feat(内存占用): 支持附件流式下载，降低大附件内存占用

assets/webui/ofdgo.js

@@ -1535,18 +1535,30 @@ async function downloadAttachment(attachment) {
 	updateControls();
 	setBusy(true, "正在读取附件", null, "正在读取附件");
 	try {
-		const result = await callWASM("ofdgoAttachmentData", attachment.id);
+		const file = window.showSaveFilePicker ? await window.showSaveFilePicker({ suggestedName: attachment.fileName }) : null;
 		if (openSeq !== state.openSeq) {
 			return;
 		}
-		downloadBytes(result.bytes, "application/octet-stream", attachment.fileName);
-		setStatus(`附件下载完成 ${formatBytes(result.bytes.length)}`);
+		const result = await callWASM("ofdgoExportAttachment", attachment.id, file);
+		if (openSeq !== state.openSeq) {
+			return;
+		}
+		if (result.blob) {
+			downloadBytes(result.blob, result.mime, attachment.fileName);
+		}
+		setStatus(`附件下载完成 ${formatBytes(result.size)}`);
 	} catch (err) {
 		if (openSeq === state.openSeq) {
-			showError(err, false);
+			if (err.name === "AbortError") {
+				setStatus("下载已取消");
+			} else {
+				showError(err, false);
+			}
 		}
 	} finally {
 		state.exporting = false;
+		state.exportRequestID = 0;
+		el.cancelExportButton.hidden = true;
 		if (openSeq === state.openSeq) {
 			setBusy(false);
 			updateControls();
@@ -3416,7 +3428,7 @@ async function callWASM(name, ...args) {
 	return new Promise((resolve, reject) => {
 		const id = ++wasmRequestID;
 		wasmRequests.set(id, { resolve, reject, openSeq: state.openSeq });
-		if (name === "ofdgoExportPage" || name === "ofdgoExportDocument") {
+		if (name === "ofdgoExportPage" || name === "ofdgoExportDocument" || name === "ofdgoExportAttachment") {
 			state.exportRequestID = id;
 			el.cancelExportButton.hidden = false;
 			el.cancelExportButton.disabled = false;

assets/webui/ofdgo.wasm.js

@@ -7,7 +7,7 @@ self.onmessage = ({ data }) => {
 		exports.get(data.id)?.abort();
 		return;
 	}
-	if (data.name === "ofdgoExportPage" || data.name === "ofdgoExportDocument") {
+	if (data.name === "ofdgoExportPage" || data.name === "ofdgoExportDocument" || data.name === "ofdgoExportAttachment") {
 		exports.set(data.id, new AbortController());
 	}
 	pending = pending.then(() => handleMessage(data));

internal/webui/wasm.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"syscall/js"
 
 	"github.com/xiaoqidun/ofdgo"
@@ -81,7 +82,6 @@ func RunWASM() {
 	registerCallback("ofdgoOpen", openDocument)
 	registerCallback("ofdgoConfigure", configureDocument)
 	registerCallback("ofdgoDocumentInfo", documentInfo)
-	registerCallback("ofdgoAttachmentData", attachmentData)
 	registerCallback("ofdgoRenderPage", renderPage)
 	registerCallback("ofdgoSVGFontData", svgFontData)
 	registerCallback("ofdgoSearchPage", searchPage)
@@ -90,6 +90,7 @@ func RunWASM() {
 	registerCallback("ofdgoParsePageRange", parsePageRange)
 	registerExportCallback("ofdgoExportPage", exportPage)
 	registerExportCallback("ofdgoExportDocument", exportDocument)
+	registerExportCallback("ofdgoExportAttachment", exportAttachment)
 	registerCallback("ofdgoMatchFontFiles", matchFontFiles)
 	select {}
 }
@@ -207,18 +208,28 @@ func documentInfo(args []js.Value) (any, error) {
 	return currentSession.Info(), nil
 }
 
-// attachmentData 读取附件数据
+// exportAttachment 分块导出附件
 // 入参: args 浏览器参数
 // 返回: any 附件数据, error 错误信息
-func attachmentData(args []js.Value) (any, error) {
+func exportAttachment(args []js.Value) (any, error) {
 	if currentSession == nil {
 		return nil, fmt.Errorf("ofd document is not opened")
 	}
-	data, err := currentSession.Reader.AttachmentData(args[0].String())
+	stream, err := currentSession.Reader.OpenAttachment(args[0].String())
 	if err != nil {
 		return nil, err
 	}
-	return successResult(map[string]any{"bytes": bytesToJS(data)}), nil
+	defer stream.Close()
+	writer := bufio.NewWriterSize(exportWriter{write: args[1]}, 1<<20)
+	if _, err := io.Copy(writer, stream); err != nil {
+		return nil, err
+	}
+	if err := writer.Flush(); err != nil {
+		return nil, err
+	}
+	return successResult(map[string]any{
+		"mime": "application/octet-stream",
+	}), nil
 }
 
 // svgFontData 读取SVG字体资源

ofdgo_reader.go

@@ -543,22 +543,34 @@ func (r *Reader) Attachments() ([]Attachment, error) {
 	return doc.Attachments.Attachment, nil
 }
 
-// AttachmentData 获取附件文件数据
+// OpenAttachment 打开附件文件流，调用方负责关闭，完整读取后校验ZIP数据
 // 入参: id 附件标识
-// 返回: []byte 附件数据, error 错误信息
-func (r *Reader) AttachmentData(id string) ([]byte, error) {
+// 返回: io.ReadCloser 附件文件流, error 错误信息
+func (r *Reader) OpenAttachment(id string) (io.ReadCloser, error) {
 	attachments, err := r.Attachments()
 	if err != nil {
 		return nil, err
 	}
 	for _, attachment := range attachments {
 		if attachment.ID == id {
-			return r.ResData(attachment.FileLoc)
+			return r.openFile(r.ResPath(attachment.FileLoc))
 		}
 	}
 	return nil, fmt.Errorf("attachment not found: %s", id)
 }
 
+// AttachmentData 获取附件文件数据
+// 入参: id 附件标识
+// 返回: []byte 附件数据, error 错误信息
+func (r *Reader) AttachmentData(id string) ([]byte, error) {
+	stream, err := r.OpenAttachment(id)
+	if err != nil {
+		return nil, err
+	}
+	defer stream.Close()
+	return io.ReadAll(stream)
+}
+
 // CustomTags 获取自定义标引
 // 返回: []CustomTag 自定义标引列表, error 错误信息
 func (r *Reader) CustomTags() ([]CustomTag, error) {