javax.realtime

Class RawMemoryFloatAccess

java.lang.Object

javax.realtime.RawMemoryAccess

javax.realtime.RawMemoryFloatAccess

Deprecated.

as of RTSJ 2.0. Use RawMemory.

@Deprecated
public class RawMemoryFloatAccess
extends RawMemoryAccess

This class holds the accessor methods for accessing a raw memory area by float and double types. Implementations are required to implement this class when and only when the underlying Java Virtual Machine supports floating point data types.

See RawMemoryAccess for commentary on changes in the preferred use of this class following RTSJ 2.0.

By default, the byte addressed by offset is the byte at the lowest address of the floating point processor's floating point representation. When the type of memory used for this RawMemoryFloatAccess region implements a non-standard floating point format, accessor methods in this class continue to select bytes starting at offset from the base address and continuing toward greater addresses. The memory type may control the mapping of these bytes into the primitive data type. The memory type could even select bytes that are not contiguous. In each case the documentation for the PhysicalMemoryTypeFilter must document any mapping other than the "normal" one specified above.

All offset values used in this class are measured in bytes.

Atomic loads and stores on raw memory are defined in terms of physical memory. This memory may be accessible to threads outside the JVM and to non-programmed access, e.g., DMA, consequently atomic access must be supported by hardware. This specification is written with the assumption that all suitable hardware platforms support atomic loads for aligned floats. Atomic access beyond the specified minimum may be supported by the implementation.

Storing values into raw memory is more hardware-dependent than loading values. Many processor architectures do not support atomic stores of variables except for aligned stores of the processor's word size.

This class supports unaligned access to data, but it does not require the implementation to make such access atomic. Accesses to data aligned on its natural boundary will be atomic when the processor implements atomic loads and stores of that data size.

Except where noted, accesses to raw memory are not atomic with respect to the memory or with respect to threads. A raw memory area could be updated by another thread, or even unmapped in the middle of a method.

The characteristics of raw-memory access are necessarily platform dependent. This specification provides a minimum requirement for the RTSJ platform, but it also supports optional system properties that identify a platform's level of support for atomic raw put and get. (See RawMemoryAccess.) The properties represent a four-dimensional sparse array with boolean values, indicating whether that combination of access attributes is atomic. The default value for array entries is false.

Many of the constructors and methods in this class throw OffsetOutOfBoundsException. This exception means that the value given in the offset parameter is either negative or outside the memory area.

Many of the constructors and methods in this class throw SizeOutOfBoundsException. This exception means that the value given in the size parameter is either negative, larger than an allowable range, or would cause an accessor method to access an address outside of the memory area.

Constructor Summary

Constructors

Constructor and Description
RawMemoryFloatAccess(java.lang.Object type, long size) Deprecated. Constructs an instance of RawMemoryFloatAccess with the given parameters, and sets the object to the mapped state.
RawMemoryFloatAccess(java.lang.Object type, long base, long size) Deprecated. Constructs an instance of RawMemoryFloatAccess with the given parameters, and sets the object to the mapped state.

Method Summary

Modifier and Type	Method and Description
double	getDouble(long offset) Deprecated. Gets the double at the given offset in the memory area associated with this object.
void	getDoubles(long offset, double[] doubles, int low, int number) Deprecated. Gets number doubles starting at the given offset in the memory area associated with this object and assigns them to the double array passed starting at position low.
float	getFloat(long offset) Deprecated. Gets the float at the given offset in the memory area associated with this object.
void	getFloats(long offset, float[] floats, int low, int number) Deprecated. Gets number floats starting at the given offset in the memory area associated with this object and assign them to the floats array passed starting at position low.
void	setDouble(long offset, double value) Deprecated. Sets the double at the given offset in the memory area associated with this object.
void	setDoubles(long offset, double[] doubles, int low, int number) Deprecated. Sets number doubles starting at the given offset in the memory area associated with this object from the doubles array passed starting at position low.
void	setFloat(long offset, float value) Deprecated. Sets the float at the given offset in the memory area associated with this object.
void	setFloats(long offset, float[] floats, int low, int number) Deprecated. Sets number floats starting at the given offset in the memory area associated with this object from the float array passed starting at position low.

Methods inherited from class javax.realtime.RawMemoryAccess

getByte, getBytes, getInt, getInts, getLong, getLongs, getMappedAddress, getShort, getShorts, map, map, map, setByte, setBytes, setInt, setInts, setLong, setLongs, setShort, setShorts, unmap

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RawMemoryFloatAccess

public RawMemoryFloatAccess(java.lang.Object type,
                            long base,
                            long size)

Deprecated.

Constructs an instance of RawMemoryFloatAccess with the given parameters, and sets the object to the mapped state. When the platform supports virtual memory, maps the raw memory into virtual memory.

The run time environment is allowed to choose the virtual address where the raw memory area corresponding to this object will be mapped. The attributes of the mapping operation are controlled by the vMFlags and vMAttributes of the PhysicalMemoryTypeFilter objects that matched this object's type parameter. (See PhysicalMemoryTypeFilter.getVMAttributes() and PhysicalMemoryTypeFilter.getVMFlags().

Parameters:

type - An instance of Object representing the type of memory required, e.g., dma, shared, for defining the base address and controlling the mapping. When the required memory has more than one attribute, type may be an array of objects. When type is null or a reference to an array with no entries, any type of memory is acceptable. Note that type values are compared by reference (==), not by value (equals).

base - The physical memory address of the region.

size - The size of the area in bytes.

Throws:

StaticSecurityException - when the application doesn't have permissions to access physical memory, the specified range of addresses, or the given type of memory.

OffsetOutOfBoundsException - when the address is invalid.

SizeOutOfBoundsException - when the size is negative or extends into an invalid range of memory.

UnsupportedPhysicalMemoryException - when the underlying hardware does not support the given type, or when no matching PhysicalMemoryTypeFilter has been registered with the PhysicalMemoryManager.

MemoryTypeConflictException - when the specified base does not point to memory that matches the request type, or when type specifies incompatible memory attributes.

java.lang.OutOfMemoryError - when the requested type of memory exists, but there is not enough of it free to satisfy the request.

RawMemoryFloatAccess

public RawMemoryFloatAccess(java.lang.Object type,
                            long size)

Deprecated.

Constructs an instance of RawMemoryFloatAccess with the given parameters, and sets the object to the mapped state. When the platform supports virtual memory, maps the raw memory into virtual memory.

The run time environment is allowed to choose the virtual address where the raw memory area corresponding to this object will be mapped. The attributes of the mapping operation are controlled by the vMFlags and vMAttributes of the PhysicalMemoryTypeFilter objects that matched this object's type parameter. (See PhysicalMemoryTypeFilter.getVMAttributes() and PhysicalMemoryTypeFilter.getVMFlags().

Parameters:

type - An instance of Object representing the type of memory required, e.g., dma, shared), for defining the base address and controlling the mapping. When the required memory has more than one attribute, type may be an array of objects. When type is null or a reference to an array with no entries, any type of memory is acceptable. Note that type values are compared by reference (==), not by value (equals).

size - The size of the area in bytes.

Throws:

StaticSecurityException - when the application doesn't have permissions to access physical memory, the specified range of addresses, or the given type of memory.

SizeOutOfBoundsException - when the size is negative or extends into an invalid range of memory.

UnsupportedPhysicalMemoryException - when the underlying hardware does not support the given type, or when no matching PhysicalMemoryTypeFilter has been registered with the PhysicalMemoryManager.

MemoryTypeConflictException - when the specified base does not point to memory that matches the request type, or when type specifies incompatible memory attributes.

java.lang.OutOfMemoryError - when the requested type of memory exists, but there is not enough of it free to satisfy the request.

Method Detail

getDouble

public double getDouble(long offset)

Deprecated.

Gets the double at the given offset in the memory area associated with this object.

The load is not required to be atomic even it is located on a natural boundary.

Caching of the memory access is controlled by the memory type requested when the RawMemoryAccess instance was created. When the memory is not cached, this method guarantees serialized access (that is, the memory access at the memory occurs in the same order as in the program. Multiple writes to the same location may not be coalesced.)

Parameters:

offset - The offset in bytes from the beginning of the raw memory area from which to load the double.

Returns:

the double from raw memory.

Throws:

OffsetOutOfBoundsException - when the offset is invalid.

SizeOutOfBoundsException - when the object is not mapped, or when the double falls in an invalid address range.

StaticSecurityException - when this access is not permitted by the security manager.

getDoubles

public void getDoubles(long offset,
                       double[] doubles,
                       int low,
                       int number)

Deprecated.

Gets number doubles starting at the given offset in the memory area associated with this object and assigns them to the double array passed starting at position low.

The loads are not required to be atomic even when they are located on natural boundaries.

Caching of the memory access is controlled by the memory type requested when the RawMemoryAccess instance was created. When the memory is not cached, this method guarantees serialized access (that is, the memory access at the memory occurs in the same order as in the program. Multiple writes to the same location may not be coalesced.)

Parameters:

offset - The offset in bytes from the beginning of the raw memory area at which to start loading.

doubles - The array into which the loaded items are placed.

low - The offset which is the starting point in the given array for the loaded items to be placed.

number - The number of doubles to load.

Throws:

OffsetOutOfBoundsException - when the offset is negative or greater than the size of the raw memory area. The role of the SizeOutOfBoundsException somewhat overlaps this exception since it is when the offset is within the object but outside the mapped area. (See RawMemoryAccess.map(long,long) ).

SizeOutOfBoundsException - when the object is not mapped, or when a double falls in an invalid address range. This is checked at every entry in the array to allow for the possibility that the memory area could be unmapped or remapped. The double array could, therefore, be partially updated when the raw memory is unmapped or remapped mid-method.

java.lang.ArrayIndexOutOfBoundsException - when low is less than 0 or greater than bytes.length - 1, or when low + number is greater than or equal to bytes.length.

StaticSecurityException - when this access is not permitted by the security manager.

getFloat

public float getFloat(long offset)

Deprecated.

Gets the float at the given offset in the memory area associated with this object. When the float is aligned on a "natural" boundary it is always loaded from memory in a single atomic operation. When it is not on a natural boundary it may not be loaded atomically, and the number and order of the load operations is unspecified.

Caching of the memory access is controlled by the memory type requested when the RawMemoryAccess instance was created. When the memory is not cached, this method guarantees serialized access (that is, the memory access at the memory occurs in the same order as in the program. Multiple writes to the same location may not be coalesced.)

Parameters:

offset - The offset in bytes from the beginning of the raw memory area from which to load the float.

Returns:

the float from raw memory.

Throws:

OffsetOutOfBoundsException - when the offset is negative or greater than the size of the raw memory area. The role of the SizeOutOfBoundsException somewhat overlaps this exception since it is when the offset is within the object but outside the mapped area. (See RawMemoryAccess.map(long,long) ).

SizeOutOfBoundsException - when the object is not mapped, or when the float falls in an invalid address range.

StaticSecurityException - when this access is not permitted by the security manager.

getFloats

public void getFloats(long offset,
                      float[] floats,
                      int low,
                      int number)

Deprecated.

Gets number floats starting at the given offset in the memory area associated with this object and assign them to the floats array passed starting at position low.

When the floats are aligned on natural boundaries each float is loaded from memory in a single atomic operation. Groups of floats may be loaded together, but this is unspecified.

When the floats are not aligned on natural boundaries they may not be loaded atomically and the number and order of load operations is unspecified.

Caching of the memory access is controlled by the memory type requested when the RawMemoryAccess instance was created. When the memory is not cached, this method guarantees serialized access (that is, the memory access at the memory occurs in the same order as in the program. Multiple writes to the same location may not be coalesced.)

Parameters:

offset - The offset in bytes from the beginning of the raw memory area at which to start loading.

floats - The array into which the floats loaded from the raw memory are placed.

low - The offset which is the starting point in the given array for the loaded items to be placed.

number - The number of floats to load.

Throws:

OffsetOutOfBoundsException - when the offset is negative or greater than the size of the raw memory area. The role of the SizeOutOfBoundsException somewhat overlaps this exception since it is when the offset is within the object but outside the mapped area. (See RawMemoryAccess.map(long,long) ).

SizeOutOfBoundsException - when the object is not mapped, or when a float falls in an invalid address range. This is checked at every entry in the array to allow for the possibility that the memory area could be unmapped or remapped. The float array could, therefore, be partially updated when the raw memory is unmapped or remapped mid-method.

java.lang.ArrayIndexOutOfBoundsException - when low is less than 0 or greater than bytes.length - 1, or when low + number is greater than or equal to bytes.length.

StaticSecurityException - when this access is not permitted by the security manager.

setDouble

public void setDouble(long offset,
                      double value)

Deprecated.

Sets the double at the given offset in the memory area associated with this object. Even when it is aligned, the double value may not be updated atomically. It is unspecified how many load and store operations will be used or in what order.

Caching of the memory access is controlled by the memory type requested when the RawMemoryAccess instance was created. When the memory is not cached, this method guarantees serialized access (that is, the memory access at the memory occurs in the same order as in the program. Multiple writes to the same location may not be coalesced.)

Parameters:

offset - The offset in bytes from the beginning of the raw memory area at which to write the double.

value - The double to write.

Throws:

OffsetOutOfBoundsException - when the offset is negative or greater than the size of the raw memory area. The role of the SizeOutOfBoundsException somewhat overlaps this exception since it is when the offset is within the object but outside the mapped area. (See RawMemoryAccess.map(long,long) ).

SizeOutOfBoundsException - when the object is not mapped, or when the double falls in an invalid address range.

StaticSecurityException - when this access is not permitted by the security manager.

setDoubles

public void setDoubles(long offset,
                       double[] doubles,
                       int low,
                       int number)

Deprecated.

Sets number doubles starting at the given offset in the memory area associated with this object from the doubles array passed starting at position low. Even when they are aligned, the double values may not be updated atomically. It is unspecified how many load and store operations will be used or in what order.

Caching of the memory access is controlled by the memory type requested when the RawMemoryAccess instance was created. When the memory is not cached, this method guarantees serialized access (that is, the memory access at the memory occurs in the same order as in the program. Multiple writes to the same location may not be coalesced.)

Parameters:

offset - The offset in bytes from the beginning of the raw memory area at which to start writing.

doubles - The array from which the items are obtained.

low - The offset which is the starting point in the given array for the items to be obtained.

number - The number of items to write.

Throws:

OffsetOutOfBoundsException - when the offset is negative or greater than the size of the raw memory area. The role of the SizeOutOfBoundsException somewhat overlaps this exception since it is when the offset is within the object but outside the mapped area. (See RawMemoryAccess.map(long,long) ).

SizeOutOfBoundsException - when the object is not mapped, or when a double falls in an invalid address range. This is checked at every entry in the array to allow for the possibility that the memory area could be unmapped or remapped. The doubles array could, therefore, be partially updated when the raw memory is unmapped or remapped mid-method.

java.lang.ArrayIndexOutOfBoundsException - when low is less than 0 or greater than bytes.length - 1, or when low + number is greater than or equal to bytes.length.

StaticSecurityException - when this access is not permitted by the security manager.

setFloat

public void setFloat(long offset,
                     float value)

Deprecated.

Sets the float at the given offset in the memory area associated with this object. On most processor architectures an aligned float can be stored in an atomic operation, but this is not required.

Caching of the memory access is controlled by the memory type requested when the RawMemoryAccess instance was created. When the memory is not cached, this method guarantees serialized access (that is, the memory access at the memory occurs in the same order as in the program. Multiple writes to the same location may not be coalesced.)

Parameters:

offset - The offset in bytes from the beginning of the raw memory area at which to write the float.

value - The float to write.

Throws:

OffsetOutOfBoundsException - when the offset is negative or greater than the size of the raw memory area. The role of the SizeOutOfBoundsException somewhat overlaps this exception since it is when the offset is within the object but outside the mapped area. (See RawMemoryAccess.map(long,long) ).

SizeOutOfBoundsException - when the object is not mapped, or when the float falls in an invalid address range.

StaticSecurityException - when this access is not permitted by the security manager.

setFloats

public void setFloats(long offset,
                      float[] floats,
                      int low,
                      int number)

Deprecated.

Sets number floats starting at the given offset in the memory area associated with this object from the float array passed starting at position low. On most processor architectures each aligned float can be stored in an atomic operation, but this is not required.

Caching of the memory access is controlled by the memory type requested when the RawMemoryAccess instance was created. When the memory is not cached, this method guarantees serialized access (that is, the memory access at the memory occurs in the same order as in the program. Multiple writes to the same location may not be coalesced.)

Parameters:

offset - The offset in bytes from the beginning of the raw memory area at which to start writing.

floats - The array from which the items are obtained.

low - The offset which is the starting point in the given array for the items to be obtained.

number - The number of floats to write.

Throws:

OffsetOutOfBoundsException - when the offset is negative or greater than the size of the raw memory area. The role of the SizeOutOfBoundsException somewhat overlaps this exception since it is when the offset is within the object but outside the mapped area. (See RawMemoryAccess.map(long, long) ).

SizeOutOfBoundsException - when the object is not mapped, or when a float falls in an invalid address range. This is checked at every entry in the array to allow for the possibility that the memory area could be unmapped or remapped. The store of the array into memory could, therefore, be only partially complete when the raw memory is unmapped or remapped mid-method.

java.lang.ArrayIndexOutOfBoundsException - when low is less than 0 or greater than bytes.length - 1, or when low + number is greater than or equal to bytes.length.

StaticSecurityException - when this access is not permitted by the security manager.