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@@ -0,0 +1,299 @@
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// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ofdgo
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"fmt"
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"slices"
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)
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// errTTInvalidLocations 表示字形索引不满足递增偏移要求
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var errTTInvalidLocations = errors.New("invalid TrueType glyph locations")
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// normalizeTrueTypeLocations 验证物理字形边界后按原编号重排，不改变空字形和分量引用
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// 入参: tables 独占字体表目录，表内容只读
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// 返回: bool 是否重建索引, error 无法可靠恢复的索引或轮廓错误
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func normalizeTrueTypeLocations(tables map[string][]byte) (bool, error) {
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if _, ok := tables["glyf"]; !ok {
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return false, nil
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}
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head, maxp, loca, glyf := tables["head"], tables["maxp"], tables["loca"], tables["glyf"]
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if len(head) < 54 || len(maxp) < 6 {
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return false, fmt.Errorf("%w: missing header", errTTInvalidLocations)
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}
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count := int(binary.BigEndian.Uint16(maxp[4:]))
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width := 2
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switch binary.BigEndian.Uint16(head[50:]) {
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case 0:
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case 1:
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width = 4
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default:
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return false, fmt.Errorf("%w: format", errTTInvalidLocations)
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}
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if count == 0 || len(loca) < (count+1)*width {
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return false, fmt.Errorf("%w: truncated index", errTTInvalidLocations)
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}
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location := func(i int) uint64 {
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if width == 2 {
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return uint64(binary.BigEndian.Uint16(loca[i*2:])) * 2
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}
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return uint64(binary.BigEndian.Uint32(loca[i*4:]))
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}
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ordered, previous := true, uint64(0)
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for i := range count + 1 {
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offset := location(i)
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if offset > uint64(len(glyf)) {
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return false, fmt.Errorf("%w: offset %d outside table", errTTInvalidLocations, i)
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}
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ordered = ordered && previous <= offset
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previous = offset
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}
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if ordered {
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return false, nil
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}
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offsets := make([]int, count+1)
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for i := range offsets {
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offsets[i] = int(location(i))
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}
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physical := slices.Clone(offsets)
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physical = append(physical, len(glyf))
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slices.Sort(physical)
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physical = slices.Compact(physical)
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bodies := make(map[int][]byte, count)
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components := make([][]uint16, count)
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var total uint64
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for id := range count {
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start := offsets[id]
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if start == offsets[id+1] {
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continue
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}
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if _, duplicate := bodies[start]; duplicate {
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return false, fmt.Errorf("%w: ambiguous shared offset %d", errTTInvalidLocations, start)
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}
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index, _ := slices.BinarySearch(physical, start)
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if index+1 >= len(physical) {
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return false, fmt.Errorf("%w: missing glyph %d body", errTTInvalidLocations, id)
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}
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data := glyf[start:physical[index+1]]
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size, refs, err := trueTypeGlyphSize(data, count)
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if err != nil {
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return false, fmt.Errorf("%w: glyph %d: %w", errTTInvalidLocations, id, err)
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}
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if len(data)-size > 3 || len(bytes.Trim(data[size:], "\x00")) != 0 {
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return false, fmt.Errorf("%w: ambiguous glyph %d padding", errTTInvalidLocations, id)
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}
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bodies[start], components[id] = data[:size], refs
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total += (uint64(size) + 3) &^ 3
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if total > uint64(^uint(0)>>1) || total > uint64(^uint32(0)) {
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return false, fmt.Errorf("%w: rebuilt table exceeds capacity", errTTInvalidLocations)
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}
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}
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state := make([]uint8, count)
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var visit func(int) error
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visit = func(id int) error {
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if state[id] == 1 {
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return fmt.Errorf("%w: cyclic component %d", errTTInvalidLocations, id)
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}
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if state[id] == 2 {
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return nil
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}
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state[id] = 1
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for _, ref := range components[id] {
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if err := visit(int(ref)); err != nil {
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return err
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}
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}
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state[id] = 2
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return nil
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}
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for id := range count {
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if err := visit(id); err != nil {
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return false, err
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}
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}
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result, locations := make([]byte, 0, total), make([]byte, (count+1)*4)
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for id := range count {
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binary.BigEndian.PutUint32(locations[id*4:], uint32(len(result)))
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if offsets[id] != offsets[id+1] {
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result = append(result, bodies[offsets[id]]...)
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result = append(result, make([]byte, (-len(result))&3)...)
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}
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}
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binary.BigEndian.PutUint32(locations[count*4:], uint32(len(result)))
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header := bytes.Clone(head)
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binary.BigEndian.PutUint16(header[50:], 1)
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tables["head"], tables["loca"], tables["glyf"] = header, locations, result
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return true, nil
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}
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// trueTypeGlyphSize 检查单个字形的完整记录长度及复合引用，不执行指令或分配坐标
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// 入参: data 字形及尾部对齐数据, count 字形总数
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// 返回: int 记录长度, []uint16 分量编号, error 结构错误
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func trueTypeGlyphSize(data []byte, count int) (int, []uint16, error) {
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if len(data) < 10 {
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return 0, nil, fmt.Errorf("truncated glyph header")
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}
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contours := int(int16(binary.BigEndian.Uint16(data)))
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pos := 10
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if contours >= 0 {
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if contours == 0 && len(data) == 10 {
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return 10, nil, nil
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}
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if contours > (len(data)-12)/2 || len(data) < 12 {
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return 0, nil, fmt.Errorf("truncated contour endpoints")
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}
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points := 0
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for range contours {
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end := int(binary.BigEndian.Uint16(data[pos:])) + 1
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if end <= points {
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return 0, nil, fmt.Errorf("unordered contour endpoints")
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}
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points, pos = end, pos+2
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}
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instructions := int(binary.BigEndian.Uint16(data[pos:]))
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pos += 2
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if instructions > len(data)-pos {
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return 0, nil, fmt.Errorf("truncated glyph instructions")
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}
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pos += instructions
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coordinates := 0
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for seen := 0; seen < points; {
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if pos >= len(data) {
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return 0, nil, fmt.Errorf("truncated glyph flags")
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}
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flag, repeat := data[pos], 1
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pos++
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if flag&0x80 != 0 {
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return 0, nil, fmt.Errorf("reserved glyph flag")
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}
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if flag&8 != 0 {
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if pos >= len(data) {
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return 0, nil, fmt.Errorf("truncated glyph repeat")
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}
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repeat += int(data[pos])
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pos++
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}
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if repeat > points-seen {
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return 0, nil, fmt.Errorf("excessive glyph repeat")
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}
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for axis := range 2 {
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if flag&byte(2<<axis) != 0 {
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coordinates += repeat
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} else if flag&byte(16<<axis) == 0 {
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coordinates += 2 * repeat
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}
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}
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seen += repeat
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}
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if coordinates > len(data)-pos {
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return 0, nil, fmt.Errorf("truncated glyph coordinates")
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}
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return pos + coordinates, nil, nil
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}
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var refs []uint16
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instructions := false
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for {
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if len(data)-pos < 6 {
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return 0, nil, fmt.Errorf("truncated glyph component")
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}
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flags, id := binary.BigEndian.Uint16(data[pos:]), binary.BigEndian.Uint16(data[pos+2:])
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if int(id) >= count || flags&0xe010 != 0 {
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return 0, nil, fmt.Errorf("invalid glyph component")
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}
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refs = append(refs, id)
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pos += 6
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if flags&1 != 0 {
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pos += 2
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}
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switch flags & 0xc8 {
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case 0:
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case 8:
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pos += 2
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case 0x40:
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pos += 4
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case 0x80:
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pos += 8
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default:
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return 0, nil, fmt.Errorf("conflicting component transforms")
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}
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if pos > len(data) {
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return 0, nil, fmt.Errorf("truncated component arguments")
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}
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instructions = instructions || flags&0x100 != 0
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if flags&0x20 == 0 {
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break
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}
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}
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if instructions {
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if len(data)-pos < 2 {
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return 0, nil, fmt.Errorf("truncated component instructions")
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}
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length := int(binary.BigEndian.Uint16(data[pos:]))
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pos += 2
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if length > len(data)-pos {
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return 0, nil, fmt.Errorf("truncated component instructions")
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}
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pos += length
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}
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return pos, refs, nil
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}
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// trueTypePointCount 按完整轮廓计算虚拟点编号，局部复用分量计数，不执行字形指令
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// 入参: tables 字体表, id 字形编号, counts 本次计数缓存, active 递归访问集合
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// 返回: int 不含虚拟点的轮廓点数, error 结构或循环引用错误
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func trueTypePointCount(tables map[string][]byte, id uint16, counts map[uint16]int, active map[uint16]bool) (int, error) {
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if count, ok := counts[id]; ok {
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return count, nil
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}
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maxp := tables["maxp"]
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if len(maxp) < 6 || id >= binary.BigEndian.Uint16(maxp[4:]) || active[id] {
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return 0, fmt.Errorf("invalid TrueType component reference %d", id)
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}
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active[id] = true
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defer delete(active, id)
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data, err := trueTypeGlyphData(tables, id)
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if err != nil {
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return 0, err
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}
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if len(data) == 0 {
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counts[id] = 0
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return 0, nil
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}
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_, refs, err := trueTypeGlyphSize(data, int(binary.BigEndian.Uint16(maxp[4:])))
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if err != nil {
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return 0, err
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}
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contours := int(int16(binary.BigEndian.Uint16(data)))
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count := 0
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if contours > 0 {
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count = int(binary.BigEndian.Uint16(data[10+2*(contours-1):])) + 1
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} else {
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for _, ref := range refs {
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points, err := trueTypePointCount(tables, ref, counts, active)
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if err != nil {
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return 0, err
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}
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count += points
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if count > 65536 {
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return 0, fmt.Errorf("excessive TrueType component points")
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}
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}
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}
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counts[id] = count
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return count, nil
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}
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