* cx, JS::Symbol* symbol) {
+  using JS::SymbolCode;
+
+  RootedString desc(cx, symbol->description());
+  SymbolCode code = symbol->code();
+  if (symbol->isWellKnownSymbol()) {
+    // Well-known symbol.
+    return desc;
+  }
+
+  if (code == SymbolCode::PrivateNameSymbol) {
+    MOZ_ASSERT(desc);
+    return desc;
+  }
+
+  MOZ_ASSERT(code == SymbolCode::InSymbolRegistry ||
+             code == SymbolCode::UniqueSymbol);
+
+  JSStringBuilder buf(cx);
+  if (code == SymbolCode::InSymbolRegistry ? !buf.append("Symbol.for(")
+                                           : !buf.append("Symbol(")) {
+    return nullptr;
+  }
+  if (desc) {
+    UniqueChars quoted = QuoteString(cx, desc, '"');
+    if (!quoted || !buf.append(quoted.get(), strlen(quoted.get()))) {
+      return nullptr;
+    }
+  }
+  if (!buf.append(')')) {
+    return nullptr;
+  }
+  return buf.finishString();
+}
+
+static JSString* BoxedToSource(JSContext* cx, HandleObject obj,
+                               const char* constructor) {
+  RootedValue value(cx);
+  if (!Unbox(cx, obj, &value)) {
+    return nullptr;
+  }
+  MOZ_ASSERT(!value.isUndefined());
+
+  RootedString str(cx, ValueToSource(cx, value));
+  if (!str) {
+    return nullptr;
+  }
+
+  JSStringBuilder buf(cx);
+  if (!buf.append("new ") || !buf.append(constructor, strlen(constructor)) ||
+      !buf.append('(') || !buf.append(str) || !buf.append(')')) {
+    return nullptr;
+  }
+
+  return buf.finishString();
+}
+
+JSString* js::ValueToSource(JSContext* cx, HandleValue v) {
+  if (!CheckRecursionLimit(cx)) {
+    return nullptr;
+  }
+  cx->check(v);
+
+  switch (v.type()) {
+    case JS::ValueType::Undefined:
+      return cx->names().void0;
+
+    case JS::ValueType::String:
+      return StringToSource(cx, v.toString());
+
+    case JS::ValueType::Symbol:
+      return SymbolToSource(cx, v.toSymbol());
+
+    case JS::ValueType::Null:
+      return cx->names().null;
+
+    case JS::ValueType::Boolean:
+      return BooleanToString(cx, v.toBoolean());
+
+    case JS::ValueType::Double:
+      /* Special case to preserve negative zero, _contra_ toString. */
+      if (IsNegativeZero(v.toDouble())) {
+        static const Latin1Char negativeZero[] = {'-', '0'};
+
+        return NewStringCopyN<CanGC>(cx, negativeZero, std::size(negativeZero));
+      }
+      [[fallthrough]];
+    case JS::ValueType::Int32:
+      return ToString<CanGC>(cx, v);
+
+    case JS::ValueType::BigInt: {
+      RootedString str(cx, ToString<CanGC>(cx, v));
+      if (!str) {
+        return nullptr;
+      }
+
+      RootedString n(cx, cx->staticStrings().getUnit('n'));
+
+      return ConcatStrings<CanGC>(cx, str, n);
+    }
+
+    case JS::ValueType::Object: {
+      RootedValue fval(cx);
+      RootedObject obj(cx, &v.toObject());
+      if (!GetProperty(cx, obj, obj, cx->names().toSource, &fval)) {
+        return nullptr;
+      }
+      if (IsCallable(fval)) {
+        RootedValue v(cx);
+        if (!js::Call(cx, fval, obj, &v)) {
+          return nullptr;
+        }
+
+        return ToString<CanGC>(cx, v);
+      }
+
+      ESClass cls;
+      if (!GetBuiltinClass(cx, obj, &cls)) {
+        return nullptr;
+      }
+
+      // All ToSource functions must be able to handle wrapped objects!
+      switch (cls) {
+        case ESClass::Function:
+          return fun_toStringHelper(cx, obj, true);
+
+        case ESClass::Array:
+          return ArrayToSource(cx, obj);
+
+        case ESClass::Error:
+          return ErrorToSource(cx, obj);
+
+        case ESClass::RegExp: {
+          FixedInvokeArgs<0> args(cx);
+          RootedValue rval(cx);
+          if (!CallSelfHostedFunction(cx, cx->names().RegExpToString, v, args,
+                                      &rval)) {
+            return nullptr;
+          }
+          return ToString<CanGC>(cx, rval);
+        }
+
+        case ESClass::Boolean:
+          return BoxedToSource(cx, obj, "Boolean");
+
+        case ESClass::Number:
+          return BoxedToSource(cx, obj, "Number");
+
+        case ESClass::String:
+          return BoxedToSource(cx, obj, "String");
+
+        case ESClass::Date:
+          return BoxedToSource(cx, obj, "Date");
+
+        default:
+          return ObjectToSource(cx, obj);
+      }
+    }
+
+    case JS::ValueType::PrivateGCThing:
+    case JS::ValueType::Magic:
+      MOZ_ASSERT_UNREACHABLE(
+          "internal value types shouldn't leak into places "
+          "wanting source representations");
+      return nullptr;
+  }
+
+  MOZ_ASSERT_UNREACHABLE("shouldn't see an unrecognized value type");
+  return nullptr;
+}