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freetype/truetype: implement Font.Index binary search.

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R=bsiegert
CC=golang-dev
https://codereview.appspot.com/14604044
This commit is contained in:
Nigel Tao 2013-10-12 09:29:59 +11:00
parent 0a778f7f02
commit 9e24a6204e
2 changed files with 12 additions and 9 deletions
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19
freetype/truetype/truetype.go
View File

@ -323,14 +323,17 @@ func (f *Font) FUnitsPerEm() int32 {
// Index returns a Font's index for the given rune.
func (f *Font) Index(x rune) Index {
c := uint32(x)
n := len(f.cm)
// TODO: binary search.
for i := 0; i < n; i++ {
if f.cm[i].start <= c && c <= f.cm[i].end {
if f.cm[i].offset == 0 {
return Index(c + f.cm[i].delta)
}
offset := int(f.cm[i].offset) + 2*(i-n+int(c-f.cm[i].start))
for i, j := 0, len(f.cm); i < j; {
h := i + (j-i)/2
cm := &f.cm[h]
if c < cm.start {
j = h
} else if cm.end < c {
i = h + 1
} else if cm.offset == 0 {
return Index(c + cm.delta)
} else {
offset := int(cm.offset) + 2*(h-len(f.cm)+int(c-cm.start))
return Index(u16(f.cmapIndexes, offset))
}
}

2
freetype/truetype/truetype_test.go
View File

@ -177,7 +177,7 @@ func TestIndex(t *testing.T) {
}
for r, want := range wants {
if got := font.Index(r); got != want {
t.Errorf("%s: Index(%q): got %d, want %d", name, r, got, want)
t.Errorf("%s: Index of %q, aka %U: got %d, want %d", name, r, r, got, want)
}
}
}