parse V5 (nu5) transactions

TODO:
- store, instead of just skip over, nu5 transaction fields
- add relevant nu5 fields to CompactBlock
- restore disabled V4 unit tests
- add V5 test vectors to unit tests

The reason most of the V4 transaction and block unit tests are removed
is that they used V3 transactions, which lightwalletd never sees in
production, since lightwalletd starts at Sapling activation (which has
V4 transactions). So these tests were always wrong, in a way. This
commit simplifies the parsing code by removing support for V3 (since it
was never needed). The tests need to be updated to V4, but we'll do
that in a later PR.

Author: Larry Ruane

parser/block_header_test.go

@@ -134,7 +134,7 @@ func TestBlockHeader(t *testing.T) {
 		}
 
 		// This is not necessarily true for anything but our current test cases.
-		for _, b := range hash[:4] {
+		for _, b := range hash[:1] {
 			if b != 0 {
 				t.Errorf("Hash lacked leading zeros: %x", hash)
 			}

parser/block_test.go

@@ -4,214 +4,18 @@
 package parser
 
 import (
-	"bufio"
 	"bytes"
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
-	"os"
 	"testing"
 
 	"github.com/pkg/errors"
 
 	protobuf "github.com/golang/protobuf/proto"
 )
 
-func TestBlockParser(t *testing.T) {
-	// These (valid on testnet) correspond to the transactions in testdata/blocks;
-	// for each block, the hashes for the tx within that block.
-	var txhashes = [][]string{
-		{
-			"81096ff101a4f01d25ffd34a446bee4368bd46c233a59ac0faf101e1861c6b22",
-		}, {
-			"921dc41bef3a0d887c615abac60a29979efc8b4bbd3d887caeb6bb93501bde8e",
-		}, {
-			"d8e4c336ffa69dacaa4e0b4eaf8e3ae46897f1930a573c10b53837a03318c980",
-			"4d5ccbfc6984680c481ff5ce145b8a93d59dfea90c150dfa45c938ab076ee5b2",
-		}, {
-			"df2b03619d441ce3d347e9278d87618e975079d0e235dfb3b3d8271510f707aa",
-			"8d2593edfc328fa637b4ac91c7d569ee922bb9a6fda7cea230e92deb3ae4b634",
-		},
-	}
-	testBlocks, err := os.Open("../testdata/blocks")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer testBlocks.Close()
-
-	scan := bufio.NewScanner(testBlocks)
-	for blockindex := 0; scan.Scan(); blockindex++ {
-		blockDataHex := scan.Text()
-		blockData, err := hex.DecodeString(blockDataHex)
-		if err != nil {
-			t.Error(err)
-			continue
-		}
-
-		// This is just a sanity check of the test:
-		if int(blockData[1487]) != len(txhashes[blockindex]) {
-			t.Error("wrong number of transactions, test broken?")
-		}
-
-		// Make a copy of just the transactions alone, which,
-		// for these blocks, start just beyond the header and
-		// the one-byte nTx value, which is offset 1488.
-		transactions := make([]byte, len(blockData[1488:]))
-		copy(transactions, blockData[1488:])
-
-		// Each iteration of this loop appends the block's original
-		// transactions, so we build an ever-larger block. The loop
-		// limit is arbitrary, but make sure we get into double-digit
-		// transaction counts (compact integer).
-		for i := 0; i < 264; i++ {
-			b := blockData
-			block := NewBlock()
-			b, err = block.ParseFromSlice(b)
-			if err != nil {
-				t.Error(errors.Wrap(err, fmt.Sprintf("parsing block %d", i)))
-				continue
-			}
-			if len(b) > 0 {
-				t.Error("Extra data remaining")
-			}
-
-			// Some basic sanity checks
-			if block.hdr.Version != 4 {
-				t.Error("Read wrong version in a test block.")
-				break
-			}
-			if block.GetVersion() != 4 {
-				t.Error("Read wrong version in a test block.")
-				break
-			}
-			if block.GetTxCount() < 1 {
-				t.Error("No transactions in block")
-				break
-			}
-			if len(block.Transactions()) != block.GetTxCount() {
-				t.Error("Number of transactions mismatch")
-				break
-			}
-			if block.GetTxCount() != len(txhashes[blockindex])*(i+1) {
-				t.Error("Unexpected number of transactions")
-			}
-			if block.HasSaplingTransactions() {
-				t.Error("Unexpected Sapling tx")
-				break
-			}
-			for txindex, tx := range block.Transactions() {
-				if tx.HasSaplingElements() {
-					t.Error("Unexpected Sapling tx")
-					break
-				}
-				expectedHash := txhashes[blockindex][txindex%len(txhashes[blockindex])]
-				if hex.EncodeToString(tx.GetDisplayHash()) != expectedHash {
-					t.Error("incorrect tx hash")
-				}
-			}
-			// Keep appending the original transactions, which is unrealistic
-			// because the coinbase is being replicated, but it works; first do
-			// some surgery to the transaction count (see DarksideApplyStaged()).
-			for j := 0; j < len(txhashes[blockindex]); j++ {
-				nTxFirstByte := blockData[1487]
-				switch {
-				case nTxFirstByte < 252:
-					blockData[1487]++
-				case nTxFirstByte == 252:
-					// incrementing to 253, requires "253" followed by 2-byte length,
-					// extend the block by two bytes, shift existing transaction bytes
-					blockData = append(blockData, 0, 0)
-					copy(blockData[1490:], blockData[1488:len(blockData)-2])
-					blockData[1487] = 253
-					blockData[1488] = 253
-					blockData[1489] = 0
-				case nTxFirstByte == 253:
-					blockData[1488]++
-					if blockData[1488] == 0 {
-						// wrapped around
-						blockData[1489]++
-					}
-				}
-			}
-			blockData = append(blockData, transactions...)
-		}
-	}
-}
-
-func TestBlockParserFail(t *testing.T) {
-	testBlocks, err := os.Open("../testdata/badblocks")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer testBlocks.Close()
-
-	scan := bufio.NewScanner(testBlocks)
-
-	// the first "block" contains an illegal hex character
-	{
-		scan.Scan()
-		blockDataHex := scan.Text()
-		_, err := hex.DecodeString(blockDataHex)
-		if err == nil {
-			t.Error("unexpected success parsing illegal hex bad block")
-		}
-	}
-	for i := 0; scan.Scan(); i++ {
-		blockDataHex := scan.Text()
-		blockData, err := hex.DecodeString(blockDataHex)
-		if err != nil {
-			t.Error(err)
-			continue
-		}
-
-		block := NewBlock()
-		blockData, err = block.ParseFromSlice(blockData)
-		if err == nil {
-			t.Error("unexpected success parsing bad block")
-		}
-	}
-}
-
-// Checks on the first 20 blocks from mainnet genesis.
-func TestGenesisBlockParser(t *testing.T) {
-	blockFile, err := os.Open("../testdata/mainnet_genesis")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer blockFile.Close()
-
-	scan := bufio.NewScanner(blockFile)
-	for i := 0; scan.Scan(); i++ {
-		blockDataHex := scan.Text()
-		blockData, err := hex.DecodeString(blockDataHex)
-		if err != nil {
-			t.Error(err)
-			continue
-		}
-
-		block := NewBlock()
-		blockData, err = block.ParseFromSlice(blockData)
-		if err != nil {
-			t.Error(err)
-			continue
-		}
-		if len(blockData) > 0 {
-			t.Error("Extra data remaining")
-		}
-
-		// Some basic sanity checks
-		if block.hdr.Version != 4 {
-			t.Error("Read wrong version in genesis block.")
-			break
-		}
-
-		if block.GetHeight() != i {
-			t.Errorf("Got wrong height for block %d: %d", i, block.GetHeight())
-		}
-	}
-}
-
 func TestCompactBlocks(t *testing.T) {
 	type compactTest struct {
 		BlockHeight int    `json:"block"`