Fixes Base64 decode when no padding is provided (#37)

* Add tests from Korio + add test reproducing and fixing the issue #64

* Fixes Base64 decoding when no padding is provided

krypto/src/commonMain/kotlin/com/soywiz/krypto/encoding/Base64.kt

@@ -33,10 +33,10 @@ object Base64 {
                 continue // skip character
             }
 
-            val b0 = DECODE[src.readU8(n++)]
-            val b1 = DECODE[src.readU8(n++)]
-            val b2 = DECODE[src.readU8(n++)]
-            val b3 = DECODE[src.readU8(n++)]
+            val b0 = if (n < src.size) DECODE[src.readU8(n++)] else 64
+            val b1 = if (n < src.size) DECODE[src.readU8(n++)] else 64
+            val b2 = if (n < src.size) DECODE[src.readU8(n++)] else 64
+            val b3 = if (n < src.size) DECODE[src.readU8(n++)] else 64
             dst[m++] = (b0 shl 2 or (b1 shr 4)).toByte()
             if (b2 < 64) {
                 dst[m++] = (b1 shl 4 or (b2 shr 2)).toByte()

krypto/src/commonTest/kotlin/com/soywiz/krypto/Base64Test.kt

@@ -0,0 +1,45 @@
+package com.soywiz.krypto
+
+import com.soywiz.krypto.encoding.Base64
+import com.soywiz.krypto.encoding.fromBase64
+import com.soywiz.krypto.encoding.toBase64
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class Base64Test {
+    @Test
+    fun name() {
+        assertEquals("AQID", Base64.encode(byteArrayOf(1, 2, 3)))
+        assertEquals("aGVsbG8=", Base64.encode("hello".encodeToByteArray()))
+        assertEquals(byteArrayOf(1, 2, 3).toList(), Base64.decode("AQID").toList())
+        assertEquals("hello", Base64.decode("aGVsbG8=").decodeToString())
+    }
+
+    @Test
+    fun testSeveral() {
+        for (item in listOf("", "a", "aa", "aaa", "aaaa", "aaaaa", "Hello World!")) {
+            assertEquals(item, item.encodeToByteArray().toBase64().fromBase64().decodeToString())
+        }
+    }
+
+    @Test
+    fun testGlobal() {
+        assertEquals("hello", globalBase64)
+        assertEquals("hello", ObjectBase64.globalBase64)
+    }
+
+    @Test
+    fun testIssue64DecodeWithMissingPadding() {
+        assertEquals(
+            "eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ==",
+            Base64.encode(Base64.decode("eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ"))
+        )
+    }
+}
+
+object ObjectBase64 {
+    val globalBase64 = "aGVsbG8=".fromBase64().decodeToString()
+}
+
+val globalBase64 = "aGVsbG8=".fromBase64().decodeToString()