From 9a1c4139a6611eb616556da221fbd4b64d62010f Mon Sep 17 00:00:00 2001
From: Nero <41307858+nero@users.noreply.github.com>
Date: Sat, 2 Jan 2021 02:07:40 +0000
Subject: [PATCH] Implement searching directory for exact matches

---
 boot/kernel.asm  | 21 ++++++++----------
 inc/fcb.asm      | 12 ++--------
 kernel/drive.asm | 24 ++++++++++----------
 kernel/fcb.asm   | 53 ++------------------------------------------
 kernel/find.asm  | 57 ++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 82 insertions(+), 85 deletions(-)
 create mode 100644 kernel/find.asm

diff --git a/boot/kernel.asm b/boot/kernel.asm
index 4bca0fe..c756f2b 100644
--- a/boot/kernel.asm
+++ b/boot/kernel.asm
@@ -31,24 +31,21 @@ init:		cli
 
 		call logdrv
 
-		xor ax, ax
-		xor dx, dx
-		call maprd
-
-		inc word [dskbuf+0x82]
-		push word [dskbuf+0x82]
-
-		call dirty
-		call flush
-
-		call printf
-		db "Current run: ",2,0x0A,0x0D,0
+		mov bx, testfcb
+		call fndfst
+		jc huh
+		call putfn
 
 hlt:		hlt
 		jmp hlt
 
+huh:		call printf
+		db "huh", 0
+		jmp hlt
+
 %include	"kernel/far.asm"
 %include	"kernel/fcb.asm"
+%include	"kernel/find.asm"
 %include        "kernel/drive.asm"
 %include	"kernel/printf.asm"
 
diff --git a/inc/fcb.asm b/inc/fcb.asm
index 5a00c81..811d677 100644
--- a/inc/fcb.asm
+++ b/inc/fcb.asm
@@ -1,10 +1,2 @@
-struc fcb
-.drive		resb 1
-.filename	resb 8
-.type		resb 3
-.fn2		resb 8
-.tp2		resb 3
-.dirpos		resw 1
-.cluster	resw 1
-.recordnum	resb 1
-endstruc
+FCBDEN:	equ 23 ; directory entry
+FCBSIZ:	equ 30
diff --git a/kernel/drive.asm b/kernel/drive.asm
index adde2a1..afcb5de 100644
--- a/kernel/drive.asm
+++ b/kernel/drive.asm
@@ -51,21 +51,21 @@ dinit:		; copy previously set DPT to our data area
 		; int 13 stub
 		; place reserved for stack switches
 int13:		; debug output
-		push bx
-		push dx
-		push cx
-		push ax
-		call printf
-		db "int13 CALL AX=",2," CX=",2," DX=",2," BX=",2,0x0A,0x0D,0
+		;push bx
+		;push dx
+		;push cx
+		;push ax
+		;call printf
+		;db "int13 CALL AX=",2," CX=",2," DX=",2," BX=",2,0x0A,0x0D,0
 		; do the call
 		int 0x13
-		jc .err
-		ret
-.err:		push ax
-		call printf
-		db "int13 ERR AX=",2,0x0A,0x0D,0
-		stc
+		;jc .err
 		ret
+.err:		;push ax
+		;call printf
+		;db "DISK ERR AX=",2,0x0A,0x0D,0
+		;stc
+		;ret
 
 		; get drive parameters
 		; read BIOS int13h/AH=8 values
diff --git a/kernel/fcb.asm b/kernel/fcb.asm
index 2e10f7b..6cca5fc 100644
--- a/kernel/fcb.asm
+++ b/kernel/fcb.asm
@@ -9,61 +9,12 @@ section .text
 		; Helper function: read the drive number from FCB,
 		; apply default if necessary,
 		; and make it current I/O drive
-setdrv:		mov dl, [es:bx+fcb.drive] ; A=1
+setdrv:		mov dl, [es:bx] ; A=1
 		test dl, dl
 		jnz .nofix
 		mov dl, [defdrv] ; A=0
 		inc dl
-		mov [es:bx+fcb.drive], dl ; A=1
+		mov [es:bx], dl ; A=1
 		; now set as current i/o drive
 .nofix:		dec dl ; A=0 for dsksel
 		jmp logdrv
-
-		; FCB open
-fcbopn:		; call fcbfst
-		; copy match
-		; store cluster number in fcb
-		; record = 0
-		ret
-
-		; FCB close
-fcbcls:		; flush disk buffer
-		ret
-
-		; FCB find first
-fcbfst:		mov word [es:bx+fcb.dirpos], 0
-		; FCB find next
-fcbnxt:		call setdrv
-		; load rootdir sector from state
-		; search until next match
-		; next sec & loop if mismatch
-		; err exit if no further matches
-		ret
-
-		; FCB delete file
-fcbdel:		; call fcbfst
-		; get search state, load root dir from there
-		; mark file as deleted
-		; mark buffer dirty
-		ret
-
-		; FCB read
-		; read sector from cluster into diskbuf
-fcbrd:		; read record from sector
-		; advance record num, carry over to cluster
-		ret
-
-		; FCB write
-fcbwr:		; read sector from cluster into diskbuf
-		; write record into sector
-		; mark buffer dirty
-		; advance record num, carry over to cluster
-		ret
-
-		; FCB create
-fcbcre:
-		ret
-
-		; FCB rename
-fcbren:
-		ret
diff --git a/kernel/find.asm b/kernel/find.asm
new file mode 100644
index 0000000..ba2f0b9
--- /dev/null
+++ b/kernel/find.asm
@@ -0,0 +1,57 @@
+		; Load root directory entry
+		; IN	ax	number of directory entry
+lddir:		push ax
+		mov cl, 4
+		shr ax, cl
+		xor dx, dx
+		call maprd
+		; get si to point to entry
+		pop si
+		mov cl, 5
+		shl si, cl
+		and si, 0x1FF
+		add si, dskbuf
+		ret
+
+		; find next file
+fnfile:		mov ax, [es:bx+FCBDEN]
+		inc word [es:bx+FCBDEN]
+		; bail out if we are at end of dir
+		cmp ax, [bpb+BPBRDE]
+		jnc .err
+		; load entry and first byte
+		push bx
+		call lddir
+		pop bx
+		; next if hidden, dir or vol label
+		test byte [si+0x0B], 0xDA
+		jnz fnfile
+		; bail out if end of dir
+		mov al, [si]
+		cmp al, 0
+		je .err
+		; next if deleted entry
+		cmp al, 0xE5
+		je fnfile
+		clc
+		ret
+.err:		stc
+		ret
+
+		; initialize a FCB for directory scanning
+fndfst:		mov word [es:bx+FCBDEN], 0
+fndnxt:		call fnfile
+		jc .ret
+		push si
+		lea di, [bx+1]
+		mov cx, 11
+		rep cmpsb
+		pop si
+		jne fndnxt
+.ret:		ret
+
+putfn:		mov cx, 11
+.loop:		lodsb
+		call pputc
+		loop .loop
+		ret