mirror of
https://github.com/xiaoqidun/ofdgo.git
synced 2026-10-29 17:27:08 +08:00
106 lines
3.5 KiB
Go
106 lines
3.5 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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"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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// pdfReferencePageKey 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 pdfReferencePageKey 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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// referencePage 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
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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 (p *pdfImporter) referencePage(ctx context.Context, source *pdfgo.Reader, reference pdfgo.ReferenceXObject) (*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 p.resolveReference != nil {
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return p.resolveReference(ctx, source, reference)
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}
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reader := p.referenceStreams[reference.File.Embedded]
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if reader == nil {
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if reference.File.Embedded == nil && p.resolveFile == nil {
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return p.referenceProxy(ctx, fmt.Errorf("external reference file unavailable"))
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}
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data, err := source.ReadFileData(ctx, reference.File, p.resolveFile)
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if err != nil {
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return p.referenceProxy(ctx, err)
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}
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key := sha256.Sum256(data)
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reader = p.referenceReaders[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: p.warning})
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if err != nil {
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return p.referenceProxy(ctx, err)
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}
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p.referenceReaders[key] = reader
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}
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if reference.File.Embedded != nil {
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p.referenceStreams[reference.File.Embedded] = reader
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}
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}
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key := pdfReferencePageKey{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 := p.referencePages[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 p.referenceProxy(ctx, err)
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}
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p.referencePages[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
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// 返回: *pdfgo.Page 空目标, error 取消错误
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func (p *pdfImporter) referenceProxy(ctx context.Context, cause error) (*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 p.warning != nil {
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p.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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// closeReferenceReaders 释放本次转换打开的引用文档，不关闭调用方提供的阅读器
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func (p *pdfImporter) closeReferenceReaders() {
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for _, reader := range p.referenceReaders {
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reader.Close()
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}
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p.referenceReaders, p.referenceStreams = nil, nil
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p.referencePages = nil
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}
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