From 641a95063946bf7f4b8fdd1e938a917bc3f75cb2 Mon Sep 17 00:00:00 2001
From: Alexander Neonxp Kiryukhin <i@neonxp.ru>
Date: Thu, 5 Feb 2026 14:35:00 +0300
Subject: initial

---
 publisher.go | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 publisher.go

(limited to 'publisher.go')

diff --git a/publisher.go b/publisher.go
new file mode 100644
index 0000000..611e4d1
--- /dev/null
+++ b/publisher.go
@@ -0,0 +1,84 @@
+package fqueue
+
+import (
+	"context"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strconv"
+	"sync"
+)
+
+// Publish записывает задачу в очередь. Использует исключительную блокировку на счетчике.
+func (b *Bus) Publish(ctx context.Context, task []byte) (seq uint64, err error) {
+	seq, err = b.nextSeq(ctx, b.seqFile)
+	if err != nil {
+		return 0, errors.Join(err, ErrCantGetExLock)
+	}
+
+	fp, err := os.OpenFile(filepath.Join(b.queuePath, strconv.Itoa(int(seq))), os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
+	if err != nil {
+		return seq, fmt.Errorf("failed create task file: %w", err)
+	}
+	defer func() {
+		err2 := errors.Join(err, fp.Close())
+		err = err2
+	}()
+
+	if _, err := fp.Write(task); err != nil {
+		return 0, fmt.Errorf("failed write task file: %w", err)
+	}
+
+	return seq, nil
+}
+
+func (*Bus) nextSeq(ctx context.Context, filename string) (seq uint64, err error) {
+	fd, err := os.OpenFile(filename, os.O_CREATE|os.O_RDWR, 0o600)
+	if err != nil {
+		// Не получилось взять блокировку
+		return 0, err
+	}
+	ch := make(chan struct{})
+	closer := sync.OnceFunc(func() {
+		fd.Close()
+	})
+	defer close(ch)
+	go func() {
+		select {
+		case <-ch:
+			return
+		case <-ctx.Done():
+			closer()
+		}
+	}()
+	defer closer()
+
+	if err := lock(int(fd.Fd()), true); err != nil {
+		return 0, err
+	}
+
+	defer unlock(int(fd.Fd()))
+
+	buf := make([]byte, 8)
+	n, err := fd.Read(buf)
+	if err == nil && n == 8 {
+		// Успешно прочитали число
+		seq = binary.BigEndian.Uint64(buf)
+	}
+	if err != nil && !errors.Is(err, io.EOF) {
+		return 0, fmt.Errorf("failed read seq file: %w", err)
+	}
+	seq++
+	if _, err := fd.Seek(0, 0); err != nil {
+		return seq, err
+	}
+	binary.BigEndian.PutUint64(buf, seq)
+	if _, err := fd.Write(buf); err != nil {
+		return 0, fmt.Errorf("failed write seq file: %w", err)
+	}
+
+	return seq, nil
+}
-- 
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