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// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
//go:build darwin || freebsd
package shm
import (
"errors"
"fmt"
"io"
"io/fs"
"os"
"strings"
"unsafe"
"github.com/kovidgoyal/kitty/tools/utils"
"golang.org/x/sys/unix"
)
var _ = fmt.Print
// ByteSliceFromString makes a zero terminated byte slice from the string
func ByteSliceFromString(s string) []byte {
a := make([]byte, len(s)+1)
copy(a, s)
return a
}
func BytePtrFromString(s string) *byte {
a := ByteSliceFromString(s)
return &a[0]
}
func shm_unlink(name string) (err error) {
bname := BytePtrFromString(name)
for {
_, _, errno := unix.Syscall(unix.SYS_SHM_UNLINK, uintptr(unsafe.Pointer(bname)), 0, 0)
if errno != unix.EINTR {
if errno != 0 {
if errno == unix.ENOENT {
err = fs.ErrNotExist
} else {
err = fmt.Errorf("shm_unlink() failed with error: %w", errno)
}
}
break
}
}
return
}
func ShmUnlink(name string) error {
return shm_unlink(name)
}
func shm_open(name string, flags, perm int) (ans *os.File, err error) {
bname := BytePtrFromString(name)
var fd uintptr
var errno unix.Errno
for {
fd, _, errno = unix.Syscall(unix.SYS_SHM_OPEN, uintptr(unsafe.Pointer(bname)), uintptr(flags), uintptr(perm))
if errno != unix.EINTR {
if errno != 0 {
err = fmt.Errorf("shm_open() failed with error: %w", errno)
}
break
}
}
if err == nil {
ans = os.NewFile(fd, name)
}
return
}
type syscall_based_mmap struct {
f *os.File
pos int64
region []byte
unlinked bool
}
func syscall_mmap(f *os.File, size uint64, access AccessFlags, truncate bool) (MMap, error) {
if truncate {
err := truncate_or_unlink(f, size, shm_unlink)
if err != nil {
return nil, fmt.Errorf("truncate failed with error: %w", err)
}
}
region, err := mmap(int(size), access, int(f.Fd()), 0)
if err != nil {
_ = f.Close()
_ = shm_unlink(f.Name())
return nil, fmt.Errorf("mmap failed with error: %w", err)
}
return &syscall_based_mmap{f: f, region: region}, nil
}
func (self *syscall_based_mmap) Name() string {
return self.f.Name()
}
func (self *syscall_based_mmap) Stat() (fs.FileInfo, error) {
return self.f.Stat()
}
func (self *syscall_based_mmap) Flush() error {
return unix.Msync(self.region, unix.MS_SYNC)
}
func (self *syscall_based_mmap) Slice() []byte {
return self.region
}
func (self *syscall_based_mmap) Close() (err error) {
if self.region != nil {
self.f.Close()
munmap(self.region)
self.region = nil
}
return
}
func (self *syscall_based_mmap) Unlink() (err error) {
if self.unlinked {
return nil
}
self.unlinked = true
return shm_unlink(self.Name())
}
func (self *syscall_based_mmap) Seek(offset int64, whence int) (ret int64, err error) {
switch whence {
case io.SeekStart:
self.pos = offset
case io.SeekEnd:
self.pos = int64(len(self.region)) + offset
case io.SeekCurrent:
self.pos += offset
}
return self.pos, nil
}
func (self *syscall_based_mmap) Read(b []byte) (n int, err error) {
return Read(self, b)
}
func (self *syscall_based_mmap) Write(b []byte) (n int, err error) {
return Write(self, b)
}
func (self *syscall_based_mmap) IsFileSystemBacked() bool { return false }
func (self *syscall_based_mmap) FileSystemName() string { return "" }
func create_temp(pattern string, size uint64) (ans MMap, err error) {
var prefix, suffix string
prefix, suffix, err = prefix_and_suffix(pattern)
if err != nil {
return
}
if SHM_REQUIRED_PREFIX != "" && !strings.HasPrefix(pattern, SHM_REQUIRED_PREFIX) {
// FreeBSD requires name to start with /
prefix = SHM_REQUIRED_PREFIX + prefix
}
var f *os.File
try := 0
for {
name := prefix + utils.RandomFilename() + suffix
if len(name) > SHM_NAME_MAX {
return nil, ErrPatternTooLong
}
f, err = shm_open(name, os.O_EXCL|os.O_CREATE|os.O_RDWR, 0600)
if err != nil && (errors.Is(err, fs.ErrExist) || errors.Unwrap(err) == unix.EEXIST) {
try += 1
if try > 10000 {
return nil, &os.PathError{Op: "createtemp", Path: prefix + "*" + suffix, Err: fs.ErrExist}
}
continue
}
break
}
if err != nil {
return nil, err
}
return syscall_mmap(f, size, WRITE, true)
}
func Open(name string, size uint64) (MMap, error) {
ans, err := shm_open(name, os.O_RDONLY, 0)
if err != nil {
return nil, err
}
if size == 0 {
s, err := ans.Stat()
if err != nil {
ans.Close()
return nil, fmt.Errorf("Failed to stat SHM file with error: %w", err)
}
size = uint64(s.Size())
}
return syscall_mmap(ans, size, READ, false)
}
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