internal/era: random access to header and receipts (ethereum#31544)

Co-authored-by: lightclient <lightclient@protonmail.com>

Add GetHeaderByNumber and GetReceiptsByNumber to allow more efficient API request filling from Era files.

Author: s1na

internal/era/e2store/e2store.go

@@ -219,3 +219,15 @@ func (r *Reader) FindAll(want uint16) ([]*Entry, error) {
 		off += int64(headerSize + length)
 	}
 }
+
+// SkipN skips `n` entries starting from `offset` and returns the new offset.
+func (r *Reader) SkipN(offset int64, n uint64) (int64, error) {
+	for i := uint64(0); i < n; i++ {
+		length, err := r.LengthAt(offset)
+		if err != nil {
+			return 0, err
+		}
+		offset += length
+	}
+	return offset, nil
+}

internal/era/era.go

@@ -70,7 +70,7 @@ func ReadDir(dir, network string) ([]string, error) {
 		}
 		parts := strings.Split(entry.Name(), "-")
 		if len(parts) != 3 || parts[0] != network {
-			// invalid era1 filename, skip
+			// Invalid era1 filename, skip.
 			continue
 		}
 		if epoch, err := strconv.ParseUint(parts[1], 10, 64); err != nil {
@@ -126,6 +126,29 @@ func (e *Era) Close() error {
 	return e.f.Close()
 }
 
+// GetHeaderByNumber returns the header for the given block number.
+func (e *Era) GetHeaderByNumber(num uint64) (*types.Header, error) {
+	if e.m.start > num || e.m.start+e.m.count <= num {
+		return nil, errors.New("out-of-bounds")
+	}
+	off, err := e.readOffset(num)
+	if err != nil {
+		return nil, err
+	}
+
+	// Read and decompress header.
+	r, _, err := newSnappyReader(e.s, TypeCompressedHeader, off)
+	if err != nil {
+		return nil, err
+	}
+	var header types.Header
+	if err := rlp.Decode(r, &header); err != nil {
+		return nil, err
+	}
+	return &header, nil
+}
+
+// GetBlockByNumber returns the block for the given block number.
 func (e *Era) GetBlockByNumber(num uint64) (*types.Block, error) {
 	if e.m.start > num || e.m.start+e.m.count <= num {
 		return nil, errors.New("out-of-bounds")
@@ -154,6 +177,34 @@ func (e *Era) GetBlockByNumber(num uint64) (*types.Block, error) {
 	return types.NewBlockWithHeader(&header).WithBody(body), nil
 }
 
+// GetReceiptsByNumber returns the receipts for the given block number.
+func (e *Era) GetReceiptsByNumber(num uint64) (types.Receipts, error) {
+	if e.m.start > num || e.m.start+e.m.count <= num {
+		return nil, errors.New("out-of-bounds")
+	}
+	off, err := e.readOffset(num)
+	if err != nil {
+		return nil, err
+	}
+
+	// Skip over header and body.
+	off, err = e.s.SkipN(off, 2)
+	if err != nil {
+		return nil, err
+	}
+
+	// Read and decompress receipts.
+	r, _, err := newSnappyReader(e.s, TypeCompressedReceipts, off)
+	if err != nil {
+		return nil, err
+	}
+	var receipts types.Receipts
+	if err := rlp.Decode(r, &receipts); err != nil {
+		return nil, err
+	}
+	return receipts, nil
+}
+
 // Accumulator reads the accumulator entry in the Era1 file.
 func (e *Era) Accumulator() (common.Hash, error) {
 	entry, err := e.s.Find(TypeAccumulator)
@@ -187,13 +238,10 @@ func (e *Era) InitialTD() (*big.Int, error) {
 	}
 	off += n
 
-	// Skip over next two records.
-	for i := 0; i < 2; i++ {
-		length, err := e.s.LengthAt(off)
-		if err != nil {
-			return nil, err
-		}
-		off += length
+	// Skip over header and body.
+	off, err = e.s.SkipN(off, 2)
+	if err != nil {
+		return nil, err
 	}
 
 	// Read total difficulty after first block.

internal/era/era_test.go

@@ -18,12 +18,15 @@ package era
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"math/big"
 	"os"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/rlp"
 )
 
 type testchain struct {
@@ -48,9 +51,9 @@ func TestEra1Builder(t *testing.T) {
 		chain   = testchain{}
 	)
 	for i := 0; i < 128; i++ {
-		chain.headers = append(chain.headers, []byte{byte('h'), byte(i)})
-		chain.bodies = append(chain.bodies, []byte{byte('b'), byte(i)})
-		chain.receipts = append(chain.receipts, []byte{byte('r'), byte(i)})
+		chain.headers = append(chain.headers, mustEncode(&types.Header{Number: big.NewInt(int64(i))}))
+		chain.bodies = append(chain.bodies, mustEncode(&types.Body{Transactions: []*types.Transaction{types.NewTransaction(0, common.Address{byte(i)}, nil, 0, nil, nil)}}))
+		chain.receipts = append(chain.receipts, mustEncode(&types.Receipts{{CumulativeGasUsed: uint64(i)}}))
 		chain.tds = append(chain.tds, big.NewInt(int64(i)))
 	}
 
@@ -91,13 +94,25 @@ func TestEra1Builder(t *testing.T) {
 			t.Fatalf("unexpected error %v", it.Error())
 		}
 		// Check headers.
-		header, err := io.ReadAll(it.Header)
+		rawHeader, err := io.ReadAll(it.Header)
+		if err != nil {
+			t.Fatalf("error reading header from iterator: %v", err)
+		}
+		if !bytes.Equal(rawHeader, chain.headers[i]) {
+			t.Fatalf("mismatched header: want %s, got %s", chain.headers[i], rawHeader)
+		}
+		header, err := e.GetHeaderByNumber(i)
 		if err != nil {
 			t.Fatalf("error reading header: %v", err)
 		}
-		if !bytes.Equal(header, chain.headers[i]) {
-			t.Fatalf("mismatched header: want %s, got %s", chain.headers[i], header)
+		encHeader, err := rlp.EncodeToBytes(header)
+		if err != nil {
+			t.Fatalf("error encoding header: %v", err)
+		}
+		if !bytes.Equal(encHeader, chain.headers[i]) {
+			t.Fatalf("mismatched header: want %s, got %s", chain.headers[i], encHeader)
 		}
+
 		// Check bodies.
 		body, err := io.ReadAll(it.Body)
 		if err != nil {
@@ -106,13 +121,25 @@ func TestEra1Builder(t *testing.T) {
 		if !bytes.Equal(body, chain.bodies[i]) {
 			t.Fatalf("mismatched body: want %s, got %s", chain.bodies[i], body)
 		}
+
 		// Check receipts.
-		receipts, err := io.ReadAll(it.Receipts)
+		rawReceipts, err := io.ReadAll(it.Receipts)
+		if err != nil {
+			t.Fatalf("error reading receipts from iterator: %v", err)
+		}
+		if !bytes.Equal(rawReceipts, chain.receipts[i]) {
+			t.Fatalf("mismatched receipts: want %s, got %s", chain.receipts[i], rawReceipts)
+		}
+		receipts, err := e.GetReceiptsByNumber(i)
 		if err != nil {
 			t.Fatalf("error reading receipts: %v", err)
 		}
-		if !bytes.Equal(receipts, chain.receipts[i]) {
-			t.Fatalf("mismatched receipts: want %s, got %s", chain.receipts[i], receipts)
+		encReceipts, err := rlp.EncodeToBytes(receipts)
+		if err != nil {
+			t.Fatalf("error encoding receipts: %v", err)
+		}
+		if !bytes.Equal(encReceipts, chain.receipts[i]) {
+			t.Fatalf("mismatched receipts: want %s, got %s", chain.receipts[i], encReceipts)
 		}
 
 		// Check total difficulty.
@@ -144,3 +171,11 @@ func TestEraFilename(t *testing.T) {
 		}
 	}
 }
+
+func mustEncode(obj any) []byte {
+	b, err := rlp.EncodeToBytes(obj)
+	if err != nil {
+		panic(fmt.Sprintf("failed in encode obj: %v", err))
+	}
+	return b
+}