1 files changed, 91 insertions, 204 deletions

diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-number-prototype.c b/jerry-core/ecma/builtin-objects/ecma-builtin-number-prototype.c
index 2e94f3a1..1d212f5f 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-number-prototype.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-number-prototype.c
@@ -21,6 +21,7 @@
 #include "ecma-exceptions.h"
 #include "ecma-gc.h"
 #include "ecma-globals.h"
+#include "ecma-helpers-number.h"
 #include "ecma-helpers.h"
 #include "ecma-objects.h"
 #include "ecma-string-object.h"
@@ -133,6 +134,11 @@ ecma_builtin_number_prototype_helper_round (lit_utf8_byte_t *digits_p, /**< [in,
 } /* ecma_builtin_number_prototype_helper_round */
 
 /**
+ * Size of Number toString digit buffers.
+ */
+#define NUMBER_TO_STRING_MAX_DIGIT_COUNT 64u
+
+/**
  * The Number.prototype object's 'toString' and 'toLocaleString' routines
  *
  * See also:
@@ -176,249 +182,130 @@ ecma_builtin_number_prototype_object_to_string (ecma_number_t this_arg_number, /
     return ecma_make_string_value (ret_str_p);
   }
 
-  int buff_size = 0;
-
+  uint8_t integer_digits[NUMBER_TO_STRING_MAX_DIGIT_COUNT];
+  uint8_t fraction_digits[NUMBER_TO_STRING_MAX_DIGIT_COUNT];
+  uint32_t integer_zeros = 0;
+  uint32_t fraction_zeros = 0;
   bool is_number_negative = false;
+
   if (ecma_number_is_negative (this_arg_number))
   {
-    /* ecma_number_to_decimal can't handle negative numbers, so we get rid of the sign. */
     this_arg_number = -this_arg_number;
     is_number_negative = true;
-
-    /* Add space for the sign in the result. */
-    buff_size += 1;
   }
 
-  /* Decompose the number. */
-  lit_utf8_byte_t digits[ECMA_MAX_CHARS_IN_STRINGIFIED_NUMBER];
-  int32_t exponent;
-  lit_utf8_size_t digit_count = ecma_number_to_decimal (this_arg_number, digits, &exponent);
-
-  /*
-   * The 'exponent' given by 'ecma_number_to_decimal' specifies where the decimal point is located
-   * compared to the first digit in 'digits'.
-   * For example: 120 -> '12', exp: 3 and 0.012 -> '12', exp: -1
-   * We convert it to be location of the decimal point compared to the last digit of 'digits':
-   * 120 -> 12 * 10^1 and 0.012 -> 12 * 10^-3
-   */
-  exponent = exponent - (int32_t) digit_count;
-
-  /* 'magnitude' will be the magnitude of the number in the specific radix. */
-  int magnitude;
-  int required_digits;
-  if (exponent >= 0)
-  {
-    /*
-     * If the exponent is non-negative that means we won't have a fractional part, and can calculate
-     * exactly how many digits we will have. This could be done via a mathematic formula, but in rare
-     * cases that can cause incorrect results due to precision issues, so we use a loop instead.
-     */
-    magnitude = 0;
-    ecma_number_t counter = this_arg_number;
-    while (counter >= radix)
-    {
-      counter /= radix;
-      magnitude++;
-    }
+  ecma_number_t integer_part = floor (this_arg_number);
+  ecma_number_t fraction_part = this_arg_number - integer_part;
 
-    /*
-     * The magnitude will only tell us how many digits we have after the first one, so we add one extra.
-     * In this case we won't be needing a radix point, so we don't need to worry about space for it.
-     */
-    required_digits = magnitude + 1;
-  }
-  else
-  {
-    /*
-     * We can't know exactly how many digits we will need, since the number may be non-terminating in the
-     * new radix, so we will have to estimate it. We do this by first calculating how many zeros we will
-     * need in the specific radix before we hit a significant digit. This is calculated from the decimal
-     * exponent, which we negate so that we get a positive number in the end.
-     */
-    magnitude = (int) floor ((log (10) / log (radix)) * -exponent);
-
-    /*
-     * We also need to add space for significant digits. The worst case is radix == 2, since this will
-     * require the most digits. In this case, the upper limit to the number of significant digits we can have is
-     * ECMA_NUMBER_FRACTION_WIDTH + 1. This should be sufficient for any number.
-     */
-    required_digits = magnitude + ECMA_NUMBER_FRACTION_WIDTH + 1;
-
-    /*
-     * We add an exta slot for the radix point. It is also likely that we will need extra space for a
-     * leading zero before the radix point. It's better to add space for that here as well, even if we may not
-     * need it, since later we won't be able to do so.
-     */
-    buff_size += 2;
-  }
-
-  /*
-   * Here we normalize the number so that it is as close to 0 as possible, which will prevent us from losing
-   * precision in case of extreme numbers when we later split the number into integer and fractional parts.
-   * This has to be done in the specific radix, otherwise it messes up the result, so we use magnitude instead.
-   */
-  if (exponent > 0)
-  {
-    for (int i = 0; i < magnitude; i++)
-    {
-      this_arg_number /= radix;
-    }
-  }
-  else if (exponent < 0)
+  uint8_t *integer_cursor_p = integer_digits + NUMBER_TO_STRING_MAX_DIGIT_COUNT;
+  uint8_t *fraction_cursor_p = fraction_digits;
+
+  if (fraction_part > 0.0)
   {
-    for (int i = 0; i < magnitude; i++)
+    uint8_t digit;
+    ecma_number_t precision = (ecma_number_get_next (this_arg_number) - this_arg_number) * 0.5f;
+    precision = JERRY_MAX (precision, ECMA_NUMBER_MIN_VALUE);
+
+    do
     {
-      this_arg_number *= radix;
-    }
-  }
+      fraction_part *= radix;
+      precision *= radix;
 
-  /* Split the number into an integer and a fractional part, since we have to handle them separately. */
-  uint64_t whole = (uint64_t) this_arg_number;
-  ecma_number_t fraction = this_arg_number - (ecma_number_t) whole;
+      digit = (uint8_t) floor (fraction_part);
 
-  bool should_round = false;
-  if (!ecma_number_is_zero (fraction) && exponent >= 0)
-  {
-    /*
-     * If the exponent is non-negative, and we get a non-zero fractional part, that means
-     * the normalization might have introduced a small error, in which case we have to correct it by rounding.
-     * We'll add one extra significant digit which we will later use to round.
-     */
-    required_digits += 1;
-    should_round = true;
-  }
+      if (digit == 0 && fraction_cursor_p == fraction_digits)
+      {
+        fraction_zeros++;
+        continue;
+      }
 
-  /* Get the total required buffer size and allocate the buffer. */
-  buff_size += required_digits;
-  ecma_value_t ret_value;
-  JMEM_DEFINE_LOCAL_ARRAY (buff, buff_size, lit_utf8_byte_t);
-  int buff_index = 0;
+      JERRY_ASSERT (fraction_cursor_p < fraction_digits + NUMBER_TO_STRING_MAX_DIGIT_COUNT);
+      *fraction_cursor_p++ = digit;
+      fraction_part -= (ecma_number_t) digit;
+    } while (fraction_part >= precision);
 
-  /* Calculate digits for whole part. */
-  while (whole > 0)
-  {
-    JERRY_ASSERT (buff_index < buff_size && buff_index < required_digits);
-    buff[buff_index++] = (lit_utf8_byte_t) (whole % radix);
-    whole /= radix;
-  }
+    /* Round to even */
+    if (fraction_part > 0.5 || (fraction_part == 0.5 && (digit & 1) != 0))
+    {
+      /* Add carry and remove overflowing trailing digits */
+      while (true)
+      {
+        (*(--fraction_cursor_p))++;
+
+        if (*fraction_cursor_p < radix)
+        {
+          /* Re-adjust cursor to point after the last significant digit */
+          fraction_cursor_p++;
+          break;
+        }
+
+        if (fraction_cursor_p == fraction_digits)
+        {
+          /* Carry overflowed to integer part */
+          integer_part += 1;
+          break;
+        }
+      }
+    }
 
-  /* The digits are backwards, we need to reverse them. */
-  for (int i = 0; i < buff_index / 2; i++)
-  {
-    lit_utf8_byte_t swap = buff[i];
-    buff[i] = buff[buff_index - i - 1];
-    buff[buff_index - i - 1] = swap;
+    /* Convert fraction digits to characters. */
+    for (uint8_t *digit_p = fraction_digits; digit_p < fraction_cursor_p; digit_p++)
+    {
+      *digit_p = digit_chars[*digit_p];
+    }
   }
 
-  /*
-   * Calculate where we have to put the radix point relative to the beginning of
-   * the new digits. If the exponent is non-negative this will be right after the number.
-   */
-  int point = exponent >= 0 ? magnitude + 1 : buff_index - magnitude;
-
-  if (point < 0)
+  while (ecma_number_biased_exp (ecma_number_to_binary (integer_part / radix))
+         > ECMA_NUMBER_EXPONENT_BIAS + ECMA_NUMBER_FRACTION_WIDTH)
   {
-    /*
-     * In this case the radix point will be before the first digit,
-     * so we need to leave space for leading zeros.
-     */
-    JERRY_ASSERT (exponent < 0);
-    required_digits += point;
+    integer_zeros++;
+    integer_part /= radix;
   }
 
-  JERRY_ASSERT (required_digits <= buff_size);
+  uint64_t integer_u64 = (uint64_t) integer_part;
 
-  /* Calculate digits for fractional part. */
-  while (buff_index < required_digits)
+  do
   {
-    fraction *= radix;
-    lit_utf8_byte_t digit = (lit_utf8_byte_t) floor (fraction);
+    uint64_t remainder = integer_u64 % radix;
+    *(--integer_cursor_p) = (uint8_t) digit_chars[remainder];
 
-    buff[buff_index++] = digit;
-    fraction -= (ecma_number_t) floor (fraction);
-  }
+    integer_u64 /= radix;
+  } while (integer_u64 > 0);
 
-  if (should_round)
-  {
-    /* Consume last digit for rounding. */
-    buff_index--;
-    if (buff[buff_index] > radix / 2)
-    {
-      /* We should be rounding up. */
-      buff[buff_index - 1]++;
+  const uint32_t integer_digit_count =
+    (uint32_t) (integer_digits + NUMBER_TO_STRING_MAX_DIGIT_COUNT - integer_cursor_p);
+  JERRY_ASSERT (integer_digit_count > 0);
 
-      /* Propagate carry forward in the digits. */
-      for (int i = buff_index - 1; i > 0 && buff[i] >= radix; i--)
-      {
-        buff[i] = (lit_utf8_byte_t) (buff[i] - radix);
-        buff[i - 1]++;
-      }
+  ecma_stringbuilder_t builder = ecma_stringbuilder_create ();
 
-      if (buff[0] >= radix)
-      {
-        /*
-         * Carry propagated over the whole number, we need to add a new leading digit.
-         * We can use the place of the original rounded digit, we just need to shift everything
-         * right by one.
-         */
-        memmove (buff + 1, buff, (size_t) buff_index);
-        buff_index++;
-        buff[0] = 1;
-      }
-    }
+  if (is_number_negative)
+  {
+    ecma_stringbuilder_append_byte (&builder, LIT_CHAR_MINUS);
   }
 
-  /* Remove trailing zeros. */
-  while (buff_index - 1 > point && buff[buff_index - 1] == 0)
+  ecma_stringbuilder_append_raw (&builder, integer_cursor_p, integer_digit_count);
+
+  while (integer_zeros--)
   {
-    buff_index--;
+    ecma_stringbuilder_append_byte (&builder, LIT_CHAR_0);
   }
 
-  /* Add leading zeros in case place of radix point is negative. */
-  if (point <= 0)
+  if (fraction_cursor_p != fraction_digits)
   {
-    /* We will have 'point' amount of zeros after the radix point, and +1 before. */
-    int zero_count = -point + 1;
-    memmove (buff + zero_count, buff, (size_t) buff_index);
-    buff_index += zero_count;
+    ecma_stringbuilder_append_byte (&builder, LIT_CHAR_DOT);
 
-    for (int i = 0; i < zero_count; i++)
+    while (fraction_zeros--)
     {
-      buff[i] = 0;
+      ecma_stringbuilder_append_byte (&builder, LIT_CHAR_0);
     }
 
-    /* We now need to place the radix point after the first zero. */
-    point = 1;
-  }
-
-  /* Convert digits to characters. */
-  for (int i = 0; i < buff_index; i++)
-  {
-    buff[i] = digit_chars[buff[i]];
-  }
-
-  /* Place radix point to the required position. */
-  if (point < buff_index)
-  {
-    memmove (buff + point + 1, buff + point, (size_t) (buff_index - point));
-    buff[point] = '.';
-    buff_index++;
-  }
+    const uint32_t fraction_digit_count = (uint32_t) (fraction_cursor_p - fraction_digits);
+    JERRY_ASSERT (fraction_digit_count > 0);
 
-  /* Add negative sign if necessary. */
-  if (is_number_negative)
-  {
-    memmove (buff + 1, buff, (size_t) buff_index);
-    buff[0] = '-';
-    buff_index++;
+    ecma_stringbuilder_append_raw (&builder, fraction_digits, fraction_digit_count);
   }
 
-  JERRY_ASSERT (buff_index <= buff_size);
-  ecma_string_t *str_p = ecma_new_ecma_string_from_utf8 (buff, (lit_utf8_size_t) buff_index);
-  ret_value = ecma_make_string_value (str_p);
-  JMEM_FINALIZE_LOCAL_ARRAY (buff);
-
-  return ret_value;
+  return ecma_make_string_value (ecma_stringbuilder_finalize (&builder));
 } /* ecma_builtin_number_prototype_object_to_string */
 
 /**