mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 14:16:55 +08:00
122 lines
4.2 KiB
Go
122 lines
4.2 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 pdf
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import (
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"bytes"
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"context"
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"crypto/sha256"
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"errors"
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"fmt"
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"github.com/xiaoqidun/pdfgo"
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)
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// ReferenceCache 保存单次会话拥有的引用文档及页面，零值可用，须串行使用且使用后不应复制
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// Close只释放缓存自行打开的阅读器，不关闭来源文档或调用方提供的阅读器
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type ReferenceCache struct {
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readers map[[32]byte]*pdfgo.Reader
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streams map[*pdfgo.Stream]*pdfgo.Reader
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pages map[referencePageKey]*pdfgo.Page
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}
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// referencePageKey 区分目标文档、索引和文本标签，避免重复遍历页面树
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type referencePageKey struct {
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reader *pdfgo.Reader
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index int64
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label string
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labeled bool
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}
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// Resolve 解析引用目标，目标不可用时按PDF标准保留代理内容
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// 入参: ctx 取消上下文, source 来源文档, reference 引用目标, fileResolver 外部文件读取, referenceResolver 调用方页面解析, warning 诊断回调
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// 返回: *pdfgo.Page 目标页面，不可用时为空, error 取消或调用方解析错误
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func (c *ReferenceCache) Resolve(ctx context.Context, source *pdfgo.Reader, reference pdfgo.ReferenceXObject, fileResolver pdfgo.FileResolver, referenceResolver pdfgo.ReferenceResolver, warning func(pdfgo.Diagnostic)) (*pdfgo.Page, error) {
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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if referenceResolver != nil {
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return referenceResolver(ctx, source, reference)
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}
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reader := c.streams[reference.File.Embedded]
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if reader == nil {
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if reference.File.Embedded == nil && fileResolver == nil {
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return referenceProxy(ctx, fmt.Errorf("external reference file unavailable"), warning)
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}
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data, err := source.ReadFileData(ctx, reference.File, fileResolver)
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if err != nil {
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return referenceProxy(ctx, err, warning)
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}
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key := sha256.Sum256(data)
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reader = c.readers[key]
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if reader == nil {
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reader, err = pdfgo.NewReaderWithOptions(bytes.NewReader(data), int64(len(data)), pdfgo.ReaderOptions{Warning: warning})
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if err != nil {
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return referenceProxy(ctx, err, warning)
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}
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if c.readers == nil {
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c.readers = make(map[[32]byte]*pdfgo.Reader)
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}
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c.readers[key] = reader
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}
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if reference.File.Embedded != nil {
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if c.streams == nil {
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c.streams = make(map[*pdfgo.Stream]*pdfgo.Reader)
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}
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c.streams[reference.File.Embedded] = reader
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}
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}
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key := referencePageKey{reader: reader, index: reference.PageIndex}
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if reference.PageLabel != nil {
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key.index, key.label, key.labeled = 0, *reference.PageLabel, true
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}
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if page := c.pages[key]; page != nil {
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return page, ctx.Err()
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}
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page, err := reader.ResolveReferencePage(ctx, reference)
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if err != nil {
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return referenceProxy(ctx, err, warning)
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}
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if c.pages == nil {
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c.pages = make(map[referencePageKey]*pdfgo.Page)
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}
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c.pages[key] = page
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return page, ctx.Err()
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}
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// referenceProxy 记录目标不可用原因，不将合法的代理绘制视为转换失败
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// 入参: ctx 取消上下文, cause 目标不可用原因, warning 诊断回调
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// 返回: *pdfgo.Page 空目标, error 取消错误
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func referenceProxy(ctx context.Context, cause error, warning func(pdfgo.Diagnostic)) (*pdfgo.Page, error) {
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if err := ctx.Err(); err != nil {
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return nil, err
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}
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if errors.Is(cause, context.Canceled) || errors.Is(cause, context.DeadlineExceeded) {
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return nil, cause
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}
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if warning != nil {
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warning(pdfgo.Diagnostic{Message: "reference XObject proxy retained: " + cause.Error()})
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}
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return nil, nil
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}
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// Close 释放本次会话打开的引用文档并清空缓存，可重复调用，之后可重新解析
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func (c *ReferenceCache) Close() {
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for _, reader := range c.readers {
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reader.Close()
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}
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c.readers, c.streams, c.pages = nil, nil, nil
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}
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