Package org.agrona.concurrent
Interface AtomicBuffer
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- All Superinterfaces:
java.lang.Comparable<DirectBuffer>
,DirectBuffer
,MutableDirectBuffer
- All Known Implementing Classes:
UnsafeBuffer
public interface AtomicBuffer extends MutableDirectBuffer
Abstraction over a range of buffer types that allows type to be accessed with memory ordering semantics.
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Field Summary
Fields Modifier and Type Field Description static int
ALIGNMENT
Buffer alignment in bytes to ensure atomic word accesses.static boolean
STRICT_ALIGNMENT_CHECKS
Should alignment checks for atomic operations be done or not.static java.lang.String
STRICT_ALIGNMENT_CHECKS_PROP_NAME
Name of the system property that specify if the alignment checks for atomic operations are strict.-
Fields inherited from interface org.agrona.DirectBuffer
DISABLE_ARRAY_CONTENT_PRINTOUT_PROP_NAME, DISABLE_BOUNDS_CHECKS_PROP_NAME, SHOULD_BOUNDS_CHECK, STR_HEADER_LEN
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description int
addIntOrdered(int index, int increment)
Add a value to a given index with ordered store semantics.long
addLongOrdered(int index, long increment)
Add a value to a given index with ordered store semantics.boolean
compareAndSetInt(int index, int expectedValue, int updateValue)
Atomic compare and set of an int given an expected value.boolean
compareAndSetLong(int index, long expectedValue, long updateValue)
Atomic compare and set of a long given an expected value.int
getAndAddInt(int index, int delta)
Atomically add a delta to a value at a location returning the previous contents.long
getAndAddLong(int index, long delta)
Atomically add a delta to a value at a location returning the previous contents.int
getAndSetInt(int index, int value)
Atomically exchange a value at a location returning the previous contents.long
getAndSetLong(int index, long value)
Atomically exchange a value at a location returning the previous contents.byte
getByteVolatile(int index)
Get the value at a given index with volatile semantics.char
getCharVolatile(int index)
Get the value at a given index with volatile semantics.int
getIntVolatile(int index)
Get the value at a given index with volatile semantics.long
getLongVolatile(int index)
Get the value at a given index with volatile semantics.short
getShortVolatile(int index)
Get the value at a given index with volatile semantics.void
putByteVolatile(int index, byte value)
Put a value to a given index with volatile semantics.void
putCharVolatile(int index, char value)
Put a value to a given index with volatile semantics.void
putIntOrdered(int index, int value)
Put a value to a given index with ordered semantics.void
putIntVolatile(int index, int value)
Put a value to a given index with volatile semantics.void
putLongOrdered(int index, long value)
Put a value to a given index with ordered store semantics.void
putLongVolatile(int index, long value)
Put a value to a given index with volatile semantics.void
putShortVolatile(int index, short value)
Put a value to a given index with volatile semantics.void
verifyAlignment()
Verify that the underlying buffer is correctly aligned to prevent word tearing, other ordering issues and the JVM crashes.-
Methods inherited from interface org.agrona.DirectBuffer
addressOffset, boundsCheck, byteArray, byteBuffer, capacity, checkLimit, getByte, getBytes, getBytes, getBytes, getBytes, getBytes, getChar, getChar, getDouble, getDouble, getFloat, getFloat, getInt, getInt, getLong, getLong, getShort, getShort, getStringAscii, getStringAscii, getStringAscii, getStringAscii, getStringAscii, getStringAscii, getStringUtf8, getStringUtf8, getStringUtf8, getStringWithoutLengthAscii, getStringWithoutLengthAscii, getStringWithoutLengthUtf8, parseIntAscii, parseLongAscii, parseNaturalIntAscii, parseNaturalLongAscii, wrap, wrap, wrap, wrap, wrap, wrap, wrap, wrapAdjustment
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Methods inherited from interface org.agrona.MutableDirectBuffer
isExpandable, putByte, putBytes, putBytes, putBytes, putBytes, putBytes, putChar, putChar, putDouble, putDouble, putFloat, putFloat, putInt, putInt, putIntAscii, putLong, putLong, putLongAscii, putNaturalIntAscii, putNaturalIntAsciiFromEnd, putNaturalLongAscii, putNaturalPaddedIntAscii, putShort, putShort, putStringAscii, putStringAscii, putStringAscii, putStringAscii, putStringUtf8, putStringUtf8, putStringUtf8, putStringUtf8, putStringWithoutLengthAscii, putStringWithoutLengthAscii, putStringWithoutLengthAscii, putStringWithoutLengthAscii, putStringWithoutLengthUtf8, setMemory
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Field Detail
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ALIGNMENT
static final int ALIGNMENT
Buffer alignment in bytes to ensure atomic word accesses.- See Also:
- Constant Field Values
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STRICT_ALIGNMENT_CHECKS_PROP_NAME
static final java.lang.String STRICT_ALIGNMENT_CHECKS_PROP_NAME
Name of the system property that specify if the alignment checks for atomic operations are strict. If the checks are strict then theverifyAlignment()
method will throw an exception if the underlying buffer is abyte[]
.- See Also:
- Constant Field Values
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STRICT_ALIGNMENT_CHECKS
static final boolean STRICT_ALIGNMENT_CHECKS
Should alignment checks for atomic operations be done or not. The value is platform-dependent:- On x64 it is controlled by the
STRICT_ALIGNMENT_CHECKS_PROP_NAME
system property. - On other platforms it is always
true
.
- See Also:
STRICT_ALIGNMENT_CHECKS_PROP_NAME
- On x64 it is controlled by the
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Method Detail
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verifyAlignment
void verifyAlignment()
Verify that the underlying buffer is correctly aligned to prevent word tearing, other ordering issues and the JVM crashes. In particular this method verifies that the starting offset of the underlying buffer is properly aligned. However, the actual atomic call must ensure that the index is properly aligned, i.e. it must be aligned to the size of the operand. For example a call to any of the following methodsputIntOrdered(int, int)
,putIntVolatile(int, int)
,addIntOrdered(int, int)
,getIntVolatile(int)
,getAndAddInt(int, int)
orgetAndSetInt(int, int)
, must have the index aligned by four bytes (e.g.0, 4, 8, 12, 60 etc.
).Users are encouraged to call this method after constructing the
AtomicBuffer
instance in order to ensure that the underlying buffer supports atomic access tolong
values.Agrona provides an agent (
org.agrona.agent.BufferAlignmentAgent
) that checks the alignment of indexes for all operations at runtime. The agent throws an exception if the unaligned access is detected.Note: on some platforms unaligned atomic access can lead to the JVM crashes, e.g.:
# Java VM: OpenJDK 64-Bit Server VM (25.352-b08 mixed mode bsd-aarch64 compressed oops) # # siginfo: si_signo: 10 (SIGBUS), si_code: 1 (BUS_ADRALN)
- Throws:
java.lang.IllegalStateException
- if the starting offset into the buffer is not properly aligned.- See Also:
ALIGNMENT
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getLongVolatile
long getLongVolatile(int index)
Get the value at a given index with volatile semantics.- Parameters:
index
- in bytes from which to get.- Returns:
- the value for at a given index.
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putLongVolatile
void putLongVolatile(int index, long value)
Put a value to a given index with volatile semantics.- Parameters:
index
- in bytes for where to put.value
- for at a given index.
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putLongOrdered
void putLongOrdered(int index, long value)
Put a value to a given index with ordered store semantics.- Parameters:
index
- in bytes for where to put.value
- for at a given index.
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addLongOrdered
long addLongOrdered(int index, long increment)
Add a value to a given index with ordered store semantics. Use a negative increment to decrement.- Parameters:
index
- in bytes for where to put.increment
- by which the value at the index will be adjusted.- Returns:
- the previous value at the index.
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compareAndSetLong
boolean compareAndSetLong(int index, long expectedValue, long updateValue)
Atomic compare and set of a long given an expected value.- Parameters:
index
- in bytes for where to put.expectedValue
- at to be compared.updateValue
- to be exchanged.- Returns:
- set successful or not.
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getAndSetLong
long getAndSetLong(int index, long value)
Atomically exchange a value at a location returning the previous contents.- Parameters:
index
- in bytes for where to put.value
- for at a given index.- Returns:
- previous value at the index.
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getAndAddLong
long getAndAddLong(int index, long delta)
Atomically add a delta to a value at a location returning the previous contents. To decrement a negative delta can be provided.- Parameters:
index
- in bytes for where to put.delta
- to be added to the value at the index.- Returns:
- previous value.
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getIntVolatile
int getIntVolatile(int index)
Get the value at a given index with volatile semantics.- Parameters:
index
- in bytes from which to get.- Returns:
- the value for at a given index.
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putIntVolatile
void putIntVolatile(int index, int value)
Put a value to a given index with volatile semantics.- Parameters:
index
- in bytes for where to put.value
- for at a given index.
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putIntOrdered
void putIntOrdered(int index, int value)
Put a value to a given index with ordered semantics.- Parameters:
index
- in bytes for where to put.value
- for at a given index.
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addIntOrdered
int addIntOrdered(int index, int increment)
Add a value to a given index with ordered store semantics. Use a negative increment to decrement.- Parameters:
index
- in bytes for where to put.increment
- by which the value at the index will be adjusted.- Returns:
- the previous value at the index.
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compareAndSetInt
boolean compareAndSetInt(int index, int expectedValue, int updateValue)
Atomic compare and set of an int given an expected value.- Parameters:
index
- in bytes for where to put.expectedValue
- at to be compared.updateValue
- to be exchanged.- Returns:
- successful or not.
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getAndSetInt
int getAndSetInt(int index, int value)
Atomically exchange a value at a location returning the previous contents.- Parameters:
index
- in bytes for where to put.value
- for at a given index.- Returns:
- previous value.
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getAndAddInt
int getAndAddInt(int index, int delta)
Atomically add a delta to a value at a location returning the previous contents. To decrement a negative delta can be provided.- Parameters:
index
- in bytes for where to put.delta
- to be added to the value at the index.- Returns:
- previous value.
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getShortVolatile
short getShortVolatile(int index)
Get the value at a given index with volatile semantics.- Parameters:
index
- in bytes from which to get.- Returns:
- the value for at a given index.
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putShortVolatile
void putShortVolatile(int index, short value)
Put a value to a given index with volatile semantics.- Parameters:
index
- in bytes for where to put.value
- for at a given index.
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getCharVolatile
char getCharVolatile(int index)
Get the value at a given index with volatile semantics.- Parameters:
index
- in bytes from which to get.- Returns:
- the value for at a given index.
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putCharVolatile
void putCharVolatile(int index, char value)
Put a value to a given index with volatile semantics.- Parameters:
index
- in bytes for where to put.value
- for at a given index.
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getByteVolatile
byte getByteVolatile(int index)
Get the value at a given index with volatile semantics.- Parameters:
index
- in bytes from which to get.- Returns:
- the value for at a given index.
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putByteVolatile
void putByteVolatile(int index, byte value)
Put a value to a given index with volatile semantics.- Parameters:
index
- in bytes for where to put.value
- for at a given index.
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