atrcheck: classify DOS type (WIP, not complete).

3 files changed, 99 insertions, 16 deletions

diff --git a/atr2xfd.1 b/atr2xfd.1
index 1eca729..a192c2c 100644
--- a/atr2xfd.1
+++ b/atr2xfd.1
@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "ATR2XFD" 1 "2024-05-03" "0.2.1" "Urchlay's Atari 8-bit Tools"
+.TH "ATR2XFD" 1 "2024-05-05" "0.2.1" "Urchlay's Atari 8-bit Tools"
 .SH NAME
 atr2xfd \- Convert an Atari 8-bit ATR disk image to a raw (XFD) image
 .\" RST source for atr2xfd(1) man page. Convert with:
@@ -43,7 +43,7 @@ atr2xfd \- Convert an Atari 8-bit ATR disk image to a raw (XFD) image
 \fBatrcheck\fP \fIinfile.atr\fP
 .SH DESCRIPTION
 .sp
-\fBatr2xfd\fP  strips  the  16\-byte  ATR header from an ATR image. While this
+\fBatr2xfd\fP strips the 16\-byte ATR header from an ATR image. While this
 could be done with a command like:
 .INDENT 0.0
 .INDENT 3.5
@@ -56,13 +56,14 @@ dd if=infile.atr outfile.xfd bs=16 skip=1
 .UNINDENT
 .UNINDENT
 .sp
-\&...**atr2xfd** first checks that its input is in fact an  ATR  file,  then
+\&...**atr2xfd** first checks that its input is in fact an ATR file, then
 checks the ATR header and reports any problems it may find.
 .sp
-\fBatrcheck\fP  performs  the  same  checks  as \fBatr2xfd\fP, but doesn\(aqt actually
-write an XFD image. In fact, \fBatrcheck\fP is a symbolic  link  to  \fBatr2xfd\fP,
-which  changes  its  behaviour  (simply  doesn\(aqt write any output) when
-called via the link.
+\fBatrcheck\fP performs the same checks as \fBatr2xfd\fP, but doesn\(aqt actually
+write an XFD image. In fact, \fBatrcheck\fP is a symbolic link to \fBatr2xfd\fP,
+which changes its behaviour (simply doesn\(aqt write any output) when
+called via the link. \fBatrcheck\fP also examines the boot sector of the ATR,
+and attempts to detect which Atari DOS is on the image (if any).
 .sp
 Neither \fBatr2xfd\fP nor \fBatrcheck\fP take any options.
 .SH NOTES
diff --git a/atr2xfd.c b/atr2xfd.c
index c941266..bed24fe 100644
--- a/atr2xfd.c
+++ b/atr2xfd.c
@@ -13,9 +13,12 @@
 #define SELF "atr2xfd"
 #define CHECK "atrcheck"
 
+char *self = SELF;
+
+void classify_boot_sector(FILE *);
+
 int main(int argc, char **argv) {
 	char *type;
-	char *self = SELF;
 	struct stat st;
 	char infile[4096], outfile[4096];
 	unsigned char buf[16];
@@ -177,7 +180,9 @@ int main(int argc, char **argv) {
 
 	fprintf(stderr, "%s: %s is a %s\n", self, infile, type);
 
-	fprintf(stderr, "%s: ATR image OK (no fatal errors).\n", self);
+	if(checkonly) {
+		classify_boot_sector(in);
+	}
 
 	hparas = buf[2] + (buf[3] << 8) + (buf[6] << 16);
 	if(hparas != paras) {
@@ -197,8 +202,11 @@ int main(int argc, char **argv) {
 				self);
 	}
 
-	if(checkonly)
+	if(checkonly) {
 		exit(0);
+	}
+
+	fprintf(stderr, "%s: ATR image OK (no fatal errors).\n", self);
 
 	/* Only open the output file after the ATR is known to be good */
 	if(strcmp(outfile, "-") == 0) {
@@ -242,3 +250,76 @@ int main(int argc, char **argv) {
 
 	return i;
 }
+
+/* these signatures are for the first N bytes of sector 1. */
+unsigned char dos1_sig[] = "\x00\x01\x00\x07\x00\x13\x4c\x12";
+unsigned char dos2_sig[] = "\x00\x03\x00\x07\x40\x15\x4c\x14";
+unsigned char dos3_sig[] = "\x01\x09\x00\x32\x06\x32";
+unsigned char mydos3_sig[] = "\x00\x03\x00\x07\xe0\x07\x4c\x14";
+unsigned char mydos4_sig[] = "\x4d\x03\x00\x07\xe0\x07\x4c\x14";
+unsigned char topdos11_sig[] = "\xc0\x03\x00\x07\x40\x15\x4c\x24";
+unsigned char topdos15_sig[] = "\x80\x03\x00\x07\x40\x15\x4c\x24";
+unsigned char blank_sig[] = "\x00\x00\x00\x00\x00\x00\x00\x00";
+unsigned char pico_sig[] = "\x00\x03\x00\x10\x10\x4c";
+
+/* these signatures are for offset $18 of sector 1. */
+unsigned char dos2_code_sig[] = "\x36\xad\x12\x07";
+unsigned char dos25_code_sig[] = "\x35\x20\x5f\x07";
+
+#define SIG_MATCH(x, y) (memcmp(x, y, sizeof(y) - 1) == 0)
+
+void classify_boot_sector(FILE *f) {
+	unsigned char buf[128];
+	char *dos_type = "Unknown", *boot_text = "";
+	int bootable = -1; /* -1 = unknown, 0 = no, 1 = yes */
+	int i;
+
+	/* read 1st sector... */
+	if( (fread(buf, 1, 128, f) < 128) ) {
+		fprintf(stderr, "%s: EOF reading sector 1, truncated image.\n", self);
+		exit(2);
+	}
+
+#if 1
+	for(i = 0; i < 8; i++) fprintf(stderr, "\\x%02x", buf[i]);
+	fputc('\n', stderr);
+#endif
+
+	/* now figure out what kind of boot sector this is */
+	if(SIG_MATCH(buf, dos1_sig)) {
+		dos_type = "DOS 1.0";
+	} else if(SIG_MATCH(buf, dos3_sig)) {
+		dos_type = "DOS 3.0";
+	} else if(SIG_MATCH(buf, dos2_sig)) {
+		if(SIG_MATCH(buf + 0x18, dos2_code_sig))
+			dos_type = "DOS 2.0";
+		else if(SIG_MATCH(buf + 0x18, dos25_code_sig))
+			dos_type = "DOS 2.5";
+		else
+			dos_type = "DOS 2.0 compatible";
+		bootable = (buf[14] != 0);
+	} else if(buf[0] == 0x00 && buf[1] == 0x03 &&
+			(buf[32] == 0x11 || buf[32] == 0x20) &&
+			buf[6] == 0x4c && buf[7] == 0x80) {
+		if(buf[32] == 0x11)
+			dos_type = "SpartaDOS 1.1";
+		else
+			dos_type = "SpartaDOS >= 2";
+	} else if(SIG_MATCH(buf, mydos3_sig)) {
+		dos_type = "MyDOS 3.x";
+	} else if(SIG_MATCH(buf, mydos4_sig)) {
+		dos_type = "MyDOS 4.x";
+	} else if(SIG_MATCH(buf, pico_sig)) {
+		dos_type = "MyPicoDOS 4.x";
+	} else if(SIG_MATCH(buf, blank_sig)) {
+		dos_type = "None (empty boot sector)";
+		bootable = 0;
+	}
+
+	if(bootable == 0)
+		boot_text = ", not bootable";
+	else if(bootable == 1)
+		boot_text = ", bootable";
+
+	fprintf(stderr, "%s: DOS type is: %s%s\n", self, dos_type, boot_text);
+}
diff --git a/atr2xfd.rst b/atr2xfd.rst
index fac2ed4..cdf041c 100644
--- a/atr2xfd.rst
+++ b/atr2xfd.rst
@@ -22,18 +22,19 @@ SYNOPSIS
 DESCRIPTION
 ===========
 
-**atr2xfd**  strips  the  16-byte  ATR header from an ATR image. While this
+**atr2xfd** strips the 16-byte ATR header from an ATR image. While this
 could be done with a command like::
 
   dd if=infile.atr outfile.xfd bs=16 skip=1
 
-...**atr2xfd** first checks that its input is in fact an  ATR  file,  then
+...**atr2xfd** first checks that its input is in fact an ATR file, then
 checks the ATR header and reports any problems it may find.
 
-**atrcheck**  performs  the  same  checks  as **atr2xfd**, but doesn't actually
-write an XFD image. In fact, **atrcheck** is a symbolic  link  to  **atr2xfd**,
-which  changes  its  behaviour  (simply  doesn't write any output) when
-called via the link.
+**atrcheck** performs the same checks as **atr2xfd**, but doesn't actually
+write an XFD image. In fact, **atrcheck** is a symbolic link to **atr2xfd**,
+which changes its behaviour (simply doesn't write any output) when
+called via the link. **atrcheck** also examines the boot sector of the ATR,
+and attempts to detect which Atari DOS is on the image (if any).
 
 Neither **atr2xfd** nor **atrcheck** take any options.