Remove bounds checking for unicode table access in Go

gen/wcwidth.py

@@ -506,6 +506,10 @@ class Property(Protocol):
     def as_go(self) -> str:
         return ''
 
+    @classmethod
+    def bitsize(cls) -> int:
+        return 0
+
 
 def get_types(sz: int) -> tuple[str, str]:
     sz *= 8
@@ -514,11 +518,15 @@ def get_types(sz: int) -> tuple[str, str]:
 
 def gen_multistage_table(
     c: Callable[..., None], g: Callable[..., None], t1: Sequence[int], t2: Sequence[int], t3: Sequence[Property], shift: int,
+    for_go_type: str, maxval: int = 0
 ) -> None:
-    ctype_t1, gotype_t1 = get_types(getsize(t1))
+    t1_type_sz = getsize(t1)
+    ctype_t1, gotype_t1 = get_types(t1_type_sz)
     mask = mask_for(shift)
     name = t3[0].__class__.__name__
-    ctype_t2, gotype_t2 = get_types(getsize(tuple(range(len(t3)))))
+    t2_type_sz = getsize(tuple(range(len(t3))))
+    ctype_t2, gotype_t2 = get_types(t2_type_sz)
+    t3_type_sz = t3[0].bitsize() // 8
     c(f'static const char_type {name}_mask = {mask}u;')
     c(f'static const char_type {name}_shift = {shift}u;')
     c(f'static const {ctype_t1} {name}_t1[{len(t1)}] = ''{')
@@ -546,6 +554,17 @@ def gen_multistage_table(
     g(f'\t{items}')
     g('}')
 
+    check = f'x = max(0, min(x, {maxval}))' if maxval else ''
+    g(f'''
+// Array accessor function that avoids bounds checking
+func {name}For(x {for_go_type}) {name} {{
+    {check}
+	t1 := uintptr(*(*{gotype_t1})(unsafe.Pointer(uintptr(unsafe.Pointer(&{lname}_t1[0])) + uintptr(x>>{lname}_shift)*{t1_type_sz})))
+    t1_shifted := (t1 << {lname}_shift) + (uintptr(x) & {lname}_mask)
+	t2 := uintptr(*(*{gotype_t2})(unsafe.Pointer(uintptr(unsafe.Pointer(&{lname}_t2[0])) + t1_shifted*{t2_type_sz})))
+	return *(*{name})(unsafe.Pointer(uintptr(unsafe.Pointer(&{lname}_t3[0])) + t2*{t3_type_sz}))
+}}
+''')
 
 width_shift = 4
 
@@ -919,7 +938,6 @@ func (r GraphemeSegmentationResult) State() (ans {base_type}) {{
         return bitfield_declaration_as_c('GraphemeSegmentationResult', fields, {'state': bits})
 
 
-
 class CharProps(NamedTuple):
 
     width: int = 3
@@ -1127,17 +1145,19 @@ def gen_char_props() -> None:
     with create_header('kitty/char-props-data.h', include_data_types=False) as c, open('tools/wcswidth/char-props-data.go', 'w') as gof:
         gp = partial(print, file=gof)
         gp('package wcswidth')
+        gp('import "unsafe"')
         generate_enum(c, gp, 'GraphemeBreakProperty', *grapheme_segmentation_maps, prefix='GBP_')
         generate_enum(c, gp, 'IndicConjunctBreak', *incb_map, prefix='ICB_')
         cen('// UCBDeclaration {{''{')
+        cen(f'#define MAX_UNICODE ({sys.maxunicode}u)')
         generate_enum(cen, gp, 'UnicodeCategory', 'Cn', *class_maps, prefix='UC_')
         cen('// EndUCBDeclaration }}''}')
         gp(make_bitfield('tools/wcswidth', 'CharProps', *CharProps.go_fields(), add_package=False)[1])
         gp(make_bitfield('tools/wcswidth', 'GraphemeSegmentationResult', *GraphemeSegmentationResult.go_fields(), add_package=False)[1])
         gp(CharProps.go_extra())
         gp(GraphemeSegmentationResult.go_extra())
-        gen_multistage_table(c, gp, t1, t2, t3, t_shift)
-        gen_multistage_table(c, gp, g1, g2, g3, g_shift)
+        gen_multistage_table(c, gp, t1, t2, t3, t_shift, 'rune', sys.maxunicode)
+        gen_multistage_table(c, gp, g1, g2, g3, g_shift, 'uint16')
         c(GraphemeSegmentationKey.code_to_convert_to_int())
         c(GraphemeSegmentationState.c_declaration())
         gp(GraphemeSegmentationKey.code_to_convert_to_int(for_go=True))

kitty/char-props.c

@@ -11,6 +11,7 @@
 
 CharProps
 char_props_for(char_type ch) {
+    if (ch > MAX_UNICODE) ch = 0;
     return CharProps_t3[CharProps_t2[(CharProps_t1[ch >> CharProps_shift] << CharProps_shift) + (ch & CharProps_mask)]];
 }
 

kitty/char-props.h

@@ -104,6 +104,7 @@ static_assert(sizeof(GraphemeSegmentationResult) == sizeof(uint16_t), "Fix the o
 // EndGraphemeSegmentationResultDeclaration }}}
 
 // UCBDeclaration {{{
+#define MAX_UNICODE (1114111u)
 typedef enum UnicodeCategory {
 	UC_Cn,
 	UC_Cc,

tools/wcswidth/char-props-data.go

@@ -1,5 +1,7 @@
 package wcswidth
 
+import "unsafe"
+
 type GraphemeBreakProperty uint8
 
 const (
@@ -384,6 +386,15 @@ var charprops_t3 = [109]CharProps{
 	((0 & 0b1) << 0) | ((CharProps(ICB_Extend) & 0b11) << 1) | ((CharProps(GBP_Extend) & 0b1111) << 3) | ((0 & 0b1) << 7) | ((0 & 0b1) << 8) | ((1 & 0b1) << 9) | ((0 & 0b1) << 10) | ((1 & 0b1) << 11) | ((0 & 0b1) << 12) | ((0 & 0b1) << 13) | ((CharProps(UC_Cf) & 0b11111) << 14) | ((0 & 0b1) << 19) | ((4 & 0b111) << 20),           // 108
 }
 
+// Array accessor function that avoids bounds checking
+func CharPropsFor(x rune) CharProps {
+	x = max(0, min(x, 1114111))
+	t1 := uintptr(*(*uint8)(unsafe.Pointer(uintptr(unsafe.Pointer(&charprops_t1[0])) + uintptr(x>>charprops_shift)*1)))
+	t1_shifted := (t1 << charprops_shift) + (uintptr(x) & charprops_mask)
+	t2 := uintptr(*(*uint8)(unsafe.Pointer(uintptr(unsafe.Pointer(&charprops_t2[0])) + t1_shifted*1)))
+	return *(*CharProps)(unsafe.Pointer(uintptr(unsafe.Pointer(&charprops_t3[0])) + t2*4))
+}
+
 const graphemesegmentationresult_mask = 15
 const graphemesegmentationresult_shift = 4
 
@@ -1026,6 +1037,15 @@ var graphemesegmentationresult_t3 = [630]GraphemeSegmentationResult{
 	((GraphemeSegmentationResult(GBP_ZWJ) & 0b1111) << 0) | ((1 & 0b1) << 4) | ((0 & 0b1) << 5) | ((1 & 0b1) << 6) | ((1 & 0b1) << 7) | ((1 & 0b1) << 8) | ((0 & 0b1) << 9),                  // 629
 }
 
+// Array accessor function that avoids bounds checking
+func GraphemeSegmentationResultFor(x uint16) GraphemeSegmentationResult {
+
+	t1 := uintptr(*(*uint8)(unsafe.Pointer(uintptr(unsafe.Pointer(&graphemesegmentationresult_t1[0])) + uintptr(x>>graphemesegmentationresult_shift)*1)))
+	t1_shifted := (t1 << graphemesegmentationresult_shift) + (uintptr(x) & graphemesegmentationresult_mask)
+	t2 := uintptr(*(*uint16)(unsafe.Pointer(uintptr(unsafe.Pointer(&graphemesegmentationresult_t2[0])) + t1_shifted*2)))
+	return *(*GraphemeSegmentationResult)(unsafe.Pointer(uintptr(unsafe.Pointer(&graphemesegmentationresult_t3[0])) + t2*2))
+}
+
 func grapheme_segmentation_key(r GraphemeSegmentationResult, ch CharProps) uint16 {
 	return (r.State() << 7) | ch.GraphemeSegmentationProperty()
 }

tools/wcswidth/char-props.go

@@ -7,10 +7,6 @@ import (
 
 var _ = fmt.Print
 
-func CharPropsFor(ch rune) CharProps {
-	return charprops_t3[charprops_t2[(rune(charprops_t1[ch>>charprops_shift])<<charprops_shift)+(ch&charprops_mask)]]
-}
-
 func IteratorOverGraphemes(text string) iter.Seq[string] {
 	var s GraphemeSegmentationResult
 	start_pos := 0
@@ -43,11 +39,7 @@ func (s *GraphemeSegmentationResult) Reset() {
 
 func (s GraphemeSegmentationResult) Step(ch CharProps) GraphemeSegmentationResult {
 	key := grapheme_segmentation_key(s, ch)
-	t1 := uint16(graphemesegmentationresult_t1[key>>graphemesegmentationresult_shift]) << graphemesegmentationresult_shift
-	t2 := graphemesegmentationresult_t2[t1+key&graphemesegmentationresult_mask]
-	ans := graphemesegmentationresult_t3[t2]
-	// fmt.Printf("state: %d gsp: %d -> key: %d t1: %d -> add_to_cell: %d\n", s.State(), ch.GraphemeSegmentationProperty(), key, t1, ans.Add_to_current_cell())
-	return ans
+	return GraphemeSegmentationResultFor(key)
 }
 
 func Runewidth(code rune) int {