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// 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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"fmt"
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"io"
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"strings"
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)
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// OutputFormat 描述文档输出格式，Paged表示逐页文件，Raster表示受DPI控制的位图
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type OutputFormat struct {
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Value string `json:"value"`
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Label string `json:"label"`
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Extension string `json:"extension"`
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MIME string `json:"mime"`
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Paged bool `json:"paged,omitempty"`
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Raster bool `json:"raster,omitempty"`
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}
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// ConvertProgress 回报open、pages、convert、prepare、write、write.*及export阶段，Total为0表示总量未知
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type ConvertProgress struct {
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Stage string `json:"stage"`
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Completed int `json:"completed"`
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Total int `json:"total"`
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}
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// ConvertOptions 设置文档转换格式、页码、阅读和渲染选项
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// Input为空时识别源格式，Format为输出格式，Pages使用零基索引，nil表示全部页面
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// PageRange使用一基页码表达式，与Pages互斥，空字符串表示全部页面
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// SkipUnchanged在源格式与目标相同且未选页时不写出数据，不校验或重新生成源文档
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// PDF先转换为OFD对象再输出，PDF选项中的进度回调仍会调用
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// Backends统一配置转换与输出，优先于PDF和RendererOptions中的后端设置
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// PageOutput仅用于逐页格式，同步调用export写出一页并自行处理提交或回滚；此时output可为nil
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// 未提供PageOutput时，逐页格式打包ZIP；所有回调返回错误均会停止转换
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type ConvertOptions struct {
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Input string
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Format string
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Pages []int
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PageRange string
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SkipUnchanged bool
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Backends *RenderBackends
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ReaderOptions []ReaderOption
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RendererOptions []RendererOption
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PDF PDFImportOptions
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OnProgress func(ConvertProgress) error
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PageOutput func(index int, export func(io.Writer) error) error
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}
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// ConvertReport 汇总源格式、输出格式、页数、字节数及PDF转换诊断
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// Unchanged表示无需转换或完整OFD原样复制，Bytes仅统计实际输出，不包含调用方额外封装
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type ConvertReport struct {
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Input string `json:"input"`
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Format OutputFormat `json:"format"`
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Pages int `json:"pages"`
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Bytes int64 `json:"bytes"`
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Unchanged bool `json:"unchanged,omitempty"`
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PDF PDFImportReport `json:"pdf"`
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}
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// convertReader 将取消上下文传递到随机读取
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type convertReader struct {
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context context.Context
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source io.ReaderAt
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}
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// convertWriter 将取消上下文传递到写入并统计实际字节数
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type convertWriter struct {
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context context.Context
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writer io.Writer
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count *int64
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}
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// OutputFormats 返回独立的输出格式列表，不依赖WebUI或具体渲染后端
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// 返回: []OutputFormat 输出格式列表
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func OutputFormats() []OutputFormat {
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return []OutputFormat{
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{Value: "ofd", Label: "OFD", Extension: "ofd", MIME: "application/ofd"},
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{Value: "pdf", Label: "PDF", Extension: "pdf", MIME: "application/pdf"},
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{Value: "svg", Label: "SVG", Extension: "svg", MIME: "image/svg+xml", Paged: true},
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{Value: "eps", Label: "EPS", Extension: "eps", MIME: "application/postscript", Paged: true},
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{Value: "png", Label: "PNG", Extension: "png", MIME: "image/png", Paged: true, Raster: true},
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{Value: "jpg", Label: "JPG", Extension: "jpg", MIME: "image/jpeg", Paged: true, Raster: true},
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{Value: "txt", Label: "TXT", Extension: "txt", MIME: "text/plain"},
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}
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}
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// Convert 将PDF或OFD转换为指定格式，不关闭调用方的输入和输出
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// 完整OFD另存保持源字节，包括制作软件、签名及加密；选页和跨格式输出重新生成文档
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// 输入按需随机读取，输出分块写出；解析对象及后端可能缓存资源，不保证恒定内存
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// 出错时报告保留已有诊断，调用方应丢弃未完成输出；只有返回nil才表示转换成功
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// 入参: ctx 取消上下文, source 源数据, size 源字节数, output 输出流, options 转换选项
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// 返回: ConvertReport 转换报告, error 错误信息
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func Convert(ctx context.Context, source io.ReaderAt, size int64, output io.Writer, options ConvertOptions) (report ConvertReport, err error) {
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if err = ctx.Err(); err != nil {
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return report, err
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}
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format := strings.ToLower(strings.TrimSpace(options.Format))
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if format == "jpeg" {
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format = "jpg"
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}
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for _, candidate := range OutputFormats() {
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if candidate.Value == format {
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report.Format = candidate
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break
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}
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}
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if report.Format.Value == "" {
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return report, fmt.Errorf("unsupported output format %s", options.Format)
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}
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if options.PageOutput != nil && !report.Format.Paged {
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return report, fmt.Errorf("page output requires a paged format")
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}
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if options.Pages != nil && len(options.Pages) == 0 {
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return report, fmt.Errorf("no pages selected")
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}
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if options.Pages != nil && strings.TrimSpace(options.PageRange) != "" {
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return report, fmt.Errorf("conflicting page selections")
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}
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progress := func(stage string, completed, total int) error {
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if err := ctx.Err(); err != nil {
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return err
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}
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if options.OnProgress != nil {
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return options.OnProgress(ConvertProgress{Stage: stage, Completed: completed, Total: total})
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}
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return nil
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}
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writeProgress := func(stage string, completed, total int) error {
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if stage == "write" {
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return progress(stage, completed, total)
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}
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return progress("write."+stage, completed, total)
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}
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if err = progress("open", 0, 0); err != nil {
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return report, err
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}
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source = convertReader{context: ctx, source: source}
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report.Input = strings.ToLower(strings.TrimSpace(options.Input))
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if report.Input == "" {
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var header [1024]byte
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n, readErr := source.ReadAt(header[:], 0)
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if readErr != nil && readErr != io.EOF {
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return report, readErr
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}
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switch {
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case bytes.HasPrefix(header[:n], []byte("PK\x03\x04")):
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report.Input = "ofd"
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case bytes.Contains(header[:n], []byte("%PDF-")):
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report.Input = "pdf"
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}
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}
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var reader *Reader
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var editor *Editor
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var count int
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if report.Input != "pdf" && report.Input != "ofd" {
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return report, fmt.Errorf("unsupported input format")
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}
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if options.SkipUnchanged && report.Input == format && options.Pages == nil && strings.TrimSpace(options.PageRange) == "" {
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report.Unchanged = true
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return report, nil
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}
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if output == nil && options.PageOutput == nil {
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return report, fmt.Errorf("missing output writer")
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}
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switch report.Input {
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case "pdf":
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pdfOptions := options.PDF
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if options.Backends != nil {
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pdfOptions.Backends = options.Backends
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}
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pdfOptions.OnProgress = func(stage string, completed, total int) error {
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if err := progress(stage, completed, total); err != nil {
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return err
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}
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if options.PDF.OnProgress != nil {
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return options.PDF.OnProgress(stage, completed, total)
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}
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return nil
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}
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editor, report.PDF, err = ImportPDF(ctx, source, size, pdfOptions)
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if err != nil {
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return report, err
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}
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count = editor.PageCount()
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case "ofd":
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reader, err = NewReader(source, size, options.ReaderOptions...)
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if err != nil {
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return report, err
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}
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defer reader.Close()
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count, err = reader.PageCount()
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if err != nil {
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return report, err
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}
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}
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if strings.TrimSpace(options.PageRange) != "" {
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options.Pages, err = ParsePageRange(options.PageRange, count)
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if err != nil {
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return report, err
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}
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}
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indices, err := exportPageIndices(count, options.Pages)
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if err != nil {
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return report, err
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}
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report.Pages = len(indices)
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writer := convertWriter{context: ctx, writer: output, count: &report.Bytes}
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if format == "ofd" {
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if options.Pages == nil && editor == nil {
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if err = progress("write", 0, 0); err != nil {
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return report, err
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}
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_, err = io.Copy(writer, io.NewSectionReader(source, 0, size))
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report.Unchanged = err == nil
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return report, err
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}
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if editor == nil {
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editor, err = reader.Editor()
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if err != nil {
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return report, err
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}
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}
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editor.OnWriteProgress = writeProgress
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if options.Pages == nil {
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_, err = editor.WriteTo(writer)
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} else {
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_, err = editor.WritePagesTo(writer, indices)
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}
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return report, err
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}
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if reader == nil {
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if err = progress("prepare", 0, count); err != nil {
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return report, err
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}
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reader, err = editor.reader(progress)
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if err != nil {
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return report, err
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}
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defer reader.Close()
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}
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renderer := NewRenderer(reader, options.RendererOptions...)
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if options.Backends != nil {
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WithRenderBackends(*options.Backends)(renderer)
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}
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renderer.OnExportProgress = func(completed, total int) error {
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return progress("export", completed, total)
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}
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switch format {
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case "pdf":
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err = renderer.RenderToMultiPagePDF(writer, indices...)
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case "txt":
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err = renderer.RenderToMultiPageText(writer, indices...)
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default:
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if options.PageOutput == nil {
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err = renderer.RenderToZIP(writer, format, indices...)
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report.Format = OutputFormat{Value: "zip", Label: "ZIP", Extension: "zip", MIME: "application/zip"}
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break
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}
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for i, index := range indices {
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if err = progress("export", i, len(indices)); err != nil {
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return report, err
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}
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page, readErr := reader.PageContentByIndex(index)
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if readErr != nil {
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return report, readErr
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}
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if err = options.PageOutput(index, func(output io.Writer) error {
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return renderer.RenderTo(page, convertWriter{context: ctx, writer: output, count: &report.Bytes}, format)
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}); err != nil {
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return report, fmt.Errorf("export page %d: %w", index+1, err)
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}
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}
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err = progress("export", len(indices), len(indices))
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}
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return report, err
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}
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// ReadAt 读取指定位置的数据并响应取消
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// 入参: data 目标缓冲, offset 源偏移
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// 返回: int 读取字节数, error 读取错误
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func (r convertReader) ReadAt(data []byte, offset int64) (int, error) {
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if err := r.context.Err(); err != nil {
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return 0, err
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}
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return r.source.ReadAt(data, offset)
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}
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// Write 写出数据并响应取消及短写
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// 入参: data 待写数据
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// 返回: int 写入字节数, error 写入错误
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func (w convertWriter) Write(data []byte) (int, error) {
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if err := w.context.Err(); err != nil {
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return 0, err
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}
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n, err := w.writer.Write(data)
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*w.count += int64(n)
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if err == nil && n != len(data) {
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err = io.ErrShortWrite
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}
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return n, err
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}
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