1 files changed, 78 insertions, 0 deletions
diff --git a/libgloss/m68k/atari/atari-open.c b/libgloss/m68k/atari/atari-open.c
new file mode 100644
index 0000000..c610718
--- /dev/null
+++ b/libgloss/m68k/atari/atari-open.c
@@ -0,0 +1,78 @@
+/*
+	Copyright (C) 2025 Mikael Hildenborg
+	SPDX-License-Identifier: BSD-2-Clause
+*/
+
+#include <unistd.h>
+#include <_ansi.h>
+#include "atari-gem_errno.h"
+#include "atari-traps.h"
+
+// I really don't like having these defines here,
+// fcntl.h where they are, also defines a function for "open",
+// that is different from the one libgloss is supposed to provide...
+#ifndef O_CREAT
+#define O_CREAT 0x0200
+#endif // O_CREAT
+#ifndef O_APPEND
+#define O_APPEND 0x0008
+#endif // O_APPEND
+#ifndef O_EXCL
+#define O_EXCL 0x0800
+#endif // O_EXCL
+#ifndef O_TRUNC
+#define O_TRUNC 0x0400
+#endif // O_TRUNC
+
+// mode is ignored. Those kind of settings is not supported by the st.
+int open(const char *buf, int flags, int mode)
+{
+	int bios_handle = -1;
+	unsigned short bios_mode = (unsigned short)(flags & 0x3); // bits 0-1 the same for st and linux.
+	int create = flags & O_CREAT;
+	int append = flags & O_APPEND; // open doc says that seek end should be done before each write call. We assume that newlib handles that.
+	int excl = flags & O_EXCL;	   // File must be created by this call.
+	int trunc = flags & O_TRUNC;   // File is forced to be created and thus truncated.
+
+	const char *bios_path = buf;
+	if (!trunc)
+	{
+		bios_handle = trap1_3d(bios_path, bios_mode);
+	}
+	if (bios_handle < 0 && (create || trunc))
+	{
+		unsigned short bios_attrib = 0;
+		bios_handle = trap1_3c(bios_path, bios_attrib);
+	}
+	else if (create && excl)
+	{
+		// We explicitly specified that file must be created, and it already existed, so error!
+		gem_error_to_errno(GEM_EACCDN);
+		// Close file.
+		trap1_3e((unsigned short)bios_handle);
+		return -1;
+	}
+
+	if (bios_handle >= 0 && append)
+	{
+		// Seek to end.
+		int new_file_pos = trap1_42(0, (unsigned short)bios_handle, 2);
+		if (new_file_pos < 0)
+		{
+			gem_error_to_errno(new_file_pos);
+			// Close file.
+			trap1_3e((unsigned short)bios_handle);
+			return -1;
+		}
+	}
+
+	if (bios_handle < 0)
+	{
+		gem_error_to_errno(bios_handle);
+		bios_handle = -1;
+	}
+	/*
+		If bios_handle is positive, then the low word is the gemdos handle, and the high word is zero.
+	*/
+	return bios_handle;
+}