if unused, convert []byte to string without allocating and copying

dimkr · dimkr · commit 28ded3e31442 · 2025-11-23T19:40:09.000+02:00
diff --git a/ap/activity.go b/ap/activity.go
@@ -22,6 +22,8 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+
+	"github.com/dimkr/tootik/danger"
 )
 
 type ActivityType string
@@ -155,8 +157,7 @@ func (a *Activity) Scan(src any) error {
 }
 
 func (a *Activity) Value() (driver.Value, error) {
-	buf, err := json.Marshal(a)
-	return string(buf), err
+	return danger.MarshalJSON(a)
 }
 
 func (a *Activity) LogValue() slog.Value {
diff --git a/ap/actor.go b/ap/actor.go
@@ -20,6 +20,8 @@ import (
 	"database/sql/driver"
 	"encoding/json"
 	"fmt"
+
+	"github.com/dimkr/tootik/danger"
 )
 
 type ActorType string
@@ -71,6 +73,5 @@ func (a *Actor) Scan(src any) error {
 }
 
 func (a *Actor) Value() (driver.Value, error) {
-	buf, err := json.Marshal(a)
-	return string(buf), err
+	return danger.MarshalJSON(a)
 }
diff --git a/ap/attachment.go b/ap/attachment.go
@@ -20,6 +20,8 @@ import (
 	"database/sql/driver"
 	"encoding/json"
 	"fmt"
+
+	"github.com/dimkr/tootik/danger"
 )
 
 type AttachmentType string
@@ -50,6 +52,5 @@ func (a *Attachment) Scan(src any) error {
 }
 
 func (a *Attachment) Value() (driver.Value, error) {
-	buf, err := json.Marshal(a)
-	return string(buf), err
+	return danger.MarshalJSON(a)
 }
diff --git a/ap/audience.go b/ap/audience.go
@@ -21,6 +21,7 @@ import (
 	"encoding/json"
 	"fmt"
 
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/data"
 )
 
@@ -89,6 +90,5 @@ func (a *Audience) Scan(src any) error {
 }
 
 func (a *Audience) Value() (driver.Value, error) {
-	buf, err := json.Marshal(a)
-	return string(buf), err
+	return danger.MarshalJSON(a)
 }
diff --git a/ap/object.go b/ap/object.go
@@ -20,6 +20,8 @@ import (
 	"database/sql/driver"
 	"encoding/json"
 	"fmt"
+
+	"github.com/dimkr/tootik/danger"
 )
 
 type ObjectType string
@@ -85,6 +87,5 @@ func (o *Object) Scan(src any) error {
 }
 
 func (o *Object) Value() (driver.Value, error) {
-	buf, err := json.Marshal(o)
-	return string(buf), err
+	return danger.MarshalJSON(o)
 }
diff --git a/ap/time.go b/ap/time.go
@@ -1,5 +1,5 @@
 /*
-Copyright 2023, 2024 Dima Krasner
+Copyright 2023 - 2025 Dima Krasner
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -16,7 +16,11 @@ limitations under the License.
 
 package ap
 
-import "time"
+import (
+	"time"
+
+	"github.com/dimkr/tootik/danger"
+)
 
 // Time is a wrapper around [time.Time] with fallback if parsing of RFC3339 fails.
 type Time struct {
@@ -27,7 +31,7 @@ func (t *Time) UnmarshalJSON(b []byte) error {
 	err := t.Time.UnmarshalJSON(b)
 	// ugly hack for Threads
 	if err != nil && len(b) > 2 && b[0] == '"' && b[len(b)-1] == '"' {
-		t.Time, err = time.Parse("2006-01-02T15:04:05-0700", string(b[1:len(b)-1]))
+		t.Time, err = time.Parse("2006-01-02T15:04:05-0700", danger.String(b[1:len(b)-1]))
 	}
 	return err
 }
diff --git a/cmd/tootik/main.go b/cmd/tootik/main.go
@@ -37,6 +37,7 @@ import (
 	"github.com/dimkr/tootik/ap"
 	"github.com/dimkr/tootik/buildinfo"
 	"github.com/dimkr/tootik/cfg"
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/data"
 	"github.com/dimkr/tootik/fed"
 	"github.com/dimkr/tootik/front"
@@ -288,7 +289,7 @@ func main() {
 			ctx,
 			"insert into icons(name, buf) values($1, $2) on conflict(name) do update set buf = $2",
 			userName,
-			string(resized),
+			danger.String(resized),
 		); err != nil {
 			panic(err)
 		}
diff --git a/danger/danger.go b/danger/danger.go
@@ -0,0 +1,18 @@
+/*
+Copyright 2025 Dima Krasner
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package danger provides memory unsafe utilities.
+package danger
diff --git a/danger/json.go b/danger/json.go
@@ -14,14 +14,17 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package inbox
+package danger
 
 import "encoding/json"
 
-func marshal(v any) (string, error) {
+// MarshalJSON encodes a value to a JSON string.
+//
+// It uses [String] to avoid memory allocation and copying.
+func MarshalJSON(v any) (string, error) {
 	if b, err := json.Marshal(v); err != nil {
 		return "", err
 	} else {
-		return string(b), nil
+		return String(b), nil
 	}
 }
diff --git a/danger/string.go b/danger/string.go
@@ -0,0 +1,26 @@
+/*
+Copyright 2025 Dima Krasner
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package danger
+
+import "unsafe"
+
+// String casts a byte slice to a string without copying the underlying array.
+//
+// The caller must not modify b afterwards because this will change the returned string.
+func String(b []byte) string {
+	return unsafe.String(unsafe.SliceData(b), len(b))
+}
diff --git a/fed/inbox.go b/fed/inbox.go
@@ -29,6 +29,7 @@ import (
 	"strings"
 
 	"github.com/dimkr/tootik/ap"
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/data"
 	"github.com/dimkr/tootik/httpsig"
 	"github.com/dimkr/tootik/proof"
@@ -341,7 +342,7 @@ func (l *Listener) doHandleInbox(w http.ResponseWriter, r *http.Request, keys [2
 
 	var activity ap.Activity
 	if err := json.Unmarshal(rawActivity, &activity); err != nil {
-		slog.Warn("Failed to unmarshal activity", "body", string(rawActivity), "error", err)
+		slog.Warn("Failed to unmarshal activity", "body", danger.String(rawActivity), "error", err)
 		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
@@ -570,7 +571,7 @@ func (l *Listener) doHandleInbox(w http.ResponseWriter, r *http.Request, keys [2
 		`INSERT OR IGNORE INTO inbox (sender, activity, raw) VALUES (?, JSONB(?), ?)`,
 		sender.ID,
 		queued,
-		string(rawActivity),
+		danger.String(rawActivity),
 	); err != nil {
 		slog.Error("Failed to insert activity", "sender", sender.ID, "error", err)
 		w.WriteHeader(http.StatusInternalServerError)
diff --git a/fed/resolve.go b/fed/resolve.go
@@ -33,6 +33,7 @@ import (
 
 	"github.com/dimkr/tootik/ap"
 	"github.com/dimkr/tootik/cfg"
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/data"
 	"github.com/dimkr/tootik/httpsig"
 	"github.com/dimkr/tootik/lock"
@@ -533,7 +534,7 @@ func (r *Resolver) fetchActor(ctx context.Context, keys [2]httpsig.Key, host, pr
 	}
 	defer tx.Rollback()
 
-	bodyString := string(body)
+	bodyString := danger.String(body)
 
 	if _, err := tx.ExecContext(
 		ctx,
diff --git a/fed/send.go b/fed/send.go
@@ -30,6 +30,7 @@ import (
 	"github.com/dimkr/tootik/ap"
 	"github.com/dimkr/tootik/buildinfo"
 	"github.com/dimkr/tootik/cfg"
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/httpsig"
 )
 
@@ -115,7 +116,7 @@ func (s *sender) send(keys [2]httpsig.Key, req *http.Request, body []byte) (*htt
 			return resp, fmt.Errorf("failed to send request to %s: %d, %w", urlString, resp.StatusCode, err)
 		}
 
-		return resp, fmt.Errorf("failed to send request to %s: %d, %s", urlString, resp.StatusCode, string(body))
+		return resp, fmt.Errorf("failed to send request to %s: %d, %s", urlString, resp.StatusCode, danger.String(body))
 	}
 
 	// other servers may ignore the signature if the request includes a valid integrity proof
diff --git a/front/avatar.go b/front/avatar.go
@@ -23,6 +23,7 @@ import (
 	"time"
 
 	"github.com/dimkr/tootik/ap"
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/front/text"
 	"github.com/dimkr/tootik/icon"
 )
@@ -116,7 +117,7 @@ func (h *Handler) uploadAvatar(w text.Writer, r *Request, args ...string) {
 		r.Context,
 		"insert into icons(name, buf) values($1, $2) on conflict(name) do update set buf = $2",
 		r.User.PreferredUsername,
-		string(resized),
+		danger.String(resized),
 	); err != nil {
 		r.Log.Error("Failed to set avatar", "error", err)
 		w.Error()
diff --git a/front/gemini/gemini.go b/front/gemini/gemini.go
@@ -33,6 +33,7 @@ import (
 
 	"github.com/dimkr/tootik/ap"
 	"github.com/dimkr/tootik/cfg"
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/data"
 	"github.com/dimkr/tootik/front"
 	"github.com/dimkr/tootik/front/text/gmi"
@@ -154,7 +155,7 @@ func (gl *Listener) Handle(ctx context.Context, conn net.Conn) {
 	}
 
 	var err error
-	reqString := string(req[:total-2])
+	reqString := danger.String(req[:total-2])
 	r.URL, err = url.Parse(reqString)
 	if err != nil {
 		slog.Warn("Failed to parse request", "request", reqString, "error", err)
diff --git a/front/graph/bars.go b/front/graph/bars.go
@@ -18,8 +18,8 @@ limitations under the License.
 package graph
 
 import (
-	"bytes"
 	"fmt"
+	"strings"
 	"unicode"
 	"unicode/utf8"
 )
@@ -77,7 +77,7 @@ outer:
 
 	unit := float64(max) / 8
 
-	var w bytes.Buffer
+	var w strings.Builder
 
 	for i := range keys {
 		if keys[i] == "" {
diff --git a/front/input.go b/front/input.go
@@ -21,6 +21,7 @@ import (
 	"net/url"
 	"strconv"
 
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/front/text"
 )
 
@@ -103,5 +104,5 @@ func (h *Handler) readBody(w text.Writer, r *Request, args []string) (string, bo
 		return "", false
 	}
 
-	return string(buf), true
+	return danger.String(buf), true
 }
diff --git a/front/static/embed.go b/front/static/embed.go
@@ -25,6 +25,7 @@ import (
 	"text/template"
 
 	"github.com/dimkr/tootik/cfg"
+	"github.com/dimkr/tootik/danger"
 )
 
 type data struct {
@@ -92,7 +93,7 @@ func readDirectory(dir string) {
 			path = fmt.Sprintf("/%s/%s", dir, base)
 		}
 
-		tmpl, err := template.New(path).Parse(string(content))
+		tmpl, err := template.New(path).Parse(danger.String(content))
 		if err != nil {
 			panic(err)
 		}
diff --git a/front/text/plain/convert.go b/front/text/plain/convert.go
@@ -27,6 +27,7 @@ import (
 	"strings"
 
 	"github.com/dimkr/tootik/ap"
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/data"
 	tokenizer "golang.org/x/net/html"
 )
@@ -90,7 +91,7 @@ func fromHTML(text string) (string, data.OrderedMap[string, string], error) {
 
 		case tokenizer.EndTagToken:
 			tagBytes, _ := tok.TagName()
-			tag := string(tagBytes)
+			tag := danger.String(tagBytes)
 
 			if len(openTags) > 0 && tag == openTags[len(openTags)-1] {
 				openTags = openTags[:len(openTags)-1]
@@ -142,7 +143,7 @@ func fromHTML(text string) (string, data.OrderedMap[string, string], error) {
 
 		case tokenizer.StartTagToken, tokenizer.SelfClosingTagToken:
 			tagBytes, hasAttrs := tok.TagName()
-			tag := string(tagBytes)
+			tag := danger.String(tagBytes)
 
 			if tag == "br" {
 				w.WriteByte('\n')
@@ -205,8 +206,8 @@ func fromHTML(text string) (string, data.OrderedMap[string, string], error) {
 				for {
 					attrBytes, value, more := tok.TagAttr()
 
-					attr := string(attrBytes)
-					valueString := string(value)
+					attr := danger.String(attrBytes)
+					valueString := danger.String(value)
 					if tt == tokenizer.StartTagToken && tag == "span" && attr == "class" {
 						if valueString == "invisible" {
 							invisibleDepth = len(openTags)
diff --git a/inbox/accept.go b/inbox/accept.go
@@ -22,6 +22,7 @@ import (
 	"fmt"
 
 	"github.com/dimkr/tootik/ap"
+	"github.com/dimkr/tootik/danger"
 	"github.com/dimkr/tootik/httpsig"
 	"github.com/dimkr/tootik/proof"
 )
@@ -59,7 +60,7 @@ func (inbox *Inbox) accept(ctx context.Context, followed *ap.Actor, key httpsig.
 		}
 	}
 
-	s, err := marshal(accept)
+	s, err := danger.MarshalJSON(accept)
 	if err != nil {
 		return err
 	}
diff --git a/inbox/announce.go b/inbox/announce.go
diff --git a/inbox/create.go b/inbox/create.go
diff --git a/inbox/delete.go b/inbox/delete.go
diff --git a/inbox/follow.go b/inbox/follow.go
diff --git a/inbox/reject.go b/inbox/reject.go
diff --git a/inbox/undo.go b/inbox/undo.go
diff --git a/inbox/unfollow.go b/inbox/unfollow.go
diff --git a/inbox/update.go b/inbox/update.go

Original file line number	Diff line number	Diff line change
`@@ -22,6 +22,8 @@ import (`
`22`	`22`	`"errors"`
`23`	`23`	`"fmt"`
`24`	`24`	`"log/slog"`
	`25`	`+`
	`26`	`+ "github.com/dimkr/tootik/danger"`
`25`	`27`	`)`
`26`	`28`
`27`	`29`	`type ActivityType string`
`@@ -155,8 +157,7 @@ func (a *Activity) Scan(src any) error {`
`155`	`157`	`}`
`156`	`158`
`157`	`159`	`func (a *Activity) Value() (driver.Value, error) {`
`158`		`- buf, err := json.Marshal(a)`
`159`		`- return string(buf), err`
	`160`	`+ return danger.MarshalJSON(a)`
`160`	`161`	`}`
`161`	`162`
`162`	`163`	`func (a *Activity) LogValue() slog.Value {`
Original file line number	Diff line number	Diff line change
`@@ -20,6 +20,8 @@ import (`
`20`	`20`	`"database/sql/driver"`
`21`	`21`	`"encoding/json"`
`22`	`22`	`"fmt"`
	`23`	`+`
	`24`	`+ "github.com/dimkr/tootik/danger"`
`23`	`25`	`)`
`24`	`26`
`25`	`27`	`type ActorType string`
`@@ -71,6 +73,5 @@ func (a *Actor) Scan(src any) error {`
`71`	`73`	`}`
`72`	`74`
`73`	`75`	`func (a *Actor) Value() (driver.Value, error) {`
`74`		`- buf, err := json.Marshal(a)`
`75`		`- return string(buf), err`
	`76`	`+ return danger.MarshalJSON(a)`
`76`	`77`	`}`
Original file line number	Diff line number	Diff line change
`@@ -21,6 +21,7 @@ import (`
`21`	`21`	`"encoding/json"`
`22`	`22`	`"fmt"`
`23`	`23`
	`24`	`+ "github.com/dimkr/tootik/danger"`
`24`	`25`	`"github.com/dimkr/tootik/data"`
`25`	`26`	`)`
`26`	`27`
`@@ -89,6 +90,5 @@ func (a *Audience) Scan(src any) error {`
`89`	`90`	`}`
`90`	`91`
`91`	`92`	`func (a *Audience) Value() (driver.Value, error) {`
`92`		`- buf, err := json.Marshal(a)`
`93`		`- return string(buf), err`
	`93`	`+ return danger.MarshalJSON(a)`
`94`	`94`	`}`