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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, available, predicted 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 next prediction header
rc, err = reader.Read(ctx.input[:1])
// Fail on error unless it is EOF
if err != nil && err != io.EOF {
return 0, err
} else if rc == 0 {
return 0, err
}
// Extend the buffer, copy the prediction header
// and calculate the number of subsequent bytes to read
ctx.input = ctx.input[:8]
flags = ctx.input[0]
predicted = int(bits.Hamming(flags))
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>
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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, available, predicted, 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 next prediction header
readHeader:
rc, err = reader.Read(ctx.input[:1])
// Fail on error unless it is EOF
if err != nil && err != io.EOF {
return total, err
} else if rc == 0 {
return total, err
}
// Extend the buffer, copy the prediction header
// and calculate the number of subsequent bytes to read
ctx.input = ctx.input[:8]
flags = ctx.input[0]
predicted = int(bits.Hamming(flags))
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// Update the hash
ctx.hash = (ctx.hash << 4) ^ uint16(ctx.input[i])
}
// rc now contains the precise amount of populated data
ctx.input = ctx.input[:rc]
available = copy(output, ctx.input)
// Check for remaining bytes that dont fit in the output buffer
if available < rc {
ctx.input = ctx.input[:copy(ctx.input, ctx.input[available:])]
} else {
// Clear the buffer
ctx.input = ctx.input[:0]
}
return available, err
})
}
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>
>
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>
>
>
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>
>
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// Update the hash
ctx.hash = (ctx.hash << 4) ^ uint16(ctx.input[i])
}
// rc now contains the precise amount of populated data
ctx.input = ctx.input[:rc]
available = copy(output, ctx.input)
total += available
// Check for remaining bytes that dont fit in the output buffer
if available < rc {
ctx.input = ctx.input[:copy(ctx.input, ctx.input[available:])]
} else {
// Clear the buffer
ctx.input = ctx.input[:0]
output = output[available:]
if len(output) > 0 && err == nil {
goto readHeader
}
}
return total, err
})
}
|