[API] Expand BigInt API

Provide a more complete BigInt API.

Bug: v8:7712
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: Ic8562d616f3125deabdf8b52c7019b191bef0e07
Reviewed-on: https://chromium-review.googlesource.com/1101198
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54122}

include/v8.h

@@ -3179,6 +3179,48 @@ class V8_EXPORT Uint32 : public Integer {
 class V8_EXPORT BigInt : public Primitive {
  public:
   static Local<BigInt> New(Isolate* isolate, int64_t value);
+  static Local<BigInt> NewFromUnsigned(Isolate* isolate, uint64_t value);
+  /**
+   * Creates a new BigInt object using a specified sign bit and a
+   * specified list of digits/words.
+   * The resulting number is calculated as:
+   *
+   * (-1)^sign_bit * (words[0] * (2^64)^0 + words[1] * (2^64)^1 + ...)
+   */
+  static MaybeLocal<BigInt> NewFromWords(Local<Context> context, int sign_bit,
+                                         int word_count, const uint64_t* words);
+
+  /**
+   * Returns the value of this BigInt as an unsigned 64-bit integer.
+   * If `lossless` is provided, it will reflect whether the return value was
+   * truncated or wrapped around. In particular, it is set to `false` if this
+   * BigInt is negative.
+   */
+  uint64_t Uint64Value(bool* lossless = nullptr) const;
+
+  /**
+   * Returns the value of this BigInt as a signed 64-bit integer.
+   * If `lossless` is provided, it will reflect whether this BigInt was
+   * truncated or not.
+   */
+  int64_t Int64Value(bool* lossless = nullptr) const;
+
+  /**
+   * Returns the number of 64-bit words needed to store the result of
+   * ToWordsArray().
+   */
+  int WordCount() const;
+
+  /**
+   * Writes the contents of this BigInt to a specified memory location.
+   * `sign_bit` must be provided and will be set to 1 if this BigInt is
+   * negative.
+   * `*word_count` has to be initialized to the length of the `words` array.
+   * Upon return, it will be set to the actual number of words that would
+   * be needed to store this BigInt (i.e. the return value of `WordCount()`).
+   */
+  void ToWordsArray(int* sign_bit, int* word_count, uint64_t* words) const;
+
   V8_INLINE static BigInt* Cast(v8::Value* obj);
 
  private:

src/api.cc

@@ -8076,6 +8076,49 @@ Local<BigInt> v8::BigInt::New(Isolate* isolate, int64_t value) {
   return Utils::ToLocal(result);
 }
 
+Local<BigInt> v8::BigInt::NewFromUnsigned(Isolate* isolate, uint64_t value) {
+  CHECK(i::FLAG_harmony_bigint);
+  i::Isolate* internal_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  ENTER_V8_NO_SCRIPT_NO_EXCEPTION(internal_isolate);
+  i::Handle<i::BigInt> result = i::BigInt::FromUint64(internal_isolate, value);
+  return Utils::ToLocal(result);
+}
+
+MaybeLocal<BigInt> v8::BigInt::NewFromWords(Local<Context> context,
+                                            int sign_bit, int word_count,
+                                            const uint64_t* words) {
+  CHECK(i::FLAG_harmony_bigint);
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(context->GetIsolate());
+  ENTER_V8_NO_SCRIPT(isolate, context, BigInt, NewFromWords,
+                     MaybeLocal<BigInt>(), InternalEscapableScope);
+  i::MaybeHandle<i::BigInt> result =
+      i::BigInt::FromWords64(isolate, sign_bit, word_count, words);
+  has_pending_exception = result.is_null();
+  RETURN_ON_FAILED_EXECUTION(BigInt);
+  RETURN_ESCAPED(Utils::ToLocal(result.ToHandleChecked()));
+}
+
+uint64_t v8::BigInt::Uint64Value(bool* lossless) const {
+  i::Handle<i::BigInt> handle = Utils::OpenHandle(this);
+  return handle->AsUint64(lossless);
+}
+
+int64_t v8::BigInt::Int64Value(bool* lossless) const {
+  i::Handle<i::BigInt> handle = Utils::OpenHandle(this);
+  return handle->AsInt64(lossless);
+}
+
+int BigInt::WordCount() const {
+  i::Handle<i::BigInt> handle = Utils::OpenHandle(this);
+  return handle->Words64Count();
+}
+
+void BigInt::ToWordsArray(int* sign_bit, int* word_count,
+                          uint64_t* words) const {
+  i::Handle<i::BigInt> handle = Utils::OpenHandle(this);
+  return handle->ToWordsArray64(sign_bit, word_count, words);
+}
+
 void Isolate::ReportExternalAllocationLimitReached() {
   i::Heap* heap = reinterpret_cast<i::Isolate*>(this)->heap();
   if (heap->gc_state() != i::Heap::NOT_IN_GC) return;

src/api.h

@@ -129,6 +129,7 @@ class RegisteredExtension {
   V(Promise, JSPromise)                        \
   V(Primitive, Object)                         \
   V(PrimitiveArray, FixedArray)                \
+  V(BigInt, BigInt)                            \
   V(ScriptOrModule, Script)
 
 class Utils {

src/counters.h

@@ -712,6 +712,7 @@ class RuntimeCallTimer final {
   V(ArrayBuffer_New)                                       \
   V(Array_CloneElementAt)                                  \
   V(Array_New)                                             \
+  V(BigInt_NewFromWords)                                   \
   V(BigInt64Array_New)                                     \
   V(BigUint64Array_New)                                    \
   V(BigIntObject_New)                                      \

src/objects/bigint.cc

@@ -2293,6 +2293,70 @@ Handle<BigInt> BigInt::FromUint64(Isolate* isolate, uint64_t n) {
   return MutableBigInt::MakeImmutable(result);
 }
 
+MaybeHandle<BigInt> BigInt::FromWords64(Isolate* isolate, int sign_bit,
+                                        int words64_count,
+                                        const uint64_t* words) {
+  if (words64_count < 0 || words64_count > kMaxLength / (64 / kDigitBits)) {
+    THROW_NEW_ERROR(isolate, NewRangeError(MessageTemplate::kBigIntTooBig),
+                    BigInt);
+  }
+  if (words64_count == 0) return MutableBigInt::Zero(isolate);
+  STATIC_ASSERT(kDigitBits == 64 || kDigitBits == 32);
+  int length = (64 / kDigitBits) * words64_count;
+  DCHECK_GT(length, 0);
+  if (kDigitBits == 32 && words[words64_count - 1] <= (1ULL << 32)) length--;
+
+  Handle<MutableBigInt> result;
+  if (!MutableBigInt::New(isolate, length).ToHandle(&result)) {
+    return MaybeHandle<BigInt>();
+  }
+
+  result->set_sign(sign_bit);
+  if (kDigitBits == 64) {
+    for (int i = 0; i < length; ++i) {
+      result->set_digit(i, static_cast<digit_t>(words[i]));
+    }
+  } else {
+    for (int i = 0; i < length; i += 2) {
+      digit_t lo = static_cast<digit_t>(words[i / 2]);
+      digit_t hi = static_cast<digit_t>(words[i / 2] >> 32);
+      result->set_digit(i, lo);
+      if (i + 1 < length) result->set_digit(i + 1, hi);
+    }
+  }
+
+  return MutableBigInt::MakeImmutable(result);
+}
+
+int BigInt::Words64Count() {
+  STATIC_ASSERT(kDigitBits == 64 || kDigitBits == 32);
+  return length() / (64 / kDigitBits) +
+         (kDigitBits == 32 && length() % 2 == 1 ? 1 : 0);
+}
+
+void BigInt::ToWordsArray64(int* sign_bit, int* words64_count,
+                            uint64_t* words) {
+  DCHECK_NE(sign_bit, nullptr);
+  DCHECK_NE(words64_count, nullptr);
+  *sign_bit = sign();
+  int available_words = *words64_count;
+  *words64_count = Words64Count();
+  if (available_words == 0) return;
+  DCHECK_NE(words, nullptr);
+
+  int len = length();
+  if (kDigitBits == 64) {
+    for (int i = 0; i < len && i < available_words; ++i) words[i] = digit(i);
+  } else {
+    for (int i = 0; i < len && available_words > 0; i += 2) {
+      uint64_t lo = digit(i);
+      uint64_t hi = (i + 1) < len ? digit(i + 1) : 0;
+      words[i / 2] = lo | (hi << 32);
+      available_words--;
+    }
+  }
+}
+
 uint64_t MutableBigInt::GetRawBits(BigIntBase* x, bool* lossless) {
   if (lossless != nullptr) *lossless = true;
   if (x->is_zero()) return 0;

src/objects/bigint.h

@@ -158,8 +158,13 @@ class V8_EXPORT_PRIVATE BigInt : public BigIntBase {
 
   static Handle<BigInt> FromInt64(Isolate* isolate, int64_t n);
   static Handle<BigInt> FromUint64(Isolate* isolate, uint64_t n);
+  static MaybeHandle<BigInt> FromWords64(Isolate* isolate, int sign_bit,
+                                         int words64_count,
+                                         const uint64_t* words);
   int64_t AsInt64(bool* lossless = nullptr);
   uint64_t AsUint64(bool* lossless = nullptr);
+  int Words64Count();
+  void ToWordsArray64(int* sign_bit, int* words64_count, uint64_t* words);
 
   DECL_CAST(BigInt)
   DECL_VERIFIER(BigInt)

test/cctest/test-api.cc

@@ -28262,3 +28262,117 @@ TEST(AtomicsWaitCallback) {
     CHECK_EQ(try_catch.Exception().As<v8::Int32>()->Value(), 42);
   }
 }
+
+TEST(BigIntAPI) {
+  LocalContext env;
+  v8::Isolate* isolate = env->GetIsolate();
+  v8::HandleScope scope(isolate);
+  bool lossless;
+  uint64_t words1[10];
+  uint64_t words2[10];
+
+  {
+    Local<Value> bi = CompileRun("12n");
+    CHECK(bi->IsBigInt());
+
+    CHECK_EQ(bi.As<v8::BigInt>()->Uint64Value(), 12);
+    CHECK_EQ(bi.As<v8::BigInt>()->Uint64Value(&lossless), 12);
+    CHECK_EQ(lossless, true);
+    CHECK_EQ(bi.As<v8::BigInt>()->Int64Value(), 12);
+    CHECK_EQ(bi.As<v8::BigInt>()->Int64Value(&lossless), 12);
+    CHECK_EQ(lossless, true);
+  }
+
+  {
+    Local<Value> bi = CompileRun("-12n");
+    CHECK(bi->IsBigInt());
+
+    CHECK_EQ(bi.As<v8::BigInt>()->Uint64Value(), static_cast<uint64_t>(-12));
+    CHECK_EQ(bi.As<v8::BigInt>()->Uint64Value(&lossless),
+             static_cast<uint64_t>(-12));
+    CHECK_EQ(lossless, false);
+    CHECK_EQ(bi.As<v8::BigInt>()->Int64Value(), -12);
+    CHECK_EQ(bi.As<v8::BigInt>()->Int64Value(&lossless), -12);
+    CHECK_EQ(lossless, true);
+  }
+
+  {
+    Local<Value> bi = CompileRun("123456789012345678901234567890n");
+    CHECK(bi->IsBigInt());
+
+    CHECK_EQ(bi.As<v8::BigInt>()->Uint64Value(), 14083847773837265618ULL);
+    CHECK_EQ(bi.As<v8::BigInt>()->Uint64Value(&lossless),
+             14083847773837265618ULL);
+    CHECK_EQ(lossless, false);
+    CHECK_EQ(bi.As<v8::BigInt>()->Int64Value(), -4362896299872285998LL);
+    CHECK_EQ(bi.As<v8::BigInt>()->Int64Value(&lossless),
+             -4362896299872285998LL);
+    CHECK_EQ(lossless, false);
+  }
+
+  {
+    Local<Value> bi = CompileRun("-123456789012345678901234567890n");
+    CHECK(bi->IsBigInt());
+
+    CHECK_EQ(bi.As<v8::BigInt>()->Uint64Value(), 4362896299872285998LL);
+    CHECK_EQ(bi.As<v8::BigInt>()->Uint64Value(&lossless),
+             4362896299872285998LL);
+    CHECK_EQ(lossless, false);
+    CHECK_EQ(bi.As<v8::BigInt>()->Int64Value(), 4362896299872285998LL);
+    CHECK_EQ(bi.As<v8::BigInt>()->Int64Value(&lossless), 4362896299872285998LL);
+    CHECK_EQ(lossless, false);
+  }
+
+  {
+    Local<v8::BigInt> bi =
+        v8::BigInt::NewFromWords(env.local(), 0, 0, words1).ToLocalChecked();
+    CHECK_EQ(bi->Uint64Value(), 0);
+    CHECK_EQ(bi->WordCount(), 0);
+  }
+
+  {
+    TryCatch try_catch(isolate);
+    v8::MaybeLocal<v8::BigInt> bi = v8::BigInt::NewFromWords(
+        env.local(), 0, std::numeric_limits<int>::max(), words1);
+    CHECK(bi.IsEmpty());
+    CHECK(try_catch.HasCaught());
+  }
+
+  {
+    TryCatch try_catch(isolate);
+    v8::MaybeLocal<v8::BigInt> bi =
+        v8::BigInt::NewFromWords(env.local(), 0, -1, words1);
+    CHECK(bi.IsEmpty());
+    CHECK(try_catch.HasCaught());
+  }
+
+  {
+    TryCatch try_catch(isolate);
+    v8::MaybeLocal<v8::BigInt> bi =
+        v8::BigInt::NewFromWords(env.local(), 0, 1 << 30, words1);
+    CHECK(bi.IsEmpty());
+    CHECK(try_catch.HasCaught());
+  }
+
+  for (int sign_bit = 0; sign_bit <= 1; sign_bit++) {
+    words1[0] = 0xffffffff00000000ULL;
+    words1[1] = 0x00000000ffffffffULL;
+    v8::Local<v8::BigInt> bi =
+        v8::BigInt::NewFromWords(env.local(), sign_bit, 2, words1)
+            .ToLocalChecked();
+    CHECK_EQ(bi->Uint64Value(&lossless),
+             sign_bit ? static_cast<uint64_t>(-static_cast<int64_t>(words1[0]))
+                      : words1[0]);
+    CHECK_EQ(lossless, false);
+    CHECK_EQ(bi->Int64Value(&lossless), sign_bit
+                                            ? -static_cast<int64_t>(words1[0])
+                                            : static_cast<int64_t>(words1[0]));
+    CHECK_EQ(lossless, false);
+    CHECK_EQ(bi->WordCount(), 2);
+    int real_sign_bit;
+    int word_count = arraysize(words2);
+    bi->ToWordsArray(&real_sign_bit, &word_count, words2);
+    CHECK_EQ(real_sign_bit, sign_bit);
+    CHECK_EQ(word_count, 2);
+  }
+}