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Comment:Removed err variable from compressor
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SHA1: 0f4bc650d1a9c78739435916114e097bab766019
User & Date: spaskalev on 2014-12-16 23:29:42.114
Other Links: manifest | tags
Context
2014-12-19
21:54
Implemented commands/pdc using predictor. Made predictor's Compressor(...) return an io.Writer. check-in: c9f3a59cb6 user: spaskalev tags: trunk
2014-12-16
23:29
Removed err variable from compressor check-in: 0f4bc650d1 user: spaskalev tags: trunk
22:56
Reworked the compressor's buffering code, switched to table testing, add step testing for the compressor. Code coverage at 88.3% check-in: 1847f77062 user: spaskalev tags: trunk
Changes
Unified Diff Ignore Whitespace Patch
Modified src/0dev.org/predictor/predictor.go from [2d1c692ccb] to [2cc1907fb9].
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	ctx.input = ctx.buffer[:0]

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

	write = func(data []byte) error {
		var (
			err          error
			blockSize    int = 8
			bufferLength int = len(ctx.input)
		)

		// Force a flush if we are called with no data to write
		if len(data) == 0 {
			// Nothing to flush if the buffer is empty though








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	ctx.input = ctx.buffer[:0]

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

	write = func(data []byte) error {
		var (

			blockSize    int = 8
			bufferLength int = len(ctx.input)
		)

		// Force a flush if we are called with no data to write
		if len(data) == 0 {
			// Nothing to flush if the buffer is empty though
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				// ... otherwise just return
				return nil
			}

			// The current buffer + new data overflow the block size
			// Complete the block, flush it ...
			ctx.input = append(ctx.input, data[:blockSize-bufferLength]...)
			err = write(nil)
			if err != nil {
				return err
			}
			// ... and stage the rest of the data in the buffer
			ctx.input = append(ctx.input, data[blockSize-bufferLength:]...)
			return nil
		}


		var buf []byte = make([]byte, 1, blockSize+1)
		for block := 0; block < len(data)/blockSize; block++ {
			for i := 0; i < blockSize; i++ {
				var current byte = data[(block*blockSize)+i]
				if ctx.table[ctx.hash] == current {
					// Guess was right - don't output
					buf[0] |= 1 << uint(i)
				} else {
					// Guess was wrong, output char
					ctx.table[ctx.hash] = current
					buf = append(buf, current)
				}
				ctx.hash = (ctx.hash << 4) ^ uint16(current)
			}

			_, err = writer.Write(buf)
			if err != nil {
				return err
			}

			// Reset the flags and buffer for the next iteration
			buf[0] ^= buf[0]
			buf = buf[:1]
		}

		var remaining int = len(data) % blockSize
		if remaining > 0 {
			ctx.input = ctx.buffer[:remaining]
			copy(ctx.input, data[len(data)-remaining:])
		} else {
			ctx.input = ctx.buffer[:0]
		}

		return nil








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				// ... otherwise just return
				return nil
			}

			// The current buffer + new data overflow the block size
			// Complete the block, flush it ...
			ctx.input = append(ctx.input, data[:blockSize-bufferLength]...)
			if err := write(nil); err != nil {

				return err
			}
			// ... and stage the rest of the data in the buffer
			ctx.input = append(ctx.input, data[blockSize-bufferLength:]...)
			return nil
		}

		// TODO allocate this on ctx.buffer ...
		var buf []byte = make([]byte, 1, blockSize+1)
		for block := 0; block < len(data)/blockSize; block++ {
			for i := 0; i < blockSize; i++ {
				var current byte = data[(block*blockSize)+i]
				if ctx.table[ctx.hash] == current {
					// Guess was right - don't output
					buf[0] |= 1 << uint(i)
				} else {
					// Guess was wrong, output char
					ctx.table[ctx.hash] = current
					buf = append(buf, current)
				}
				ctx.hash = (ctx.hash << 4) ^ uint16(current)
			}

			if _, err := writer.Write(buf); err != nil {

				return err
			}

			// Reset the flags and buffer for the next iteration

			buf, buf[0] = buf[:1], 0
		}


		if remaining := len(data) % blockSize; remaining > 0 {
			ctx.input = ctx.buffer[:remaining]
			copy(ctx.input, data[len(data)-remaining:])
		} else {
			ctx.input = ctx.buffer[:0]
		}

		return nil
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