[common] Fix warnings in Bech32 implementation

1 files changed, 79 insertions, 54 deletions

diff --git a/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt b/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt
index 32885df..4b77f85 100644
--- a/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt
+++ b/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt
@@ -13,6 +13,7 @@
  * You should have received a copy of the GNU General Public License along with
  * GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
  */
+
 // Copyright (c) 2020 Figure Technologies Inc.
 // The contents of this file were derived from an implementation
 // by the btcsuite developers https://github.com/btcsuite/btcutil.
@@ -23,27 +24,17 @@
 
 // modified version of https://gist.github.com/iramiller/4ebfcdfbc332a9722c4a4abeb4e16454
 
-import net.taler.common.CyptoUtils
+package net.taler.common
+
+import java.util.Locale.ROOT
 import kotlin.experimental.and
 import kotlin.experimental.or
 
-
 infix fun Int.min(b: Int): Int = b.takeIf { this > b } ?: this
 infix fun UByte.shl(bitCount: Int) = ((this.toInt() shl bitCount) and 0xff).toUByte()
 infix fun UByte.shr(bitCount: Int) = (this.toInt() shr bitCount).toUByte()
 
 /**
- * Given an array of bytes, associate an HRP and return a Bech32Data instance.
- */
-fun ByteArray.toBech32Data(hrp: String) =
-    Bech32Data(hrp, Bech32.convertBits(this, 8, 5, true))
-
-/**
- * Using a string in bech32 encoded address format, parses out and returns a Bech32Data instance
- */
-fun String.toBech32Data() = Bech32.decode(this)
-
-/**
  * Bech32 Data encoding instance containing data for encoding as well as a human readable prefix
  */
 data class Bech32Data(val hrp: String, val fiveBitData: ByteArray) {
@@ -71,6 +62,30 @@ data class Bech32Data(val hrp: String, val fiveBitData: ByteArray) {
     override fun toString(): String {
         return "bech32 : ${this.address}\nhuman: ${this.hrp} \nbytes"
     }
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (javaClass != other?.javaClass) return false
+
+        other as Bech32Data
+
+        if (hrp != other.hrp) return false
+        if (!fiveBitData.contentEquals(other.fiveBitData)) return false
+        if (!data.contentEquals(other.data)) return false
+        if (address != other.address) return false
+        if (!checksum.contentEquals(other.checksum)) return false
+
+        return true
+    }
+
+    override fun hashCode(): Int {
+        var result = hrp.hashCode()
+        result = 31 * result + fiveBitData.contentHashCode()
+        result = 31 * result + data.contentHashCode()
+        result = 31 * result + address.hashCode()
+        result = 31 * result + checksum.contentHashCode()
+        return result
+    }
 }
 
 /**
@@ -80,32 +95,32 @@ class Bech32 {
 
     companion object {
         const val CHECKSUM_SIZE = 6
-        const val MIN_VALID_LENGTH = 8
-        const val MAX_VALID_LENGTH = 90
+        private const val MIN_VALID_LENGTH = 8
+        private const val MAX_VALID_LENGTH = 90
         const val MIN_VALID_CODEPOINT = 33
-        const val MAX_VALID_CODEPOINT = 126
+        private const val MAX_VALID_CODEPOINT = 126
 
         const val charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
-        val gen = intArrayOf(0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3)
+        private val gen = intArrayOf(0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3)
 
         fun generateFakeSegwitAddress(reservePub: String?, addr: String): List<String> {
-            if (reservePub == null || reservePub.isEmpty()) return listOf<String>()
+            if (reservePub == null || reservePub.isEmpty()) return listOf()
             val pub = CyptoUtils.decodeCrock(reservePub)
             if (pub.size != 32) return listOf()
 
-            val first_rnd = pub.copyOfRange(0,4)
-            val second_rnd = pub.copyOfRange(0,4)
+            val firstRnd = pub.copyOfRange(0, 4)
+            val secondRnd = pub.copyOfRange(0, 4)
 
-            first_rnd[0] = first_rnd[0].and(0b0111_1111);
-            second_rnd[0] = second_rnd[0].or(0b1000_0000.toByte());
+            firstRnd[0] = firstRnd[0].and(0b0111_1111)
+            secondRnd[0] = secondRnd[0].or(0b1000_0000.toByte())
 
-            val first_part = ByteArray(20);
-            first_rnd.copyInto( first_part, 0, 0, 4)
-            pub.copyInto( first_part, 4, 0, 16)
+            val firstPart = ByteArray(20)
+            firstRnd.copyInto(firstPart, 0, 0, 4)
+            pub.copyInto(firstPart, 4, 0, 16)
 
-            val second_part = ByteArray(20);
-            second_rnd.copyInto( second_part, 0, 0, 4)
-            pub.copyInto( second_part, 4, 16, 32)
+            val secondPart = ByteArray(20)
+            secondRnd.copyInto(secondPart, 0, 0, 4)
+            pub.copyInto(secondPart, 4, 16, 32)
 
             val zero = ByteArray(1)
             zero[0] = 0
@@ -117,8 +132,8 @@ class Bech32 {
             }
 
             return listOf(
-                Bech32Data(hrp, zero + convertBits(first_part, 8, 5, true)).address,
-                Bech32Data(hrp, zero + convertBits(second_part, 8, 5, true)).address,
+                Bech32Data(hrp, zero + convertBits(firstPart, 8, 5, true)).address,
+                Bech32Data(hrp, zero + convertBits(secondPart, 8, 5, true)).address,
             )
         }
 
@@ -126,22 +141,31 @@ class Bech32 {
          * Decodes a Bech32 String
          */
         fun decode(bech32: String): Bech32Data {
-            require(bech32.length >= MIN_VALID_LENGTH && bech32.length <= MAX_VALID_LENGTH) { "invalid bech32 string length" }
-            require(bech32.toCharArray().none { c -> c.toInt() < MIN_VALID_CODEPOINT || c.toInt() > MAX_VALID_CODEPOINT })
-            { "invalid character in bech32: ${bech32.toCharArray().map { c -> c.toInt() }
-                .filter { c -> c.toInt() < MIN_VALID_CODEPOINT || c.toInt() > MAX_VALID_CODEPOINT }}" }
+            require(bech32.length in MIN_VALID_LENGTH..MAX_VALID_LENGTH) { "invalid bech32 string length" }
+            require(bech32.toCharArray()
+                .none { c -> c.code < MIN_VALID_CODEPOINT || c.code > MAX_VALID_CODEPOINT })
+            {
+                "invalid character in bech32: ${
+                    bech32.toCharArray().map { c -> c.code }
+                        .filter { c -> c < MIN_VALID_CODEPOINT || c > MAX_VALID_CODEPOINT }
+                }"
+            }
 
-            require(bech32.equals(bech32.toLowerCase()) || bech32.equals(bech32.toUpperCase()))
+            require(bech32 == bech32.lowercase(ROOT) || bech32 == bech32.uppercase(ROOT))
             { "bech32 must be either all upper or lower case" }
-            require(bech32.substring(1).dropLast(CHECKSUM_SIZE).contains('1')) { "invalid index of '1'" }
+            require(bech32.substring(1).dropLast(CHECKSUM_SIZE)
+                .contains('1')) { "invalid index of '1'" }
 
-            val hrp = bech32.substringBeforeLast('1').toLowerCase()
-            val dataString = bech32.substringAfterLast('1').toLowerCase()
+            val hrp = bech32.substringBeforeLast('1').lowercase(ROOT)
+            val dataString = bech32.substringAfterLast('1').lowercase(ROOT)
 
-            require(dataString.toCharArray().all { c -> charset.contains(c) }) { "invalid data encoding character in bech32"}
+            require(dataString.toCharArray()
+                .all { c -> charset.contains(c) }) { "invalid data encoding character in bech32" }
 
             val dataBytes = dataString.map { c -> charset.indexOf(c).toByte() }.toByteArray()
-            val checkBytes = dataString.takeLast(CHECKSUM_SIZE).map { c -> charset.indexOf(c).toByte() }.toByteArray()
+            val checkBytes =
+                dataString.takeLast(CHECKSUM_SIZE).map { c -> charset.indexOf(c).toByte() }
+                    .toByteArray()
 
             val actualSum = checksum(hrp, dataBytes.dropLast(CHECKSUM_SIZE).toTypedArray())
             require(1 == polymod(expandHrp(hrp).plus(dataBytes.map { d -> d.toInt() }))) { "checksum failed: $checkBytes != $actualSum" }
@@ -154,10 +178,10 @@ class Bech32 {
          * This process is used to convert from base64 (from 8) to base32 (to 5) or the inverse.
          */
         fun convertBits(data: ByteArray, fromBits: Int, toBits: Int, pad: Boolean): ByteArray {
-            require (fromBits in 1..8 && toBits in 1..8) { "only bit groups between 1 and 8 are supported"}
+            require(fromBits in 1..8 && toBits in 1..8) { "only bit groups between 1 and 8 are supported" }
 
             // resulting bytes with each containing the toBits bits from the input set.
-            var regrouped = arrayListOf<Byte>()
+            val regrouped = arrayListOf<Byte>()
 
             var nextByte = 0.toUByte()
             var filledBits = 0
@@ -174,8 +198,9 @@ class Bech32 {
                     val remainToBits = toBits - filledBits
 
                     // we extract the remaining bits unless that is more than we need.
-                    val toExtract = remainFromBits.takeUnless { remainToBits < remainFromBits } ?: remainToBits
-                    check(toExtract >= 0) { "extract should be positive"}
+                    val toExtract =
+                        remainFromBits.takeUnless { remainToBits < remainFromBits } ?: remainToBits
+                    check(toExtract >= 0) { "extract should be positive" }
 
                     // move existing bits to the left to make room for bits toExtract, copy in bits to extract
                     nextByte = (nextByte shl toExtract) or (b shr (8 - toExtract))
@@ -218,24 +243,24 @@ class Bech32 {
          * Calculates a bech32 checksum based on BIP 173 specification
          */
         fun checksum(hrp: String, data: Array<Byte>): ByteArray {
-            var values = expandHrp(hrp)
+            val values = expandHrp(hrp)
                 .plus(data.map { d -> d.toInt() })
-                .plus(Array<Int>(6){ _ -> 0}.toIntArray())
+                .plus(Array(6) { 0 }.toIntArray())
 
-            var poly = polymod(values) xor 1
+            val poly = polymod(values) xor 1
 
             return (0..5).map {
-                ((poly shr (5 * (5-it))) and 31).toByte()
+                ((poly shr (5 * (5 - it))) and 31).toByte()
             }.toByteArray()
         }
 
         /**
          * Expands the human readable prefix per BIP173 for Checksum encoding
          */
-        fun expandHrp(hrp: String) =
-            hrp.map { c -> c.toInt() shr 5 }
+        private fun expandHrp(hrp: String) =
+            hrp.map { c -> c.code shr 5 }
                 .plus(0)
-                .plus(hrp.map { c -> c.toInt() and 31 })
+                .plus(hrp.map { c -> c.code and 31 })
                 .toIntArray()
 
         /**
@@ -243,9 +268,9 @@ class Bech32 {
          */
         fun polymod(values: IntArray): Int {
             var chk = 1
-            return values.map {
-                var b = chk shr 25
-                chk = ((chk and 0x1ffffff) shl 5) xor it
+            return values.map { num ->
+                val b = chk shr 25
+                chk = ((chk and 0x1ffffff) shl 5) xor num
                 (0..4).map {
                     if (((b shr it) and 1) == 1) {
                         chk = chk xor gen[it]