feat(文件拆分): 拆分PDF格式适配模块

internal/codec/pdf/clip.go

@@ -0,0 +1,67 @@
+// 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 pdf
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/binary"
+	"math"
+
+	"github.com/xiaoqidun/pdfgo"
+)
+
+// ClipPathKey 按路径完整内容与变换生成键，不依赖可变切片的地址
+// 入参: ctx 取消上下文, path 裁剪路径, matrix 页面变换
+// 返回: [32]byte 内容摘要, error 取消错误
+func ClipPathKey(ctx context.Context, path pdfgo.Path, matrix pdfgo.Matrix) ([32]byte, error) {
+	hash := sha256.New()
+	var value [16]byte
+	for _, number := range matrix {
+		binary.LittleEndian.PutUint64(value[:8], math.Float64bits(number))
+		hash.Write(value[:8])
+	}
+	binary.LittleEndian.PutUint64(value[:8], uint64(len(path.Segments)))
+	value[8] = 0
+	if path.EvenOdd {
+		value[8] = 1
+	}
+	hash.Write(value[:9])
+	for _, segment := range path.Segments {
+		if err := ctx.Err(); err != nil {
+			return [32]byte{}, err
+		}
+		binary.LittleEndian.PutUint64(value[:8], uint64(len(segment.Operator)))
+		binary.LittleEndian.PutUint64(value[8:], uint64(len(segment.Points)))
+		hash.Write(value[:])
+		hash.Write([]byte(segment.Operator))
+		for index, point := range segment.Points {
+			if index&255 == 0 {
+				if err := ctx.Err(); err != nil {
+					return [32]byte{}, err
+				}
+			}
+			binary.LittleEndian.PutUint64(value[:8], math.Float64bits(point.X))
+			binary.LittleEndian.PutUint64(value[8:], math.Float64bits(point.Y))
+			hash.Write(value[:])
+		}
+	}
+	if err := ctx.Err(); err != nil {
+		return [32]byte{}, err
+	}
+	var key [32]byte
+	hash.Sum(key[:0])
+	return key, nil
+}