From 434f410f7605196c8f2c3ac0ce1073b5002bf2ef Mon Sep 17 00:00:00 2001
From: mikeplotean <mike@walt.id>
Date: Wed, 5 Feb 2025 22:01:24 +0200
Subject: [PATCH] fix: revocation policy encoded list decoding - condider bit
 order left-to-right

---
 .../policies/policies/RevocationPolicy.jvm.kt | 25 +++++++++++++------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/waltid-libraries/credentials/waltid-verification-policies/src/jvmMain/kotlin/id/walt/policies/policies/RevocationPolicy.jvm.kt b/waltid-libraries/credentials/waltid-verification-policies/src/jvmMain/kotlin/id/walt/policies/policies/RevocationPolicy.jvm.kt
index 066defa45..46dde112f 100644
--- a/waltid-libraries/credentials/waltid-verification-policies/src/jvmMain/kotlin/id/walt/policies/policies/RevocationPolicy.jvm.kt
+++ b/waltid-libraries/credentials/waltid-verification-policies/src/jvmMain/kotlin/id/walt/policies/policies/RevocationPolicy.jvm.kt
@@ -1,5 +1,6 @@
 package id.walt.policies.policies
 
+import id.walt.policies.policies.StreamUtils.getBitValue
 import io.github.oshai.kotlinlogging.KotlinLogging
 import io.ktor.client.*
 import io.ktor.client.plugins.contentnegotiation.*
@@ -100,20 +101,30 @@ object StreamUtils {
     }
 
     private fun extractBitValue(bytes: ByteArray, index: ULong, bitSize: UInt): List<Char> {
-        val bitSet = BitSet.valueOf(bytes)
+        val bits = bytes.toBitSequence()
         val bitStart = index * bitSize % BITS_PER_BYTE
-        val result = mutableListOf<Char>()
-        for (i in bitStart..<bitStart + bitSize) {
-            val b = bitSet[i.toInt()].takeIf { it }?.let { 1 } ?: 0
-            result.add(b.digitToChar())
+        val bitSet = bits.drop(bitStart.toInt())
+        var b = 0u
+        val result = mutableListOf<Boolean>()
+        while (b++ < bitSize) {
+            result.add(bitSet.iterator().next())
         }
-        return result
+        return result.map { if (it) '1' else '0' }
     }
 }
 
 fun get(bitstring: String, idx: ULong? = null, bitSize: Int = 1) =
-    idx?.let { StreamUtils.getBitValue(GZIPInputStream(Base64Utils.decode(bitstring).inputStream()), it, bitSize) }
+    idx?.let { getBitValue(GZIPInputStream(Base64Utils.decode(bitstring).inputStream()), it, bitSize) }
 
 fun isBinaryValue(value: List<Char>) = setOf('0', '1').let { valid ->
     value.all { it in valid }
+}
+
+fun ByteArray.toBitSequence(): Sequence<Boolean> = sequence {
+    for (byte in this@toBitSequence) {
+        for (i in 7 downTo 0) { // Iterate through bits from left to right (MSB to LSB)
+            val bit = (byte.toInt() shr i) and 1 == 1 // Extract the i-th bit
+            yield(bit)
+        }
+    }
 }
\ No newline at end of file