core: implement Float::to_precision in C without callbacks

[nit.git] / lib / core / text / abstract_text.nit

diff --git a/lib/core/text/abstract_text.nit b/lib/core/text/abstract_text.nit
index ea438de..3f37a81 100644 (file)
--- a/lib/core/text/abstract_text.nit
+++ b/lib/core/text/abstract_text.nit
@@ -789,17 +789,17 @@ abstract class Text
                if pos == null then pos = 0
                if ln == null then ln = length - pos
                if ln < 6 then return 0xFFFD.code_point
-               var cp = from_utf16_digit(pos + 2)
-               if cp < 0xD800 then return cp.code_point
-               if cp > 0xDFFF then return cp.code_point
-               if cp > 0xDBFF then return 0xFFFD.code_point
+               var cp = from_utf16_digit(pos + 2).to_u32
+               if cp < 0xD800u32 then return cp.code_point
+               if cp > 0xDFFFu32 then return cp.code_point
+               if cp > 0xDBFFu32 then return 0xFFFD.code_point
                if ln == 6 then return 0xFFFD.code_point
                if ln < 12 then return 0xFFFD.code_point
                cp <<= 16
-               cp += from_utf16_digit(pos + 8)
-               var cplo = cp & 0xFFFF
-               if cplo < 0xDC00 then return 0xFFFD.code_point
-               if cplo > 0xDFFF then return 0xFFFD.code_point
+               cp += from_utf16_digit(pos + 8).to_u32
+               var cplo = cp & 0xFFFFu32
+               if cplo < 0xDC00u32 then return 0xFFFD.code_point
+               if cplo > 0xDFFFu32 then return 0xFFFD.code_point
                return cp.from_utf16_surr.code_point
        end
 
@@ -1915,35 +1915,23 @@ redef class Float
                        return  "-inf"
                end
 
-               if decimals == 0 then return self.to_i.to_s
-               var f = self
-               for i in [0..decimals[ do f = f * 10.0
-               if self > 0.0 then
-                       f = f + 0.5
-               else
-                       f = f - 0.5
-               end
-               var i = f.to_i
-               if i == 0 then return "0." + "0"*decimals
-
-               # Prepare both parts of the float, before and after the "."
-               var s = i.abs.to_s
-               var sl = s.length
-               var p1
-               var p2
-               if sl > decimals then
-                       # Has something before the "."
-                       p1 = s.substring(0, sl-decimals)
-                       p2 = s.substring(sl-decimals, decimals)
-               else
-                       p1 = "0"
-                       p2 = "0"*(decimals-sl) + s
-               end
+               var size = to_precision_size(decimals)
+               var cstr = new CString(size+1)
+               to_precision_fill(decimals, size+1, cstr)
+               return cstr.to_s_unsafe(byte_length=size, copy=false)
+       end
 
-               if i < 0 then p1 = "-" + p1
+       # Required string length to hold `self` with `nb` decimals
+       #
+       # The length does not include the terminating null byte.
+       private fun to_precision_size(nb: Int): Int `{
+               return snprintf(NULL, 0, "%.*f", (int)nb, self);
+       `}
 
-               return p1 + "." + p2
-       end
+       # Fill `cstr` with `self` and `nb` decimals
+       private fun to_precision_fill(nb, size: Int, cstr: CString) `{
+               snprintf(cstr, size, "%.*f", (int)nb, self);
+       `}
 end
 
 redef class Char