feat(渲染编辑): 优化渲染编辑完善资源保存

ofdgo_pdf_buffer.go

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+// 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 "context"
+
+// pdfObjectChunkLimit 限制导入暂存片段的容量，不限制页面对象数量
+const pdfObjectChunkLimit = 256
+
+// pdfObjectBuffer 分块收集导入对象，提交前只整理一次连续数据
+type pdfObjectBuffer struct {
+	parts [][]GraphicObject
+	size  int
+}
+
+// appendObject 追加本次导入对象，按需建立独立暂存缓冲
+// 入参: object 独立导入对象
+func (p *pdfImporter) appendObject(object GraphicObject) {
+	if p.objects == nil {
+		p.objects = &pdfObjectBuffer{}
+	}
+	p.objects.append(object)
+}
+
+// append 追加对象，小批量连续存储，超过阈值后不复制前序片段
+// 入参: object 独立对象
+func (b *pdfObjectBuffer) append(object GraphicObject) {
+	index := len(b.parts) - 1
+	if index == 0 && len(b.parts[0]) == cap(b.parts[0]) && cap(b.parts[0]) < pdfObjectChunkLimit {
+		part := b.parts[0]
+		next := make([]GraphicObject, len(part), min(pdfObjectChunkLimit, max(1, cap(part)*2)))
+		copy(next, part)
+		b.parts[0] = next
+	}
+	if index < 0 || len(b.parts[index]) == cap(b.parts[index]) {
+		capacity := pdfObjectChunkLimit
+		if index < 0 {
+			capacity = 1
+		}
+		b.parts = append(b.parts, make([]GraphicObject, 0, capacity))
+		index++
+	}
+	b.parts[index] = append(b.parts[index], object)
+	b.size++
+}
+
+// len 获取暂存对象数量，空缓冲返回零
+// 返回: int 对象数量
+func (b *pdfObjectBuffer) len() int {
+	if b == nil {
+		return 0
+	}
+	return b.size
+}
+
+// truncate 回滚到已有对象位置，清理丢弃对象及片段引用
+// 入参: size 保留对象数量
+func (b *pdfObjectBuffer) truncate(size int) {
+	if size < 0 || size > b.len() {
+		panic("invalid PDF object buffer size")
+	}
+	if size == b.len() {
+		return
+	}
+	remaining := size
+	for index, part := range b.parts {
+		if remaining <= len(part) {
+			clear(part[remaining:])
+			b.parts[index] = part[:remaining]
+			clear(b.parts[index+1:])
+			b.parts = b.parts[:index+1]
+			b.size = size
+			return
+		}
+		remaining -= len(part)
+	}
+}
+
+// data 按绘制顺序整理独立对象数组，取消时保留原片段供重试
+// 入参: ctx 取消上下文
+// 返回: []GraphicObject 暂存数据, error 取消错误
+func (b *pdfObjectBuffer) data(ctx context.Context) ([]GraphicObject, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	if b.len() == 0 {
+		return nil, nil
+	}
+	if len(b.parts) == 1 {
+		return b.parts[0][:b.size:b.size], nil
+	}
+	objects := make([]GraphicObject, b.size)
+	offset := 0
+	for _, part := range b.parts {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		offset += copy(objects[offset:], part)
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	b.parts[0] = objects
+	clear(b.parts[1:])
+	b.parts = b.parts[:1]
+	return objects, nil
+}