Flexible and Economical UTF-8 Decoder
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/** | |
* https://bjoern.hoehrmann.de/utf-8/decoder/dfa/ | |
*/ | |
object Utf8Decoder { | |
private val Utf8Accept: Int = 0 | |
private val Utf8Reject: Int = 1 | |
//@formatter:off | |
private val utf8d : Array[Int] = Array( | |
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 00..1f | |
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 20..3f | |
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 40..5f | |
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 60..7f | |
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, // 80..9f | |
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, // a0..bf | |
8,8,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, // c0..df | |
0xa,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x4,0x3,0x3, // e0..ef | |
0xb,0x6,0x6,0x6,0x5,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8, // f0..ff | |
0x0,0x1,0x2,0x3,0x5,0x8,0x7,0x1,0x1,0x1,0x4,0x6,0x1,0x1,0x1,0x1, // s0..s0 | |
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,1,1,0,1,0,1,1,1,1,1,1, // s1..s2 | |
1,2,1,1,1,1,1,2,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1, // s3..s4 | |
1,2,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,3,1,3,1,1,1,1,1,1, // s5..s6 | |
1,3,1,1,1,1,1,3,1,3,1,1,1,1,1,1,1,3,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // s7..s8 | |
) | |
//@formatter:on | |
private def decode(state: Int, codep: Array[Int], byte: Int): Int = { | |
val t = utf8d(byte) | |
codep(0) = if (state != Utf8Accept) (byte & 0x3f) | (codep(0) << 6) else (0xff >> t) & byte | |
utf8d(256 + state * 16 + t) | |
} | |
private def toUInt(b: Byte): Int = 0xff & b.asInstanceOf[Int] | |
def decode(bytes: Array[Byte]): String = { | |
val codes = Array.ofDim[Int](bytes.length) | |
var i, j = 0 | |
val buff = Array(0) | |
var state = 0 | |
while (i < bytes.length) { | |
state = decode(state, buff, toUInt(bytes(i))) | |
if (state == Utf8Accept) { | |
codes(j) = buff(0) | |
j = j + 1 | |
} | |
i = i + 1 | |
} | |
new String(codes, 0, j) | |
} | |
} |
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