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Improve TryReadStream with simplification & fix of Stream Invalid Length cutting off Streams (#838)

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* Improve TryReadStream with simplification & fix of Stream Invalid Length cutting off Streams

- Fix of Stream invalid Length issue causing stream data being cut off: fix https://github.com/UglyToad/PdfPig/issues/809

- Improve Stream Token read performance by:
  -  simplifying TryReadStream(), avoiding use of MemoryStream, with benefice of already existing Memory Span of "inputBytes"
  - removing the unecessary List<>

* Add Stream with Invalid Length unit test

* Use of Memory<> instead of direct Span to avoid byte array allocation .ToArray.
Suggestion from (4153e4a1b4 (r1619509165))
This commit is contained in:
Sylvain Bruyere
2024-05-31 08:16:56 +02:00
committed by GitHub
parent d7e434edaa
commit 65a18b200f
2 changed files with 136 additions and 118 deletions
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38
src/UglyToad.PdfPig.Tests/Tokenization/Scanner/PdfTokenScannerTests.cs
View File

@@ -256,6 +256,44 @@ A¡¬àð‰É©ˆ°‘¼›‚%¥×s³®í»š}%§X{{tøNåÝž¶ö¢ÖÞ¾
Assert.Equal(2, locationProvider.Offsets[new IndirectReference(352, 0)]);
}
[Fact]
public void ReadsStreamObjectWithInvalidLength()
{
string invalidLengthStream = "ABCD" + new string('e', 3996);
string s = $@"
352 0 obj
<< /S 1273 /Filter /FlateDecode /Length 353 0 R >>
stream
{invalidLengthStream}
endstream
endobj
353 0 obj
1479
endobj";
var locationProvider = new TestObjectLocationProvider();
// Mark location of "353 0 obj"
locationProvider.Offsets[new IndirectReference(353, 0)] = 1643;
var scanner = GetScanner(s, locationProvider);
var tokens = ReadToEnd(scanner);
Assert.Equal(2, tokens.Count);
var stream = Assert.IsType<StreamToken>(tokens[0].Data);
var data = stream.Data.ToArray();
var str = Encoding.UTF8.GetString(data);
Assert.Equal(data.Length, invalidLengthStream.Length);
Assert.StartsWith("ABCDeeeee", str);
Assert.Equal(2, locationProvider.Offsets[new IndirectReference(352, 0)]);
}
[Fact]
public void ReadsSimpleStreamObject()
{

216
src/UglyToad.PdfPig/Tokenization/Scanner/PdfTokenScanner.cs
View File

@@ -7,6 +7,7 @@
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using Core;
using Encryption;
@@ -320,7 +321,7 @@
int endStreamPosition = 0;
int commonPartPosition = 0;
const string commonPart = "end";
const string endWordPart = "end";
const string streamPart = "stream";
const string objPart = "obj";
@@ -330,151 +331,130 @@
return true;
}
// Track any 'endobj' or 'endstream' operators we see.
var observedEndLocations = new List<PossibleStreamEndLocation>();
long streamDataStart = inputBytes.CurrentOffset;
// Begin reading the stream.
using (var memoryStream = new MemoryStream())
using (var binaryWrite = new BinaryWriter(memoryStream))
PossibleStreamEndLocation? possibleEndLocation = null;
while (inputBytes.MoveNext())
{
while (inputBytes.MoveNext())
if (length.HasValue && read == length)
{
if (length.HasValue && read == length)
{
// TODO: read ahead and check we're at the end...
// break;
}
// TODO: read ahead and check we're at the end...
// break;
}
// We are reading 'end' (possibly).
if (commonPartPosition < commonPart.Length && inputBytes.CurrentByte == commonPart[commonPartPosition])
// We are reading 'end' (possibly).
if (commonPartPosition < endWordPart.Length && inputBytes.CurrentByte == endWordPart[commonPartPosition])
{
commonPartPosition++;
}
else if (commonPartPosition == endWordPart.Length)
{
// We are reading 'stream' after 'end'
if (inputBytes.CurrentByte == streamPart[endStreamPosition])
{
commonPartPosition++;
}
else if (commonPartPosition == commonPart.Length)
{
// We are reading 'stream' after 'end'
if (inputBytes.CurrentByte == streamPart[endStreamPosition])
endObjPosition = 0;
endStreamPosition++;
// We've finished reading 'endstream', add it to the end tokens we've seen.
if (endStreamPosition == streamPart.Length && (!inputBytes.MoveNext() || ReadHelper.IsWhitespace(inputBytes.CurrentByte)))
{
endObjPosition = 0;
endStreamPosition++;
var token = new PossibleStreamEndLocation(inputBytes.CurrentOffset - OperatorToken.EndStream.Data.Length, OperatorToken.EndStream);
// We've finished reading 'endstream', add it to the end tokens we've seen.
if (endStreamPosition == streamPart.Length && (!inputBytes.MoveNext() || ReadHelper.IsWhitespace(inputBytes.CurrentByte)))
possibleEndLocation = token;
if (length.HasValue && read > length)
{
var token = new PossibleStreamEndLocation(inputBytes.CurrentOffset - OperatorToken.EndStream.Data.Length, OperatorToken.EndStream);
observedEndLocations.Add(token);
if (length.HasValue && read > length)
{
break;
}
endStreamPosition = 0;
break;
}
}
else if (inputBytes.CurrentByte == objPart[endObjPosition])
{
// We are reading 'obj' after 'end'
endStreamPosition = 0;
endObjPosition++;
// We have finished reading 'endobj'.
if (endObjPosition == objPart.Length)
{
// If we saw an 'endstream' or 'endobj' previously we've definitely hit the end now.
if (observedEndLocations.Count > 0)
{
var lastEndToken = observedEndLocations[observedEndLocations.Count - 1];
inputBytes.Seek(lastEndToken.Offset + lastEndToken.Type.Data.Length + 1);
break;
}
var token = new PossibleStreamEndLocation(inputBytes.CurrentOffset - OperatorToken.EndObject.Data.Length, OperatorToken.EndObject);
observedEndLocations.Add(token);
if (read > length)
{
break;
}
}
}
else
{
// We were reading 'end' but then we had a character mismatch.
// Reset all the counters.
}
else if (inputBytes.CurrentByte == objPart[endObjPosition])
{
// We are reading 'obj' after 'end'
endStreamPosition = 0;
endObjPosition = 0;
commonPartPosition = 0;
endStreamPosition = 0;
endObjPosition++;
// We have finished reading 'endobj'.
if (endObjPosition == objPart.Length)
{
// If we saw an 'endstream' or 'endobj' previously we've definitely hit the end now.
if (possibleEndLocation != null)
{
var lastEndToken = possibleEndLocation.Value;
inputBytes.Seek(lastEndToken.Offset + lastEndToken.Type.Data.Length + 1);
break;
}
var token = new PossibleStreamEndLocation(inputBytes.CurrentOffset - OperatorToken.EndObject.Data.Length, OperatorToken.EndObject);
possibleEndLocation = token;
if (read > length)
{
break;
}
}
}
else
{
// For safety reset every counter in case we had a partial read.
// We were reading 'end' but then we had a character mismatch.
// Reset all the counters.
endStreamPosition = 0;
endObjPosition = 0;
commonPartPosition = (inputBytes.CurrentByte == commonPart[0]) ? 1 : 0;
commonPartPosition = 0;
}
binaryWrite.Write(inputBytes.CurrentByte);
read++;
}
binaryWrite.Flush();
if (observedEndLocations.Count == 0)
{
return false;
}
memoryStream.Seek(0, SeekOrigin.Begin);
if (length.HasValue && memoryStream.Length >= length)
{
// Use the declared length to copy just the data we want.
byte[] data = new byte[length.Value];
memoryStream.Read(data, 0, (int)length.Value);
stream = new StreamToken(streamDictionaryToken, data);
}
else
{
// Work out where '\r\nendobj' or '\r\nendstream' occurs and read everything up to that.
var lastEnd = observedEndLocations[observedEndLocations.Count - 1];
// For safety reset every counter in case we had a partial read.
var dataLength = lastEnd.Offset - startDataOffset;
var current = inputBytes.CurrentOffset;
// 3 characters, 'e', '\n' and possibly '\r'
inputBytes.Seek(lastEnd.Offset - 3);
inputBytes.MoveNext();
if (inputBytes.CurrentByte == '\r')
{
dataLength -= 3;
}
else
{
dataLength -= 2;
}
inputBytes.Seek(current);
byte[] data = new byte[dataLength];
memoryStream.Read(data, 0, (int)dataLength);
stream = new StreamToken(streamDictionaryToken, data);
endStreamPosition = 0;
endObjPosition = 0;
commonPartPosition = (inputBytes.CurrentByte == endWordPart[0]) ? 1 : 0;
}
read++;
}
long streamDataEnd = inputBytes.CurrentOffset + 1;
if (possibleEndLocation == null)
return false;
var lastEnd = possibleEndLocation;
var dataLength = lastEnd.Value.Offset - startDataOffset;
// 3 characters, 'e', '\n' and possibly '\r'
inputBytes.Seek(lastEnd.Value.Offset - 3);
inputBytes.MoveNext();
if (inputBytes.CurrentByte == '\r')
{
dataLength -= 3;
}
else
{
dataLength -= 2;
}
Memory<byte> data = new byte[dataLength];
inputBytes.Seek(streamDataStart);
inputBytes.Read(data.Span);
inputBytes.Seek(streamDataEnd);
stream = new StreamToken(streamDictionaryToken, data);
return true;
}