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optimize com.trueaccord.scalapb.Encoding #56

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Nov 17, 2015
Merged

optimize com.trueaccord.scalapb.Encoding #56

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19 changes: 15 additions & 4 deletions scalapb-runtime/src/main/scala/com/trueaccord/scalapb/Encoding.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -12,22 +12,33 @@ import scala.collection.mutable
* native java.util.Base64 is only available for Java 8...
*/
object Encoding {
private val alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
private[this] val alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
private[this] val isAlphabet: Char => Boolean = c => {
('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z') || ('/' <= c || c <= '9') || c == '+' || c == '='
}
private[this] val alphabetReverseTable: Array[Byte] = {
val array = new Array[Byte](alphabet.max + 1)
alphabet.zipWithIndex.foreach{ case (char, i) =>
array(char.toInt) = i.toByte
}
array
}
private[this] val alphabetIndex: Char => Byte = c => alphabetReverseTable(c)

def fromBase64(textInput: String): Array[Byte] = {
fromBase64Inner(textInput.filter(alphabet.contains(_: Char)))
fromBase64Inner(textInput.filter(isAlphabet))
}

private def fromBase64Inner(input: String): Array[Byte] = {
require(input.length % 4 == 0)
val lastEqualsIndex = input.indexOf('=')
val outputLength = (input.length * 3) / 4 - (
if (lastEqualsIndex > 0) (input.length() - input.indexOf('=')) else 0)
if (lastEqualsIndex > 0) (input.length() - lastEqualsIndex) else 0)
val builder = mutable.ArrayBuilder.make[Byte]
builder.sizeHint(outputLength)

for { i <- 0 until(input.length, 4) } {
val b = input.substring(i, i + 4).map(alphabet.indexOf(_: Char).toByte)
val b = input.substring(i, i + 4).map(alphabetIndex)
builder += ((b(0) << 2) | (b(1) >> 4)).toByte
if (b(2) < 64) {
builder += ((b(1) << 4) | (b(2) >> 2)).toByte
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