Implement the Dragonbox algorithm for Float#to_s (#10913)

crystal-lang · Aug 31, 2022 · d192a97 · d192a97
1 parent 34fe2c2
commit d192a97
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diff --git a/spec/std/crystal/compiler_rt/spec_helper.cr b/spec/std/crystal/compiler_rt/spec_helper.cr
@@ -1,4 +1,5 @@
 require "spec"
+require "../../../support/number"
 
 # TODO: Replace helper methods with literals once possible
 
@@ -9,82 +10,3 @@ end
 def make_tu(a : UInt128, b : UInt128)
   (a.to_u128! << 64) + b
 end
-
-# TODO: merge these helpers with #10913
-private module HexFloatConverter(F, U)
-  # Converts `str`, a hexadecimal floating-point literal, to an `F`. Truncates
-  # all unused bits in the mantissa.
-  def self.to_f(str : String) : F
-    m = str.match(/^(-?)0x([0-9A-Fa-f]+)(?:\.([0-9A-Fa-f]+))?p([+-]?)([0-9]+)#{"_?f32" if F == Float32}$/).not_nil!
-
-    total_bits = F == Float32 ? 32 : 64
-    mantissa_bits = F::MANT_DIGITS - 1
-    exponent_bias = F::MAX_EXP - 1
-
-    is_negative = m[1] == "-"
-    int_part = U.new(m[2], base: 16)
-    frac = m[3]?.try(&.[0, (mantissa_bits + 3) // 4]) || "0"
-    frac_part = U.new(frac, base: 16) << (mantissa_bits - frac.size * 4)
-    exponent = m[5].to_i * (m[4] == "-" ? -1 : 1)
-
-    if int_part > 1
-      last_bit = U.zero
-      while int_part > 1
-        last_bit = frac_part & 1
-        frac_part |= (U.new!(1) << mantissa_bits) if int_part & 1 != 0
-        frac_part >>= 1
-        int_part >>= 1
-        exponent += 1
-      end
-      if last_bit != 0
-        frac_part += 1
-        if frac_part >= U.new!(1) << mantissa_bits
-          frac_part = U.new!(0)
-          int_part += 1
-        end
-      end
-    elsif int_part == 0
-      while int_part == 0
-        frac_part <<= 1
-        if frac_part >= U.new!(1) << mantissa_bits
-          frac_part &= ~(U::MAX << mantissa_bits)
-          int_part += 1
-        end
-        exponent -= 1
-      end
-    end
-
-    exponent += exponent_bias
-    if exponent >= exponent_bias * 2 + 1
-      F::INFINITY * (is_negative ? -1 : 1)
-    elsif exponent < -mantissa_bits
-      F.zero * (is_negative ? -1 : 1)
-    elsif exponent <= 0
-      f = (frac_part >> (1 - exponent)) | (int_part << (mantissa_bits - 1 + exponent))
-      f |= U.new!(1) << (total_bits - 1) if is_negative
-      f.unsafe_as(F)
-    else
-      f = frac_part
-      f |= U.new!(exponent) << mantissa_bits
-      f |= U.new!(1) << (total_bits - 1) if is_negative
-      f.unsafe_as(F)
-    end
-  end
-end
-
-def hexfloat_f64(str : String) : Float64
-  HexFloatConverter(Float64, UInt64).to_f(str)
-end
-
-def hexfloat_f32(str : String) : Float32
-  HexFloatConverter(Float32, UInt32).to_f(str)
-end
-
-macro hexfloat(str)
-  {% raise "`str` must be a StringLiteral, not #{str.class_name}" unless str.is_a?(StringLiteral) %}
-  {% if str.ends_with?("_f32") %}
-    hexfloat_f32({{ str }})
-  {% else %}
-    hexfloat_f64({{ str }})
-  {% end %}
-end