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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
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 rc == 0 || (err != nil && err != io.EOF) {
return rc, err
if err != nil && err != io.EOF {
return 0, err
}
if rc == 0 {
return total, err
}
ctx.input = ctx.input[:8]
flags = ctx.input[0]
var i uint = 0
for ; i < 8; i++ {
if flags&(1<<i) > 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 rc, err
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 uint(rc) < i {
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
})
}
|