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Comment:The decompressor now tries to fill in the whole output buffer in a single call.
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SHA1: 1f73d90f65ec364f62075e5c5a5b0666be2b116b
User & Date: spaskalev on 2014-12-21 23:24:04
Other Links: manifest | tags
Context
2014-12-22
16:41
Integrate the decompressor2 branch into trunk now that it is faster. check-in: 6d10a1d28f user: spaskalev tags: trunk
2014-12-21
23:24
The decompressor now tries to fill in the whole output buffer in a single call. check-in: 1f73d90f65 user: spaskalev tags: trunk
22:52
Removed TODOs, renamed readCount->rc, wrapped->reader check-in: 630530df49 user: spaskalev tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Modified src/0dev.org/predictor/predictor.go from [090d2f3fd4] to [9dfe9174f8].

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// and decompresses data according to the predictor algorithm
func Decompressor(reader io.Reader) io.Reader {
	var ctx context
	ctx.input = make([]byte, 0, 8)

	return decompressor(func(output []byte) (int, error) {
		var (
			err       error
			flags     byte
			rc, total 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 {
			rc = copy(output, ctx.input)

			// Check whether we still have leftover data in the buffer :)
			if rc < len(ctx.input) {
				ctx.input = ctx.input[:copy(ctx.input, ctx.input[rc:])]
			}
			return rc, nil
		}


		// Read the flags
		rc, err = reader.Read(ctx.input[:1])
		if rc == 0 || (err != nil && err != io.EOF) {
			return rc, err



		}

		ctx.input = ctx.input[:8]
		flags = ctx.input[0]

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

				if err == io.EOF {
					break
				}

				if err != nil {
					return rc, err
				}

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

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

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

		rc = copy(output, ctx.input[:i])

		total += rc

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

			ctx.input = ctx.input[:0]







		}

		return total, err
	})
}








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// and decompresses data according to the predictor algorithm
func Decompressor(reader io.Reader) io.Reader {
	var ctx context
	ctx.input = make([]byte, 0, 8)

	return decompressor(func(output []byte) (int, error) {
		var (
			err          error
			flags        byte
			i, rc, total 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 {
			rc = copy(output, ctx.input)

			// Check whether we still have leftover data in the buffer :)
			if rc < len(ctx.input) {
				ctx.input = ctx.input[:copy(ctx.input, ctx.input[rc:])]
			}
			return rc, nil
		}

	loop:
		// Read the flags
		rc, err = reader.Read(ctx.input[:1])
		if err != nil && err != io.EOF {
			return 0, err
		}
		if rc == 0 {
			return total, err
		}

		ctx.input = ctx.input[:8]
		flags = ctx.input[0]


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

				if err == io.EOF {
					break
				}

				if err != nil {
					return total, err
				}

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

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

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

		rc = copy(output, ctx.input[:i])

		total += rc

		// Place any remaining bytes in the buffer
		if rc < i {
			ctx.input = ctx.input[:copy(ctx.input, ctx.input[rc:i])]
		} else {
			// Clear the buffer
			ctx.input = ctx.input[:0]

			// Advance the output buffer ...
			output = output[i:]
			// ... and decompress the next block if there is any space left
			if len(output) > 0 && err != io.EOF {
				goto loop
			}
		}

		return total, err
	})
}

Modified src/0dev.org/predictor/predictor_test.go from [dd11cf49de] to [0dde784b22].

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	// Diff the result against the initial input
	delta := diff.Diff(diff.D{len(input), len(decompressed),
		func(i, j int) bool { return input[i] == decompressed[j] }})

	// Return a well-formated error if any differences are found
	if len(delta.Added) > 0 || len(delta.Removed) > 0 {
		return fmt.Errorf("Unexpected decompressed output %v\ninput:  %#x\ntrace:  %#x\noutput: %#x\n",
			delta, input, trace, decompressed)
	}

	// All is good :)
	return nil
}








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	// Diff the result against the initial input
	delta := diff.Diff(diff.D{len(input), len(decompressed),
		func(i, j int) bool { return input[i] == decompressed[j] }})

	// Return a well-formated error if any differences are found
	if len(delta.Added) > 0 || len(delta.Removed) > 0 {
		return fmt.Errorf("Unexpected decompressed output %v\ninput: (%d) %#x\ntrace: (%d) %#x\noutput: (%d) %#x\n",
			delta, len(input), input, len(trace), trace, len(decompressed), decompressed)
	}

	// All is good :)
	return nil
}

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