mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 08:46:55 +08:00
123 lines
3.7 KiB
Go
123 lines
3.7 KiB
Go
// 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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)
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// normalizeCmap 转换旧式双字节子表，保留各编码记录及原字形编号
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// 入参: data 字符映射表
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// 返回: []byte 等价字符映射表, error 子表错误
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func normalizeCmap(data []byte) ([]byte, error) {
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if len(data) < 4 {
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return data, nil
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}
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count := int(binary.BigEndian.Uint16(data[2:]))
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if count > (len(data)-4)/8 {
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return nil, fmt.Errorf("invalid cmap encoding records")
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}
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var out []byte
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converted := make(map[uint32]uint32)
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for n := 0; n < count; n++ {
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record := 8 + 8*n
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offset := binary.BigEndian.Uint32(data[record:])
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if uint64(offset)+2 > uint64(len(data)) {
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return nil, fmt.Errorf("invalid cmap subtable offset")
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}
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if binary.BigEndian.Uint16(data[offset:]) != 2 {
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continue
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}
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if out == nil {
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out = bytes.Clone(data)
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}
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next, ok := converted[offset]
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if !ok {
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mapping, err := parseCmapFormat2(data[offset:])
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if err != nil {
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return nil, err
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}
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table := buildCmapTable(0, mapping)
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subtable := table[binary.BigEndian.Uint32(table[8:]):]
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language := binary.BigEndian.Uint16(data[offset+4:])
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if binary.BigEndian.Uint16(subtable) == 12 {
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binary.BigEndian.PutUint32(subtable[8:], uint32(language))
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} else {
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binary.BigEndian.PutUint16(subtable[4:], language)
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}
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next = uint32(len(out))
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converted[offset] = next
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out = append(out, subtable...)
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}
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binary.BigEndian.PutUint32(out[record:], next)
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}
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if out == nil {
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return data, nil
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}
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return out, nil
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}
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// parseCmapFormat2 解析混合单字节与双字节字符的子头映射
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// 入参: data format 2子表
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// 返回: map[rune]uint16 编码值到字形编号, error 子头或字形数组越界
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func parseCmapFormat2(data []byte) (map[rune]uint16, error) {
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if len(data) < 526 {
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return nil, fmt.Errorf("truncated cmap format 2")
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}
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length := int(binary.BigEndian.Uint16(data[2:]))
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if length < 526 || length > len(data) {
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return nil, fmt.Errorf("invalid cmap format 2 length")
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}
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data = data[:length]
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maxKey := 0
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for n := 0; n < 256; n++ {
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key := int(binary.BigEndian.Uint16(data[6+2*n:]))
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if key%8 != 0 || 518+key+8 > len(data) {
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return nil, fmt.Errorf("invalid cmap format 2 subheader")
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}
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maxKey = max(maxKey, key)
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}
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mapping := make(map[rune]uint16)
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for high := 0; high < 256; high++ {
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key := 0
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if high != 0 {
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key = int(binary.BigEndian.Uint16(data[6+2*high:]))
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if key == 0 {
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continue
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}
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}
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pos := 518 + key
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first, count := int(binary.BigEndian.Uint16(data[pos:])), int(binary.BigEndian.Uint16(data[pos+2:]))
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delta := binary.BigEndian.Uint16(data[pos+4:])
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start := pos + 6 + int(binary.BigEndian.Uint16(data[pos+6:]))
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if first+count > 256 || count > 0 && (start < 526+maxKey || start+count*2 > len(data)) {
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return nil, fmt.Errorf("invalid cmap format 2 glyph array")
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}
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for n := 0; n < count; n++ {
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low := first + n
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if high == 0 && binary.BigEndian.Uint16(data[6+2*low:]) != 0 {
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continue
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}
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glyph := binary.BigEndian.Uint16(data[start+2*n:])
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if glyph != 0 {
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mapping[rune(high*256+low)] = glyph + delta
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}
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}
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}
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return mapping, nil
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}
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