Implement BigInt asIntN and asUintN methods (#5165)

The following methods were implemented:
- BigInt.asIntN
- BigInt.asUintN

Custom dispatcher also added to builtin_bigint.

The implementation is based on PR #4736, only applied the requested changes.

Co-authored-by: Daniel Batiz [email protected]
JerryScript-DCO-1.0-Signed-off-by: Gergo Csizi [email protected]

Author: gergocs

jerry-core/ecma/builtin-objects/ecma-builtin-bigint.c

@@ -13,6 +13,7 @@
  * limitations under the License.
  */
 
+#include "ecma-big-uint.h"
 #include "ecma-bigint.h"
 #include "ecma-builtins.h"
 #include "ecma-exceptions.h"
@@ -22,6 +23,21 @@
 #define ECMA_BUILTINS_INTERNAL
 #include "ecma-builtins-internal.h"
 
+/**
+ * This object has a custom dispatch function.
+ */
+#define BUILTIN_CUSTOM_DISPATCH
+
+/**
+ * List of built-in routine identifiers.
+ */
+enum
+{
+  ECMA_BUILTIN_BIGINT_START = 0, /**< Special value, should be ignored */
+  ECMA_BUILTIN_BIGINT_AS_INT_N, /**< The 'asIntN' routine of the BigInt object */
+  ECMA_BUILTIN_BIGINT_AS_U_INT_N, /**< The 'asUintN' routine of the BigInt object */
+};
+
 #define BUILTIN_INC_HEADER_NAME "ecma-builtin-bigint.inc.h"
 #define BUILTIN_UNDERSCORED_ID  bigint
 #include "ecma-builtin-internal-routines-template.inc.h"
@@ -36,6 +52,286 @@
  * @{
  */
 
+/**
+ * The BigInt object's 'asIntN' and 'asUintN' routines
+ *
+ * See also:
+ *          ECMA-262 v15, 21.2.2
+ *
+ * @return ecma value
+ *         Truncated BigInt value for the given number of LSBs
+ *         as an integer or unsigned integer.
+ *         Returned value must be freed with ecma_free_value.
+ */
+static ecma_value_t
+ecma_builtin_bigint_object_as_int_n (ecma_value_t bits, /**< number of bits */
+                                     ecma_value_t bigint, /**< bigint number */
+                                     bool is_signed) /**< The operation is signed */
+{
+  ecma_number_t input_bits;
+  ecma_value_t bit_value = ecma_op_to_index (bits, &input_bits);
+
+  if (ECMA_IS_VALUE_ERROR (bit_value))
+  {
+    return bit_value;
+  }
+
+  ecma_value_t bigint_value = ecma_bigint_to_bigint (bigint, false);
+
+  if (ECMA_IS_VALUE_ERROR (bigint_value))
+  {
+    return bigint_value;
+  }
+
+  if (input_bits == 0 || bigint_value == ECMA_BIGINT_ZERO)
+  {
+    ecma_free_value (bigint_value);
+    return ECMA_BIGINT_ZERO;
+  }
+
+  ecma_extended_primitive_t *input_bigint_p = ecma_get_extended_primitive_from_value (bigint_value);
+  uint32_t bigint_size = ECMA_BIGINT_GET_SIZE (input_bigint_p);
+
+  if (input_bits >= UINT32_MAX)
+  {
+    return bigint_value;
+  }
+
+  uint8_t input_bigint_sign = input_bigint_p->u.bigint_sign_and_size & ECMA_BIGINT_SIGN;
+  const uint32_t size_of_divisor_in_bits = sizeof (uint32_t) * JERRY_BITSINBYTE;
+  uint32_t whole_part = (uint32_t) input_bits / size_of_divisor_in_bits;
+  uint32_t remainder = (uint32_t) input_bits % size_of_divisor_in_bits;
+  uint32_t input_bit_length =
+    (whole_part == 0 || remainder == 0) ? (uint32_t) input_bits : (whole_part + 1) * size_of_divisor_in_bits;
+
+  uint32_t input_byte_size = (uint32_t) input_bits / JERRY_BITSINBYTE;
+
+  if ((uint32_t) input_bits % JERRY_BITSINBYTE != 0)
+  {
+    input_byte_size += 1;
+  }
+
+  const uint32_t input_bits_in_byte = (uint32_t) input_bit_length / JERRY_BITSINBYTE;
+  uint32_t min_size = (input_bits_in_byte < bigint_size) ? input_bits_in_byte : bigint_size;
+
+  if (input_bigint_sign && (input_byte_size > bigint_size))
+  {
+    min_size = (input_bits_in_byte > bigint_size) ? input_bits_in_byte : bigint_size;
+  }
+
+  if (min_size < sizeof (uint32_t))
+  {
+    min_size = sizeof (uint32_t);
+  }
+
+  ecma_extended_primitive_t *result_p = ecma_bigint_create ((uint32_t) min_size);
+
+  if (JERRY_UNLIKELY (result_p == NULL))
+  {
+    ecma_deref_bigint (input_bigint_p);
+    return ECMA_VALUE_ERROR;
+  }
+
+  ecma_bigint_digit_t *last_digit_p = ECMA_BIGINT_GET_DIGITS (input_bigint_p, bigint_size);
+
+  /* Calculate the leading zeros of the input_bigint */
+
+  ecma_bigint_digit_t zeros = ecma_big_uint_count_leading_zero (last_digit_p[-1]);
+  uint32_t bits_of_bigint = (uint32_t) (bigint_size * JERRY_BITSINBYTE) - zeros;
+  uint32_t exact_size =
+    (input_bigint_sign || ((bits_of_bigint > (size_of_divisor_in_bits - 1)) && (input_byte_size < bigint_size)))
+      ? (uint32_t) input_byte_size
+      : bigint_size;
+
+  if (input_bigint_sign)
+  {
+    bits_of_bigint += 1;
+  }
+
+  if (bits_of_bigint > (input_bits - 1) || input_bigint_sign)
+  {
+    ecma_bigint_digit_t *digits_p = ECMA_BIGINT_GET_DIGITS (input_bigint_p, 0);
+    ecma_bigint_digit_t *digits_end_p = ECMA_BIGINT_GET_DIGITS (input_bigint_p, exact_size);
+    ecma_bigint_digit_t *result_number_p = ECMA_BIGINT_GET_DIGITS (result_p, 0);
+    int32_t first_cell = 0;
+    uint32_t surplus_bits =
+      (whole_part > 0) ? (uint32_t) (whole_part * size_of_divisor_in_bits) : (uint32_t) size_of_divisor_in_bits;
+    uint32_t mask_bit = (whole_part == 0) ? (uint32_t) input_bits : (uint32_t) input_bits - surplus_bits;
+
+    if (mask_bit == 0)
+    {
+      mask_bit = size_of_divisor_in_bits - 1;
+    }
+
+    uint32_t check_sign_mask = (uint32_t) 1 << (mask_bit - 1);
+    uint32_t mask = ((uint32_t) 1 << mask_bit) - 1;
+    uint32_t last_cell = (exact_size >= sizeof (uint32_t)) ? (uint32_t) (min_size / sizeof (uint32_t)) - 1 : 0;
+    bool is_positive = false;
+    bool is_representation_positive = false;
+
+    if (is_signed)
+    {
+      if (input_bigint_sign && ((~digits_p[last_cell] + 1) & check_sign_mask) == 0)
+      {
+        is_positive = true;
+      }
+
+      if ((digits_p[last_cell] & check_sign_mask) == 0)
+      {
+        is_representation_positive = true;
+      }
+    }
+
+    do
+    {
+      *result_number_p++ =
+        (is_representation_positive || (!is_signed && !input_bigint_sign)) ? *digits_p++ : ~(*digits_p++);
+      first_cell--;
+    } while (digits_p < digits_end_p);
+
+    int16_t equal_bits = 0;
+
+    if (remainder != 0)
+    {
+      equal_bits = -1;
+    }
+
+    int32_t last_cell_negative = (last_cell != 0) ? ((int32_t) last_cell * (-1)) : -1;
+    bool is_zero_values = false;
+
+    if (!is_signed)
+    {
+      if (input_bigint_sign)
+      {
+        is_zero_values = true;
+      }
+    }
+    else
+    {
+      if (((digits_p[-1] & check_sign_mask) > 0) || (result_number_p[-1] & check_sign_mask) > 0)
+      {
+        is_zero_values = true;
+      }
+    }
+
+    if (is_zero_values)
+    {
+      result_number_p[first_cell] += 1;
+
+      if (result_number_p[first_cell] == 0)
+      {
+        do
+        {
+          result_number_p[++first_cell] += 1;
+        } while (first_cell != equal_bits);
+
+        first_cell = last_cell_negative;
+      }
+    }
+
+    result_number_p[-1] &= mask;
+    uint32_t surplus = (uint32_t) (min_size - exact_size) / sizeof (ecma_char_t);
+    uint32_t new_size = result_p->u.bigint_sign_and_size;
+
+    if ((min_size - exact_size) % (sizeof (ecma_char_t)) > 0 && surplus == 0)
+    {
+      surplus += (uint32_t) sizeof (ecma_char_t);
+    }
+    else
+    {
+      surplus = (uint32_t) (surplus * sizeof (ecma_char_t));
+    }
+
+    if (min_size / JERRY_BITSINBYTE < 1)
+    {
+      surplus = 0;
+    }
+
+    if (is_signed)
+    {
+      if (result_p->u.bigint_sign_and_size > exact_size && min_size > sizeof (uint32_t)
+          && result_number_p[last_cell_negative] < 1)
+      {
+        new_size -= surplus;
+      }
+
+      new_size += 1;
+
+      if (is_positive || ((digits_p[-1] & check_sign_mask) == 0 && !input_bigint_sign))
+      {
+        new_size -= 1;
+      }
+    }
+
+    while (first_cell != 0 && result_number_p[first_cell] == 0)
+    {
+      first_cell++;
+    }
+
+    if (first_cell == 0)
+    {
+      ecma_deref_bigint (result_p);
+      ecma_deref_bigint (input_bigint_p);
+
+      return ECMA_BIGINT_ZERO;
+    }
+
+    last_cell_negative = first_cell + (int32_t) last_cell;
+    int16_t zero_section_cnt = 0;
+
+    while (last_cell_negative > first_cell)
+    {
+      if (result_number_p[last_cell_negative] == 0)
+      {
+        zero_section_cnt++;
+      }
+
+      last_cell_negative--;
+    }
+
+    uint32_t size_limit = sizeof (uint32_t);
+
+    if (zero_section_cnt >= 1)
+    {
+      size_limit = new_size - (uint32_t) zero_section_cnt * size_limit;
+      new_size = (size_limit < sizeof (uint32_t)) ? (uint32_t) (JERRY_BITSINBYTE - size_limit) : size_limit;
+    }
+
+    if (new_size < result_p->u.bigint_sign_and_size)
+    {
+      result_p->refs_and_type = ECMA_EXTENDED_PRIMITIVE_REF_ONE | ECMA_TYPE_BIGINT;
+      uint32_t new_size_remainder = new_size % sizeof (uint32_t);
+      ecma_extended_primitive_t *new_result_p = ecma_bigint_create (new_size - new_size_remainder);
+
+      new_result_p->u.bigint_sign_and_size += new_size_remainder;
+      memcpy (new_result_p + 1, result_p + 1, new_size - new_size_remainder);
+
+      ecma_deref_bigint (result_p);
+      ecma_deref_bigint (input_bigint_p);
+
+      return ecma_make_extended_primitive_value (new_result_p, ECMA_TYPE_BIGINT);
+    }
+
+    result_p->u.bigint_sign_and_size = new_size;
+    result_p->refs_and_type = ECMA_EXTENDED_PRIMITIVE_REF_ONE | ECMA_TYPE_BIGINT;
+
+    ecma_deref_bigint (input_bigint_p);
+    return ecma_make_extended_primitive_value (result_p, ECMA_TYPE_BIGINT);
+  }
+
+  memcpy (result_p + 1, input_bigint_p + 1, exact_size);
+  result_p->refs_and_type = ECMA_EXTENDED_PRIMITIVE_REF_ONE | ECMA_TYPE_BIGINT;
+
+  if (input_bigint_p->u.bigint_sign_and_size & ECMA_BIGINT_SIGN)
+  {
+    ecma_deref_bigint (input_bigint_p);
+    return ecma_bigint_negate (result_p);
+  }
+
+  ecma_deref_bigint (input_bigint_p);
+  return ecma_make_extended_primitive_value (result_p, ECMA_TYPE_BIGINT);
+} /* ecma_builtin_bigint_object_as_int_n */
+
 /**
  * Handle calling [[Call]] of built-in BigInt object
  *
@@ -71,6 +367,38 @@ ecma_builtin_bigint_dispatch_construct (const ecma_value_t *arguments_list_p, /*
   return ecma_raise_type_error (ECMA_ERR_BIGINT_FUNCTION_NOT_CONSTRUCTOR);
 } /* ecma_builtin_bigint_dispatch_construct */
 
+/**
+ * Dispatcher of the built-in's routines
+ *
+ * @return ecma value
+ *         Returned value must be freed with ecma_free_value.
+ */
+ecma_value_t
+ecma_builtin_bigint_dispatch_routine (uint8_t builtin_routine_id, /**< built-in wide routine identifier */
+                                      ecma_value_t this_arg, /**< 'this' argument value */
+                                      const ecma_value_t arguments_list_p[], /**< list of arguments
+                                                                              *   passed to routine */
+                                      uint32_t arguments_number) /**< length of arguments' list */
+{
+  JERRY_UNUSED_2 (this_arg, arguments_number);
+
+  switch (builtin_routine_id)
+  {
+    case ECMA_BUILTIN_BIGINT_AS_INT_N:
+    {
+      return ecma_builtin_bigint_object_as_int_n (arguments_list_p[0], arguments_list_p[1], true);
+    }
+    case ECMA_BUILTIN_BIGINT_AS_U_INT_N:
+    {
+      return ecma_builtin_bigint_object_as_int_n (arguments_list_p[0], arguments_list_p[1], false);
+    }
+    default:
+    {
+      JERRY_UNREACHABLE ();
+    }
+  }
+} /* ecma_builtin_bigint_dispatch_routine */
+
 /**
  * @}
  * @}

jerry-core/ecma/builtin-objects/ecma-builtin-bigint.inc.h

@@ -36,6 +36,11 @@ STRING_VALUE (LIT_MAGIC_STRING_NAME, LIT_MAGIC_STRING_BIGINT_UL, ECMA_PROPERTY_F
 /* ECMA-262 v11, 20.2.2.3 */
 OBJECT_VALUE (LIT_MAGIC_STRING_PROTOTYPE, ECMA_BUILTIN_ID_BIGINT_PROTOTYPE, ECMA_PROPERTY_FIXED)
 
+/* Routine properties:
+ *  (property name, C routine name, arguments number or NON_FIXED, value of the routine's length property) */
+
+ROUTINE (LIT_MAGIC_STRING_AS_INT_N, ECMA_BUILTIN_BIGINT_AS_INT_N, 2, 2)
+ROUTINE (LIT_MAGIC_STRING_AS_U_INT_N, ECMA_BUILTIN_BIGINT_AS_U_INT_N, 2, 2)
 #endif /* JERRY_BUILTIN_BIGINT */
 
 #include "ecma-builtin-helpers-macro-undefs.inc.h"

jerry-core/lit/lit-magic-strings.inc.h

@@ -294,6 +294,9 @@ LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_SCRIPT_UL, "Script")
 #endif /* JERRY_PARSER */
 LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_STRING_UL, "String")
 LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_SYMBOL_UL, "Symbol")
+#if JERRY_BUILTIN_BIGINT
+LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_AS_INT_N, "asIntN")
+#endif /* JERRY_BUILTIN_BIGINT */
 LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_ASSIGN, "assign")
 #if JERRY_BUILTIN_BIGINT
 LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_BIGINT, "bigint")
@@ -411,6 +414,9 @@ LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_WEAKREF_UL, "WeakRef")
 #if JERRY_BUILTIN_CONTAINER
 LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_WEAKSET_UL, "WeakSet")
 #endif /* JERRY_BUILTIN_CONTAINER */
+#if JERRY_BUILTIN_BIGINT
+LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_AS_U_INT_N, "asUintN")
+#endif /* JERRY_BUILTIN_BIGINT */
 LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_BOOLEAN, "boolean")
 #if JERRY_BUILTIN_ANNEXB && JERRY_BUILTIN_REGEXP
 LIT_MAGIC_STRING_DEF (LIT_MAGIC_STRING_COMPILE, "compile")

jerry-core/lit/lit-magic-strings.ini

@@ -144,6 +144,8 @@ LIT_MAGIC_STRING_THROW = "throw"
 LIT_MAGIC_STRING_TRUNC = "trunc"
 LIT_MAGIC_STRING_VALUE = "value"
 LIT_MAGIC_STRING_SOURCE_NAME_EVAL = "<eval>"
+LIT_MAGIC_STRING_AS_INT_N = "asIntN"
+LIT_MAGIC_STRING_AS_U_INT_N = "asUintN"
 LIT_MAGIC_STRING_BIGINT_UL = "BigInt"
 LIT_MAGIC_STRING_ERRORS_UL = "errors"
 LIT_MAGIC_STRING_HAS_OWN_UL = "hasOwn"