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package predictor

import (
	"io"
)

type context struct {
	table [65536]byte
	hash  uint16
	input []byte

}

// Returns a closure over the provided writer that compresses data when called.
//
// It can buffer data as the predictor mandates 8-byte blocks with a header.
// A call with no data will force a flush.
func Compressor(writer io.Writer) func([]byte) error {
	var ctx context
	ctx.input = make([]byte, 8)

	// Forward declaration as it is required for recursion
	var write func(data []byte) error

	write = func(data []byte) error {
		var (
			err          error
................................................................................
			buf = buf[:1]
		}
		return nil
	}

	return write
}



























































































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package predictor

import (
	"io"
)

type context struct {
	table  [1 << 16]byte
	buffer [1 << 3]byte
	input  []byte
	hash   uint16
}

// Returns a closure over the provided writer that compresses data when called.
//
// It can buffer data as the predictor mandates 8-byte blocks with a header.
// A call with no data will force a flush.
func Compressor(writer io.Writer) func([]byte) error {
	var ctx context
	ctx.input = ctx.buffer[:]

	// Forward declaration as it is required for recursion
	var write func(data []byte) error

	write = func(data []byte) error {
		var (
			err          error
................................................................................
			buf = buf[:1]
		}
		return nil
	}

	return write
}

type reader func([]byte) (int, error)

func (r reader) Read(output []byte) (int, error) {
	return r(output)
}

// TODO - document
func Decompressor(reader io.Reader) reader {
	var ctx context
	ctx.input = ctx.buffer[:0]

	return func(output []byte) (int, error) {
		var (
			err       error
			flags     byte
			readCount int
		)

		// Sanity check for space to read into
		if len(output) == 0 {
			return 0, nil
		}

		// Check whether we have leftover data in the buffer
		if len(ctx.input) > 0 {
			readCount = copy(output, ctx.input)
			ctx.input = ctx.input[readCount:]
			return readCount, nil
		}

		// // The buffer will shrink as it empties, restore it if it is needed
		// if len(ctx.input) == 0 {
		// 	ctx.input = ctx.buffer[:1]
		// }

		// Read the flags
		readCount, err = reader.Read(ctx.buffer[:1])
		if readCount == 0 || err != nil {
			return readCount, err
		}

		// This is single-iteration only but it is fine according to io.Reader's contract ?!
		// TODO - read all bytes from a block based on the hamming weight of the flag
		// and just shuffle them for predictions instead of bite-sized reads ;)

		flags = ctx.buffer[0]

		var i uint = 0
		for ; i < 8; i++ {
			if flags&(1<<i) > 0 {
				// Guess was right
				ctx.buffer[i] = ctx.table[ctx.hash]
			} else {
				readCount, err = reader.Read(ctx.buffer[i:(i + 1)])

				if err == io.EOF {
					break
				}

				if err != nil {
					return readCount, err
				}

				if readCount == 0 { // treat as EoF
					break
				}

				ctx.table[ctx.hash] = ctx.buffer[i]
			}

			ctx.hash = (ctx.hash << 4) ^ uint16(ctx.buffer[i])
		}

		readCount = copy(output, ctx.buffer[:i])

		// Place any remaining bytes in the buffer
		if uint(readCount) < i {
			ctx.input = ctx.buffer[readCount:i]
		}

		return readCount, nil
	}
}