[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/ncruces/go-sqlite3/util/osutil/open.go

@@ -0,0 +1,16 @@
+//go:build !windows
+
+package osutil
+
+import (
+	"io/fs"
+	"os"
+)
+
+// OpenFile behaves the same as [os.OpenFile],
+// except on Windows it sets [syscall.FILE_SHARE_DELETE].
+//
+// See: https://go.dev/issue/32088#issuecomment-502850674
+func OpenFile(name string, flag int, perm fs.FileMode) (*os.File, error) {
+	return os.OpenFile(name, flag, perm)
+}

vendor/github.com/ncruces/go-sqlite3/util/osutil/open_windows.go

@@ -0,0 +1,112 @@
+package osutil
+
+import (
+	"io/fs"
+	"os"
+	. "syscall"
+	"unsafe"
+)
+
+// OpenFile behaves the same as [os.OpenFile],
+// except on Windows it sets [syscall.FILE_SHARE_DELETE].
+//
+// See: https://go.dev/issue/32088#issuecomment-502850674
+func OpenFile(name string, flag int, perm fs.FileMode) (*os.File, error) {
+	if name == "" {
+		return nil, &os.PathError{Op: "open", Path: name, Err: ENOENT}
+	}
+	r, e := syscallOpen(name, flag, uint32(perm.Perm()))
+	if e != nil {
+		return nil, &os.PathError{Op: "open", Path: name, Err: e}
+	}
+	return os.NewFile(uintptr(r), name), nil
+}
+
+// syscallOpen is a copy of [syscall.Open]
+// that uses [syscall.FILE_SHARE_DELETE].
+//
+// https://go.dev/src/syscall/syscall_windows.go
+func syscallOpen(path string, mode int, perm uint32) (fd Handle, err error) {
+	if len(path) == 0 {
+		return InvalidHandle, ERROR_FILE_NOT_FOUND
+	}
+	pathp, err := UTF16PtrFromString(path)
+	if err != nil {
+		return InvalidHandle, err
+	}
+	var access uint32
+	switch mode & (O_RDONLY | O_WRONLY | O_RDWR) {
+	case O_RDONLY:
+		access = GENERIC_READ
+	case O_WRONLY:
+		access = GENERIC_WRITE
+	case O_RDWR:
+		access = GENERIC_READ | GENERIC_WRITE
+	}
+	if mode&O_CREAT != 0 {
+		access |= GENERIC_WRITE
+	}
+	if mode&O_APPEND != 0 {
+		access &^= GENERIC_WRITE
+		access |= FILE_APPEND_DATA
+	}
+	sharemode := uint32(FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE)
+	var sa *SecurityAttributes
+	if mode&O_CLOEXEC == 0 {
+		sa = makeInheritSa()
+	}
+	var createmode uint32
+	switch {
+	case mode&(O_CREAT|O_EXCL) == (O_CREAT | O_EXCL):
+		createmode = CREATE_NEW
+	case mode&(O_CREAT|O_TRUNC) == (O_CREAT | O_TRUNC):
+		createmode = CREATE_ALWAYS
+	case mode&O_CREAT == O_CREAT:
+		createmode = OPEN_ALWAYS
+	case mode&O_TRUNC == O_TRUNC:
+		createmode = TRUNCATE_EXISTING
+	default:
+		createmode = OPEN_EXISTING
+	}
+	var attrs uint32 = FILE_ATTRIBUTE_NORMAL
+	if perm&S_IWRITE == 0 {
+		attrs = FILE_ATTRIBUTE_READONLY
+		if createmode == CREATE_ALWAYS {
+			const _ERROR_BAD_NETPATH = Errno(53)
+			// We have been asked to create a read-only file.
+			// If the file already exists, the semantics of
+			// the Unix open system call is to preserve the
+			// existing permissions. If we pass CREATE_ALWAYS
+			// and FILE_ATTRIBUTE_READONLY to CreateFile,
+			// and the file already exists, CreateFile will
+			// change the file permissions.
+			// Avoid that to preserve the Unix semantics.
+			h, e := CreateFile(pathp, access, sharemode, sa, TRUNCATE_EXISTING, FILE_ATTRIBUTE_NORMAL, 0)
+			switch e {
+			case ERROR_FILE_NOT_FOUND, _ERROR_BAD_NETPATH, ERROR_PATH_NOT_FOUND:
+				// File does not exist. These are the same
+				// errors as Errno.Is checks for ErrNotExist.
+				// Carry on to create the file.
+			default:
+				// Success or some different error.
+				return h, e
+			}
+		}
+	}
+	if createmode == OPEN_EXISTING && access == GENERIC_READ {
+		// Necessary for opening directory handles.
+		attrs |= FILE_FLAG_BACKUP_SEMANTICS
+	}
+	if mode&O_SYNC != 0 {
+		const _FILE_FLAG_WRITE_THROUGH = 0x80000000
+		attrs |= _FILE_FLAG_WRITE_THROUGH
+	}
+	return CreateFile(pathp, access, sharemode, sa, createmode, attrs, 0)
+}
+
+func makeInheritSa() *SecurityAttributes {
+	var sa SecurityAttributes
+	sa.Length = uint32(unsafe.Sizeof(sa))
+	sa.InheritHandle = 1
+	return &sa
+}

vendor/github.com/ncruces/go-sqlite3/util/osutil/osfs.go

@@ -0,0 +1,33 @@
+package osutil
+
+import (
+	"io/fs"
+	"os"
+)
+
+// FS implements [fs.FS], [fs.StatFS], and [fs.ReadFileFS]
+// using package [os].
+//
+// This filesystem does not respect [fs.ValidPath] rules,
+// and fails [testing/fstest.TestFS]!
+//
+// Still, it can be a useful tool to unify implementations
+// that can access either the [os] filesystem or an [fs.FS].
+// It's OK to use this to open files, but you should avoid
+// opening directories, resolving paths, or walking the file system.
+type FS struct{}
+
+// Open implements [fs.FS].
+func (FS) Open(name string) (fs.File, error) {
+	return OpenFile(name, os.O_RDONLY, 0)
+}
+
+// ReadFileFS implements [fs.StatFS].
+func (FS) Stat(name string) (fs.FileInfo, error) {
+	return os.Stat(name)
+}
+
+// ReadFile implements [fs.ReadFileFS].
+func (FS) ReadFile(name string) ([]byte, error) {
+	return os.ReadFile(name)
+}

vendor/github.com/ncruces/go-sqlite3/util/osutil/osutil.go

@@ -0,0 +1,2 @@
+// Package osutil implements operating system utility functions.
+package osutil