From 1eefa2fe2e9740243be4b09ee9c9d6c01749cb1c Mon Sep 17 00:00:00 2001
From: Mustafa Elbehery <melbeher@redhat.com>
Date: Thu, 30 Nov 2023 19:55:06 +0100
Subject: [PATCH] add plan9 support

---
 bolt_plan9.go  | 119 +++++++++++++++++++++++++++++++++++++++++++++++++
 mlock_plan9.go |  11 +++++
 mlock_unix.go  |   4 +-
 3 files changed, 132 insertions(+), 2 deletions(-)
 create mode 100644 bolt_plan9.go
 create mode 100644 mlock_plan9.go

diff --git a/bolt_plan9.go b/bolt_plan9.go
new file mode 100644
index 000000000..faf9f3fd1
--- /dev/null
+++ b/bolt_plan9.go
@@ -0,0 +1,119 @@
+package bbolt
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+	"time"
+	"unsafe"
+
+	"golang.org/x/sys/plan9"
+
+	"go.etcd.io/bbolt/errors"
+)
+
+// fdatasync flushes written data to a file descriptor.
+func fdatasync(db *DB) error {
+	return db.file.Sync()
+}
+
+// flock acquires an advisory lock on a file descriptor.
+func flock(db *DB, exclusive bool, timeout time.Duration) error {
+	var t time.Time
+	if timeout != 0 {
+		t = time.Now()
+	}
+	var flags uint32 = plan9.LOCKFILE_FAIL_IMMEDIATELY
+	if exclusive {
+		flags |= plan9.LOCKFILE_EXCLUSIVE_LOCK
+	}
+	for {
+		// Fix for https://github.com/etcd-io/bbolt/issues/121. Use byte-range
+		// -1..0 as the lock on the database file.
+		var m1 uint32 = (1 << 32) - 1 // -1 in a uint32
+		err := plan9.LockFileEx(plan9.Handle(db.file.Fd()), flags, 0, 1, 0, &plan9.Overlapped{
+			Offset:     m1,
+			OffsetHigh: m1,
+		})
+
+		if err == nil {
+			return nil
+		} else if err != plan9.ERROR_LOCK_VIOLATION {
+			return err
+		}
+
+		// If we timed oumercit then return an error.
+		if timeout != 0 && time.Since(t) > timeout-flockRetryTimeout {
+			return errors.ErrTimeout
+		}
+
+		// Wait for a bit and try again.
+		time.Sleep(flockRetryTimeout)
+	}
+}
+
+// funlock releases an advisory lock on a file descriptor.
+func funlock(db *DB) error {
+	var m1 uint32 = (1 << 32) - 1 // -1 in a uint32
+	return plan9.UnlockFileEx(plan9.Handle(db.file.Fd()), 0, 1, 0, &plan9.Overlapped{
+		Offset:     m1,
+		OffsetHigh: m1,
+	})
+}
+
+// mmap memory maps a DB's data file.
+// Based on: https://github.com/edsrzf/mmap-go
+func mmap(db *DB, sz int) error {
+	var sizelo, sizehi uint32
+
+	if !db.readOnly {
+		// Truncate the database to the size of the mmap.
+		if err := db.file.Truncate(int64(sz)); err != nil {
+			return fmt.Errorf("truncate: %s", err)
+		}
+		sizehi = uint32(sz >> 32)
+		sizelo = uint32(sz)
+	}
+
+	// Open a file mapping handle.
+	h, errno := syscall.CreateFileMapping(syscall.Handle(db.file.Fd()), nil, syscall.PAGE_READONLY, sizehi, sizelo, nil)
+	if h == 0 {
+		return os.NewSyscallError("CreateFileMapping", errno)
+	}
+
+	// Create the memory map.
+	addr, errno := syscall.MapViewOfFile(h, syscall.FILE_MAP_READ, 0, 0, 0)
+	if addr == 0 {
+		// Do our best and report error returned from MapViewOfFile.
+		_ = syscall.CloseHandle(h)
+		return os.NewSyscallError("MapViewOfFile", errno)
+	}
+
+	// Close mapping handle.
+	if err := syscall.CloseHandle(syscall.Handle(h)); err != nil {
+		return os.NewSyscallError("CloseHandle", err)
+	}
+
+	// Convert to a byte array.
+	db.data = (*[maxMapSize]byte)(unsafe.Pointer(addr))
+	db.datasz = sz
+
+	return nil
+}
+
+// munmap unmaps a pointer from a file.
+// Based on: https://github.com/edsrzf/mmap-go
+func munmap(db *DB) error {
+	if db.data == nil {
+		return nil
+	}
+
+	addr := (uintptr)(unsafe.Pointer(&db.data[0]))
+	var err1 error
+	if err := syscall.UnmapViewOfFile(addr); err != nil {
+		err1 = os.NewSyscallError("UnmapViewOfFile", err)
+	}
+	db.data = nil
+	db.datasz = 0
+	return err1
+}
diff --git a/mlock_plan9.go b/mlock_plan9.go
new file mode 100644
index 000000000..00b0fb431
--- /dev/null
+++ b/mlock_plan9.go
@@ -0,0 +1,11 @@
+package bbolt
+
+// mlock locks memory of db file
+func mlock(_ *DB, _ int) error {
+	panic("mlock is supported only on UNIX systems")
+}
+
+// munlock unlocks memory of db file
+func munlock(_ *DB, _ int) error {
+	panic("munlock is supported only on UNIX systems")
+}
diff --git a/mlock_unix.go b/mlock_unix.go
index 744a972f5..78fc6a890 100644
--- a/mlock_unix.go
+++ b/mlock_unix.go
@@ -1,5 +1,5 @@
-//go:build !windows
-// +build !windows
+//go:build !windows && !plan9
+// +build !windows,!plan9
 
 package bbolt