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Merged
JimBobSquarePants merged 12 commits into from
Jan 9, 2022
Merged

Jpeg HuffmanTable improvements #1926

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6cf7ab9
Removed Configure() method
Jan 6, 2022
2334bcf
Testing commit, lot of out of bounds guards
Jan 6, 2022
1694a5b
Added sanity check for generated huffman codes
Jan 7, 2022
8b01f13
Removed debug checks
Jan 7, 2022
3354ae6
Reduced stackallock pressure by changing char to byte
Jan 7, 2022
499ddf8
More readable and maybe even faster code
Jan 8, 2022
51127b6
Removed 257 bytes of stack memory pressure
Jan 8, 2022
e7ee0fd
[WIP] outer scope memory propagation
Jan 8, 2022
46226bf
Reduced memory pressure, removed unnecessary buffer
Jan 8, 2022
5e1eb1a
Removed stack pressure, pooling single buffer for entire huffman tabl…
Jan 9, 2022
7bb1a50
Docs, faster span slice method
Jan 9, 2022
544c557
Merge branch 'master' into dp/huff-table-improvements
JimBobSquarePants Jan 9, 2022
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30 changes: 3 additions & 27 deletions src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanScanDecoder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -167,18 +167,6 @@ private void ParseBaselineDataInterleaved()
int mcusPerLine = this.frame.McusPerLine;
ref HuffmanScanBuffer buffer = ref this.scanBuffer;

// Pre-derive the huffman table to avoid in-loop checks.
for (int i = 0; i < this.componentsCount; i++)
{
int order = this.frame.ComponentOrder[i];
JpegComponent component = this.components[order];

ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.ACHuffmanTableId];
dcHuffmanTable.Configure();
acHuffmanTable.Configure();
}

for (int j = 0; j < mcusPerColumn; j++)
{
this.cancellationToken.ThrowIfCancellationRequested();
Expand Down Expand Up @@ -248,8 +236,6 @@ private void ParseBaselineDataNonInterleaved()

ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.ACHuffmanTableId];
dcHuffmanTable.Configure();
acHuffmanTable.Configure();

for (int j = 0; j < h; j++)
{
Expand Down Expand Up @@ -347,15 +333,6 @@ private void ParseProgressiveDataInterleaved()
int mcusPerLine = this.frame.McusPerLine;
ref HuffmanScanBuffer buffer = ref this.scanBuffer;

// Pre-derive the huffman table to avoid in-loop checks.
for (int k = 0; k < this.componentsCount; k++)
{
int order = this.frame.ComponentOrder[k];
JpegComponent component = this.components[order];
ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
dcHuffmanTable.Configure();
}

for (int j = 0; j < mcusPerColumn; j++)
{
for (int i = 0; i < mcusPerLine; i++)
Expand Down Expand Up @@ -416,7 +393,6 @@ private void ParseProgressiveDataNonInterleaved()
if (this.SpectralStart == 0)
{
ref HuffmanTable dcHuffmanTable = ref this.dcHuffmanTables[component.DCHuffmanTableId];
dcHuffmanTable.Configure();

for (int j = 0; j < h; j++)
{
Expand Down Expand Up @@ -444,7 +420,6 @@ ref Unsafe.Add(ref blockRef, i),
else
{
ref HuffmanTable acHuffmanTable = ref this.acHuffmanTables[component.ACHuffmanTableId];
acHuffmanTable.Configure();

for (int j = 0; j < h; j++)
{
Expand Down Expand Up @@ -752,11 +727,12 @@ private bool HandleRestart()
/// <param name="index">Table index.</param>
/// <param name="codeLengths">Code lengths.</param>
/// <param name="values">Code values.</param>
/// <param name="workspace">The provided spare workspace memory, can be dirty.</param>
[MethodImpl(InliningOptions.ShortMethod)]
public void BuildHuffmanTable(int type, int index, ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values)
public void BuildHuffmanTable(int type, int index, ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values, Span<uint> workspace)
{
HuffmanTable[] tables = type == 0 ? this.dcHuffmanTables : this.acHuffmanTables;
tables[index] = new HuffmanTable(codeLengths, values);
tables[index] = new HuffmanTable(codeLengths, values, workspace);
}
}
}
76 changes: 28 additions & 48 deletions src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanTable.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,12 +13,10 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
[StructLayout(LayoutKind.Sequential)]
internal unsafe struct HuffmanTable
{
private bool isConfigured;

/// <summary>
/// Derived from the DHT marker. Sizes[k] = # of symbols with codes of length k bits; Sizes[0] is unused.
/// Memory workspace buffer size used in <see cref="HuffmanTable"/> ctor.
/// </summary>
public fixed byte Sizes[17];
public const int WorkspaceByteSize = 256 * sizeof(uint);

/// <summary>
/// Derived from the DHT marker. Contains the symbols, in order of incremental code length.
Expand Down Expand Up @@ -58,51 +56,35 @@ internal unsafe struct HuffmanTable
/// <summary>
/// Initializes a new instance of the <see cref="HuffmanTable"/> struct.
/// </summary>
/// <param name="codeLengths">The code lengths</param>
/// <param name="values">The huffman values</param>
public HuffmanTable(ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values)
/// <param name="codeLengths">The code lengths.</param>
/// <param name="values">The huffman values.</param>
/// <param name="workspace">The provided spare workspace memory, can be dirty.</param>
public HuffmanTable(ReadOnlySpan<byte> codeLengths, ReadOnlySpan<byte> values, Span<uint> workspace)
{
this.isConfigured = false;
Unsafe.CopyBlockUnaligned(ref this.Sizes[0], ref MemoryMarshal.GetReference(codeLengths), (uint)codeLengths.Length);
Unsafe.CopyBlockUnaligned(ref this.Values[0], ref MemoryMarshal.GetReference(values), (uint)values.Length);
}

/// <summary>
/// Expands the HuffmanTable into its readable form.
/// </summary>
public void Configure()
{
if (this.isConfigured)
{
return;
}

Span<char> huffSize = stackalloc char[257];
Span<uint> huffCode = stackalloc uint[257];

// Figure C.1: make table of Huffman code length for each symbol
// Generate codes
uint code = 0;
int si = 1;
int p = 0;
for (int j = 1; j <= 16; j++)
for (int i = 1; i <= 16; i++)
{
int i = this.Sizes[j];
while (i-- != 0)
int count = codeLengths[i];
for (int j = 0; j < count; j++)
{
huffSize[p++] = (char)j;
workspace[p++] = code;
code++;
}
}

huffSize[p] = (char)0;

// Figure C.2: generate the codes themselves
uint code = 0;
int si = huffSize[0];
p = 0;
while (huffSize[p] != 0)
{
while (huffSize[p] == si)
// 'code' is now 1 more than the last code used for codelength 'si'
// in the valid worst possible case 'code' would have the least
// significant bit set to 1, e.g. 1111(0) +1 => 1111(1)
// but it must still fit in 'si' bits since no huffman code can be equal to all 1s
// if last code is all ones, e.g. 1111(1), then incrementing it by 1 would yield
// a new code which occupies one extra bit, e.g. 1111(1) +1 => (1)1111(0)
if (code >= (1 << si))
{
huffCode[p++] = code;
code++;
JpegThrowHelper.ThrowInvalidImageContentException("Bad huffman table.");
}

code <<= 1;
Expand All @@ -113,11 +95,11 @@ public void Configure()
p = 0;
for (int j = 1; j <= 16; j++)
{
if (this.Sizes[j] != 0)
if (codeLengths[j] != 0)
{
this.ValOffset[j] = p - (int)huffCode[p];
p += this.Sizes[j];
this.MaxCode[j] = huffCode[p - 1]; // Maximum code of length l
this.ValOffset[j] = p - (int)workspace[p];
p += codeLengths[j];
this.MaxCode[j] = workspace[p - 1]; // Maximum code of length l
this.MaxCode[j] <<= JpegConstants.Huffman.RegisterSize - j; // Left justify
this.MaxCode[j] |= (1ul << (JpegConstants.Huffman.RegisterSize - j)) - 1;
}
Expand All @@ -142,11 +124,11 @@ public void Configure()
for (int length = 1; length <= JpegConstants.Huffman.LookupBits; length++)
{
int jShift = JpegConstants.Huffman.LookupBits - length;
for (int i = 1; i <= this.Sizes[length]; i++, p++)
for (int i = 1; i <= codeLengths[length]; i++, p++)
{
// length = current code's length, p = its index in huffCode[] & Values[].
// Generate left-justified code followed by all possible bit sequences
int lookBits = (int)(huffCode[p] << jShift);
int lookBits = (int)(workspace[p] << jShift);
for (int ctr = 1 << (JpegConstants.Huffman.LookupBits - length); ctr > 0; ctr--)
{
this.LookaheadSize[lookBits] = (byte)length;
Expand All @@ -155,8 +137,6 @@ public void Configure()
}
}
}

this.isConfigured = true;
}
}
}
63 changes: 30 additions & 33 deletions src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1095,12 +1095,18 @@ private void ProcessStartOfFrameMarker(BufferedReadStream stream, int remaining,
/// <param name="remaining">The remaining bytes in the segment block.</param>
private void ProcessDefineHuffmanTablesMarker(BufferedReadStream stream, int remaining)
{
int length = remaining;
const int codeLengthsByteSize = 17;
const int codeValuesMaxByteSize = 256;
const int totalBufferSize = codeLengthsByteSize + codeValuesMaxByteSize + HuffmanTable.WorkspaceByteSize;

using (IMemoryOwner<byte> huffmanData = this.Configuration.MemoryAllocator.Allocate<byte>(256, AllocationOptions.Clean))
int length = remaining;
using (IMemoryOwner<byte> buffer = this.Configuration.MemoryAllocator.Allocate<byte>(totalBufferSize))
{
Span<byte> huffmanDataSpan = huffmanData.GetSpan();
ref byte huffmanDataRef = ref MemoryMarshal.GetReference(huffmanDataSpan);
Span<byte> bufferSpan = buffer.GetSpan();
Span<byte> huffmanLegthsSpan = bufferSpan.Slice(0, codeLengthsByteSize);
Span<byte> huffmanValuesSpan = bufferSpan.Slice(codeLengthsByteSize, codeValuesMaxByteSize);
Span<uint> tableWorkspace = MemoryMarshal.Cast<byte, uint>(bufferSpan.Slice(codeLengthsByteSize + codeValuesMaxByteSize));

for (int i = 2; i < remaining;)
{
byte huffmanTableSpec = (byte)stream.ReadByte();
Expand All @@ -1110,49 +1116,40 @@ private void ProcessDefineHuffmanTablesMarker(BufferedReadStream stream, int rem
// Types 0..1 DC..AC
if (tableType > 1)
{
JpegThrowHelper.ThrowInvalidImageContentException($"Bad huffman table type: {tableType}");
JpegThrowHelper.ThrowInvalidImageContentException($"Bad huffman table type: {tableType}.");
}

// Max tables of each type
if (tableIndex > 3)
{
JpegThrowHelper.ThrowInvalidImageContentException($"Bad huffman table index: {tableIndex}");
JpegThrowHelper.ThrowInvalidImageContentException($"Bad huffman table index: {tableIndex}.");
}

stream.Read(huffmanDataSpan, 0, 16);
stream.Read(huffmanLegthsSpan, 1, 16);

using (IMemoryOwner<byte> codeLengths = this.Configuration.MemoryAllocator.Allocate<byte>(17, AllocationOptions.Clean))
int codeLengthSum = 0;
for (int j = 1; j < 17; j++)
{
Span<byte> codeLengthsSpan = codeLengths.GetSpan();
ref byte codeLengthsRef = ref MemoryMarshal.GetReference(codeLengthsSpan);
int codeLengthSum = 0;

for (int j = 1; j < 17; j++)
{
codeLengthSum += Unsafe.Add(ref codeLengthsRef, j) = Unsafe.Add(ref huffmanDataRef, j - 1);
}
codeLengthSum += huffmanLegthsSpan[j];
}

length -= 17;
length -= 17;

if (codeLengthSum > 256 || codeLengthSum > length)
{
JpegThrowHelper.ThrowInvalidImageContentException("Huffman table has excessive length.");
}
if (codeLengthSum > 256 || codeLengthSum > length)
{
JpegThrowHelper.ThrowInvalidImageContentException("Huffman table has excessive length.");
}

using (IMemoryOwner<byte> huffmanValues = this.Configuration.MemoryAllocator.Allocate<byte>(256, AllocationOptions.Clean))
{
Span<byte> huffmanValuesSpan = huffmanValues.GetSpan();
stream.Read(huffmanValuesSpan, 0, codeLengthSum);
stream.Read(huffmanValuesSpan, 0, codeLengthSum);

i += 17 + codeLengthSum;
i += 17 + codeLengthSum;

this.scanDecoder.BuildHuffmanTable(
tableType,
tableIndex,
codeLengthsSpan,
huffmanValuesSpan);
}
}
this.scanDecoder.BuildHuffmanTable(
tableType,
tableIndex,
huffmanLegthsSpan,
huffmanValuesSpan.Slice(0, codeLengthSum),
tableWorkspace);
}
}
}
Expand Down