Add the brother240tool program.

doc/disk-brother.md

@@ -129,8 +129,8 @@ reverse engineered it to find out.
 
 Standard Linux mtools will access the filesystem image and allow you to move
 files in and out. However, you'll need to change the media type bytes at
-offsets 0x015 and 0x100 from 0x58 to 0xf0 before mtools will touch it. Once
-done, this will work:
+offsets 0x015 and 0x100 from 0x58 to 0xf0 before mtools will touch it. The
+supplied `brother240tool` will do this. Once done, this will work:
 
 ```
 mdir -i brother.img

mkninja.sh

@@ -233,6 +233,13 @@ buildsimpleprogram brother120tool \
     libemu.a \
     libfmt.a \
 
+buildsimpleprogram brother240tool \
+	-Idep/emu \
+    tools/brother240tool.cc \
+    libbackend.a \
+    libemu.a \
+    libfmt.a \
+
 runtest bitaccumulator-test tests/bitaccumulator.cc
 runtest bytes-test          tests/bytes.cc
 runtest compression-test    tests/compression.cc

tools/brother240tool.cc

@@ -0,0 +1,56 @@
+#include "globals.h"
+#include "fmt/format.h"
+#include <fstream>
+
+static std::fstream inputFile;
+
+void syntax()
+{
+    std::cout << "Syntax: brother240tool <image>\n"
+                 "The disk image will be flipped from Brother to DOS format and back\n"
+                 "again.\n";
+    exit(0);
+}
+
+uint8_t getbyte(uint32_t offset)
+{
+    inputFile.seekg(offset, std::ifstream::beg);
+    return inputFile.get();
+}
+
+void putbyte(uint32_t offset, uint8_t value)
+{
+    inputFile.seekp(offset, std::ifstream::beg);
+    inputFile.put(value);
+}
+
+int main(int argc, const char* argv[])
+{
+    if (argc < 2)
+        syntax();
+    
+    inputFile.open(argv[1], std::ios::in | std::ios::out | std::ios::binary);
+    if (!inputFile.is_open())
+		Error() << fmt::format("cannot open input file '{}'", argv[1]);
+
+    uint8_t b1 = getbyte(0x015);
+    uint8_t b2 = getbyte(0x100);
+    if ((b1 == 0x58) && (b2 == 0x58))
+    {
+        std::cerr << "Flipping from Brother to DOS.\n";
+        putbyte(0x015, 0xf0);
+        putbyte(0x100, 0xf0);
+    }
+    else if ((b1 == 0xf0) && (b2 == 0xf0))
+    {
+        std::cerr << "Flipping from DOS to Brother.\n";
+        putbyte(0x015, 0x58);
+        putbyte(0x100, 0x58);
+    }
+    else
+        Error() << "Unknown image format.";
+
+    inputFile.close();
+    return 0;
+}
+