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perf(plc4j/spi/buffers): speed up byte-aligned integer read/write #2650

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Merged
sruehl merged 4 commits into from
Jul 21, 2026
Merged

perf(plc4j/spi/buffers): speed up byte-aligned integer read/write #2650

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f0c07e7
perf(plc4j/spi/buffers): speed up byte-aligned integer read/write
LivingLikeKrillin Jul 15, 2026
0c1face
fix(plc4j/spi/buffers): correct byte alignment for non-byte-aligned s…
LivingLikeKrillin Jul 20, 2026
7c3b965
perf(plc4j/spi/buffers): resolve encoding/byte order once per integer…
LivingLikeKrillin Jul 21, 2026
6a8d06a
fix(plc4j/spi/buffers): honour startBit in writeBit; gate the fast pa…
LivingLikeKrillin Jul 21, 2026
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11 changes: 8 additions & 3 deletions ...j/spi/buffers/api/src/main/java/org/apache/plc4x/java/spi/buffers/api/AbstractBuffer.java
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Expand Up @@ -20,16 +20,21 @@

import org.apache.plc4x.java.spi.buffers.api.exceptions.BufferException;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashMap;
import java.util.Map;
import java.util.Stack;

public abstract class AbstractBuffer implements Buffer {

protected final Stack<WithOption[]> context;
// Used as a stack (push/pop/peek). ArrayDeque instead of java.util.Stack: a buffer is a
// single-threaded, per-message scratch object (positionInBits and the backing array are
// themselves unsynchronized), so Stack's synchronization (it extends the synchronized Vector)
// guards nothing here while adding a monitor enter/exit to getContext() on every field.
protected final Deque<WithOption[]> context;

public AbstractBuffer(WithOption... options) {
context = new Stack<>();
context = new ArrayDeque<>();
context.push(options);
}

Expand Down
36 changes: 34 additions & 2 deletions ...te/src/main/java/org/apache/plc4x/java/spi/buffers/bytebased/AbstractBufferByteBased.java
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Expand Up @@ -65,7 +65,31 @@ protected ByteOrder getByteOrder(WithOption... options) {
return byteOrder.get();
}
}
return new ByteOrderBigEndian();
return ByteOrderBigEndian.INSTANCE;
}

// ---- Byte-aligned integer fast-path helpers (shared by Read/Write byte buffers) ----

/**
* Structural fast-path eligibility for the byte-aligned integer fast path: no per-field
* options, the cursor on an absolute byte boundary (see {@link #isAligned()}), and a
* whole number of bytes requested. The caller combines this with EXACT-CLASS checks
* ({@code getClass() == ...}, not {@code instanceof}) on the ALREADY RESOLVED encoding/byte
* order (plain binary / two's-complement, big-endian) so resolution happens exactly once per
* field, and a registered subclass with overridden codec behaviour falls through to the
* virtual-dispatch slow path instead of being silently bypassed by the fast path.
*/
protected boolean isByteAlignedWholeBytes(int numBits, WithOption[] options) {
// isAligned() tests the ABSOLUTE bit index (startBit + positionInBits) — the same predicate the
// readBits/writeBits whole-byte fast paths use — so a non-byte-aligned sub-buffer correctly
// falls through to the generic path (the aligned fast paths index by (startBit+positionInBits)/8).
return options.length == 0 && isAligned() && (numBits & 7) == 0;
}

/** Big-endian two's-complement sign extension of the low {@code numBits} of {@code raw}. */
protected static long signExtend(long raw, int numBits) {
int shift = 64 - numBits;
return (raw << shift) >> shift;
}

protected Optional<Encoding> getUnsignedIntegerEncoding(WithOption... options) {
Expand Down Expand Up @@ -156,8 +180,16 @@ protected void ensureAvailable(int bitsNeeded) throws BufferException {
}
}

/**
* Whether the current cursor sits on a byte boundary of the BACKING ARRAY. This must be tested on
* the absolute bit index ({@code startBit + positionInBits}), not on {@code positionInBits} alone:
* a sub-buffer created at a non-byte-aligned offset (see {@code createSubBuffer}) has a non-zero
* {@code startBit} while its own {@code positionInBits} is 0. The whole-byte {@code arraycopy}
* fast paths in {@code readBits}/{@code writeBits} index the backing array by
* {@code (startBit + positionInBits) / 8}, so only absolute alignment makes that copy correct.
*/
protected boolean isAligned() {
return (positionInBits % 8) == 0;
return ((startBit + positionInBits) % 8) == 0;
}

}
77 changes: 71 additions & 6 deletions ...s/byte/src/main/java/org/apache/plc4x/java/spi/buffers/bytebased/ReadBufferByteBased.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,11 +21,15 @@
import org.apache.plc4x.java.spi.buffers.api.ReadBuffer;
import org.apache.plc4x.java.spi.buffers.api.WithOption;
import org.apache.plc4x.java.spi.buffers.api.exceptions.BufferException;
import org.apache.plc4x.java.spi.buffers.bytebased.byteorder.ByteOrder;
import org.apache.plc4x.java.spi.buffers.bytebased.byteorder.ByteOrderBigEndian;
import org.apache.plc4x.java.spi.buffers.bytebased.byteorder.ByteOrderManager;
import org.apache.plc4x.java.spi.buffers.bytebased.encoding.Encoding;
import org.apache.plc4x.java.spi.buffers.bytebased.encoding.EncodingDefault;
import org.apache.plc4x.java.spi.buffers.bytebased.encoding.EncodingManager;
import org.apache.plc4x.java.spi.buffers.bytebased.encoding.EncodingRaw;
import org.apache.plc4x.java.spi.buffers.bytebased.encoding.EncodingTwosComplement;
import org.apache.plc4x.java.spi.buffers.bytebased.encoding.EncodingUnsignedBinary;

import java.math.BigDecimal;
import java.math.BigInteger;
Expand Down Expand Up @@ -91,6 +95,23 @@ public byte[] readBits(int numBits, WithOption... options) throws BufferExceptio
}
}

/**
* Reads {@code numBits} (a whole number of bytes) big-endian from the current byte-aligned
* position into a long and advances the position. Callers gate this behind the fast-path
* eligibility checks; no intermediate byte[] or per-field ByteOrder object is allocated.
*/
private long readAlignedBytesBE(int numBits) throws BufferException {
ensureAvailable(numBits);
int byteIndex = (startBit + positionInBits) / 8;
int numBytes = numBits / 8;
long v = 0;
for (int i = 0; i < numBytes; i++) {
v = (v << 8) | (buffer[byteIndex + i] & 0xFF);
}
positionInBits += numBits;
return v;
}

@Override
public byte readUnsignedByte(int numBits, WithOption... options) throws BufferException {
if (numBits < 1 || numBits > 7) {
Expand Down Expand Up @@ -118,10 +139,17 @@ public short readUnsignedShort(int numBits, WithOption... options) throws Buffer

Optional<Encoding> encodingOptional = getUnsignedIntegerEncoding(options);
Encoding encoding = encodingOptional.orElseThrow(() -> new BufferException("No encoding defined for unsigned integer values"));
ByteOrder byteOrder = getByteOrder(options);
if (isByteAlignedWholeBytes(numBits, options)
&& encoding.getClass() == EncodingUnsignedBinary.class
&& byteOrder.getClass() == ByteOrderBigEndian.class) {
return (short) readAlignedBytesBE(numBits);
}

if(encoding instanceof EncodingDefault encodingDefault) {
ensureAvailable(numBits);
byte[] bytes = readBits(numBits);
bytes = getByteOrder(options).process(bytes);
bytes = byteOrder.process(bytes);
return encodingDefault.decodeShort(numBits, bytes);
} else if(encoding instanceof EncodingRaw encodingRaw) {
return encodingRaw.decodeShort(numBits, this);
Expand All @@ -137,10 +165,19 @@ public int readUnsignedInt(int numBits, WithOption... options) throws BufferExce

Optional<Encoding> encodingOptional = getUnsignedIntegerEncoding(options);
Encoding encoding = encodingOptional.orElseThrow(() -> new BufferException("No encoding defined for unsigned integer values"));
ByteOrder byteOrder = getByteOrder(options);
// Fast path: byte-aligned whole-byte plain-binary big-endian read straight from the backing
// array; encoding/byte order are resolved once above and reused by the slow path below.
if (isByteAlignedWholeBytes(numBits, options)
&& encoding.getClass() == EncodingUnsignedBinary.class
&& byteOrder.getClass() == ByteOrderBigEndian.class) {
return (int) readAlignedBytesBE(numBits);
}

if(encoding instanceof EncodingDefault encodingDefault) {
ensureAvailable(numBits);
byte[] bytes = readBits(numBits);
bytes = getByteOrder(options).process(bytes);
bytes = byteOrder.process(bytes);
return encodingDefault.decodeInt(numBits, bytes);
} else if(encoding instanceof EncodingRaw encodingRaw) {
return encodingRaw.decodeInt(numBits, this);
Expand All @@ -156,10 +193,17 @@ public long readUnsignedLong(int numBits, WithOption... options) throws BufferEx

Optional<Encoding> encodingOptional = getUnsignedIntegerEncoding(options);
Encoding encoding = encodingOptional.orElseThrow(() -> new BufferException("No encoding defined for unsigned integer values"));
ByteOrder byteOrder = getByteOrder(options);
if (isByteAlignedWholeBytes(numBits, options)
&& encoding.getClass() == EncodingUnsignedBinary.class
&& byteOrder.getClass() == ByteOrderBigEndian.class) {
return readAlignedBytesBE(numBits);
}

if(encoding instanceof EncodingDefault encodingDefault) {
ensureAvailable(numBits);
byte[] bytes = readBits(numBits);
bytes = getByteOrder(options).process(bytes);
bytes = byteOrder.process(bytes);
return encodingDefault.decodeLong(numBits, bytes);
} else if(encoding instanceof EncodingRaw encodingRaw) {
return encodingRaw.decodeLong(numBits, this);
Expand Down Expand Up @@ -213,10 +257,17 @@ public short readSignedShort(int numBits, WithOption... options) throws BufferEx

Optional<Encoding> encodingOptional = getSignedIntegerEncoding(options);
Encoding encoding = encodingOptional.orElseThrow(() -> new BufferException("No encoding defined for signed integer values"));
ByteOrder byteOrder = getByteOrder(options);
if (isByteAlignedWholeBytes(numBits, options)
&& encoding.getClass() == EncodingTwosComplement.class
&& byteOrder.getClass() == ByteOrderBigEndian.class) {
return (short) signExtend(readAlignedBytesBE(numBits), numBits);
}

if(encoding instanceof EncodingDefault encodingDefault) {
ensureAvailable(numBits);
byte[] bytes = readBits(numBits);
bytes = getByteOrder(options).process(bytes);
bytes = byteOrder.process(bytes);
return encodingDefault.decodeShort(numBits, bytes);
} else if(encoding instanceof EncodingRaw encodingRaw) {
return encodingRaw.decodeShort(numBits, this);
Expand All @@ -232,10 +283,17 @@ public int readSignedInt(int numBits, WithOption... options) throws BufferExcept

Optional<Encoding> encodingOptional = getSignedIntegerEncoding(options);
Encoding encoding = encodingOptional.orElseThrow(() -> new BufferException("No encoding defined for signed integer values"));
ByteOrder byteOrder = getByteOrder(options);
if (isByteAlignedWholeBytes(numBits, options)
&& encoding.getClass() == EncodingTwosComplement.class
&& byteOrder.getClass() == ByteOrderBigEndian.class) {
return (int) signExtend(readAlignedBytesBE(numBits), numBits);
}

if(encoding instanceof EncodingDefault encodingDefault) {
ensureAvailable(numBits);
byte[] bytes = readBits(numBits);
bytes = getByteOrder(options).process(bytes);
bytes = byteOrder.process(bytes);
return encodingDefault.decodeInt(numBits, bytes);
} else if(encoding instanceof EncodingRaw encodingRaw) {
return encodingRaw.decodeInt(numBits, this);
Expand All @@ -251,10 +309,17 @@ public long readSignedLong(int numBits, WithOption... options) throws BufferExce

Optional<Encoding> encodingOptional = getSignedIntegerEncoding(options);
Encoding encoding = encodingOptional.orElseThrow(() -> new BufferException("No encoding defined for signed integer values"));
ByteOrder byteOrder = getByteOrder(options);
if (isByteAlignedWholeBytes(numBits, options)
&& encoding.getClass() == EncodingTwosComplement.class
&& byteOrder.getClass() == ByteOrderBigEndian.class) {
return signExtend(readAlignedBytesBE(numBits), numBits);
}

if(encoding instanceof EncodingDefault encodingDefault) {
ensureAvailable(numBits);
byte[] bytes = readBits(numBits);
bytes = getByteOrder(options).process(bytes);
bytes = byteOrder.process(bytes);
return encodingDefault.decodeLong(numBits, bytes);
} else if(encoding instanceof EncodingRaw encodingRaw) {
return encodingRaw.decodeLong(numBits, this);
Expand Down
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