[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/tetratelabs/wazero/internal/sysfs/sock.go

@@ -0,0 +1,187 @@
+package sysfs
+
+import (
+	"net"
+	"os"
+
+	experimentalsys "github.com/tetratelabs/wazero/experimental/sys"
+	"github.com/tetratelabs/wazero/internal/fsapi"
+	socketapi "github.com/tetratelabs/wazero/internal/sock"
+	"github.com/tetratelabs/wazero/sys"
+)
+
+// NewTCPListenerFile creates a socketapi.TCPSock for a given *net.TCPListener.
+func NewTCPListenerFile(tl *net.TCPListener) socketapi.TCPSock {
+	return newTCPListenerFile(tl)
+}
+
+// baseSockFile implements base behavior for all TCPSock, TCPConn files,
+// regardless the platform.
+type baseSockFile struct {
+	experimentalsys.UnimplementedFile
+}
+
+var _ experimentalsys.File = (*baseSockFile)(nil)
+
+// IsDir implements the same method as documented on File.IsDir
+func (*baseSockFile) IsDir() (bool, experimentalsys.Errno) {
+	// We need to override this method because WASI-libc prestats the FD
+	// and the default impl returns ENOSYS otherwise.
+	return false, 0
+}
+
+// Stat implements the same method as documented on File.Stat
+func (f *baseSockFile) Stat() (fs sys.Stat_t, errno experimentalsys.Errno) {
+	// The mode is not really important, but it should be neither a regular file nor a directory.
+	fs.Mode = os.ModeIrregular
+	return
+}
+
+var _ socketapi.TCPSock = (*tcpListenerFile)(nil)
+
+type tcpListenerFile struct {
+	baseSockFile
+
+	tl       *net.TCPListener
+	closed   bool
+	nonblock bool
+}
+
+// newTCPListenerFile is a constructor for a socketapi.TCPSock.
+//
+// The current strategy is to wrap a net.TCPListener
+// and invoking raw syscalls using syscallConnControl:
+// this internal calls RawConn.Control(func(fd)), making sure
+// that the underlying file descriptor is valid throughout
+// the duration of the syscall.
+func newDefaultTCPListenerFile(tl *net.TCPListener) socketapi.TCPSock {
+	return &tcpListenerFile{tl: tl}
+}
+
+// Close implements the same method as documented on experimentalsys.File
+func (f *tcpListenerFile) Close() experimentalsys.Errno {
+	if !f.closed {
+		return experimentalsys.UnwrapOSError(f.tl.Close())
+	}
+	return 0
+}
+
+// Addr is exposed for testing.
+func (f *tcpListenerFile) Addr() *net.TCPAddr {
+	return f.tl.Addr().(*net.TCPAddr)
+}
+
+// IsNonblock implements the same method as documented on fsapi.File
+func (f *tcpListenerFile) IsNonblock() bool {
+	return f.nonblock
+}
+
+// Poll implements the same method as documented on fsapi.File
+func (f *tcpListenerFile) Poll(flag fsapi.Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno) {
+	return false, experimentalsys.ENOSYS
+}
+
+var _ socketapi.TCPConn = (*tcpConnFile)(nil)
+
+type tcpConnFile struct {
+	baseSockFile
+
+	tc *net.TCPConn
+
+	// nonblock is true when the underlying connection is flagged as non-blocking.
+	// This ensures that reads and writes return experimentalsys.EAGAIN without blocking the caller.
+	nonblock bool
+	// closed is true when closed was called. This ensures proper experimentalsys.EBADF
+	closed bool
+}
+
+func newTcpConn(tc *net.TCPConn) socketapi.TCPConn {
+	return &tcpConnFile{tc: tc}
+}
+
+// Read implements the same method as documented on experimentalsys.File
+func (f *tcpConnFile) Read(buf []byte) (n int, errno experimentalsys.Errno) {
+	if len(buf) == 0 {
+		return 0, 0 // Short-circuit 0-len reads.
+	}
+	if nonBlockingFileReadSupported && f.IsNonblock() {
+		n, errno = syscallConnControl(f.tc, func(fd uintptr) (int, experimentalsys.Errno) {
+			n, err := readSocket(fd, buf)
+			errno = experimentalsys.UnwrapOSError(err)
+			errno = fileError(f, f.closed, errno)
+			return n, errno
+		})
+	} else {
+		n, errno = read(f.tc, buf)
+	}
+	if errno != 0 {
+		// Defer validation overhead until we've already had an error.
+		errno = fileError(f, f.closed, errno)
+	}
+	return
+}
+
+// Write implements the same method as documented on experimentalsys.File
+func (f *tcpConnFile) Write(buf []byte) (n int, errno experimentalsys.Errno) {
+	if nonBlockingFileWriteSupported && f.IsNonblock() {
+		return syscallConnControl(f.tc, func(fd uintptr) (int, experimentalsys.Errno) {
+			n, err := writeSocket(fd, buf)
+			errno = experimentalsys.UnwrapOSError(err)
+			errno = fileError(f, f.closed, errno)
+			return n, errno
+		})
+	} else {
+		n, errno = write(f.tc, buf)
+	}
+	if errno != 0 {
+		// Defer validation overhead until we've already had an error.
+		errno = fileError(f, f.closed, errno)
+	}
+	return
+}
+
+// Recvfrom implements the same method as documented on socketapi.TCPConn
+func (f *tcpConnFile) Recvfrom(p []byte, flags int) (n int, errno experimentalsys.Errno) {
+	if flags != MSG_PEEK {
+		errno = experimentalsys.EINVAL
+		return
+	}
+	return syscallConnControl(f.tc, func(fd uintptr) (int, experimentalsys.Errno) {
+		n, err := recvfrom(fd, p, MSG_PEEK)
+		errno = experimentalsys.UnwrapOSError(err)
+		errno = fileError(f, f.closed, errno)
+		return n, errno
+	})
+}
+
+// Close implements the same method as documented on experimentalsys.File
+func (f *tcpConnFile) Close() experimentalsys.Errno {
+	return f.close()
+}
+
+func (f *tcpConnFile) close() experimentalsys.Errno {
+	if f.closed {
+		return 0
+	}
+	f.closed = true
+	return f.Shutdown(socketapi.SHUT_RDWR)
+}
+
+// SetNonblock implements the same method as documented on fsapi.File
+func (f *tcpConnFile) SetNonblock(enabled bool) (errno experimentalsys.Errno) {
+	f.nonblock = enabled
+	_, errno = syscallConnControl(f.tc, func(fd uintptr) (int, experimentalsys.Errno) {
+		return 0, experimentalsys.UnwrapOSError(setNonblockSocket(fd, enabled))
+	})
+	return
+}
+
+// IsNonblock implements the same method as documented on fsapi.File
+func (f *tcpConnFile) IsNonblock() bool {
+	return f.nonblock
+}
+
+// Poll implements the same method as documented on fsapi.File
+func (f *tcpConnFile) Poll(flag fsapi.Pflag, timeoutMillis int32) (ready bool, errno experimentalsys.Errno) {
+	return false, experimentalsys.ENOSYS
+}