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@@ -0,0 +1,225 @@
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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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"fmt"
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"maps"
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)
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// subsetNamedCFFFont 裁剪非CID的CFF字体，保留字形编号、组合组件和度量
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// 入参: sfnt 已解析字体, glyphs 使用的字形
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// 返回: []byte 字体子集, error 裁剪错误
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func subsetNamedCFFFont(sfnt *sfntFont, glyphs []uint16) ([]byte, error) {
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keep := map[uint16]bool{0: true}
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for _, gid := range glyphs {
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if gid >= sfnt.NumGlyphs() {
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return nil, fmt.Errorf("CFF glyph index out of range")
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}
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keep[gid] = true
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}
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data, err := subsetCFFCharstrings(sfnt.Tables["CFF "], keep)
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if err != nil {
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return bytes.Clone(sfnt.Write()), nil
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}
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tables := maps.Clone(sfnt.Tables)
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tables["CFF "] = data
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mapping := make(map[rune]uint16)
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for gid := range keep {
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for _, char := range sfnt.glyphCharacters(gid) {
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mapping[char] = gid
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}
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}
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tables["cmap"] = buildCmapTable(sfnt.NumGlyphs(), mapping)
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for _, tag := range []string{"DSIG", "GSUB", "GPOS", "GDEF"} {
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delete(tables, tag)
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}
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return serializeOTF(tables)
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}
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// subsetCFFCharstrings 清空未引用的Type2轮廓，保留原字宽、提示和子程序
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// 入参: data 非CID的CFF数据, keep 保留的字形，调用后包含组合组件
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// 返回: []byte 重建的CFF数据, error 结构或依赖错误
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func subsetCFFCharstrings(data []byte, keep map[uint16]bool) ([]byte, error) {
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font, err := readType2Font(data)
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if err != nil {
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return nil, err
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}
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keep[0] = true
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for gid := range keep {
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if int(gid) >= len(font.chars) {
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return nil, fmt.Errorf("CFF glyph index out of range")
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}
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steps := 0
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state := type2State{font: font, width: font.def, seed: font.seed + uint64(gid), steps: &steps, dependencies: keep}
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if _, err := state.run(font.chars[gid], 0); err != nil {
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return nil, err
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}
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}
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chars := make([][]byte, len(font.chars))
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empty := make(map[float64][]byte)
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for gid, program := range font.chars {
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if keep[uint16(gid)] {
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chars[gid] = program
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continue
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}
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steps := 0
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state := type2State{font: font, width: font.def, widthOnly: true, seed: font.seed + uint64(gid), steps: &steps, dependencies: keep}
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if _, err := state.run(program, 0); err != nil {
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return nil, err
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}
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if encoded, ok := empty[state.width]; ok {
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chars[gid] = encoded
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continue
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}
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var encoded bytes.Buffer
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if state.width != font.def {
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value := state.width - font.nominal
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if err := encodeType2Number(&encoded, value); err != nil {
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return nil, err
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}
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if parseNumberType2(encoded.Bytes(), 0) != value {
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return nil, fmt.Errorf("CFF width cannot be represented exactly")
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}
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}
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encoded.WriteByte(14)
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chars[gid] = encoded.Bytes()
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empty[state.width] = chars[gid]
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}
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return rebuildNamedCFF(data, font, chars)
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}
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// rebuildNamedCFF 重建非CID的CFF偏移，保留字符集、编码和私有提示参数
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// 入参: data 原始CFF数据, font 执行资源, chars 替换后的字形程序
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// 返回: []byte 重建的CFF数据, error 不支持的结构
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func rebuildNamedCFF(data []byte, font *type2Font, chars [][]byte) ([]byte, error) {
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names, end, err := readType2Index(data, int(data[2]))
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if err != nil {
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return nil, err
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}
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tops, end, err := readType2Index(data, end)
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if err != nil || len(tops) != 1 {
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return nil, fmt.Errorf("invalid CFF top dictionary")
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}
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strings, _, err := readType2Index(data, end)
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if err != nil {
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return nil, err
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}
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dict, err := readCFFDict(tops[0])
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if err != nil {
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return nil, err
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}
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for op := range dict {
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switch op {
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case 0, 1, 2, 3, 4, 5, 13, 14, 15, 16, 17, 18, 1200, 1201, 1202, 1203, 1204, 1205, 1206, 1207, 1208, 1222, 1223:
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default:
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return nil, fmt.Errorf("unsupported CFF top operator %d", op)
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}
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}
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sids, _, _, _, ok := getCFFCharsetInfo(data, len(chars))
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if !ok {
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return nil, fmt.Errorf("invalid CFF charset")
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}
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charset := []byte{0}
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for _, sid := range sids[1:] {
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charset = binary.BigEndian.AppendUint16(charset, uint16(sid))
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}
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encoding, err := cffSubsetEncoding(data, dict)
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if err != nil {
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return nil, err
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}
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private, err := readType2Private(data, dict[18], font)
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if err != nil {
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return nil, err
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}
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for op := range private {
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switch op {
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case 6, 7, 8, 9, 10, 11, 19, 20, 21, 1209, 1210, 1211, 1212, 1213, 1214, 1217, 1218, 1219:
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default:
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return nil, fmt.Errorf("unsupported CFF private operator %d", op)
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}
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}
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privateData := encodeCFFDict(private)
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if _, ok := private[19]; ok {
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for private[19][0] != float64(len(privateData)) {
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private[19] = []float64{float64(len(privateData))}
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privateData = encodeCFFDict(private)
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}
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}
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prefix := bytes.Clone(data[:int(data[2])])
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prefix = append(prefix, encodeCFFIndex(names)...)
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suffix := encodeCFFIndex(strings)
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suffix = append(suffix, encodeCFFIndex(font.globals)...)
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encodedChars := encodeCFFIndex(chars)
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var top []byte
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for attempt := 0; attempt < 16; attempt++ {
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top = encodeCFFIndex([][]byte{encodeCFFDict(dict)})
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offset := len(prefix) + len(top) + len(suffix)
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updated := maps.Clone(dict)
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updated[15] = []float64{float64(offset)}
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offset += len(charset)
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if encoding != nil {
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updated[16] = []float64{float64(offset)}
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}
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offset += len(encoding)
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updated[17] = []float64{float64(offset)}
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updated[18] = []float64{float64(len(privateData)), float64(offset + len(encodedChars))}
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encoded := encodeCFFIndex([][]byte{encodeCFFDict(updated)})
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if len(encoded) == len(top) {
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result := prefix
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for _, part := range [][]byte{encoded, suffix, charset, encoding, encodedChars, privateData, encodeCFFIndex(font.locals)} {
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result = append(result, part...)
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}
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return result, nil
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}
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dict = updated
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}
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return nil, fmt.Errorf("CFF dictionary offsets did not converge")
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}
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// cffSubsetEncoding 读取自定义CFF编码及补充映射，预定义编码无需复制
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// 入参: data CFF数据, dict 顶层字典
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// 返回: []byte 编码数据, error 编码格式错误
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func cffSubsetEncoding(data []byte, dict cffDict) ([]byte, error) {
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values := dict[16]
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if values == nil || len(values) == 1 && (values[0] == 0 || values[0] == 1) {
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return nil, nil
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}
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start, err := cffDictOffset(data, dict, 16)
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if err != nil || start > len(data)-2 {
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return nil, fmt.Errorf("invalid CFF encoding offset")
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}
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end := start + 2
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switch data[start] & 0x7f {
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case 0:
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end += int(data[start+1])
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case 1:
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end += 2 * int(data[start+1])
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default:
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return nil, fmt.Errorf("invalid CFF encoding format")
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}
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if data[start]&0x80 != 0 {
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if end >= len(data) {
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return nil, fmt.Errorf("truncated CFF encoding supplements")
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}
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end += 1 + 3*int(data[end])
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}
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if end > len(data) {
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return nil, fmt.Errorf("truncated CFF encoding")
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}
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return data[start:end], nil
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}
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