wasi: support conversion of wasi.Errno values to syscall.Errno (#71)

This PR adds the `wasi.Errno.Syscall` method to convert errno values to
error codes of the host platform.

Signed-off-by: Achille Roussel <[email protected]>

error.go

@@ -2,6 +2,7 @@ package wasi
 
 import (
 	"fmt"
+	"syscall"
 )
 
 // Errno are the error codes returned by functions.
@@ -263,6 +264,15 @@ func (e Errno) Name() string {
 	return fmt.Sprintf("errno(%d)", int(e))
 }
 
+// Syscall convers the error to a native error number of the host platform.
+//
+// The method does the inverse of passing the syscall.Errno value to
+// wasi.MakeErrno tho some error numbers may differ on the host platform,
+// therefore there is no guarantee that the wasi.Errno value obtained by a
+// call to wasi.MakeErrno will yield the same syscall.Errno returned by this
+// method.
+func (e Errno) Syscall() syscall.Errno { return errnoToSyscall(e) }
+
 var errorStrings = [...]string{
 	ESUCCESS:        "OK",
 	E2BIG:           "Argument list too long",

error_darwin.go

@@ -1,7 +1,6 @@
 package wasi
 
 import (
-	"fmt"
 	"syscall"
 )
 
@@ -198,6 +197,6 @@ func syscallErrnoToWASI(err syscall.Errno) Errno {
 	// case syscall.ETOOMANYREFS:
 
 	default:
-		panic(fmt.Errorf("unexpected syscall.Errno(%d): %v", int(err), err))
+		panic("unsupported syscall errno: " + err.Error())
 	}
 }

error_linux.go

@@ -1,7 +1,6 @@
 package wasi
 
 import (
-	"fmt"
 	"syscall"
 )
 
@@ -222,6 +221,6 @@ func syscallErrnoToWASI(err syscall.Errno) Errno {
 	// case syscall.EXFULL:
 
 	default:
-		panic(fmt.Errorf("unexpected syscall.Errno(%d): %v", int(err), err))
+		panic("unsupported syscall errno: " + err.Error())
 	}
 }

error_test.go

@@ -0,0 +1,19 @@
+package wasi_test
+
+import (
+	"testing"
+
+	"github.com/stealthrocket/wasi-go"
+)
+
+func TestErrno(t *testing.T) {
+	for errno := wasi.Errno(0); errno < wasi.ENOTCAPABLE; errno++ {
+		t.Run(errno.Name(), func(t *testing.T) {
+			e1 := errno.Syscall()
+			e2 := wasi.MakeErrno(e1)
+			if e2 != errno {
+				t.Errorf("conversion to syscall.Errno did not yield the same error code: want=%d got=%d", errno, e2)
+			}
+		})
+	}
+}

error_unix.go

@@ -36,3 +36,164 @@ func makeErrnoSlow(err error) Errno {
 	}
 	panic(fmt.Errorf("unexpected error: %v", err))
 }
+
+func errnoToSyscall(errno Errno) syscall.Errno {
+	switch errno {
+	case ESUCCESS:
+		return 0
+	case E2BIG:
+		return syscall.E2BIG
+	case EACCES:
+		return syscall.EACCES
+	case EADDRINUSE:
+		return syscall.EADDRINUSE
+	case EADDRNOTAVAIL:
+		return syscall.EADDRNOTAVAIL
+	case EAFNOSUPPORT:
+		return syscall.EAFNOSUPPORT
+	case EAGAIN:
+		return syscall.EAGAIN
+	case EALREADY:
+		return syscall.EALREADY
+	case EBADF:
+		return syscall.EBADF
+	case EBADMSG:
+		return syscall.EBADMSG
+	case EBUSY:
+		return syscall.EBUSY
+	case ECANCELED:
+		return syscall.ECANCELED
+	case ECHILD:
+		return syscall.ECHILD
+	case ECONNABORTED:
+		return syscall.ECONNABORTED
+	case ECONNREFUSED:
+		return syscall.ECONNREFUSED
+	case ECONNRESET:
+		return syscall.ECONNRESET
+	case EDEADLK:
+		return syscall.EDEADLK
+	case EDESTADDRREQ:
+		return syscall.EDESTADDRREQ
+	case EDOM:
+		return syscall.EDOM
+	case EDQUOT:
+		return syscall.EDQUOT
+	case EEXIST:
+		return syscall.EEXIST
+	case EFAULT:
+		return syscall.EFAULT
+	case EFBIG:
+		return syscall.EFBIG
+	case EHOSTUNREACH:
+		return syscall.EHOSTUNREACH
+	case EIDRM:
+		return syscall.EIDRM
+	case EILSEQ:
+		return syscall.EILSEQ
+	case EINPROGRESS:
+		return syscall.EINPROGRESS
+	case EINTR:
+		return syscall.EINTR
+	case EINVAL:
+		return syscall.EINVAL
+	case EIO:
+		return syscall.EIO
+	case EISCONN:
+		return syscall.EISCONN
+	case EISDIR:
+		return syscall.EISDIR
+	case ELOOP:
+		return syscall.ELOOP
+	case EMFILE:
+		return syscall.EMFILE
+	case EMLINK:
+		return syscall.EMLINK
+	case EMSGSIZE:
+		return syscall.EMSGSIZE
+	case EMULTIHOP:
+		return syscall.EMULTIHOP
+	case ENAMETOOLONG:
+		return syscall.ENAMETOOLONG
+	case ENETDOWN:
+		return syscall.ENETDOWN
+	case ENETRESET:
+		return syscall.ENETRESET
+	case ENETUNREACH:
+		return syscall.ENETUNREACH
+	case ENFILE:
+		return syscall.ENFILE
+	case ENOBUFS:
+		return syscall.ENOBUFS
+	case ENODEV:
+		return syscall.ENODEV
+	case ENOENT:
+		return syscall.ENOENT
+	case ENOEXEC:
+		return syscall.ENOEXEC
+	case ENOLCK:
+		return syscall.ENOLCK
+	case ENOLINK:
+		return syscall.ENOLINK
+	case ENOMEM:
+		return syscall.ENOMEM
+	case ENOMSG:
+		return syscall.ENOMSG
+	case ENOPROTOOPT:
+		return syscall.ENOPROTOOPT
+	case ENOSPC:
+		return syscall.ENOSPC
+	case ENOSYS:
+		return syscall.ENOSYS
+	case ENOTCONN:
+		return syscall.ENOTCONN
+	case ENOTDIR:
+		return syscall.ENOTDIR
+	case ENOTEMPTY:
+		return syscall.ENOTEMPTY
+	case ENOTRECOVERABLE:
+		return syscall.ENOTRECOVERABLE
+	case ENOTSOCK:
+		return syscall.ENOTSOCK
+	case ENOTSUP:
+		return syscall.ENOTSUP
+	case ENOTTY:
+		return syscall.ENOTTY
+	case ENXIO:
+		return syscall.ENXIO
+	case EOVERFLOW:
+		return syscall.EOVERFLOW
+	case EOWNERDEAD:
+		return syscall.EOWNERDEAD
+	case EPERM:
+		return syscall.EPERM
+	case EPIPE:
+		return syscall.EPIPE
+	case EPROTO:
+		return syscall.EPROTO
+	case EPROTONOSUPPORT:
+		return syscall.EPROTONOSUPPORT
+	case EPROTOTYPE:
+		return syscall.EPROTOTYPE
+	case ERANGE:
+		return syscall.ERANGE
+	case EROFS:
+		return syscall.EROFS
+	case ESPIPE:
+		return syscall.ESPIPE
+	case ESRCH:
+		return syscall.ESRCH
+	case ESTALE:
+		return syscall.ESTALE
+	case ETIMEDOUT:
+		return syscall.ETIMEDOUT
+	case ETXTBSY:
+		return syscall.ETXTBSY
+	case EXDEV:
+		return syscall.EXDEV
+	case ENOTCAPABLE:
+		return syscall.EPERM
+	default:
+		panic("unsupport wasi errno: " + errno.Error())
+	}
+}