duskos

commit 2a0b4df730a6991fc76475c6e016f7677b3fd981
parent 0c9a2b553c59f74be6b0e158b41249edb0e7276c
Author: Virgil Dupras <hsoft@hardcoded.net>
Date:   Fri,  1 Jul 2022 20:54:31 -0400

fs/boot: Add FAT12 support

Diffstat:
M
Makefile
 | 
4
++--
M
fs/fs/boot.fs
 | 
22
+++++++++++++++-------
M
fs/tests/sys/drive.fs
 | 
2
+-

3 files changed, 18 insertions(+), 10 deletions(-)
diff --git a/Makefile b/Makefile
@@ -15,8 +15,8 @@ boot.fs: $(BOOTFS_SRC)
 	cat $(BOOTFS_SRC) > $@
 
 fatfs: fs
-	dd if=/dev/zero of=$@ bs=4M count=1
-	mformat -d 1 -i $@ ::
+	dd if=/dev/zero of=$@ bs=1M count=1
+	mformat -M 512 -d 1 -i $@ ::
 	mcopy -sQ -i $@ fs/* ::
 
 .PHONY: run
diff --git a/fs/fs/boot.fs b/fs/fs/boot.fs
@@ -9,8 +9,7 @@
 \ This unit has access to a very small set of words, that it, words implemented
 \ by boot.fs as well as the "drive" protocol, which is implemented by a driver
 \ that is inserted between boot.fs and this unit.
-create bpb drvblksz allot
-0 bpb (drv@)
+create bpb 0 here (drv@) $18 allot
 
 : BPB_BytsPerSec bpb $0b + w@ ;
 : BPB_SecPerClus bpb $0d + c@ ;
@@ -25,15 +24,18 @@ create bpb drvblksz allot
 : FirstSectorOfCluster ( n -- sec ) 1- 1- BPB_SecPerClus * FirstDataSector + ;
 : FirstRootDirSecNum BPB_RsvdSecCnt BPB_NumFATs BPB_FATSz16 * + ;
 : ClusterSize BPB_SecPerClus BPB_BytsPerSec * ;
+: DataSec
+  BPB_TotSec16 BPB_FATSz16 BPB_NumFATs * BPB_RsvdSecCnt + RootDirSectors + - ;
+: CountOfClusters DataSec BPB_SecPerClus / ;
+: FAT12? CountOfClusters 4085 < ;
 
 \ read multiple sectors in buf
 : readsectors ( sec u buf -- )
   A>r swap >r swap >A begin ( buf )
     A> over (drv@) A+ drvblksz + next ( buf ) drop r>A ;
 
-create FAT16( BPB_BytsPerSec BPB_FATSz16 * allot
-here value )FAT16
-: readFAT BPB_RsvdSecCnt BPB_FATSz16 FAT16( readsectors ;
+create FAT( BPB_BytsPerSec BPB_FATSz16 * allot
+: readFAT BPB_RsvdSecCnt BPB_FATSz16 FAT( readsectors ;
 
 32 const DIRENTRYSZ
 11 const FNAMESZ
@@ -71,10 +73,16 @@ here const )fnbuf
 \ Make the current dir the root
 : readroot FirstRootDirSecNum RootDirSectors dirbuf( readsectors ;
 
-: EOC? ( cluster -- f ) $fff8 and $fff8 = ;
+: EOC? ( cluster -- f )
+  FAT12? if $ff8 else $fff8 then tuck and = ;
 
 \ get cluster following this one in the FAT
-: nextcluster ( cluster -- nextcluster ) << FAT16( + w@ ;
+: nextcluster ( cluster -- nextcluster )
+  FAT12? if
+    dup dup >> + ( cl off )
+    FAT( + w@ ( cl ncl ) swap 1 and if 4 rshift else $fff and then
+  else
+    << FAT( + w@ then ;
 
 : readcluster ( cluster dst -- )
   over << BPB_BytsPerSec BPB_FATSz16 * >= if abort" cluster out of range" then
diff --git a/fs/tests/sys/drive.fs b/fs/tests/sys/drive.fs
@@ -1,5 +1,5 @@
 ?f<< tests/harness.fs
 testbegin
 \ Tests for sys/ramdrive (already loaded in init.fs)
-$36 8 drvseek ( a ) 8 []>str S" FAT16   " #s=
+$36 8 drvseek ( a ) 8 []>str S" FAT12   " #s=
 testend