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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2007-2011, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package dotty.tools.dotc.core.classfile
object ByteCodecs {
def avoidZero(src: Array[Byte]): Array[Byte] = {
var i = 0
val srclen = src.length
var count = 0
while (i < srclen) {
if (src(i) == 0x7f) count += 1
i += 1
}
val dst = new Array[Byte](srclen + count)
i = 0
var j = 0
while (i < srclen) {
val in = src(i)
if (in == 0x7f) {
dst(j) = (0xc0).toByte
dst(j + 1) = (0x80).toByte
j += 2
} else {
dst(j) = (in + 1).toByte
j += 1
}
i += 1
}
dst
}
def regenerateZero(src: Array[Byte]): Int = {
var i = 0
val srclen = src.length
var j = 0
while (i < srclen) {
val in: Int = src(i) & 0xff
if (in == 0xc0 && (src(i + 1) & 0xff) == 0x80) {
src(j) = 0x7f
i += 2
} else if (in == 0) {
src(j) = 0x7f
i += 1
} else {
src(j) = (in - 1).toByte
i += 1
}
j += 1
}
j
}
def encode8to7(src: Array[Byte]): Array[Byte] = {
val srclen = src.length
val dstlen = (srclen * 8 + 6) / 7
val dst = new Array[Byte](dstlen)
var i = 0
var j = 0
while (i + 6 < srclen) {
var in: Int = src(i) & 0xff
dst(j) = (in & 0x7f).toByte
var out: Int = in >>> 7
in = src(i + 1) & 0xff
dst(j + 1) = (out | (in << 1) & 0x7f).toByte
out = in >>> 6
in = src(i + 2) & 0xff
dst(j + 2) = (out | (in << 2) & 0x7f).toByte
out = in >>> 5
in = src(i + 3) & 0xff
dst(j + 3) = (out | (in << 3) & 0x7f).toByte
out = in >>> 4
in = src(i + 4) & 0xff
dst(j + 4) = (out | (in << 4) & 0x7f).toByte
out = in >>> 3
in = src(i + 5) & 0xff
dst(j + 5) = (out | (in << 5) & 0x7f).toByte
out = in >>> 2
in = src(i + 6) & 0xff
dst(j + 6) = (out | (in << 6) & 0x7f).toByte
out = in >>> 1
dst(j + 7) = out.toByte
i += 7
j += 8
}
if (i < srclen) {
var in: Int = src(i) & 0xff
dst(j) = (in & 0x7f).toByte; j += 1
var out: Int = in >>> 7
if (i + 1 < srclen) {
in = src(i + 1) & 0xff
dst(j) = (out | (in << 1) & 0x7f).toByte; j += 1
out = in >>> 6
if (i + 2 < srclen) {
in = src(i + 2) & 0xff
dst(j) = (out | (in << 2) & 0x7f).toByte; j += 1
out = in >>> 5
if (i + 3 < srclen) {
in = src(i + 3) & 0xff
dst(j) = (out | (in << 3) & 0x7f).toByte; j += 1
out = in >>> 4
if (i + 4 < srclen) {
in = src(i + 4) & 0xff
dst(j) = (out | (in << 4) & 0x7f).toByte; j += 1
out = in >>> 3
if (i + 5 < srclen) {
in = src(i + 5) & 0xff
dst(j) = (out | (in << 5) & 0x7f).toByte; j += 1
out = in >>> 2
}
}
}
}
}
if (j < dstlen) dst(j) = out.toByte
}
dst
}
def decode7to8(src: Array[Byte], srclen: Int): Int = {
var i = 0
var j = 0
val dstlen = (srclen * 7 + 7) / 8
while (i + 7 < srclen) {
var out: Int = src(i)
var in: Byte = src(i + 1)
src(j) = (out | (in & 0x01) << 7).toByte
out = in >>> 1
in = src(i + 2)
src(j + 1) = (out | (in & 0x03) << 6).toByte
out = in >>> 2
in = src(i + 3)
src(j + 2) = (out | (in & 0x07) << 5).toByte
out = in >>> 3
in = src(i + 4)
src(j + 3) = (out | (in & 0x0f) << 4).toByte
out = in >>> 4
in = src(i + 5)
src(j + 4) = (out | (in & 0x1f) << 3).toByte
out = in >>> 5
in = src(i + 6)
src(j + 5) = (out | (in & 0x3f) << 2).toByte
out = in >>> 6
in = src(i + 7)
src(j + 6) = (out | in << 1).toByte
i += 8
j += 7
}
if (i < srclen) {
var out: Int = src(i)
if (i + 1 < srclen) {
var in: Byte = src(i + 1)
src(j) = (out | (in & 0x01) << 7).toByte; j += 1
out = in >>> 1
if (i + 2 < srclen) {
in = src(i + 2)
src(j) = (out | (in & 0x03) << 6).toByte; j += 1
out = in >>> 2
if (i + 3 < srclen) {
in = src(i + 3)
src(j) = (out | (in & 0x07) << 5).toByte; j += 1
out = in >>> 3
if (i + 4 < srclen) {
in = src(i + 4)
src(j) = (out | (in & 0x0f) << 4).toByte; j += 1
out = in >>> 4
if (i + 5 < srclen) {
in = src(i + 5)
src(j) = (out | (in & 0x1f) << 3).toByte; j += 1
out = in >>> 5
if (i + 6 < srclen) {
in = src(i + 6)
src(j) = (out | (in & 0x3f) << 2).toByte; j += 1
out = in >>> 6
}
}
}
}
}
}
if (j < dstlen) src(j) = out.toByte
}
dstlen
}
def encode(xs: Array[Byte]): Array[Byte] = avoidZero(encode8to7(xs))
/**
* Destructively decodes array xs and returns the length of the decoded array.
*
* Sometimes returns (length + 1) of the decoded array. Example:
*
* scala> val enc = reflect.generic.ByteCodecs.encode(Array(1,2,3))
* enc: Array[Byte] = Array(2, 5, 13, 1)
*
* scala> reflect.generic.ByteCodecs.decode(enc)
* res43: Int = 4
*
* scala> enc
* res44: Array[Byte] = Array(1, 2, 3, 0)
*
* However, this does not always happen.
*/
def decode(xs: Array[Byte]): Int = {
val len = regenerateZero(xs)
decode7to8(xs, len)
}
}
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