From fca6a1494396d260cf6a4e9c08f3aa2ec86fdf4f Mon Sep 17 00:00:00 2001
From: David Korth <gerbilsoft@gerbilsoft.com>
Date: Sun, 25 Feb 2024 20:23:11 -0500
Subject: [PATCH] [libromdata] CBMDOS::loadFileData: Parse the disk name as
 ASCII if it has a GEOS ID string.

The ID string may indicate "V1.0" or "V1.1", so we're only checking
for the presence of "GEOS".
---
 src/libromdata/Media/CBMDOS.cpp       | 21 ++++++++++++++-------
 src/libromdata/Media/cbmdos_structs.h |  8 ++++++++
 2 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/src/libromdata/Media/CBMDOS.cpp b/src/libromdata/Media/CBMDOS.cpp
index 8bca3f55d4..ef117e48b9 100644
--- a/src/libromdata/Media/CBMDOS.cpp
+++ b/src/libromdata/Media/CBMDOS.cpp
@@ -1090,15 +1090,22 @@ int CBMDOS::loadFieldData(void)
 		}
 
 		// Disk name
+		const char *const s_disk_name_title = C_("CBMDOS", "Disk Name");
 		remove_A0_padding(disk_name, disk_name_len);
-		string s_disk_name = cpN_to_utf8(codepage, disk_name, disk_name_len);
-		if (s_disk_name.find(uFFFD) != string::npos) {
-			// Disk name has invalid characters when using Unshifted.
-			// Try again with Shifted.
-			codepage = CP_RP_PETSCII_Shifted;
-			s_disk_name = cpN_to_utf8(codepage, disk_name, disk_name_len);
+		if (unlikely(!memcmp(c1541_bam.geos.geos_id_string, "GEOS", 4))) {
+			// GEOS ID is present. Parse the disk name as ASCII. (well, Latin-1)
+			d->fields.addField_string(s_disk_name_title,
+				latin1_to_utf8(disk_name, disk_name_len));
+		} else {
+			string s_disk_name = cpN_to_utf8(codepage, disk_name, disk_name_len);
+			if (s_disk_name.find(uFFFD) != string::npos) {
+				// Disk name has invalid characters when using Unshifted.
+				// Try again with Shifted.
+				codepage = CP_RP_PETSCII_Shifted;
+				s_disk_name = cpN_to_utf8(codepage, disk_name, disk_name_len);
+			}
+			d->fields.addField_string(s_disk_name_title, s_disk_name);
 		}
-		d->fields.addField_string(C_("CBMDOS", "Disk Name"), s_disk_name);
 
 		// Disk ID
 		d->fields.addField_string(C_("CBMDOS", "Disk ID"),
diff --git a/src/libromdata/Media/cbmdos_structs.h b/src/libromdata/Media/cbmdos_structs.h
index 6ae8f49320..4b4c65f4b5 100644
--- a/src/libromdata/Media/cbmdos_structs.h
+++ b/src/libromdata/Media/cbmdos_structs.h
@@ -42,6 +42,7 @@ ASSERT_STRUCT(cbmdos_TS_ptr_t, 2);
 /**
  * CBMDOS: C1541 Block Allocation Map (18/0)
  */
+#define GEOS_ID_STRING "GEOS format V1.x"	// the 'x' may be 0 or 1; the '.' may be missing
 typedef struct _cbmdos_C1541_BAM_t {
 	cbmdos_TS_ptr_t next;	// $00: Location of the first directory sector
 	                        //      NOTE: Ignore this; it should always be 18/1.
@@ -70,6 +71,13 @@ typedef struct _cbmdos_C1541_BAM_t {
 			uint8_t unused_C1571_AB[0x32];	// $AB
 			uint8_t free_sector_count[35];	// $DD: [C1571] Free sector count for tracks 36-70
 		};
+		struct {
+			cbmdos_TS_ptr_t border_sector;	// $AB: Border sector location
+			char geos_id_string[16];	// $AC: GEOS ID string, in ASCII
+			                                // (check first 4 char for "GEOS" in ASCII)
+			uint8_t unused_other_BD[16];	// $BD
+			uint8_t free_sector_count[35];	// $DD: [C1571] Free sector count for tracks 36-70
+		} geos;
 	};
 } cbmdos_C1541_BAM_t;
 ASSERT_STRUCT(cbmdos_C1541_BAM_t, CBMDOS_SECTOR_SIZE);