After commit c018f5fd29 Fenrir is being switched over to go. If you do not want to be part of the testing process, please switch to master.

internal/spellcheck/exceptions.go

@@ -0,0 +1,147 @@
+// Copyright (c) 2026 Storm Dragon
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package spellcheck
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"syscall"
+	"time"
+)
+
+func Exceptions_path(home string) string {
+	return filepath.Join(home, ".local/share/stormux/fenrirscreenreader/spelling/exceptions.json")
+}
+
+func load_exceptions(path string) (map[string]string, error) {
+	words := make(map[string]string)
+	file, err := os.Open(path)
+	if errors.Is(err, os.ErrNotExist) {
+		return words, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+	data, err := io.ReadAll(io.LimitReader(file, (1<<20)+1))
+	if err != nil {
+		return nil, err
+	}
+	if len(data) > 1<<20 {
+		return nil, fmt.Errorf("exceptions file exceeds 1 MiB")
+	}
+	var entries []string
+	if err := json.Unmarshal(data, &entries); err != nil {
+		return nil, err
+	}
+	for _, word := range entries {
+		if !valid_word(word) {
+			return nil, fmt.Errorf("invalid exceptions file")
+		}
+		words[strings.ToLower(word)] = word
+	}
+	return words, nil
+}
+
+func exception_list(words map[string]string) []string {
+	entries := make([]string, 0, len(words))
+	for _, word := range words {
+		entries = append(entries, word)
+	}
+	sort.Slice(entries, func(i, j int) bool { return strings.ToLower(entries[i]) < strings.ToLower(entries[j]) })
+	return entries
+}
+
+// Each edit reloads the latest list while holding a stable, per-file lock.
+// Atomic replacement alone cannot protect against another reader's stale copy.
+func update_exceptions(ctx context.Context, path string, operation Operation, word string) (map[string]string, error) {
+	if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
+		return nil, err
+	}
+	lock, err := os.OpenFile(path+".lock", os.O_CREATE|os.O_RDWR|syscall.O_NOFOLLOW|syscall.O_NONBLOCK, 0600)
+	if err != nil {
+		return nil, err
+	}
+	defer lock.Close()
+	info, err := lock.Stat()
+	if err != nil {
+		return nil, err
+	}
+	if !info.Mode().IsRegular() || info.Mode().Perm()&0077 != 0 || info.Sys().(*syscall.Stat_t).Uid != uint32(os.Geteuid()) {
+		return nil, fmt.Errorf("exceptions lock must be private and owned by the current account")
+	}
+	waitCtx, cancel := context.WithTimeout(ctx, 2*time.Second)
+	defer cancel()
+	for {
+		if err := waitCtx.Err(); err != nil {
+			return nil, err
+		}
+		err = syscall.Flock(int(lock.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
+		if err == nil {
+			break
+		}
+		if !errors.Is(err, syscall.EWOULDBLOCK) {
+			return nil, err
+		}
+		timer := time.NewTimer(10 * time.Millisecond)
+		select {
+		case <-waitCtx.Done():
+			timer.Stop()
+			return nil, waitCtx.Err()
+		case <-timer.C:
+		}
+	}
+	words, err := load_exceptions(path)
+	if err != nil {
+		return nil, err
+	}
+	key := strings.ToLower(word)
+	if operation == Add {
+		words[key] = word
+	} else {
+		delete(words, key)
+	}
+	if err := save_exceptions(path, words); err != nil {
+		return nil, err
+	}
+	return words, nil
+}
+
+func save_exceptions(path string, words map[string]string) error {
+	data, err := json.MarshalIndent(exception_list(words), "", "  ")
+	if err != nil {
+		return err
+	}
+	if len(data) > 1<<20 {
+		return fmt.Errorf("exceptions file exceeds 1 MiB")
+	}
+	dir := filepath.Dir(path)
+	if err := os.MkdirAll(dir, 0700); err != nil {
+		return err
+	}
+	file, err := os.CreateTemp(dir, ".exceptions-*.json")
+	if err != nil {
+		return err
+	}
+	defer os.Remove(file.Name())
+	if _, err := file.Write(append(data, '\n')); err != nil {
+		file.Close()
+		return err
+	}
+	if err := file.Sync(); err != nil {
+		file.Close()
+		return err
+	}
+	if err := file.Close(); err != nil {
+		return err
+	}
+	return os.Rename(file.Name(), path)
+}