Initial QSfera import

Server/vendor/github.com/kovidgoyal/go-shm/shm_fs.go

@@ -0,0 +1,187 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+//go:build linux || netbsd || openbsd || dragonfly
+
+package shm
+
+import (
+	"crypto/sha256"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	"golang.org/x/sys/unix"
+)
+
+var _ = fmt.Print
+
+type file_based_mmap struct {
+	f            *os.File
+	pos          int64
+	region       []byte
+	unlinked     bool
+	special_name string
+}
+
+func ShmUnlink(name string) error {
+	if runtime.GOOS == "openbsd" {
+		return os.Remove(openbsd_shm_path(name))
+	}
+	name = strings.TrimPrefix(name, "/")
+	return os.Remove(filepath.Join(SHM_DIR, name))
+}
+
+func file_mmap(f *os.File, size uint64, access AccessFlags, truncate bool, special_name string) (MMap, error) {
+	if truncate {
+		err := truncate_or_unlink(f, size, os.Remove)
+		if err != nil {
+			return nil, err
+		}
+	}
+	region, err := mmap(int(size), access, int(f.Fd()), 0)
+	if err != nil {
+		f.Close()
+		os.Remove(f.Name())
+		return nil, err
+	}
+	return &file_based_mmap{f: f, region: region, special_name: special_name}, nil
+}
+
+func (self *file_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 *file_based_mmap) Read(b []byte) (n int, err error) {
+	return Read(self, b)
+}
+
+func (self *file_based_mmap) Write(b []byte) (n int, err error) {
+	return Write(self, b)
+}
+
+func (self *file_based_mmap) Stat() (fs.FileInfo, error) {
+	return self.f.Stat()
+}
+
+func (self *file_based_mmap) Name() string {
+	if self.special_name != "" {
+		return self.special_name
+	}
+	return filepath.Base(self.f.Name())
+}
+
+func (self *file_based_mmap) Flush() error {
+	return unix.Msync(self.region, unix.MS_SYNC)
+}
+
+func (self *file_based_mmap) FileSystemName() string {
+	return self.f.Name()
+}
+
+func (self *file_based_mmap) Slice() []byte {
+	return self.region
+}
+
+func (self *file_based_mmap) Close() (err error) {
+	if self.region != nil {
+		self.f.Close()
+		err = munmap(self.region)
+		self.region = nil
+	}
+	return err
+}
+
+func (self *file_based_mmap) Unlink() (err error) {
+	if self.unlinked {
+		return nil
+	}
+	self.unlinked = true
+	return os.Remove(self.f.Name())
+}
+
+func (self *file_based_mmap) IsFileSystemBacked() bool { return true }
+
+func openbsd_shm_path(name string) string {
+	hash := sha256.Sum256(UnsafeStringToBytes(name))
+	return filepath.Join(SHM_DIR, UnsafeBytesToString(hash[:])+".shm")
+}
+
+func file_path_from_name(name string) string {
+	// See https://github.com/openbsd/src/blob/master/lib/libc/gen/shm_open.c
+	if runtime.GOOS == "openbsd" {
+		return openbsd_shm_path(name)
+	}
+	return filepath.Join(SHM_DIR, name)
+}
+
+func create_temp(pattern string, size uint64) (ans MMap, err error) {
+	special_name := ""
+	var prefix, suffix string
+	prefix, suffix, err = prefix_and_suffix(pattern)
+	if err != nil {
+		return
+	}
+	var f *os.File
+	try := 0
+	for {
+		name := prefix + RandomFilename() + suffix
+		path := file_path_from_name(name)
+		f, err = os.OpenFile(path, os.O_EXCL|os.O_CREATE|os.O_RDWR, 0600)
+		if err != nil {
+			if errors.Is(err, fs.ErrExist) {
+				try += 1
+				if try > 10000 {
+					return nil, &os.PathError{Op: "createtemp", Path: prefix + "*" + suffix, Err: fs.ErrExist}
+				}
+				continue
+			}
+			if errors.Is(err, fs.ErrNotExist) {
+				return nil, &ErrNotSupported{err: err}
+			}
+			return
+		}
+		break
+	}
+	return file_mmap(f, size, WRITE, true, special_name)
+}
+
+func open(name string) (*os.File, error) {
+	ans, err := os.OpenFile(file_path_from_name(name), os.O_RDONLY, 0)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			if _, serr := os.Stat(SHM_DIR); serr != nil && errors.Is(serr, fs.ErrNotExist) {
+				return nil, &ErrNotSupported{err: serr}
+			}
+		}
+		return nil, err
+	}
+	return ans, nil
+}
+
+func Open(name string, size uint64) (MMap, error) {
+	ans, err := open(name)
+	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 file_mmap(ans, size, READ, false, name)
+}