bring in khatru and eventstore.

eventstore/mmm/betterbinary/codec.go

@@ -0,0 +1,139 @@
+package betterbinary
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"math"
+
+	"github.com/nbd-wtf/go-nostr"
+)
+
+const (
+	MaxKind         = math.MaxUint16
+	MaxCreatedAt    = math.MaxUint32
+	MaxContentSize  = math.MaxUint16
+	MaxTagCount     = math.MaxUint16
+	MaxTagItemCount = math.MaxUint8
+	MaxTagItemSize  = math.MaxUint16
+)
+
+func Measure(evt nostr.Event) int {
+	n := 135 // static base
+
+	n += 2 + // tag section length
+		2 + // number of tags
+		len(evt.Tags)*3 // each tag offset + each tag item count
+	for _, tag := range evt.Tags {
+		n += len(tag) * 2 // item length for each item in this tag
+		for _, item := range tag {
+			n += len(item) // actual tag item
+		}
+	}
+
+	// content length and actual content
+	n += 2 + len(evt.Content)
+
+	return n
+}
+
+func Marshal(evt nostr.Event, buf []byte) error {
+	buf[0] = 0
+
+	if evt.Kind > MaxKind {
+		return fmt.Errorf("kind is too big: %d, max is %d", evt.Kind, MaxKind)
+	}
+	binary.LittleEndian.PutUint16(buf[1:3], uint16(evt.Kind))
+
+	if evt.CreatedAt > MaxCreatedAt {
+		return fmt.Errorf("created_at is too big: %d, max is %d", evt.CreatedAt, MaxCreatedAt)
+	}
+	binary.LittleEndian.PutUint32(buf[3:7], uint32(evt.CreatedAt))
+
+	hex.Decode(buf[7:39], []byte(evt.ID))
+	hex.Decode(buf[39:71], []byte(evt.PubKey))
+	hex.Decode(buf[71:135], []byte(evt.Sig))
+
+	tagBase := 135
+	// buf[135:137] (tagsSectionLength) will be set later when we know the absolute size of the tags section
+
+	ntags := len(evt.Tags)
+	if ntags > MaxTagCount {
+		return fmt.Errorf("can't encode too many tags: %d, max is %d", ntags, MaxTagCount)
+	}
+	binary.LittleEndian.PutUint16(buf[137:139], uint16(ntags))
+
+	tagOffset := 2 + 2 + ntags*2
+	for t, tag := range evt.Tags {
+		binary.LittleEndian.PutUint16(buf[tagBase+2+2+t*2:], uint16(tagOffset))
+
+		itemCount := len(tag)
+		if itemCount > MaxTagItemCount {
+			return fmt.Errorf("can't encode a tag with so many items: %d, max is %d", itemCount, MaxTagItemCount)
+		}
+		buf[tagBase+tagOffset] = uint8(itemCount)
+
+		itemOffset := 1
+		for _, item := range tag {
+			itemSize := len(item)
+			if itemSize > MaxTagItemSize {
+				return fmt.Errorf("tag item is too large: %d, max is %d", itemSize, MaxTagItemSize)
+			}
+
+			binary.LittleEndian.PutUint16(buf[tagBase+tagOffset+itemOffset:], uint16(itemSize))
+			copy(buf[tagBase+tagOffset+itemOffset+2:], []byte(item))
+			itemOffset += 2 + len(item)
+		}
+		tagOffset += itemOffset
+	}
+
+	tagsSectionLength := tagOffset
+	binary.LittleEndian.PutUint16(buf[tagBase:], uint16(tagsSectionLength))
+
+	// content
+	if contentLength := len(evt.Content); contentLength > MaxContentSize {
+		return fmt.Errorf("content is too large: %d, max is %d", contentLength, MaxContentSize)
+	} else {
+		binary.LittleEndian.PutUint16(buf[tagBase+tagsSectionLength:], uint16(contentLength))
+	}
+	copy(buf[tagBase+tagsSectionLength+2:], []byte(evt.Content))
+
+	return nil
+}
+
+func Unmarshal(data []byte, evt *nostr.Event) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("failed to decode binary: %v", r)
+		}
+	}()
+
+	evt.Kind = int(binary.LittleEndian.Uint16(data[1:3]))
+	evt.CreatedAt = nostr.Timestamp(binary.LittleEndian.Uint32(data[3:7]))
+	evt.ID = hex.EncodeToString(data[7:39])
+	evt.PubKey = hex.EncodeToString(data[39:71])
+	evt.Sig = hex.EncodeToString(data[71:135])
+
+	const tagbase = 135
+	tagsSectionLength := binary.LittleEndian.Uint16(data[tagbase:])
+	ntags := binary.LittleEndian.Uint16(data[tagbase+2:])
+	evt.Tags = make(nostr.Tags, ntags)
+	for t := range evt.Tags {
+		offset := binary.LittleEndian.Uint16(data[tagbase+4+t*2:])
+		nitems := int(data[tagbase+offset])
+		tag := make(nostr.Tag, nitems)
+
+		curr := tagbase + offset + 1
+		for i := range tag {
+			length := binary.LittleEndian.Uint16(data[curr:])
+			tag[i] = string(data[curr+2 : curr+2+length])
+			curr += 2 + length
+		}
+		evt.Tags[t] = tag
+	}
+
+	contentLength := binary.LittleEndian.Uint16(data[tagbase+tagsSectionLength:])
+	evt.Content = string(data[tagbase+tagsSectionLength+2 : tagbase+tagsSectionLength+2+contentLength])
+
+	return err
+}