problem: zero bytes when requesting block with tx

src/main/kotlin/io/emeraldpay/dshackle/upstream/ethereum/EthereumFullBlocksReader.kt

@@ -81,7 +81,7 @@ class EthereumFullBlocksReader(
                 } else {
                     joinWithTransactions(blockSplit.t1, blockSplit.t2, Flux.fromIterable(transactionsData).map { it.json!! })
                             .reduce(ByteBuffer.allocate(block.json.size * 4), accumulate)
-                            .map { it.flip().array() }
+                            .map(this@EthereumFullBlocksReader::extractContent)
                             .map { json ->
                                 BlockContainer(block.height, block.hash, block.difficulty, block.timestamp,
                                         true,
@@ -95,6 +95,13 @@ class EthereumFullBlocksReader(
         }
     }
 
+    fun extractContent(it: ByteBuffer): ByteArray {
+        val pos = it.position()
+        val result = ByteArray(pos)
+        it.flip().get(result, 0, pos)
+        return result
+    }
+
     fun splitByTransactions(json: ByteArray): Tuple2<ByteArray, ByteArray> {
         //TODO find a lib that implements Knuth-Morris-Pratt Pattern Matching Algorithm for byte arrays
         // and reimplement without making a string copy from bytes

src/test/groovy/io/emeraldpay/dshackle/upstream/ethereum/EthereumFullBlocksReaderSpec.groovy

@@ -15,7 +15,6 @@
  */
 package io.emeraldpay.dshackle.upstream.ethereum
 
-import com.fasterxml.jackson.core.PrettyPrinter
 import com.fasterxml.jackson.core.util.DefaultPrettyPrinter
 import com.fasterxml.jackson.databind.ObjectMapper
 import io.emeraldpay.dshackle.Global
@@ -32,8 +31,10 @@ import io.infinitape.etherjar.domain.TransactionId
 import io.infinitape.etherjar.rpc.json.BlockJson
 import io.infinitape.etherjar.rpc.json.TransactionJson
 import io.infinitape.etherjar.rpc.json.TransactionRefJson
+import org.apache.commons.codec.binary.Hex
 import spock.lang.Specification
 
+import java.nio.ByteBuffer
 import java.time.Instant
 
 class EthereumFullBlocksReaderSpec extends Specification {
@@ -374,4 +375,42 @@ class EthereumFullBlocksReaderSpec extends Specification {
         new String(act.getT1()).endsWith('"transactions":[')
         new String(act.getT2()) == ']}'
     }
+
+    def "Extract from buffer without trailing zeroes"() {
+        setup:
+        def reader = new EthereumFullBlocksReader(Stub(Reader), Stub(Reader))
+        when:
+        def buffer = ByteBuffer.allocate(8)
+        buffer.put(1 as byte)
+        buffer.put(2 as byte)
+        def act = reader.extractContent(buffer)
+        then:
+        act.size() == 2
+        Hex.encodeHexString(act) == "0102"
+
+        when:
+        buffer = ByteBuffer.allocate(8)
+        buffer.put(1 as byte)
+        buffer.put(2 as byte)
+        buffer.put(3 as byte)
+        act = reader.extractContent(buffer)
+        then:
+        act.size() == 3
+        Hex.encodeHexString(act) == "010203"
+
+        when:
+        buffer = ByteBuffer.allocate(8)
+        buffer.put(1 as byte)
+        buffer.put(2 as byte)
+        buffer.put(3 as byte)
+        buffer.put(4 as byte)
+        buffer.put(5 as byte)
+        buffer.put(6 as byte)
+        buffer.put(7 as byte)
+        buffer.put(8 as byte)
+        act = reader.extractContent(buffer)
+        then:
+        act.size() == 8
+        Hex.encodeHexString(act) == "0102030405060708"
+    }
 }