From: H. Peter Anvin <hpa@zytor.com>
Date: Wed, 27 Feb 2008 03:57:26 +0000 (-0800)
Subject: getc: support for unknown file sizes
X-Git-Tag: syslinux-3.70-pre1~10
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=95df473c076649078c291bf0c6ffb2a367f6829a;p=profile%2Fivi%2Fsyslinux.git

getc: support for unknown file sizes

Handle unknown file sizes in getc
---

diff --git a/getc.inc b/getc.inc
index eddba80..b36115c 100644
--- a/getc.inc
+++ b/getc.inc
@@ -23,12 +23,11 @@ MAX_GETC	equ (1 << MAX_GETC_LG2)
 bytes_per_getc_lg2	equ 16-MAX_GETC_LG2
 bytes_per_getc		equ (1 << bytes_per_getc_lg2)
 secs_per_getc	equ bytes_per_getc/SECTOR_SIZE
-MAX_UNGET	equ 5			; Max bytes that can be pushed back
+MAX_UNGET	equ 9			; Max bytes that can be pushed back
 
 		struc getc_file
 gc_file		resw 1			; File pointer
 gc_bufbytes	resw 1			; Bytes left in buffer
-gc_bytes	resd 1			; Bytes left in file
 gc_bufdata	resw 1			; Pointer to data in buffer
 gc_unget_cnt	resb 1			; Character pushed back count
 gc_unget_buf	resb MAX_UNGET		; Character pushed back buffer
@@ -73,7 +72,6 @@ openfd:
 		mov [CurrentGetC],bx
 
 		mov [bx+gc_file],si	; File pointer
-		mov [bx+gc_bytes],eax	; Bytes available
 		xor ax,ax
 		mov [bx+gc_bufbytes],ax		; Buffer empty
 		mov [bx+gc_unget_cnt],al	; ungetc buffer empty
@@ -132,27 +130,22 @@ getc:
 
 		mov [di+gc_bufdata],bx
 		mov si,[di+gc_file]
-		mov ecx,[di+gc_bytes]
-		jecxz .empty
-		cmp ecx,bytes_per_getc
-		jna .sizeok
-		mov ecx,bytes_per_getc
-.sizeok:
-		mov [di+gc_bufbytes],cx
-		sub [di+gc_bytes],ecx
-		add cx,SECTOR_SIZE-1
-		shr cx,SECTOR_SHIFT
+		and si,si
+		mov [di+gc_bufbytes],si	; In case SI == 0
+		jz .empty
+		mov cx,bytes_per_getc >> SECTOR_SHIFT
 		call getfssec
+		mov [di+gc_bufbytes],cx
 		mov [di+gc_file],si
+		jcxz .empty
 		popad
+		TRACER 'd'
 		jmp .got_data
 
 .empty:
-		; CX == 0 at this point; gc_bufbytes was clobbered
-		; by the subtract; we need to restore it to zero so
-		; we will continue to get EOF on any further attempts
-		; to read the file.
-		mov [di+gc_bufbytes],cx
+		TRACER 'e'
+		; [di+gc_bufbytes] is zero already, thus we will continue
+		; to get EOF on any further attempts to read the file.
 		popad
 		xor al,al		; Return a predictable zero
 		stc