ofdgo/ofdgo_font_cff.go

// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package ofdgo

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"math"
	"sort"
	"strconv"
	"strings"
)

// wrapCFFToOTF 将 CFF 裸数据包装为 OpenType 字体格式
// 入参: cffData CFF字体数据
// 返回: []byte OTF字体数据, map[rune]uint16 字符映射, error 错误信息
func wrapCFFToOTF(cffData []byte) ([]byte, map[rune]uint16, error) {
	sanitized, err := sanitizeCFF(cffData)
	if err == nil {
		cffData = sanitized
	} else {
		return nil, nil, err
	}
	numGlyphs, err := parseCFFAndCountGlyphs(cffData)
	if err != nil {
		return nil, nil, err
	}
	widths, err := parseCFFWidths(cffData, numGlyphs)
	if err != nil {
		widths = make([]uint16, numGlyphs)
		for i := range widths {
			widths[i] = 500
		}
	}
	var unitsPerEm uint16 = 1000
	if len(cffData) > 4 {
		hdrSize := int(cffData[2])
		off := hdrSize
		_, sz := getCFFIndexCount(cffData, off)
		off += sz
		topDictData, _ := getCFFIndexData(cffData, off)
		if topDictData != nil {
			td := parseCFFDict(topDictData)
			if mat, ok := td[1207]; ok && len(mat) > 0 {
				if mat[0] != 0 {
					val := 1.0 / mat[0]
					if val > 0 {
						unitsPerEm = uint16(math.Round(val))
					}
				}
			}
		}
	}
	mapping := getCmapFromCFF(cffData, int(numGlyphs))
	tables := make(map[string][]byte)
	tables["CFF "] = cffData
	tables["head"] = buildHeadTable(unitsPerEm)
	tables["hhea"] = buildHheaTable(uint16(numGlyphs))
	tables["maxp"] = buildMaxpTable(uint16(numGlyphs))
	tables["OS/2"] = buildOS2Table()
	tables["name"] = buildNameTable()
	tables["post"] = buildPostTable()
	tables["hmtx"] = buildHmtxTable(widths)
	tables["cmap"] = buildCmapTable(uint16(numGlyphs), mapping)
	data, err := serializeOTF(tables)
	return data, mapping, err
}

// cffDict 使用 float64 存储所有数值，以统一处理整数和实数
type cffDict map[int][]float64

// sanitizeCFF 尝试清洗CFF数据，转换CID字体并合并FontMatrix
// 入参: data 原始CFF数据
// 返回: []byte 清洗后的CFF数据, error 错误信息
func sanitizeCFF(data []byte) ([]byte, error) {
	if len(data) < 4 {
		return nil, fmt.Errorf("data too short")
	}
	hdrSize := int(data[2])
	offset := hdrSize
	if offset >= len(data) {
		return nil, fmt.Errorf("truncated")
	}
	nameCount, nameSz := getCFFIndexCount(data, offset)
	if nameCount != 1 {
		return nil, fmt.Errorf("multi-font cff not supported")
	}
	nameIndexData := data[offset : offset+nameSz]
	offset += nameSz
	if offset >= len(data) {
		return nil, fmt.Errorf("truncated")
	}
	topCount, topSz := getCFFIndexCount(data, offset)
	if topCount != 1 {
		return nil, fmt.Errorf("top dict count != 1")
	}
	topDictData, _ := getCFFIndexData(data, offset)
	offset += topSz
	if offset >= len(data) {
		return nil, fmt.Errorf("truncated")
	}
	_, strSz := getCFFIndexCount(data, offset)
	stringIndexData := data[offset : offset+strSz]
	offset += strSz
	if offset >= len(data) {
		return nil, fmt.Errorf("truncated")
	}
	_, glbSz := getCFFIndexCount(data, offset)
	globalSubrIndexData := data[offset : offset+glbSz]
	topDict := parseCFFDict(topDictData)
	if _, isCID := topDict[1230]; !isCID {
		return data, nil
	}
	fdArrOffs, ok := topDict[1236]
	if !ok || len(fdArrOffs) == 0 {
		return nil, fmt.Errorf("cid without fdarray")
	}
	fdArrOff := int(fdArrOffs[0])
	if fdArrOff >= len(data) {
		return nil, fmt.Errorf("fdarray offset oob")
	}
	fdCount, _ := getCFFIndexCount(data, fdArrOff)
	if fdCount != 1 {
		return nil, fmt.Errorf("complex cid (fdarray count=%d) not supported", fdCount)
	}
	fontDictData, _ := getCFFIndexData(data, fdArrOff)
	fontDict := parseCFFDict(fontDictData)
	if fdMat, ok := fontDict[1207]; ok && len(fdMat) == 6 {
		topMat, hasTop := topDict[1207]
		if !hasTop || len(topMat) != 6 {
			topMat = []float64{0.001, 0, 0, 0.001, 0, 0}
		}
		newMat := multiplyAffine(topMat, fdMat)
		topDict[1207] = newMat
	}
	privVals, ok := fontDict[18]
	if !ok || len(privVals) != 2 {
		privVals = []float64{0, 0}
	}
	privSize := int(privVals[0])
	privOff := int(privVals[1])
	var localSubrData []byte
	var privDictData []byte
	if privSize > 0 && privOff < len(data) && privOff+privSize <= len(data) {
		privDictData = data[privOff : privOff+privSize]
	}
	var subrsOffRel int
	if len(privDictData) > 0 {
		pDict := parseCFFDict(privDictData)
		if sVals, ok := pDict[19]; ok && len(sVals) > 0 {
			subrsOffRel = int(sVals[0])
		}
	}
	if subrsOffRel > 0 {
		subrsAbs := privOff + subrsOffRel
		if subrsAbs < len(data) {
			_, subSz := getCFFIndexCount(data, subrsAbs)
			if subrsAbs+subSz <= len(data) {
				localSubrData = data[subrsAbs : subrsAbs+subSz]
			}
		}
	}
	charStringsOffs, ok := topDict[17]
	if !ok || len(charStringsOffs) == 0 {
		return nil, fmt.Errorf("missing charstrings")
	}
	charStringsOff := int(charStringsOffs[0])
	_, charStrSz := getCFFIndexCount(data, charStringsOff)
	charStringsData := data[charStringsOff : charStringsOff+charStrSz]
	delete(topDict, 1230)
	delete(topDict, 1236)
	delete(topDict, 1237)
	delete(topDict, 1234)
	delete(topDict, 15)
	delete(topDict, 16)
	topDict[18] = []float64{float64(privSize), 0}
	var newCFF bytes.Buffer
	newCFF.Write(data[:hdrSize])
	newCFF.Write(nameIndexData)
	dummyDict := make(map[int][]float64)
	for k, v := range topDict {
		dummyDict[k] = v
	}
	dummyDict[17] = []float64{0}
	dummyDict[18] = []float64{float64(privSize), 0}
	dummyTopData := encodeCFFDict(dummyDict)
	topIdxSize := 2 + 1 + 8 + len(dummyTopData)
	dataStart := hdrSize + len(nameIndexData) + topIdxSize + len(stringIndexData) + len(globalSubrIndexData)
	charStringsPos := dataStart
	privatePos := charStringsPos + len(charStringsData)
	privateLen := privSize
	var finalPrivData []byte
	if len(privDictData) > 0 {
		pDict := parseCFFDict(privDictData)
		if _, ok := pDict[19]; ok || len(localSubrData) > 0 {
			pDict[19] = []float64{float64(privateLen)}
		}
		finalPrivData = encodeCFFDict(pDict)
		privateLen = len(finalPrivData)
	}
	localSubrsPos := privatePos + privateLen
	topDict[17] = []float64{float64(charStringsPos)}
	topDict[18] = []float64{float64(privateLen), float64(privatePos)}
	finalTopData := encodeCFFDict(topDict)
	topIndex := encodeCFFIndex([]([]byte){finalTopData})
	newCFF.Reset()
	newCFF.Write(data[:hdrSize])
	newCFF.Write(nameIndexData)
	newCFF.Write(topIndex)
	newCFF.Write(stringIndexData)
	newCFF.Write(globalSubrIndexData)
	if newCFF.Len() != dataStart {
		diff := newCFF.Len() - dataStart
		charStringsPos += diff
		privatePos += diff
		localSubrsPos += diff
		topDict[17] = []float64{float64(charStringsPos)}
		topDict[18] = []float64{float64(privateLen), float64(privatePos)}
		finalTopData = encodeCFFDict(topDict)
		topIndex = encodeCFFIndex([]([]byte){finalTopData})
		newCFF.Reset()
		newCFF.Write(data[:hdrSize])
		newCFF.Write(nameIndexData)
		newCFF.Write(topIndex)
		newCFF.Write(stringIndexData)
		newCFF.Write(globalSubrIndexData)
	}
	newCFF.Write(charStringsData)
	newCFF.Write(finalPrivData)
	if len(localSubrData) > 0 {
		newCFF.Write(localSubrData)
	}
	return newCFF.Bytes(), nil
}

// parseCFFAndCountGlyphs 解析 CFF 头部并统计字形数量
// 入参: data CFF数据
// 返回: int 字形数量, error 错误信息
func parseCFFAndCountGlyphs(data []byte) (int, error) {
	if len(data) < 4 {
		return 0, fmt.Errorf("data too short")
	}
	hdrSize := int(data[2])
	offset := hdrSize
	if offset >= len(data) {
		return 0, fmt.Errorf("truncated")
	}
	count, sz := getCFFIndexCount(data, offset)
	if count != 1 {
		return 0, fmt.Errorf("multi-font cff not supported")
	}
	offset += sz
	if offset >= len(data) {
		return 0, fmt.Errorf("truncated")
	}
	count, _ = getCFFIndexCount(data, offset)
	if count != 1 {
		return 0, fmt.Errorf("top dict count mismatch")
	}
	topDictData, _ := getCFFIndexData(data, offset)
	if topDictData != nil {
		dict := parseCFFDict(topDictData)
		if offsetVals, ok := dict[17]; ok && len(offsetVals) > 0 {
			charStrOff := int(offsetVals[0])
			if charStrOff > 0 && charStrOff < len(data) {
				count, _ := getCFFIndexCount(data, charStrOff)
				return count, nil
			}
		}
	}
	return 0, fmt.Errorf("failed to parse top dict")
}

// multiplyAffine 2x3 仿射矩阵乘法
// 入参: a 矩阵A, b 矩阵B
// 返回: []float64 结果矩阵
func multiplyAffine(a, b []float64) []float64 {
	return []float64{
		a[0]*b[0] + a[2]*b[1],
		a[1]*b[0] + a[3]*b[1],
		a[0]*b[2] + a[2]*b[3],
		a[1]*b[2] + a[3]*b[3],
		a[0]*b[4] + a[2]*b[5] + a[4],
		a[1]*b[4] + a[3]*b[5] + a[5],
	}
}

// parseCFFDict 解析 CFF 字典数据
// 入参: data 字典数据
// 返回: cffDict 解析后的字典映射
func parseCFFDict(data []byte) cffDict {
	dict := make(cffDict)
	var operands []float64
	i := 0
	for i < len(data) {
		b := data[i]
		i++
		if b <= 27 {
			op := int(b)
			if b == 12 {
				if i >= len(data) {
					break
				}
				op = 1200 + int(data[i])
				i++
			}
			dict[op] = operands
			operands = nil
		} else if b == 28 {
			if i+1 < len(data) {
				val := int(int16(binary.BigEndian.Uint16(data[i:])))
				operands = append(operands, float64(val))
				i += 2
			}
		} else if b == 29 {
			if i+3 < len(data) {
				val := int(int32(binary.BigEndian.Uint32(data[i:])))
				operands = append(operands, float64(val))
				i += 4
			}
		} else if b == 30 {
			s, n := parseCFFReal(data[i:])
			if f, err := strconv.ParseFloat(s, 64); err == nil {
				operands = append(operands, f)
			}
			i += n
		} else if b >= 32 && b <= 246 {
			operands = append(operands, float64(int(b)-139))
		} else if b >= 247 && b <= 250 {
			if i < len(data) {
				b1 := int(data[i])
				i++
				operands = append(operands, float64((int(b)-247)*256+b1+108))
			}
		} else if b >= 251 && b <= 254 {
			if i < len(data) {
				b1 := int(data[i])
				i++
				operands = append(operands, float64(-(int(b)-251)*256-b1-108))
			}
		}
	}
	return dict
}

// parseCFFReal 解析 CFF 实数编码
// 入参: data 数据切片
// 返回: string 实数字符串, int 消耗字节数
func parseCFFReal(data []byte) (string, int) {
	var sb strings.Builder
	i := 0
	done := false
	for i < len(data) && !done {
		b := data[i]
		i++
		nibbles := []byte{b >> 4, b & 0x0F}
		for _, n := range nibbles {
			if n == 0xF {
				done = true
				break
			}
			if n <= 9 {
				sb.WriteString(strconv.Itoa(int(n)))
			}
			if n == 0xA {
				sb.WriteString(".")
			}
			if n == 0xB {
				sb.WriteString("E")
			}
			if n == 0xC {
				sb.WriteString("E-")
			}
			if n == 0xE {
				sb.WriteString("-")
			}
		}
	}
	return sb.String(), i
}

// encodeCFFDict 编码 CFF 字典 (仅使用 float64 操作数)
// 入参: dict CFF字典映射
// 返回: []byte 编码后的字典数据
func encodeCFFDict(dict cffDict) []byte {
	buf := new(bytes.Buffer)
	var keys []int
	for k := range dict {
		keys = append(keys, k)
	}
	sort.Ints(keys)
	for _, op := range keys {
		vals := dict[op]
		for _, val := range vals {
			encodeNumberCFF(buf, val)
		}
		if op >= 1200 {
			buf.WriteByte(12)
			buf.WriteByte(byte(op - 1200))
		} else {
			buf.WriteByte(byte(op))
		}
	}
	return buf.Bytes()
}

// encodeNumberCFF 编码单个数值到 CFF 格式
// 入参: buf 缓冲区, val 数值
func encodeNumberCFF(buf *bytes.Buffer, val float64) {
	if val == math.Trunc(val) {
		iv := int(val)
		if iv >= -107 && iv <= 107 {
			buf.WriteByte(byte(iv + 139))
		} else if iv >= 108 && iv <= 1131 {
			iv -= 108
			buf.WriteByte(byte((iv >> 8) + 247))
			buf.WriteByte(byte(iv & 0xFF))
		} else if iv >= -1131 && iv <= -108 {
			iv = -iv - 108
			buf.WriteByte(byte((iv >> 8) + 251))
			buf.WriteByte(byte(iv & 0xFF))
		} else if iv >= -32768 && iv <= 32767 {
			buf.WriteByte(28)
			binary.Write(buf, binary.BigEndian, int16(iv))
		} else {
			buf.WriteByte(29)
			binary.Write(buf, binary.BigEndian, int32(iv))
		}
	} else {
		s := fmt.Sprintf("%g", val)
		buf.WriteByte(30)
		var nibbles []byte
		for _, c := range s {
			var n byte
			switch c {
			case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
				n = byte(c - '0')
			case '.':
				n = 0xA
			case 'E', 'e':
				n = 0xB
			case '-':
				n = 0xE
			}
			nibbles = append(nibbles, n)
		}
		nibbles = append(nibbles, 0xF)
		if len(nibbles)%2 != 0 {
			nibbles = append(nibbles, 0xF)
		}
		for i := 0; i < len(nibbles); i += 2 {
			b := nibbles[i] << 4
			if i+1 < len(nibbles) {
				b |= nibbles[i+1]
			}
			buf.WriteByte(b)
		}
	}
}

// encodeCFFIndex 编码 CFF 索引结构
// 入参: items 数据项列表
// 返回: []byte 编码后的索引数据
func encodeCFFIndex(items []([]byte)) []byte {
	count := len(items)
	buf := new(bytes.Buffer)
	binary.Write(buf, binary.BigEndian, uint16(count))
	if count == 0 {
		return buf.Bytes()
	}
	totalSize := 0
	for _, item := range items {
		totalSize += len(item)
	}
	offSize := 1
	if totalSize+1 > 255 {
		offSize = 2
	}
	if totalSize+1 > 65535 {
		offSize = 3
	}
	if totalSize+1 > 16777215 {
		offSize = 4
	}
	buf.WriteByte(byte(offSize))
	offset := 1
	putOffset(buf, offset, offSize)
	for _, item := range items {
		offset += len(item)
		putOffset(buf, offset, offSize)
	}
	for _, item := range items {
		buf.Write(item)
	}
	return buf.Bytes()
}

// putOffset 写入指定大小的偏移量
// 入参: buf 缓冲区, val 偏移值, size 字节大小
func putOffset(buf *bytes.Buffer, val int, size int) {
	tmp := make([]byte, 4)
	binary.BigEndian.PutUint32(tmp, uint32(val))
	buf.Write(tmp[4-size:])
}

// getCFFIndexCount 读取 CFF 索引的计数和大小
// 入参: data CFF数据, offset 偏移量
// 返回: int 数量, int 索引结构总大小
func getCFFIndexCount(data []byte, offset int) (int, int) {
	if offset+2 > len(data) {
		return 0, 0
	}
	count := int(binary.BigEndian.Uint16(data[offset:]))
	if count == 0 {
		return 0, 2
	}
	if offset+3 > len(data) {
		return 0, 0
	}
	offSize := int(data[offset+2])
	if offSize < 1 || offSize > 4 {
		return 0, 0
	}
	dataSizeLen := (count + 1) * offSize
	if offset+3+dataSizeLen > len(data) {
		return 0, 0
	}
	endOffsetPos := offset + 3 + count*offSize
	if endOffsetPos+offSize > len(data) {
		return 0, 0
	}
	dataEnd := readCFFOffset(data, endOffsetPos, offSize)
	if dataEnd < 1 {
		return 0, 0
	}
	return count, 3 + (count+1)*offSize + (dataEnd - 1)
}

// getCFFIndexData 读取 CFF 索引的数据块
// 入参: data CFF数据, offset 偏移量
// 返回: []byte 索引数据(已去除offsets), int 索引结构总大小
func getCFFIndexData(data []byte, offset int) ([]byte, int) {
	count, size := getCFFIndexCount(data, offset)
	if count == 0 {
		return nil, size
	}
	if offset+3 > len(data) {
		return nil, size
	}
	offSize := int(data[offset+2])
	if offset+3+offSize > len(data) {
		return nil, size
	}
	off0 := readCFFOffset(data, offset+3, offSize)
	if offset+3+offSize*2 > len(data) {
		return nil, size
	}
	off1 := readCFFOffset(data, offset+3+offSize, offSize)
	dataStartRel := 3 + (count+1)*offSize
	dataStartAbs := offset + dataStartRel
	start := dataStartAbs + (off0 - 1)
	length := off1 - off0
	if start < 0 || length < 0 || start+length > len(data) {
		return nil, size
	}
	return data[start : start+length], size
}

// parseCFFWidths 从 CFF 数据中解析 Glyph 宽度
// 入参: data CFF数据, numGlyphs 字形数量
// 返回: []uint16 宽度列表, error 错误信息
func parseCFFWidths(data []byte, numGlyphs int) ([]uint16, error) {
	if len(data) < 4 {
		return nil, fmt.Errorf("data too short")
	}
	hdrSize := int(data[2])
	offset := hdrSize
	_, sz := getCFFIndexCount(data, offset)
	offset += sz
	topDictData, sz := getCFFIndexData(data, offset)
	offset += sz
	if topDictData == nil {
		return nil, fmt.Errorf("failed to read top dict")
	}
	topDict := parseCFFDict(topDictData)
	_, sz = getCFFIndexCount(data, offset)
	offset += sz
	_, sz = getCFFIndexCount(data, offset)
	offset += sz
	var nominalWidthX float64 = 0
	var defaultWidthX float64 = 0
	if vals, ok := topDict[18]; ok && len(vals) == 2 {
		privSize := int(vals[0])
		privOff := int(vals[1])
		if privSize > 0 && privOff+privSize <= len(data) {
			privData := data[privOff : privOff+privSize]
			privDict := parseCFFDict(privData)
			if v, ok := privDict[20]; ok && len(v) > 0 {
				defaultWidthX = v[0]
			}
			if v, ok := privDict[21]; ok && len(v) > 0 {
				nominalWidthX = v[0]
			}
		}
	}
	if vals, ok := topDict[17]; ok && len(vals) > 0 {
		charStrOff := int(vals[0])
		count, _ := getCFFIndexCount(data, charStrOff)
		limit := count
		if numGlyphs < limit {
			limit = numGlyphs
		}
		widths := make([]uint16, numGlyphs)
		for i := range widths {
			widths[i] = uint16(defaultWidthX)
		}
		for i := 0; i < limit; i++ {
			offSize := int(data[charStrOff+2])
			p1 := charStrOff + 3 + i*offSize
			p2 := p1 + offSize
			off1 := readCFFOffset(data, p1, offSize)
			off2 := readCFFOffset(data, p2, offSize)
			dataStartBase := charStrOff + 3 + (count+1)*offSize
			start := dataStartBase + (off1 - 1)
			length := off2 - off1
			if start < 0 || start+length > len(data) {
				widths[i] = uint16(defaultWidthX)
				continue
			}
			csData := data[start : start+length]
			w := scanCharStringWidth(csData, nominalWidthX, defaultWidthX)
			widths[i] = uint16(w)
		}
		return widths, nil
	}
	return nil, fmt.Errorf("no charstrings")
}

// scanCharStringWidth 扫描 CharString 获取宽度
// 入参: data CharString数据, nominal, def 默认宽度值
// 返回: float64 宽度值
func scanCharStringWidth(data []byte, nominal, def float64) float64 {
	stackDepth := 0
	i := 0
	firstVal := 0.0
	for i < len(data) {
		b := data[i]
		if b <= 31 {
			if b == 28 {
				i += 3
				stackDepth++
				if stackDepth == 1 {
					firstVal = parseShortInt(data, i-3)
				}
			} else if b == 29 {
				i += 5
				stackDepth++
			} else if b == 12 {
				i += 2
				if stackDepth%2 != 0 {
					return nominal + firstVal
				}
				return def
			} else if b == 19 || b == 20 {
				if stackDepth%2 != 0 {
					return nominal + firstVal
				}
				return def
			} else {
				if stackDepth%2 != 0 {
					return nominal + firstVal
				}
				return def
			}
		} else {
			stackDepth++
			if stackDepth == 1 {
				firstVal = parseNumberType2(data, i)
			}
			if b >= 32 && b <= 246 {
				i++
			} else if b >= 247 && b <= 250 {
				i += 2
			} else if b >= 251 && b <= 254 {
				i += 2
			} else if b == 255 {
				i += 5
			}
		}
	}
	return def
}

// parseShortInt 解析短整数 (Type 2 CharString)
// 入参: data 数据, idx 索引
// 返回: float64 浮点值
func parseShortInt(data []byte, idx int) float64 {
	return float64(int16(binary.BigEndian.Uint16(data[idx+1:])))
}

// parseNumberType2 解析 Number (Type 2)
// 入参: data 数据, idx 索引
// 返回: float64 浮点值
func parseNumberType2(data []byte, idx int) float64 {
	b := data[idx]
	if b >= 32 && b <= 246 {
		return float64(int(b) - 139)
	}
	if b >= 247 && b <= 250 {
		return float64((int(b)-247)*256 + int(data[idx+1]) + 108)
	}
	if b >= 251 && b <= 254 {
		return float64(-(int(b)-251)*256 - int(data[idx+1]) - 108)
	}
	if b == 28 {
		return float64(int16(binary.BigEndian.Uint16(data[idx+1:])))
	}
	if b == 255 {
		return float64(int16(binary.BigEndian.Uint16(data[idx+1:]))) + float64(binary.BigEndian.Uint16(data[idx+3:]))/65536.0
	}
	return 0
}

// readCFFOffset 读取指定大小的偏移量
// 入参: data 数据, pos 位置, size 大小
// 返回: int 偏移量
func readCFFOffset(data []byte, pos, size int) int {
	var val int
	for i := 0; i < size; i++ {
		if pos+i < len(data) {
			val = (val << 8) | int(data[pos+i])
		}
	}
	return val
}

// getCmapFromCFF 从 CFF 数据中恢复 Unicode 映射
// 入参: data CFF数据, numGlyphs 字形数量
// 返回: map[rune]uint16 恢复的映射表
func getCmapFromCFF(data []byte, numGlyphs int) map[rune]uint16 {
	if len(data) < 4 {
		return nil
	}
	hdrSize := int(data[2])
	offset := hdrSize
	_, sz := getCFFIndexCount(data, offset)
	offset += sz
	_, szTD := getCFFIndexCount(data, offset)
	topDictData, _ := getCFFIndexData(data, offset)
	offset += szTD
	stringIndexOff := offset
	if topDictData == nil {
		return nil
	}
	td := parseCFFDict(topDictData)
	charsetOff := 0
	if vals, ok := td[15]; ok && len(vals) > 0 {
		charsetOff = int(vals[0])
	}
	sids := make([]int, numGlyphs)
	sids[0] = 0
	if charsetOff > 2 {
		sidsParsed := parseCFFCharset(data, charsetOff, numGlyphs)
		copy(sids[1:], sidsParsed)
	} else if charsetOff == 0 {
		count := 228
		if numGlyphs-1 < count {
			count = numGlyphs - 1
		}
		for i := 1; i <= count; i++ {
			sids[i] = i
		}
	} else {
		return nil
	}
	mapping := make(map[rune]uint16)
	for gid, sid := range sids {
		if gid == 0 {
			continue
		}
		var name string
		if sid <= 390 {
			if sid >= 0 && sid < len(cffStandardStrings) {
				name = cffStandardStrings[sid]
			}
		} else {
			idx := sid - 391
			name = readStringIndexItem(data, stringIndexOff, idx)
		}
		r := rune(0)
		if name != "" {
			r = getUnicodeFromName(name)
		}
		if r == 0 {
			r = 0xE000 + rune(gid)
		}
		mapping[r] = uint16(gid)
	}
	return mapping
}

// parseCFFCharset 解析 CFF 字符集并返回 SID 列表
// 入参: data CFF数据, offset 偏移量, numGlyphs 字形数量
// 返回: []int SID列表
func parseCFFCharset(data []byte, offset int, numGlyphs int) []int {
	if offset >= len(data) {
		return nil
	}
	format := data[offset]
	var sids []int
	count := numGlyphs - 1
	pos := offset + 1
	switch format {
	case 0:
		for i := 0; i < count && pos+2 <= len(data); i++ {
			sid := int(binary.BigEndian.Uint16(data[pos:]))
			sids = append(sids, sid)
			pos += 2
		}
	case 1:
		for len(sids) < count && pos+3 <= len(data) {
			first := int(binary.BigEndian.Uint16(data[pos:]))
			nLeft := int(data[pos+2])
			pos += 3
			for j := 0; j <= nLeft; j++ {
				sids = append(sids, first+j)
			}
		}
	case 2:
		for len(sids) < count && pos+4 <= len(data) {
			first := int(binary.BigEndian.Uint16(data[pos:]))
			nLeft := int(binary.BigEndian.Uint16(data[pos+2:]))
			pos += 4
			for j := 0; j <= nLeft; j++ {
				sids = append(sids, first+j)
			}
		}
	}
	if len(sids) > count {
		sids = sids[:count]
	}
	return sids
}

// readStringIndexItem 读取 CFF 字符串索引项
// 入参: data CFF数据, offset 索引偏移, idx 索引号
// 返回: string 读取的字符串
func readStringIndexItem(data []byte, offset int, idx int) string {
	if offset >= len(data) {
		return ""
	}
	count := int(binary.BigEndian.Uint16(data[offset:]))
	offSize := int(data[offset+2])
	if idx >= count {
		return ""
	}
	offArrayStart := offset + 3
	p1 := offArrayStart + idx*offSize
	p2 := p1 + offSize
	if p2+offSize > len(data) {
		return ""
	}
	loc1 := readCFFOffset(data, p1, offSize)
	loc2 := readCFFOffset(data, p2, offSize)
	dataStart := offArrayStart + (count+1)*offSize
	start := dataStart + loc1 - 1
	length := loc2 - loc1
	if start < 0 || start+length > len(data) {
		return ""
	}
	return string(data[start : start+length])
}

// getUnicodeFromName 根据字形名称获取对应的Unicode字符
// 入参: name 字形名称
// 返回: rune Unicode字符
func getUnicodeFromName(name string) rune {
	if strings.HasPrefix(name, "uni") && len(name) == 7 {
		hexStr := strings.ToUpper(name[3:])
		if val, err := strconv.ParseInt(hexStr, 16, 32); err == nil {
			return rune(val)
		}
	}
	if strings.HasPrefix(name, "u") && len(name) >= 5 && len(name) <= 7 && !strings.HasPrefix(name, "uni") {
		hexStr := strings.ToUpper(name[1:])
		if val, err := strconv.ParseInt(hexStr, 16, 32); err == nil {
			return rune(val)
		}
	}
	switch name {
	case "space":
		return ' '
	case "exclam":
		return '!'
	case "quotedbl":
		return '"'
	case "numbersign":
		return '#'
	case "dollar":
		return '$'
	case "percent":
		return '%'
	case "ampersand":
		return '&'
	case "quotesingle":
		return '\''
	case "parenleft":
		return '('
	case "parenright":
		return ')'
	case "asterisk":
		return '*'
	case "plus":
		return '+'
	case "comma":
		return ','
	case "hyphen":
		return '-'
	case "period":
		return '.'
	case "slash":
		return '/'
	case "colon":
		return ':'
	case "semicolon":
		return ';'
	case "less":
		return '<'
	case "equal":
		return '='
	case "greater":
		return '>'
	case "question":
		return '?'
	case "at":
		return '@'
	case "bracketleft":
		return '['
	case "backslash":
		return '\\'
	case "bracketright":
		return ']'
	case "asciicircum":
		return '^'
	case "underscore":
		return '_'
	case "grave":
		return '`'
	case "braceleft":
		return '{'
	case "bar":
		return '|'
	case "braceright":
		return '}'
	case "asciitilde":
		return '~'
	}
	if len(name) == 1 {
		return rune(name[0])
	}
	return 0
}

// cffStandardStrings CFF 标准字符串表
var cffStandardStrings = []string{
	".notdef", "space", "exclam", "quotedbl", "numbersign", "dollar", "percent", "ampersand", "quoteright", "parenleft", "parenright", "asterisk", "plus", "comma", "hyphen", "period", "slash", "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "colon", "semicolon", "less", "equal", "greater", "question", "at", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "bracketleft", "backslash", "bracketright", "asciicircum", "underscore", "quoteleft", "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "braceleft", "bar", "braceright", "asciitilde", "exclamdown", "cent", "sterling", "fraction", "yen", "florin", "section", "currency", "quotesingle", "quotedblleft", "quotedblright", "guillemotleft", "guillemotright", "dagger", "daggerdbl", "fi", "fl", "endash", "emdash", "paragraph", "bullet", "quotesinglbase", "quotedblbase", "second", "circumflex", "breve", "dotaccent", "dieresis", "grave", "ring", "cedilla", "hungarumlaut", "ogonek", "caron", "emspace",
	"AE", "ordfeminine", "Lslash", "Oslash", "OE", "ordmasculine", "ae", "dotlessi", "lslash", "oslash", "oe", "germandbls", "onesuperior", "logicalnot", "mu", "trademark", "Eth", "onehalf", "plusminus", "Thorn", "onequarter", "divide", "brokenbar", "degree", "thorn", "threequarters", "twosuperior", "registered", "minus", "eth", "multiply", "threesuperior", "copyright", "Aacute", "Acircumflex", "Adieresis", "Agrave", "Aring", "Atilde", "Ccedilla", "Eacute", "Ecircumflex", "Edieresis", "Egrave", "Iacute", "Icircumflex", "Idieresis", "Igrave", "Ntilde", "Oacute", "Ocircumflex", "Odieresis", "Ograve", "Otilde", "Scaron", "Uacute", "Ucircumflex", "Udieresis", "Ugrave", "Yacute", "Ydieresis", "Zcaron", "aacute", "acircumflex", "adieresis", "agrave", "aring", "atilde", "ccedilla", "eacute", "ecircumflex", "edieresis", "egrave", "iacute", "icircumflex", "idieresis", "igrave", "ntilde", "oacute", "ocircumflex", "odieresis", "ograve", "otilde", "scaron", "uacute", "ucircumflex", "udieresis", "ugrave", "yacute", "ydieresis", "zcaron", "exclamsmall", "Hungarumlautsmall", "dollaroldstyle", "dollarsuperior", "ampersandsmall", "Acutesmall", "parenleftsuperior", "parenrightsuperior", "2dotlead", "nbspace", "1dotlead", "zerooldstyle", "oneoldstyle", "twooldstyle", "threeoldstyle", "fouroldstyle", "fiveoldstyle", "sixoldstyle", "sevenoldstyle", "eightoldstyle", "nineoldstyle", "commasuperior", "threequartersemdash", "periodsuperior", "questionsmall", "asuperior", "bsuperior", "centsuperior", "dsuperior", "esuperior", "isuperior", "lsuperior", "msuperior", "nsuperior", "osuperior", "rsuperior", "ssuperior", "tsuperior", "ff", "ffi", "ffl", "parenleftinferior", "parenrightinferior", "Circumflexsmall", "hyphensuperior", "Gravesmall", "Asmall", "Bsmall", "Csmall", "Dsmall", "Esmall", "Fsmall", "Gsmall", "Hsmall", "Ismall", "Jsmall", "Ksmall", "Lsmall", "Msmall", "Nsmall", "Osmall", "Psmall", "Qsmall", "Rsmall", "Ssmall", "Tsmall", "Usmall", "Vsmall", "Wsmall", "Xsmall", "Ysmall", "Zsmall", "colonmonetary", "onefitted", "rupiah", "Tildesmall", "exclamdownsmall", "centoldstyle", "Lslashsmall", "Scaronsmall", "Zcaronsmall", "Dieresissmall", "Brevesmall", "Caronsmall", "Dotaccentsmall", "Macronsmall", "figuredash", "hypheninferior", "Ogoneksmall", "Ringsmall", "Cedillasmall", "questiondownsmall", "oneeighth", "threeeighths", "fiveeighths", "seveneighths", "onethird", "twothirds", "zerosuperior", "foursuperior", "fivesuperior", "sixsuperior", "sevensuperior", "eightsuperior", "ninesuperior", "zeroinferior", "oneinferior", "twoinferior", "threeinferior", "fourinferior", "fiveinferior", "sixinferior", "seveninferior", "eightinferior", "nineinferior", "centinferior", "dollarinferior", "periodinferior", "commainferior", "Agravesmall", "Aacutesmall", "Acircumflexsmall", "Atildesmall", "Adieresissmall", "Aringsmall", "AEsmall", "Ccedillasmall", "Egravesmall", "Eacutesmall", "Ecircumflexsmall", "Edieresissmall", "Igravesmall", "Iacutesmall", "Icircumflexsmall", "Idieresissmall", "Ethsmall", "Ntildesmall", "Ogravesmall", "Oacutesmall", "Ocircumflexsmall", "Otildesmall", "Odieresissmall", "OEsmall", "Oslashsmall", "Ugravesmall", "Uacutesmall", "Ucircumflexsmall", "Udieresissmall", "Yacutesmall", "Thornsmall", "Ydieresissmall", "001.000", "001.001", "001.002", "001.003", "Black", "Bold", "Book", "Light", "Medium", "Regular", "Roman", "Semibold",
}