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Blazor WASM Load and display large pdfs by splitting them as streams

I'm working on a Blazor WASM App and I want my users to easily open pdf files on specific pages that contain additional information.
I cannot distribute those files myself or upload them to any kind of server. Each user has to provide them themselves.
Because the files are up to 60MB big I cannot convert the uploaded file to base64 and display them as described here.
However I don't have to display the whole file and could just load the needed page +- some pages around them.
For that I tried using iText7 ExtractPageRange(). This answer indicates, that I have to override the GetNextPdfWriter() Method and to store all streams in an collection.
class ByteArrayPdfSplitter : PdfSplitter {
public ByteArrayPdfSplitter(PdfDocument pdfDocument) : base(pdfDocument) {
}
protected override PdfWriter GetNextPdfWriter(PageRange documentPageRange) {
CurrentMemoryStream = new MemoryStream();
UsedStreams.Add(CurrentMemoryStream);
return new PdfWriter(CurrentMemoryStream);
}
public MemoryStream CurrentMemoryStream { get; private set; }
public List<MemoryStream> UsedStreams { get; set; } = new List<MemoryStream>();
Then I thought I could merge those streams and convert them to base64
var file = loadedFiles.First();
using (MemoryStream ms = new MemoryStream())
{
var rs = file.OpenReadStream(maxFileSize);
await rs.CopyToAsync(ms);
ms.Position = 0;
//rs needed to be converted to ms, because the PdfReader constructer uses a
//synchronious read that isn't supported by rs and throws an exception.
PdfReader pdfReader = new PdfReader(ms);
var document = new PdfDocument(pdfReader);
var splitter = new ByteArrayPdfSplitter(document);
var range = new PageRange();
range.AddPageSequence(1, 10);
var splitDoc = splitter.ExtractPageRange(range);
//Edit commented this out, shouldn't have been here at all leads to an exception
//splitDoc.Close();
var outputMs = new MemoryStream();
foreach (var usedMs in splitter.UsedStreams)
{
usedMs.Position = 0;
outputMs.Position = outputMs.Length;
await usedMs.CopyToAsync(outputMs);
}
var data = outputMs.ToArray();
currentPdfContent = "data:application/pdf;base64,";
currentPdfContent += Convert.ToBase64String(data);
pdfLoaded = true;
}
This however doesn't work.
Has anyone a suggestion how to get this working? Or maybe a simpler solution I could try.
Edit:
I took a closer look in debug and it seems like, the resulting stream outputMs is always empty. So it is probably a problem in how I split the pdf.

After at least partially clearing up my misconception of what it means to not being able to access the file system from blazor WASM I managed to find a working solution.
await using MemoryStream ms = new MemoryStream();
var rs = file.OpenReadStream(maxFileSize);
await using var fs = new FileStream("test.pdf", FileMode.Create)
fs.Position = 0;
await rs.CopyToAsync(fs);
fs.Close();
string path = "test.pdf";
string range = "10 - 15";
var pdfDocument = new PdfDocument(new PdfReader("test.pdf"));
var split = new MySplitter(pdfDocument);
var result = split.ExtractPageRange(new PageRange(range));
result.Close();
await using var splitFs = new FileStream("split.pdf", FileMode.Open))
await splitFs.CopyToAsync(ms);
var data = ms.ToArray();
var pdfContent = "data:application/pdf;base64,";
pdfContent += System.Convert.ToBase64String(data);
Console.WriteLine(pdfContent);
currentPdfContent = pdfContent;
With the MySplitter Class from this answer.
class MySplitter : PdfSplitter
{
public MySplitter(PdfDocument pdfDocument) : base(pdfDocument)
{
}
protected override PdfWriter GetNextPdfWriter(PageRange documentPageRange)
{
String toFile = "split.pdf";
return new PdfWriter(toFile);
}
}

Memory leak with a memory stream

I know this code is far from perfect but in my case this was the only
way to do it correctly because im embedding WPF in C#, and when
applying text regulary the Spellcheck does not work correctly
So this is my code:
RichTextBox temphotfix = new RichTextBox();
temphotfix.Font = new Font(temphotfix.Font.Name, 14);
System.Windows.Documents.TextRange range = new System.Windows.Documents.TextRange(omschrijving.Document.ContentStart, omschrijving.Document.ContentEnd);
temphotfix.Text = oms;
string temp = temphotfix.Rtf;
byte[] byteArray = Encoding.ASCII.GetBytes(temp);
MemoryStream stream = new MemoryStream(byteArray);
range.Load(stream, DataFormats.Rtf);
range = null;
temp = null;
byteArray = null;
temphotfix.Dispose();
stream.Dispose();
I stress tested this, and it seems like ever about 5 times the script gets ran, it adds about 1 MB ram.
What am i doing wrong, i litterly made everyting i used null, or desposed them.

As I told above in comment you can using, you can try this code. hope this should help.
using (RichTextBox temphotfix = new RichTextBox())
{
temphotfix.Font = new Font(temphotfix.Font.Name, 14);
System.Windows.Documents.TextRange range = new System.Windows.Documents.TextRange(omschrijving.Document.ContentStart, omschrijving.Document.ContentEnd);
temphotfix.Text = oms;
string temp = temphotfix.Rtf;
byte[] byteArray = Encoding.ASCII.GetBytes(temp);
using (MemoryStream stream = new MemoryStream(byteArray))
{
range.Load(stream, DataFormats.Rtf);
}
range = null;
temp = null;
byteArray = null;
//temphotfix.Dispose();
//stream.Dispose();
}

ZipArchive Created with System.IO.Compression is Damaged

I am having a hard time creating a ZipArchive successfully on Asp.net core MVC. I have an excel file generated with data that works and I need to put in an archive. This is what I've done so far
public FileResult ExportGoodsReceiptData()
{
var records = _salesService.GetAllReceipts();
var lineRecords = _salesService.GetAllReceiptLines();
var result = _salesService.ExportGoodsReceiptData(records);
var lineResult = _salesService.ExportGoodsReceiptLineData(lineRecords);
byte[] resultArr = StreamToByteArray(result);
byte[] lineResultArr = StreamToByteArray(lineResult);
using(MemoryStream stream = new MemoryStream())
{
using (var archive = new ZipArchive(stream, ZipArchiveMode.Create, true))
{
var zipArchiveEntry = archive.CreateEntry("GoodsReceipts.csv", CompressionLevel.Fastest);
using (var zipStream = zipArchiveEntry.Open())
using (var resultCom = new MemoryStream(resultArr))
{
resultCom.CopyTo(zipStream);
}
}
return new FileStreamResult(stream, "application/zip") { FileDownloadName = "GoodsReceiptsArchive.zip" };
}
}
When I run it, I get the zipfile, but can't open it. It throws error stating that it may have been damaged. I debugged the code to notice that one of the properties (length property) throws an invalidOperation exception. My approach looks identical to most samples I found online. Don't know how else to solve this. Please help.

Your problem is that you're disposing of your memory stream before you return it. Remove this using:
using(MemoryStream stream = new MemoryStream())
Replace it with:
var stream = new MemoryStream();
Asp.Net MVC will automatically dispose of the stream for you.

Convert wav streamed over HTTP to mp3, in real-time

Background: I am consuming a service which returns data with a MIME type of audio/wav. I need to provide a playback mechanism for this audio (currently built as an MVC application). As an example, my endpoint looks something like https://audio.fooservice.com/GetAudio?audioId=123
The audio is 8kHz, 1-channel u-law.
Due to varying format support across browsers when using the HTML5 <audio> tag, I am unable to use the original u-law wav because Internet Explorer will not play it.
My proposed solution is to do a real-time conversion from the source format to mp3.
I've cobbled together a partially working solution from various other questions here and in the NAudio forums, but it throws an exception as noted in the comments below:
private void NAudioTest(string url)
{
Stream outStream = new MemoryStream();
var format = WaveFormat.CreateMuLawFormat(8000, 1);
using (Stream ms = new MemoryStream())
{
var request = (HttpWebRequest)WebRequest.Create(url);
request.KeepAlive = false;
request.ProtocolVersion = HttpVersion.Version10;
using (Stream stream = request.GetResponse().GetResponseStream())
{
using (var reader = new RawSourceWaveStream(stream, format))
{
// reader is not seekable; we need to convert to a byte array to seek
var bytes = reader.ToByteArray();
// create a new stream from the byte aray
var seekableStream = new MemoryStream(bytes);
// instantiating a WaveFileReader as follows will throw an exception:
// "System.FormatException: Not a WAVE file - no RIFF header"
using (var waveReader = new WaveFileReader(seekableStream))
{
using (var pcmStream = WaveFormatConversionStream.CreatePcmStream(waveReader))
{
var pcmBytes = pcmStream.ToByteArray();
var mp3 = pcmBytes.ToMp3();
}
}
}
}
}
}
public static class StreamExtensions
{
public static byte[] ToByteArray(this Stream stream)
{
var ms = new MemoryStream();
var buffer = new byte[1024];
int bytes = 0;
while ((bytes = stream.Read(buffer, 0, buffer.Length)) > 0)
ms.Write(buffer, 0, bytes);
return ms.ToArray();
}
}
public static class ByteExtensions
{
public static byte[] ToMp3(this byte[] bytes)
{
using (var outStream = new MemoryStream())
{
using (var ms = new MemoryStream(bytes))
{
using (var reader = new WaveFileReader(ms))
{
using (var writer = new LameMP3FileWriter(outStream, reader.WaveFormat, 64))
{
reader.CopyTo(writer);
return outStream.ToArray();
}
}
}
}
}
}
I've been poking around at this for most of the day and I feel like I'm introducing unnecessary complexity into something that seems like it should be fairly straightforward.
Any help would be much appreciated.
Note: I cannot change the source format and supporting IE is a requirement.
EDIT: I resolved the RIFF exception and am able to produce a stream of the MP3, but it's nothing but white noise. Hopefully I can resolve that as well. My new code is as follows:
[HttpGet]
public ActionResult GetMp3(string url)
{
if (String.IsNullOrWhiteSpace(url))
return null;
var muLawFormat = WaveFormat.CreateMuLawFormat(8000, 1);
var compressedStream = new MemoryStream();
using (var ms = new MemoryStream())
{
var request = (HttpWebRequest)WebRequest.Create(url);
request.KeepAlive = false;
request.ProtocolVersion = HttpVersion.Version10;
using (Stream webStream = request.GetResponse().GetResponseStream())
{
var buffer = new byte[4096];
int read;
while (webStream != null && (read = webStream.Read(buffer, 0, buffer.Length)) > 0)
ms.Write(buffer, 0, read);
}
ms.Position = 0;
using (WaveStream wav = WaveFormatConversionStream.CreatePcmStream(new RawSourceWaveStream(ms, muLawFormat)))
using (var mp3 = new LameMP3FileWriter(compressedStream, new WaveFormat(), LAMEPreset.MEDIUM_FAST))
wav.CopyTo(mp3);
}
compressedStream.Seek(0, 0);
return new FileStreamResult(compressedStream, "audio/mpeg");
}

This works for me (and I needed to do exactly what you wanted to do). Hope this helps someone else as well. I used NAudio with LAME.
You have to make sure that you copy the libmp3lamexx.dll files to your webserver's BIN location or to some folder in the %PATH% variable, else it won't work.
string sq = /* URL of WAV file (http://foo.com/blah.wav) */
Response.ContentType = "audio/mpeg";
using (WebClient wc = new WebClient())
{
if (!sq.ToLower().EndsWith(".wav"))
{
byte[] rawFile = wc.DownloadData(sq.Trim());
Response.OutputStream.Write(rawFile, 0, rawFile.Length);
}
else
{
using (var wavReader = new WaveFileReader(new MemoryStream(wc.DownloadData(sq.Trim()))))
{
try
{
using (var wavWriter = new LameMP3FileWriter(Response.OutputStream, wavReader.WaveFormat, LAMEPreset.ABR_128))
{
wavReader.CopyTo(wavWriter);
}
}
catch (ArgumentException)
{
var newFormat = new WaveFormat(wavReader.WaveFormat.SampleRate, 16, 2);
using (var pcmStream = new WaveFormatConversionStream(newFormat, wavReader))
{
using (var wavWriter = new LameMP3FileWriter(Response.OutputStream, pcmStream.WaveFormat, LAMEPreset.ABR_128))
{
pcmStream.CopyTo(wavWriter);
}
}
}
}
}
Response.Flush();
Response.End();
}

ICSharpZipLib - unziping file issue

I have an application in ASP.NET where user can upload ZIP file. I'm trying to extract file using ICSharpZipLib (I also tried DotNetZip, but had same issue).
This zip file contains single xml document (9KB before compress).
When I open this file with other applications on my desktop (7zip, windows explorer) it seems to be ok.
My unzip method throws System.OutOfMemoryException and I have no idea why is that. When I debugged my unziping method I noticed that zipInputStreams' Length property throws Exception and is not available:
Stream UnZipSingleFile(Stream memoryStream)
{
var zipInputStream = new ZipInputStream(memoryStream);
memoryStream.Position = 0;
zipInputStream.GetNextEntry();
MemoryStream unzippedStream = new MemoryStream();
int len;
byte[] buf = new byte[4096];
while ((len = zipInputStream.Read(buf, 0, buf.Length)) > 0)
{
unzippedStream.Write(buf, 0, len);
}
unzippedStream.Position = 0;
memoryStream.Position = 0;
return unzippedStream;
}
and here's how I get string of unzippedStream:
string GetString()
{
var reader = new StreamReader(unzippedStream);
var result = reader.ReadToEnd();
unzippedStream.Position = 0;
return result;
}

From their wiki:
"Sharpzip supports Zip files using both stored and deflate compression methods and also supports old (PKZIP 2.0) style and AES encryption"
Are you sure the format of the uploaded zip file is acceptable for SharpZipLib?

While this post is quite old, I think it could be beneficial to illustrate how I did this for compression and decompression using ICSharpZipLib (C# package version 1.1.0). I put this together by looking into the examples shown here (see ie. these compression and decompression examples).
Assumption: The input to the compression and decompression below should be in bytes. If you have ie. an xml file you could load it to an XDocument, and convert it into an XmlDocument with .ToXmlDocument(). From there, you could access the string contents by calling .OuterXml, and converting the string to a byte array.
// Compression (inputBytes = ie. string-to-compress, as bytes)
using var dataStream = new MemoryStream(inputBytes);
var outputStream = new MemoryStream();
using (var zipStream = new ZipOutputStream(outputStream))
{
zipStream.SetLevel(3);
var newEntry = new ZipEntry("someFilename.someExtension");
newEntry.DateTime = DateTime.Now;
zipStream.PutNextEntry(newEntry);
StreamUtils.Copy(dataStream, zipStream, new byte[4096]);
zipStream.CloseEntry();
zipStream.IsStreamOwner = false;
}
outputStream.Position = 0;
var outputBytes = outputStream.ToArray();
// Decompression (inputBytes = ie. string-to-decompress, as bytes)
using var dataStream = new MemoryStream(inputBytes);
var outputStream = new MemoryStream();
using (var zipStream = new ZipInputStream(dataStream))
{
while (zipStream.GetNextEntry() is ZipEntry zipEntry)
{
var buffer = new byte[4096];
StreamUtils.Copy(zipStream, outputStream, buffer);
}
}
var outputBytes = outputStream.ToArray();