org.das2.qds.buffer.BufferDataSet

rank 1, 2, 3, and 4 datasets backed by NIO buffers. These have the advantage that data can be stored outside of the JVM, and in fact they can be backed by a huge file on disk. This code was copied from BinaryDataSource.

BufferDataSet( int rank, int reclen, int recoffs, int len0, int len1, int len2, Object type, java.nio.ByteBuffer back )

Create a new BufferDataSet of the given type. Simple sanity checks are made, including:

• rank 1 dataset may not have len1>1.
• reclen cannot be shorter than the byte length of the field type.
• buffer must have room for the dataset

BufferDataSet( int rank, int reclen, int recoffs, int len0, int len1, int len2, int len3, Object type, java.nio.ByteBuffer back )

Create a new BufferDataSet of the given type. Simple sanity checks are made, including:

• rank 1 dataset may not have len1>1.
• reclen cannot be shorter than the byte length of the field type.
• buffer must have room for the dataset

BufferDataSet( int rank, int reclen, int recoffs, Object bitByte, int len0, int len1, int len2, int len3, Object type, java.nio.ByteBuffer back )

Create a new BufferDataSet of the given type. Simple sanity checks are made, including:

• rank 1 dataset may not have len1>1.
• reclen cannot be shorter than the byte length of the field type.
• buffer must have room for the dataset

DOUBLE

the data is in 8 byte doubles.

FLOAT

the data is in 4 byte floats.

TRUNCATEDFLOAT

the data is in 16 bit real that has exponent like a FLOAT but mantissa precision is reduced.

VAX_FLOAT

VAX floats.

INT24

three-byte ints.

UINT24

three-byte unsigned ints.

NYBBLE

four-bit unsigned ints.

LONG

8 byte signed longs.

INT

4 byte signed integers.

INTEGER

4 byte signed integers, INT is canonical but INTEGER should be accepted.

UINT

4 byte unsigned integers. Note 4-byte signed ints are used to store the data which is unpacked in the value() method.

SHORT

2 byte short integer.

USHORT

2 byte unsigned short.

BYTE

1 byte signed byte.

UBYTE

1 byte unsigned byte.

BYTES

constructor units are in bytes.

BITS

constructor units are in bits.

about

print some info about this BufferDataSet.

Returns:

append

append the dataset with the same geometry but different number of records (zeroth dim) to this. An IllegalArgumentException is thrown when there is not enough room. See grow(newRecCount). This buffer's capacity will be something like java.nio.DirectByteBuffer[pos=0 lim=6256 cap=13760] and the dataset ds's buffer will have java.nio.DirectByteBufferR[pos=0 lim=6256 cap=6256]. After this append operation, the buffer of the second will be copied into the first's: java.nio.DirectByteBuffer[pos=0 lim=12512 cap=13760]. Not thread safe--we need to go through and make it so...

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See Also:

bitCount

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byteCount

return the number of bytes of each type (double=8, etc).

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canAppend

return true if the dataset can be appended. Note this assumes that the same length, etc. This just checks that we have the number of spare records in the backing store.

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compact

get rid of extra spaces between records.

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copy

return a copy of the data. If the data is a BufferDataSet, then a new BufferDataSet is used for the copy. Note this does not consider isMutable. If the dataset is not mutable, then the original data could be returned (probably).

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create

create a dataset backed by the given type.

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createRank0

create a rank 0 dataset backed by the given type.

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createRank1

create a rank 1 dataset backed by the given type.

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createRank2

create a rank 2 dataset backed by the given type.

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createRank3

create a rank 3 dataset backed by the given type.

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createRank4

create a rank 4 dataset backed by the given type.

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getCompatibleComponentType

return the Java type that is capable of containing elements of this dataset. For unsigned types, the next Java class is used, for example int.class is used to store unsigned shorts.

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getFieldStride

return the number of bytes to advance for each field.

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getRecordStride

return the number of bytes to advance for each record.

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getType

return the type of this dataset, for example BufferDataSet.INT, BufferDataSet.DOUBLE, etc...

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grow

grow the internal store so that append may be used to resize the dataset. This simply grows the internal buffer, so for example length() will return the same value after.

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See Also:

guessBackingStore

guess the type of the backing store, returning double.class if it cannot be determined.

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isCompact

returns true if the dataset is compact, meaning that there are no gaps between records, and no byte offset.

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jvmMemory

estimate the jvmMemory occupied by this dataset, looking at the NIO buffer to see if it is direct as has no JVM memory cost, or if it has been made into an array.

Returns:

length

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makeDataSet

Make a BufferDataSet of the given type.

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makeDataSetBits

support binary types that are not a multiple of 8 bits. This was added to support Nybbles, and 12-bit ints.

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maybeCopy

Copy the dataset to an BufferDataSet only if the dataset is not already an BufferDataSet.

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rank

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setFieldStride

allow clients to override the cadence of data. By default, this is just the number of bytes in each field.

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setLength

reset the number of records.

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setLength1

reset the length (in fields) of each record of the rank 2 dataset.

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See Also:

setRecordStride

allow clients to override the cadece of the records. By default, this is the number of bytes in each record.

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shouldAllocateDirect

return 1 if direct allocate should be used, 0 if not. Direct allocations are memory allocations outside of the JVM heap memory. (The internal variable has a -1 initial state, which is why this is not boolean.) This looks for 32bit Javas, and if more than 1/2 Gig is being used then it will allocate direct. This is because 32bit Javas cannot access any memory outside of 1Gig.

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See Also:

slice

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trim

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typeFor

Return the type for the given class. Note that there is a type for each native type (Byte,Short,Float,etc), but not a class for each type. (E.g. UBYTE is unsigned byte.)

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value

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