faster signature verification by serializing directly into the sha with less allocations.

2026-04-23 20:31:57 -03:00
parent 696f377109
commit b899ef8865
6 changed files with 224 additions and 70 deletions
@@ -2,7 +2,9 @@ package nostr

 import (
 	"crypto/sha256"
+	"hash"
 	"strconv"
+	"unsafe"

 	"github.com/mailru/easyjson"
 	"github.com/templexxx/xhex"
@@ -26,10 +28,17 @@ func (evt Event) String() string {

 // GetID serializes and returns the event ID as a string.
 func (evt Event) GetID() ID {
-	return sha256.Sum256(evt.Serialize())
+	var id ID
+	evt.serializedHash(&id)
+	return id
 }

-// CheckID checks if the implied ID matches the given ID more efficiently.
+// SetID calculates and sets the id to the event in a single operation.
+func (evt *Event) SetID() {
+	evt.serializedHash(&evt.ID)
+}
+
+// CheckID checks if the implied ID matches the currently assigned ID.
 func (evt Event) CheckID() bool {
 	return evt.GetID() == evt.ID
 }
@@ -38,17 +47,56 @@ func (evt Event) CheckID() bool {
 func (evt Event) Serialize() []byte {
 	// the serialization process is just putting everything into a JSON array
 	// so the order is kept. See NIP-01
-	dst := make([]byte, 4+64, 100+len(evt.Content)+len(evt.Tags)*80)
+	dst := make([]byte, 0, 100+len(evt.Content)+len(evt.Tags)*80)
+	return evt.appendSerialized(dst)
+}

-	// the header portion is easy to serialize
-	// [0,"pubkey",created_at,kind,[
-	copy(dst, `[0,"`)
-	xhex.Encode(dst[4:4+64], evt.PubKey[:]) // there will always be such capacity
+var escTable [256]bool
+
+// pre-built escape sequences; index by the offending byte.
+var escSeq [256][2]byte
+
+// pre-built []byte slices for hash.Write calls (no per-call allocation).
+var escSlice [256][]byte
+
+var (
+	jsonQuote           = []byte{'"'}
+	serializedStart     = []byte(`[0,"`)
+	serializedPubkeyEnd = []byte(`",`)
+	serializedTagsEnd   = []byte("],")
+	serializedTagStart  = []byte{'['}
+	serializedTagEnd    = []byte{']'}
+	serializedComma     = []byte{','}
+	serializedEnd       = []byte{']'}
+)
+
+func init() {
+	for _, b := range []byte{'"', '\\', '\n', '\r', '\t'} {
+		escTable[b] = true
+	}
+
+	escSeq['"'] = [2]byte{'\\', '"'}
+	escSeq['\\'] = [2]byte{'\\', '\\'}
+	escSeq['\n'] = [2]byte{'\\', 'n'}
+	escSeq['\r'] = [2]byte{'\\', 'r'}
+	escSeq['\t'] = [2]byte{'\\', 't'}
+	for b, seq := range escSeq {
+		if escTable[b] {
+			escSlice[b] = seq[:]
+		}
+	}
+}
+
+func (evt Event) appendSerialized(dst []byte) []byte {
+	start := len(dst)
+	dst = append(dst, `[0,"`...)
+	dst = append(dst, make([]byte, 64)...)
+	xhex.Encode(dst[start+4:start+4+64], evt.PubKey[:])
 	dst = append(dst, `",`...)
-	dst = append(dst, strconv.FormatInt(int64(evt.CreatedAt), 10)...)
-	dst = append(dst, `,`...)
-	dst = append(dst, strconv.FormatUint(uint64(evt.Kind), 10)...)
-	dst = append(dst, `,`...)
+	dst = strconv.AppendInt(dst, int64(evt.CreatedAt), 10)
+	dst = append(dst, ',')
+	dst = strconv.AppendUint(dst, uint64(evt.Kind), 10)
+	dst = append(dst, ',')

 	// tags
 	dst = append(dst, '[')
@@ -62,15 +110,167 @@ func (evt Event) Serialize() []byte {
 			if i > 0 {
 				dst = append(dst, ',')
 			}
-			dst = escapeString(dst, s)
+			dst = appendJSONString(dst, s)
 		}
 		dst = append(dst, ']')
 	}
 	dst = append(dst, "],"...)

 	// content needs to be escaped in general as it is user generated.
-	dst = escapeString(dst, evt.Content)
+	dst = appendJSONString(dst, evt.Content)
 	dst = append(dst, ']')

 	return dst
 }
+
+func (evt Event) serializedHash(dst *ID) {
+	h := sha256.New()
+	h.Write(serializedStart)
+
+	var pubkeyHex [64]byte
+	xhex.Encode(pubkeyHex[:], evt.PubKey[:])
+	h.Write(pubkeyHex[:])
+	h.Write(serializedPubkeyEnd)
+
+	var numBuf [20]byte
+	b := strconv.AppendInt(numBuf[:0], int64(evt.CreatedAt), 10)
+	h.Write(b)
+	h.Write(serializedComma)
+	b = strconv.AppendUint(numBuf[:0], uint64(evt.Kind), 10)
+	h.Write(b)
+	h.Write(serializedComma)
+
+	h.Write(serializedTagStart)
+	for i, tag := range evt.Tags {
+		if i > 0 {
+			h.Write(serializedComma)
+		}
+		h.Write(serializedTagStart)
+		for j, s := range tag {
+			if j > 0 {
+				h.Write(serializedComma)
+			}
+			writeJSONString(h, s)
+		}
+		h.Write(serializedTagEnd)
+	}
+	h.Write(serializedTagsEnd)
+
+	writeJSONString(h, evt.Content)
+	h.Write(serializedEnd)
+
+	h.Sum((*dst)[:0])
+}
+
+// ── SWAR helper ──────────────────────────────────────────────────────────────
+
+// hasSpecial returns non-zero if any byte in w is one of: \t 0x09, \n 0x0A,
+// " 0x22, \ 0x5C. Uses the classic "hasvalue" bit-trick — no branches, no
+// memory, pure ALU. Works regardless of endianness because we only care
+// whether a match exists, not where.
+//
+//go:nosplit
+func hasSpecial(w uint64) bool {
+	match := func(w, v uint64) uint64 {
+		x := w ^ (0x0101010101010101 * v)
+		return (x - 0x0101010101010101) & ^x & 0x8080808080808080
+	}
+	return match(w, 0x09)|match(w, 0x0A)|match(w, 0x0D)|match(w, 0x22)|match(w, 0x5C) != 0
+}
+
+func appendJSONString(dst []byte, s string) []byte {
+	dst = append(dst, '"')
+
+	n := len(s)
+	if n == 0 {
+		return append(dst, '"')
+	}
+
+	base := uintptr(unsafe.Pointer(unsafe.StringData(s)))
+	start, i := 0, 0
+
+	// consume 8 bytes at a time;
+	// if the whole word is clean, advance without touching dst at all;
+	// but when a word is dirty, fall back to the byte loop only for that 8-byte window
+	for i+8 <= n {
+		w := *(*uint64)(unsafe.Pointer(base + uintptr(i)))
+		if hasSpecial(w) {
+			for end := i + 8; i < end; i++ {
+				if escTable[s[i]] {
+					// append everything since the start or the last time we did this up to here
+					dst = append(dst, s[start:i]...)
+
+					// append this special sequence
+					seq := escSeq[s[i]]
+					dst = append(dst, seq[0], seq[1])
+
+					// set this as a checkpoint
+					start = i + 1
+				}
+			}
+		} else {
+			i += 8
+		}
+	}
+
+	// scalar tail for the remaining <8 bytes (same logic used for the hasSpecial branch above)
+	for ; i < n; i++ {
+		if escTable[s[i]] {
+			dst = append(dst, s[start:i]...)
+			seq := escSeq[s[i]]
+			dst = append(dst, seq[0], seq[1])
+			start = i + 1
+		}
+	}
+
+	// add the remaining chunk (in a string without any specials this will add everything at once)
+	dst = append(dst, s[start:]...)
+
+	return append(dst, '"')
+}
+
+func writeJSONString(h hash.Hash, s string) {
+	h.Write(jsonQuote)
+
+	n := len(s)
+	if n == 0 {
+		h.Write(jsonQuote)
+		return
+	}
+
+	base := uintptr(unsafe.Pointer(unsafe.StringData(s)))
+	start, i := 0, 0
+
+	for i+8 <= n {
+		w := *(*uint64)(unsafe.Pointer(base + uintptr(i)))
+		// apply same logic as of appendJSONString()
+		if hasSpecial(w) {
+			for end := i + 8; i < end; i++ {
+				if escTable[s[i]] {
+					if i > start {
+						h.Write(unsafe.Slice(unsafe.StringData(s[start:i]), i-start))
+					}
+					h.Write(escSlice[s[i]])
+					start = i + 1
+				}
+			}
+		} else {
+			i += 8
+		}
+	}
+
+	for ; i < n; i++ {
+		if escTable[s[i]] {
+			if i > start {
+				h.Write(unsafe.Slice(unsafe.StringData(s[start:i]), i-start))
+			}
+			h.Write(escSlice[s[i]])
+			start = i + 1
+		}
+	}
+
+	if start < n {
+		h.Write(unsafe.Slice(unsafe.StringData(s[start:]), len(s)-start))
+	}
+	h.Write(jsonQuote)
+}