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Better sanitation for scan decoder.

af/merge-core
James Jackson-South 8 years ago
parent
b85375b254
commit
fd55ea8f8d
2 changed files with 162 additions and 116 deletions
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  1. 276
      src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsScanDecoder.cs
  2. 2
      src/ImageSharp/Formats/Jpeg/PdfJsPort/PdfJsJpegDecoderCore.cs

276
src/ImageSharp/Formats/Jpeg/PdfJsPort/Components/PdfJsScanDecoder.cs
View File

@ -5,7 +5,6 @@ using System;
#if DEBUG
using System.Diagnostics;
#endif
using System.IO;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using SixLabors.ImageSharp.Formats.Jpeg.Common;
@ -95,7 +94,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
mcuExpected = mcusPerLine * frame.McusPerColumn;
}
PdfJsFileMarker fileMarker;
while (mcu < mcuExpected)
{
// Reset interval stuff
@ -120,21 +118,15 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
this.DecodeScanProgressive(huffmanTables, isAc, isFirst, components, componentsLength, mcusPerLine, mcuToRead, ref mcu, stream);
}
// Find marker
// Reset
this.bitsCount = 0;
this.bitsData = 0;
fileMarker = PdfJsJpegDecoderCore.FindNextFileMarker(this.markerBuffer, stream);
this.unexpectedMarkerReached = false;
// Some bad images seem to pad Scan blocks with e.g. zero bytes, skip past
// those to attempt to find a valid marker (fixes issue4090.pdf) in original code.
if (fileMarker.Invalid)
{
#if DEBUG
Debug.WriteLine($"DecodeScan - Unexpected MCU data at {stream.Position}, next marker is: {fileMarker.Marker:X}");
#endif
}
ushort marker = fileMarker.Marker;
// Some images include more scan blocks than expected, skip past those and
// attempt to find the next valid marker
PdfJsFileMarker fileMarker = PdfJsJpegDecoderCore.FindNextFileMarker(this.markerBuffer, stream);
byte marker = fileMarker.Marker;
// RSTn - We've already read the bytes and altered the position so no need to skip
if (marker >= PdfJsJpegConstants.Markers.RST0 && marker <= PdfJsJpegConstants.Markers.RST7)
@ -149,24 +141,11 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
stream.Position = fileMarker.Position;
break;
}
}
fileMarker = PdfJsJpegDecoderCore.FindNextFileMarker(this.markerBuffer, stream);
// Some images include more Scan blocks than expected, skip past those and
// attempt to find the next valid marker (fixes issue8182.pdf) ref original code.
if (fileMarker.Invalid)
{
#if DEBUG
Debug.WriteLine($"DecodeScan - Unexpected MCU data at {stream.Position}, next marker is: {fileMarker.Marker:X}");
#endif
}
else
{
// We've found a valid marker.
// Rewind the stream to the position of the marker
stream.Position = fileMarker.Position;
}
}
private void DecodeScanBaseline(
@ -295,9 +274,10 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
for (int k = 0; k < h; k++)
{
// No need to continue here.
if (this.endOfStreamReached || this.unexpectedMarkerReached)
{
continue;
break;
}
if (isAC)
@ -432,19 +412,24 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private int ReadBit(DoubleBufferedStreamReader stream)
private bool TryReadBit(DoubleBufferedStreamReader stream, out int bits)
{
if (this.bitsCount == 0)
{
this.FillBits(stream);
if (!this.TryFillBits(stream))
{
bits = 0;
return false;
}
}
this.bitsCount--;
return (this.bitsData >> this.bitsCount) & 1;
bits = (this.bitsData >> this.bitsCount) & 1;
return true;
}
[MethodImpl(MethodImplOptions.NoInlining)]
private void FillBits(DoubleBufferedStreamReader stream)
private bool TryFillBits(DoubleBufferedStreamReader stream)
{
// TODO: Read more then 1 byte at a time.
// In LibJpegTurbo this is be 25 bits (32-7) but I cannot get this to work
@ -452,46 +437,61 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
// to detect it.
const int MinGetBits = 7;
// Attempt to load to the minimum bit count.
while (this.bitsCount < MinGetBits)
if (!this.unexpectedMarkerReached)
{
int c = stream.ReadByte();
if (c == -0x1)
// Attempt to load to the minimum bit count.
while (this.bitsCount < MinGetBits)
{
// We've encountered the end of the file stream which means there's no EOI marker in the image.
this.endOfStreamReached = true;
int c = stream.ReadByte();
// Fill buffer with zero bits.
this.bitsData <<= MinGetBits - this.bitsCount;
this.bitsCount = MinGetBits;
break;
}
if (c == PdfJsJpegConstants.Markers.Prefix)
{
int nextByte = stream.ReadByte();
if (nextByte != 0)
switch (c)
{
case -0x1:
// We've encountered the end of the file stream which means there's no EOI marker in the image.
this.endOfStreamReached = true;
return false;
case PdfJsJpegConstants.Markers.Prefix:
int nextByte = stream.ReadByte();
if (nextByte == -0x1)
{
this.endOfStreamReached = true;
return false;
}
if (nextByte != 0)
{
#if DEBUG
Debug.WriteLine($"DecodeScan - Unexpected marker {(c << 8) | nextByte:X} at {stream.Position}");
Debug.WriteLine($"DecodeScan - Unexpected marker {(c << 8) | nextByte:X} at {stream.Position}");
#endif
// We've encountered an unexpected marker. Reverse the stream and exit.
this.unexpectedMarkerReached = true;
stream.Position -= 2;
// We've encountered an unexpected marker. Reverse the stream and exit.
this.unexpectedMarkerReached = true;
stream.Position -= 2;
// Fill buffer with zero bits.
this.bitsData <<= MinGetBits - this.bitsCount;
this.bitsCount = MinGetBits;
break;
// TODO: double check we need this.
// Fill buffer with zero bits.
if (this.bitsCount == 0)
{
this.bitsData <<= MinGetBits;
this.bitsCount = MinGetBits;
}
return true;
}
break;
}
}
// OK, load c into get_buffer
this.bitsData = (this.bitsData << 8) | c;
this.bitsCount += 8;
// OK, load the next byte into bitsData
this.bitsData = (this.bitsData << 8) | c;
this.bitsCount += 8;
}
}
return true;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
@ -507,14 +507,16 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private short DecodeHuffman(ref PdfJsHuffmanTable tree, DoubleBufferedStreamReader stream)
private bool TryDecodeHuffman(ref PdfJsHuffmanTable tree, DoubleBufferedStreamReader stream, out short value)
{
value = -1;
// TODO: Implement fast Huffman decoding.
// In LibJpegTurbo a minimum of 25 bits (32-7) is collected from the stream
// Then a LUT is used to avoid the loop when decoding the Huffman value.
// using 3 methods: FillBits, PeekBits, and DropBits.
// The LUT has been ported from LibJpegTurbo as has this code but it doesn't work.
// this.FillBits(stream);
// this.TryFillBits(stream);
//
// const int LookAhead = 8;
// int look = this.PeekBits(LookAhead);
@ -524,86 +526,104 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
// if (bits <= LookAhead)
// {
// this.DropBits(bits);
// return (short)(look & ((1 << LookAhead) - 1));
// value = (short)(look & ((1 << LookAhead) - 1));
// return true;
// }
short code = (short)this.ReadBit(stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryReadBit(stream, out int bit))
{
return -1;
return false;
}
short code = (short)bit;
// "DECODE", section F.2.2.3, figure F.16, page 109 of T.81
int i = 1;
while (code > tree.MaxCode[i])
{
code <<= 1;
code |= (short)this.ReadBit(stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryReadBit(stream, out bit))
{
return -1;
return false;
}
code <<= 1;
code |= (short)bit;
i++;
}
int j = tree.ValOffset[i];
return tree.HuffVal[(j + code) & 0xFF];
value = tree.HuffVal[(j + code) & 0xFF];
return true;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private int Receive(int length, DoubleBufferedStreamReader stream)
private bool TryReceive(int length, DoubleBufferedStreamReader stream, out int value)
{
int n = 0;
value = 0;
while (length > 0)
{
int bit = this.ReadBit(stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryReadBit(stream, out int bit))
{
return -1;
return false;
}
n = (n << 1) | bit;
value = (value << 1) | bit;
length--;
}
return n;
return true;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private int ReceiveAndExtend(int length, DoubleBufferedStreamReader stream)
private bool TryReceiveAndExtend(int length, DoubleBufferedStreamReader stream, out int value)
{
if (length == 1)
{
return this.ReadBit(stream) == 1 ? 1 : -1;
}
if (!this.TryReadBit(stream, out value))
{
return false;
}
int n = this.Receive(length, stream);
if (n >= 1 << (length - 1))
value = value == 1 ? 1 : -1;
}
else
{
return n;
if (!this.TryReceive(length, stream, out value))
{
return false;
}
if (value < 1 << (length - 1))
{
value += (-1 << length) + 1;
}
}
return n + (-1 << length) + 1;
return true;
}
private void DecodeBaseline(PdfJsFrameComponent component, ref short blockDataRef, int offset, ref PdfJsHuffmanTable dcHuffmanTable, ref PdfJsHuffmanTable acHuffmanTable, DoubleBufferedStreamReader stream)
{
short t = this.DecodeHuffman(ref dcHuffmanTable, stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryDecodeHuffman(ref dcHuffmanTable, stream, out short t))
{
return;
}
int diff = t == 0 ? 0 : this.ReceiveAndExtend(t, stream);
int diff = 0;
if (t != 0)
{
if (!this.TryReceiveAndExtend(t, stream, out diff))
{
return;
}
}
Unsafe.Add(ref blockDataRef, offset) = (short)(component.Pred += diff);
int k = 1;
while (k < 64)
{
short rs = this.DecodeHuffman(ref acHuffmanTable, stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryDecodeHuffman(ref acHuffmanTable, stream, out short rs))
{
return;
}
@ -625,8 +645,13 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
k += r;
byte z = this.dctZigZag[k];
short re = (short)this.ReceiveAndExtend(s, stream);
Unsafe.Add(ref blockDataRef, offset + z) = re;
if (!this.TryReceiveAndExtend(s, stream, out int re))
{
return;
}
Unsafe.Add(ref blockDataRef, offset + z) = (short)re;
k++;
}
}
@ -634,21 +659,27 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private void DecodeDCFirst(PdfJsFrameComponent component, ref short blockDataRef, int offset, ref PdfJsHuffmanTable dcHuffmanTable, DoubleBufferedStreamReader stream)
{
short t = this.DecodeHuffman(ref dcHuffmanTable, stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryDecodeHuffman(ref dcHuffmanTable, stream, out short t))
{
return;
}
int diff = t == 0 ? 0 : this.ReceiveAndExtend(t, stream) << this.successiveState;
Unsafe.Add(ref blockDataRef, offset) = (short)(component.Pred += diff);
int diff = 0;
if (t != 0)
{
if (!this.TryReceiveAndExtend(t, stream, out diff))
{
return;
}
}
Unsafe.Add(ref blockDataRef, offset) = (short)(component.Pred += diff << this.successiveState);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private void DecodeDCSuccessive(PdfJsFrameComponent component, ref short blockDataRef, int offset, DoubleBufferedStreamReader stream)
{
int bit = this.ReadBit(stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryReadBit(stream, out int bit))
{
return;
}
@ -668,8 +699,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
int e = this.specEnd;
while (k <= e)
{
short rs = this.DecodeHuffman(ref acHuffmanTable, stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryDecodeHuffman(ref acHuffmanTable, stream, out short rs))
{
return;
}
@ -681,7 +711,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (r < 15)
{
this.eobrun = this.Receive(r, stream) + (1 << r) - 1;
if (!this.TryReceive(r, stream, out int eob))
{
return;
}
this.eobrun = eob + (1 << r) - 1;
break;
}
@ -692,7 +727,13 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
k += r;
byte z = this.dctZigZag[k];
Unsafe.Add(ref blockDataRef, offset + z) = (short)(this.ReceiveAndExtend(s, stream) * (1 << this.successiveState));
if (!this.TryReceiveAndExtend(s, stream, out int v))
{
return;
}
Unsafe.Add(ref blockDataRef, offset + z) = (short)(v * (1 << this.successiveState));
k++;
}
}
@ -712,8 +753,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
switch (this.successiveACState)
{
case 0: // Initial state
short rs = this.DecodeHuffman(ref acHuffmanTable, stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryDecodeHuffman(ref acHuffmanTable, stream, out short rs))
{
return;
}
@ -724,7 +765,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
{
if (r < 15)
{
this.eobrun = this.Receive(r, stream) + (1 << r);
if (!this.TryReceive(r, stream, out int eob))
{
return;
}
this.eobrun = eob + (1 << r);
this.successiveACState = 4;
}
else
@ -740,7 +786,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
throw new ImageFormatException("Invalid ACn encoding");
}
this.successiveACNextValue = this.ReceiveAndExtend(s, stream);
if (!this.TryReceiveAndExtend(s, stream, out int v))
{
return;
}
this.successiveACNextValue = v;
this.successiveACState = r > 0 ? 2 : 3;
}
@ -749,8 +800,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
case 2:
if (blockOffsetZRef != 0)
{
int bit = this.ReadBit(stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryReadBit(stream, out int bit))
{
return;
}
@ -770,8 +820,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
case 3: // Set value for a zero item
if (blockOffsetZRef != 0)
{
int bit = this.ReadBit(stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryReadBit(stream, out int bit))
{
return;
}
@ -788,8 +837,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort.Components
case 4: // Eob
if (blockOffsetZRef != 0)
{
int bit = this.ReadBit(stream);
if (this.endOfStreamReached || this.unexpectedMarkerReached)
if (!this.TryReadBit(stream, out int bit))
{
return;
}

2
src/ImageSharp/Formats/Jpeg/PdfJsPort/PdfJsJpegDecoderCore.cs
View File

@ -169,8 +169,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.PdfJsPort
m = suffix;
}
marker[1] = (byte)m;
return new PdfJsFileMarker((byte)m, stream.Position - 2);
}

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