WASI & darwin: support basic file io based on libc

Signed-off-by: Takeshi Yoneda <takeshi@tetrate.io>

src/syscall/syscall_libc_wasi.go

@@ -33,7 +33,6 @@ const (
 	O_RDWR   = O_RDONLY | O_WRONLY
 
 	O_CREAT  = __WASI_OFLAGS_CREAT << 12
-	O_CREATE = O_CREAT
 	O_TRUNC  = __WASI_OFLAGS_TRUNC << 12
 	O_APPEND = __WASI_FDFLAGS_APPEND
 	O_EXCL   = __WASI_OFLAGS_EXCL << 12
@@ -48,3 +47,95 @@ var libcErrno uintptr
 func getErrno() error {
 	return Errno(libcErrno)
 }
+
+func (e Errno) Is(target error) bool {
+	switch target.Error() {
+	case "permission denied":
+		return e == EACCES || e == EPERM || e == ENOTCAPABLE // ENOTCAPABLE is unique in WASI
+	case "file already exists":
+		return e == EEXIST || e == ENOTEMPTY
+	case "file does not exist":
+		return e == ENOENT
+	}
+	return false
+}
+
+// https://github.com/WebAssembly/wasi-libc/blob/main/libc-bottom-half/headers/public/__errno.h
+const (
+	E2BIG           Errno = 1      /* Argument list too long */
+	EACCES          Errno = 2      /* Permission denied */
+	EADDRINUSE      Errno = 3      /* Address already in use */
+	EADDRNOTAVAIL   Errno = 4      /* Address not available */
+	EAFNOSUPPORT    Errno = 5      /* Address family not supported by protocol family */
+	EAGAIN          Errno = 6      /* Try again */
+	EWOULDBLOCK     Errno = EAGAIN /* Operation would block */
+	EALREADY        Errno = 7      /* Socket already connected */
+	EBADF           Errno = 8      /* Bad file number */
+	EBADMSG         Errno = 9      /* Trying to read unreadable message */
+	EBUSY           Errno = 10     /* Device or resource busy */
+	ECANCELED       Errno = 11     /* Operation canceled. */
+	ECHILD          Errno = 12     /* No child processes */
+	ECONNABORTED    Errno = 13     /* Connection aborted */
+	ECONNREFUSED    Errno = 14     /* Connection refused */
+	ECONNRESET      Errno = 15     /* Connection reset by peer */
+	EDEADLK         Errno = 16     /* Deadlock condition */
+	EDESTADDRREQ    Errno = 17     /* Destination address required */
+	EDOM            Errno = 18     /* Math arg out of domain of func */
+	EDQUOT          Errno = 19     /* Quota exceeded */
+	EEXIST          Errno = 20     /* File exists */
+	EFAULT          Errno = 21     /* Bad address */
+	EFBIG           Errno = 22     /* File too large */
+	EHOSTUNREACH    Errno = 23     /* Host is unreachable */
+	EIDRM           Errno = 24     /* Identifier removed */
+	EILSEQ          Errno = 25
+	EINPROGRESS     Errno = 26 /* Connection already in progress */
+	EINTR           Errno = 27 /* Interrupted system call */
+	EINVAL          Errno = 28 /* Invalid argument */
+	EIO             Errno = 29 /* I/O error */
+	EISCONN         Errno = 30 /* Socket is already connected */
+	EISDIR          Errno = 31 /* Is a directory */
+	ELOOP           Errno = 32 /* Too many symbolic links */
+	EMFILE          Errno = 33 /* Too many open files */
+	EMLINK          Errno = 34 /* Too many links */
+	EMSGSIZE        Errno = 35 /* Message too long */
+	EMULTIHOP       Errno = 36 /* Multihop attempted */
+	ENAMETOOLONG    Errno = 37 /* File name too long */
+	ENETDOWN        Errno = 38 /* Network interface is not configured */
+	ENETRESET       Errno = 39
+	ENETUNREACH     Errno = 40         /* Network is unreachable */
+	ENFILE          Errno = 41         /* File table overflow */
+	ENOBUFS         Errno = 42         /* No buffer space available */
+	ENODEV          Errno = 43         /* No such device */
+	ENOENT          Errno = 44         /* No such file or directory */
+	ENOEXEC         Errno = 45         /* Exec format error */
+	ENOLCK          Errno = 46         /* No record locks available */
+	ENOLINK         Errno = 47         /* The link has been severed */
+	ENOMEM          Errno = 48         /* Out of memory */
+	ENOMSG          Errno = 49         /* No message of desired type */
+	ENOPROTOOPT     Errno = 50         /* Protocol not available */
+	ENOSPC          Errno = 51         /* No space left on device */
+	ENOSYS          Errno = 52         /* Function not implemented */
+	ENOTCONN        Errno = 53         /* Socket is not connected */
+	ENOTDIR         Errno = 54         /* Not a directory */
+	ENOTEMPTY       Errno = 55         /* Directory not empty */
+	ENOTSOCK        Errno = 57         /* Socket operation on non-socket */
+	ESOCKTNOSUPPORT Errno = 58         /* Socket type not supported */
+	EOPNOTSUPP      Errno = 58         /* Operation not supported on transport endpoint */
+	ENOTSUP         Errno = EOPNOTSUPP /* Not supported */
+	ENOTTY          Errno = 59         /* Not a typewriter */
+	ENXIO           Errno = 60         /* No such device or address */
+	EOVERFLOW       Errno = 61         /* Value too large for defined data type */
+	EPERM           Errno = 63         /* Operation not permitted */
+	EPIPE           Errno = 64         /* Broken pipe */
+	EPROTO          Errno = 65         /* Protocol error */
+	EPROTONOSUPPORT Errno = 66         /* Unknown protocol */
+	EPROTOTYPE      Errno = 67         /* Protocol wrong type for socket */
+	ERANGE          Errno = 68         /* Math result not representable */
+	EROFS           Errno = 69         /* Read-only file system */
+	ESPIPE          Errno = 70         /* Illegal seek */
+	ESRCH           Errno = 71         /* No such process */
+	ESTALE          Errno = 72
+	ETIMEDOUT       Errno = 73 /* Connection timed out */
+	EXDEV           Errno = 75 /* Cross-device link */
+	ENOTCAPABLE     Errno = 76 /* Extension: Capabilities insufficient. */
+)