bytearray

bytearray

Package bytearray provides a fixed size chunk []byte array with slab allocation. ByteArrays utilize next-chunk-linking which provides full reader/writer compatibility with any size you need. It uses an automatic chunk allocation with manual deallocation, which means that all ByteArrays must be manually released when not used anymore. The slab and chunk sizes are globally configurable and must be done before any chunks are allocated.

Usage

import "github.com/fredli74/bytearray"

Example

	// Setup bytearray sizes to 2048 bytes (2KiB) chunks, 4MiB memory slabs and limit to 4096 slabs (16GiB memory)
	// These are global values and can only be setup once before anything is allocated
	bytearray.Setup(2048, 2048 * 2048, 4096)

	// Enable automatic garbage collect to run every 60 seconds and remove anything slab that has had no allocations for at least 120 seconds
	bytearray.EnableAutoGC(60, 120)

	// Open a file
	f, err := os.Open("input.txt")

	// Declare a byte array variable
	var ba ByteArray

	// Copy file content to the byte array
	io.Copy(ba, f)

	// Print size of array
	fmt.Printf("Size is %v", ba.Len())

	// Print debug memory stats
	fmt.Printf("Stats: %v", bytearray.Stats())
	
	// Release the array (important, this is never done automatically, if a variable falls out of scope before it has been Released, the data will still remain in the slab)
	ba.Release()

Reference

const (
	SEEK_SET int = os.SEEK_SET // seek relative to the origin of the array
	SEEK_CUR int = os.SEEK_CUR // seek relative to the current offset
	SEEK_END int = os.SEEK_END // seek relative to the end of the array
)

var ChunkSize int = 2048

ChunkSize defaults to 2048 bytes (2KiB) chunks. Use Setup function to change.

var MaxSlabs int = 4097 // +1 because slab 0 is never used (or allocated), it is reserved for emptyLocation pointers

MaxSlabs defaults to 4096 slabs (16GiB memory with default SlabSize and ChunkSize). Use Setup function to change.

var SlabSize int = ChunkSize * 2048

SlabSize defaults to 2048 slabs (4MiB memory with default ChunkSize). Use Setup function to change.

func ChunkQuantize

func ChunkQuantize(size int64) int64

ChunkQuantize takes a size and round it up to an even chunk size (this can be used to calculate used memory)

func DisableAutoGC

func DisableAutoGC()

DisableAutoGC disables the automatic GC goroutine

func EnableAutoGC

func EnableAutoGC(releaseInterval int, maxAge int)

EnableAutoGC enables the automatic GC goroutine releaseInterval is how often the GC is run. maxAge is the number of seconds since the slab was touched before it can be freed

func GC

func GC(maxAge int)

Not really a GC, more of a slab releaser in case it has not been used for a while. maxAge is the number of seconds since the slab was touched before it can be freed

func Setup

func Setup(chunkSize int, slabSize int, maxSlabs int)

Setup the ByteArray global sizes. IMPORTANT, Setup can only be called before any chunks have been allocated or it will throw a panic.

func Stats

func Stats() (AllocatedSlabs int64, GrabbedChunks int64, ReleasedChunks int64, MemoryAllocated int64, MemoryInUse int64)

Stats returns the current allocation statistics

type ByteArray

type ByteArray struct {
}

Byte array read and write is not concurrency safe however the underlying slab structures are so you can use multiple ByteArrays at the same time

func (ByteArray) Len

func (b ByteArray) Len() int

Len returns the current length of the ByteArray

func (*ByteArray) Read

func (b *ByteArray) Read(p []byte) (n int, err error)

Read from the byte array into a buffer and advance the current read position

func (*ByteArray) ReadFrom

func (b *ByteArray) ReadFrom(r io.Reader) (n int64, err error)

ReadFrom reads from the Reader until EOF and fills up the ByteArray (at the current write position)

func (ByteArray) ReadPosition

func (b ByteArray) ReadPosition() int

ReadPosition returns the current write position

func (*ByteArray) ReadSeek

func (b *ByteArray) ReadSeek(offset int, whence int) (absolute int, err error)

ReadSeek will check bounds and return EOF error if seeking outside

func (*ByteArray) ReadSlice

func (b *ByteArray) ReadSlice() ([]byte, error)

ReadSlice returns a byte slice chunk for the current read position (it does not advance read position)

func (*ByteArray) Release

func (b *ByteArray) Release()

Release will release all chunks associated with the ByteArray

func (*ByteArray) Split

func (b *ByteArray) Split(offset int) (newArray ByteArray)

Split a byte array into a new ByteArray at the specified offset, the old byte array will be truncated at the split offset

func (*ByteArray) Truncate

func (b *ByteArray) Truncate(offset int) int

Truncate sets the length, it also expands the length in case offset > usedBytes

func (*ByteArray) Write

func (b *ByteArray) Write(p []byte) (n int, err error)

Write to the byte array from a buffer and advance the current write position

func (ByteArray) WritePosition

func (b ByteArray) WritePosition() int

WritePosition returns the current write position

func (*ByteArray) WriteSeek

func (b *ByteArray) WriteSeek(offset int, whence int) int

WriteSeek will allocate and expand bounds if needed

func (*ByteArray) WriteSlice

func (b *ByteArray) WriteSlice() []byte

WriteSlice returns a byte slice chunk for the current write position (it does not advance write position)

func (*ByteArray) WriteTo

func (b *ByteArray) WriteTo(w io.Writer) (n int64, err error)

WriteTo writes all ByteArray data (from the current read position) to a writer interface