From a099543f2193948ba604165d2824ac3b9dbd8d4d Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Tue, 9 Jul 2024 20:07:56 -0400
Subject: whichbas: add BASIC/A+ detection.

---
 whichbas.1   |  5 ++++-
 whichbas.c   | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++--------
 whichbas.rst |  5 ++++-
 3 files changed, 63 insertions(+), 10 deletions(-)

diff --git a/whichbas.1 b/whichbas.1
index baead4f..7f422c3 100644
--- a/whichbas.1
+++ b/whichbas.1
@@ -36,7 +36,7 @@ whichbas [\-v] \fIinput\-file\fP
 .SH DESCRIPTION
 .sp
 \fBwhichbas\fP reads a tokenized Atari 8\-bit BASIC, Turbo BASIC,
-BASIC XL, BASIC XE, or Atari Microsoft BASIC program and attempts to
+BASIC XL, BASIC XE, BASIC/A+, or Atari Microsoft BASIC program and attempts to
 discover which BASIC is required to run it.
 .sp
 \fIinput\-file\fP must be an actual file. \fBwhichbas\fP can\(aqt read from
@@ -186,6 +186,9 @@ EXTENDed OSS BASIC XE detected.
 .B \fB13\fP
 Compiled Turbo BASIC detected.
 .TP
+.B \fB14\fP
+OSS BASIC/A+ detected.
+.TP
 .B \fB64\fP
 None of the above; not BASIC.
 .UNINDENT
diff --git a/whichbas.c b/whichbas.c
index 3b74415..13289f0 100644
--- a/whichbas.c
+++ b/whichbas.c
@@ -28,6 +28,7 @@ int bas_type = 0x0f; /* start out with all enabled */
 #define SRET_AMSB                 11
 #define SRET_EXTENDED_BXE         12
 #define SRET_COMPILED_TURBO       13
+#define SRET_APLUS                14
 #define SRET_NOT_BASIC            64
 
 int script_mode = 0; /* -s flag */
@@ -712,7 +713,7 @@ int detect_amsb(void) {
 }
 
 void foreign(const char *name, int srval) {
-	fclose(input_file);
+	if(input_file) fclose(input_file);
 	if(script_mode) {
 		exit(srval);
 	} else {
@@ -806,6 +807,57 @@ void check_variables(void) {
 	   to disk. Too bad. */
 }
 
+/* BASIC/A+ support is *very* simple. It's similar to BASIC XL (no
+   surprise there)... but unlike Turbo, BXL, and BXE, it's *not*
+   token-compatible with original Atari BASIC. Rather than add
+   their new tokens to the end of the lists, they're mixed in with
+   the others. So A+ can't even LOAD or RUN Atari BASIC files. I
+   suppose the manual told you to LIST in BASIC, reboot, ENTER in
+   A+, to "port" your BASIC programs to A+.
+
+   While this was probably a PITA for BASIC/A+ users back in the day,
+   it makes it *really* easy to detect A+ here. The last line of
+   every SAVEed program is the direct-mode command, and contains either
+   a SAVE or CSAVE cmd token. Which is the same token in Atari, Turbo,
+   BXL, and BXE... but *different* in A+. */
+CALLBACK(check_aplus_cmd) {
+	unsigned char nexttok;
+	int aplus_found = 0;
+
+	nexttok = program[pos + 1];
+
+	if(tok == 0x1d) {
+		/* SAVE in A+ (OP_STRCONST next).
+		   XIO in anything else (OP_HASH next). */
+		/* Note that A+ still uses the same tokens as BASIC for OP_STRCONST,
+		   OP_EOS, and OP_EOL. */
+		aplus_found = (nexttok == OP_STRCONST);
+	} else if(tok == 0x48) {
+		/* CSAVE in A+ (no arg).
+		   RND in anything else (OP_FUNC_LPAR next). */
+		aplus_found = (nexttok == OP_EOS || nexttok == OP_EOL);
+	}
+
+	if(aplus_found) {
+		foreign("OSS BASIC/A+", SRET_APLUS);
+	}
+}
+
+void check_aplus(void) {
+	on_cmd_token = check_aplus_cmd;
+	walk_code(32768, 32768);
+}
+
+void check_atari_turbo_oss(void) {
+	allow_hex_const = 1;
+
+	on_cmd_token = handle_cmd;
+	on_exp_token = handle_op;
+	on_end_stmt = handle_end_stmt;
+
+	walk_all_code();
+}
+
 int main(int argc, char **argv) {
 	set_self(*argv);
 	parse_general_args(argc, argv, print_help);
@@ -817,13 +869,8 @@ int main(int argc, char **argv) {
 	parse_header();
 
 	check_variables();
-
-	allow_hex_const = 1;
-	on_cmd_token = handle_cmd;
-	on_exp_token = handle_op;
-	on_end_stmt = handle_end_stmt;
-
-	walk_all_code();
+	check_aplus();
+	check_atari_turbo_oss();
 
 	print_result(); /* always exits */
 	return 0; /* never happens, shuts up gcc's warning though */
diff --git a/whichbas.rst b/whichbas.rst
index 327e8dc..497b0ff 100644
--- a/whichbas.rst
+++ b/whichbas.rst
@@ -15,7 +15,7 @@ whichbas [-v] *input-file*
 DESCRIPTION
 ===========
 **whichbas** reads a tokenized Atari 8-bit BASIC, Turbo BASIC,
-BASIC XL, BASIC XE, or Atari Microsoft BASIC program and attempts to
+BASIC XL, BASIC XE, BASIC/A+, or Atari Microsoft BASIC program and attempts to
 discover which BASIC is required to run it.
 
 *input-file* must be an actual file. **whichbas** can't read from
@@ -154,6 +154,9 @@ With the **-s** option, the exit status is:
 **13**
   Compiled Turbo BASIC detected.
 
+**14**
+  OSS BASIC/A+ detected.
+
 **64**
   None of the above; not BASIC.
 
-- 
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