scalapb.Encoding.scala Maven / Gradle / Ivy
package scalapb
import scala.collection.mutable
/** Utility functions to encode/decode byte arrays as Base64 strings.
*
* Used internally between the protocol buffer compiler and the runtime to encode messages.
*
* We could have used Apache Commons, but we would like to avoid an additional dependency.
* java.xml.bind.DataTypeConverter.parseBase64Binary is not available on Android. And the Java
* native java.util.Base64 is only available for Java 8...
*/
object Encoding {
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.toInt)
def fromBase64(textInput: String): Array[Byte] = {
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() - 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(alphabetIndex)
builder += ((b(0) << 2) | (b(1) >> 4)).toByte
if (b(2) < 64) {
builder += ((b(1) << 4) | (b(2) >> 2)).toByte
if (b(3) < 64) {
builder += ((b(2) << 6) | b(3)).toByte
}
}
}
builder.result()
}
def toBase64(in: Array[Byte]): String = {
val out = new mutable.StringBuilder()
var b: Int = 0
for { i <- 0.until(in.length, 3) } {
b = (in(i) & 0xfc) >> 2
out.append(alphabet(b))
b = (in(i) & 0x03) << 4
if (i + 1 < in.length) {
b |= (in(i + 1) & 0xf0) >> 4
out.append(alphabet(b))
b = (in(i + 1) & 0x0f) << 2
if (i + 2 < in.length) {
b |= (in(i + 2) & 0xc0) >> 6
out.append(alphabet(b))
b = in(i + 2) & 0x3f
out.append(alphabet(b))
} else {
out.append(alphabet(b))
out.append('=')
}
} else {
out.append(alphabet(b))
out.append("==")
}
}
out.result()
}
}