minor listing formatting
This commit is contained in:
Dennis Yurichev
parent
a07f8de883
commit
5ece9ece8c
2 changed files with 166 additions and 166 deletions
252
src/chapter-22.md
Normal file → Executable file
252
src/chapter-22.md
Normal file → Executable file
|
|
@ -68,29 +68,29 @@ BufSeg dw ? ;buffer segment
|
|||
EndMrk db ? ;marker for the end of the stack frame
|
||||
OnStack ends
|
||||
;
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
Start: cld ;make STOSW count up
|
||||
mov ax,[bp].Attrib ;load AX with attribute parameter
|
||||
and ax,0ff00h ;prepare for merging with fill char
|
||||
mov bx,[bp].Filler ;load BX with fill char
|
||||
and bx,0ffh ;prepare for merging with attribute
|
||||
or ax,bx ;combine attribute and fill char
|
||||
mov bx,[bp].BufOfs ;load DI with target buffer offset
|
||||
mov di,bx
|
||||
mov bx,[bp].BufSeg ;load ES with target buffer segment
|
||||
mov es,bx
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
Bye:mov sp,bp ;restore original stack pointer
|
||||
pop bp ; and caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
Start: cld ;make STOSW count up
|
||||
mov ax,[bp].Attrib ;load AX with attribute parameter
|
||||
and ax,0ff00h ;prepare for merging with fill char
|
||||
mov bx,[bp].Filler ;load BX with fill char
|
||||
and bx,0ffh ;prepare for merging with attribute
|
||||
or ax,bx ;combine attribute and fill char
|
||||
mov bx,[bp].BufOfs ;load DI with target buffer offset
|
||||
mov di,bx
|
||||
mov bx,[bp].BufSeg ;load ES with target buffer segment
|
||||
mov es,bx
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
Bye: mov sp,bp ;restore original stack pointer
|
||||
pop bp ; and caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
```
|
||||
|
||||
The first thing you'll notice about Listing 22.1 is that `ClearS` uses
|
||||
|
|
@ -121,27 +121,27 @@ DI directly as shown in Listing 22.2.
|
|||
**LISTING 22.2 L22-2.ASM**
|
||||
|
||||
```nasm
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
Start: cld ;make STOSW count up
|
||||
mov ax,[bp].Attrib ;load AX with attribute parameter
|
||||
and ax,0ff00h ;prepare for merging with fill char
|
||||
mov bx,[bp].Filler ;load BX with fill char
|
||||
and bx,0ffh ;prepare for merging with attribute
|
||||
or ax,bx ;combine attribute and fill char
|
||||
mov di,[bp].BufOfs ;load DI with target buffer offset
|
||||
mov es,[bp].BufSeg ;load ES with target buffer segment
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
mov ax,[bp].Attrib ;load AX with attribute parameter
|
||||
and ax,0ff00h ;prepare for merging with fill char
|
||||
mov bx,[bp].Filler ;load BX with fill char
|
||||
and bx,0ffh ;prepare for merging with attribute
|
||||
or ax,bx ;combine attribute and fill char
|
||||
mov di,[bp].BufOfs ;load DI with target buffer offset
|
||||
mov es,[bp].BufSeg ;load ES with target buffer segment
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
Bye:
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
```
|
||||
|
||||
(The `OnStack` structure definition doesn't change in any of our
|
||||
|
|
@ -158,27 +158,27 @@ loading ES and DI as shown in Listing 22.3.
|
|||
**LISTING 22.3 L22-3.ASM**
|
||||
|
||||
```nasm
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
Start: cld ;make STOSW count up
|
||||
mov ax,[bp].Attrib ;load AX with attribute parameter
|
||||
and ax,0ff00h ;prepare for merging with fill char
|
||||
mov bx,[bp].Filler ;load BX with fill char
|
||||
and bx,0ffh ;prepare for merging with attribute
|
||||
or ax,bx ;combine attribute and fill char
|
||||
les di,dword ptr [bp].BufOfs ;load ES:DI with target buffer
|
||||
mov ax,[bp].Attrib ;load AX with attribute parameter
|
||||
and ax,0ff00h ;prepare for merging with fill char
|
||||
mov bx,[bp].Filler ;load BX with fill char
|
||||
and bx,0ffh ;prepare for merging with attribute
|
||||
or ax,bx ;combine attribute and fill char
|
||||
les di,dword ptr [bp].BufOfs ;load ES:DI with target buffer
|
||||
;segment:offset
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
Bye:
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
```
|
||||
|
||||
That's good for another three bytes. We're down to 43 bytes, and
|
||||
|
|
@ -190,27 +190,27 @@ values as shown in Listing 22.4.
|
|||
|
||||
**LISTING 22.4 L22-4.ASM**
|
||||
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
Start: cld ;make STOSW count up
|
||||
mov ax,[bp].Attrib ;load AX with attribute parameter
|
||||
sub al,al ;prepare for merging with fill char
|
||||
mov bx,[bp].Filler ;load BX with fill char
|
||||
sub bh,bh ;prepare for merging with attribute
|
||||
or ax,bx ;combine attribute and fill char
|
||||
les di,dword ptr [bp].BufOfs ;load ES:DI with target buffer
|
||||
;segment:offset
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
Start: cld ;make STOSW count up
|
||||
mov ax,[bp].Attrib ;load AX with attribute parameter
|
||||
sub al,al ;prepare for merging with fill char
|
||||
mov bx,[bp].Filler ;load BX with fill char
|
||||
sub bh,bh ;prepare for merging with attribute
|
||||
or ax,bx ;combine attribute and fill char
|
||||
les di,dword ptr [bp].BufOfs ;load ES:DI with target buffer
|
||||
;segment:offset
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
Bye:
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
|
||||
Now we're down to 40 bytes—more than 20 percent smaller than the
|
||||
original code. That's pretty much it for simple instruction
|
||||
|
|
@ -232,23 +232,23 @@ shows the new code.
|
|||
**LISTING 22.5 L22-5.ASM**
|
||||
|
||||
```nasm
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
Start: cld ;make STOSW count up
|
||||
mov ah,byte ptr [bp].Attrib[1];load AH with attribute
|
||||
mov al,byte ptr [bp].Filler ;load AL with fill char
|
||||
les di,dword ptr [bp].BufOfs ;load ES:DI with target buffer segment:offset
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
cmp word ptr [bp].BufSeg,0 ;skip the fill if a null
|
||||
jne Start ; pointer is passed
|
||||
cmp word ptr [bp].BufOfs,0
|
||||
je Bye
|
||||
Start: cld ;make STOSW count up
|
||||
mov ah,byte ptr [bp].Attrib[1] ;load AH with attribute
|
||||
mov al,byte ptr [bp].Filler ;load AL with fill char
|
||||
les di,dword ptr [bp].BufOfs ;load ES:DI with target buffer segment:offset
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
Bye:
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
```
|
||||
|
||||
(We could get rid of yet another instruction by having the calling code
|
||||
|
|
@ -266,22 +266,22 @@ shown in Listing 22.6.
|
|||
**LISTING 22.6 L22-6.ASM**
|
||||
|
||||
```nasm
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
les di,dword ptr [bp].BufOfs ;load ES:DI with target buffer;segment:offset
|
||||
mov ax,es ;put segment where we can test it
|
||||
or ax,di ;is it a null pointer?
|
||||
je Bye ;yes, so we're done
|
||||
Start: cld ;make STOSW count up
|
||||
mov ah,byte ptr [bp].Attrib[1];load AH with attribute
|
||||
mov al,byte ptr [bp].Filler ;load AL with fill char
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
ClearS proc near
|
||||
push bp ;save caller's BP
|
||||
mov bp,sp ;point to stack frame
|
||||
les di,dword ptr [bp].BufOfs ;load ES:DI with target buffer;segment:offset
|
||||
mov ax,es ;put segment where we can test it
|
||||
or ax,di ;is it a null pointer?
|
||||
je Bye ;yes, so we're done
|
||||
Start: cld ;make STOSW count up
|
||||
mov ah,byte ptr [bp].Attrib[1] ;load AH with attribute
|
||||
mov al,byte ptr [bp].Filler ;load AL with fill char
|
||||
mov cx,[bp].BufSize ;load CX with buffer size
|
||||
rep stosw ;fill the buffer
|
||||
Bye:
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
pop bp ;restore caller's BP
|
||||
ret EndMrk-RetAddr-2 ;return, clearing the parms from the stack
|
||||
ClearS endp
|
||||
```
|
||||
|
||||
Well. Now we're down to 28 bytes, having reduced the size of this
|
||||
|
|
@ -327,22 +327,22 @@ With that problem dealt with, Listing 22.7 shows the Zenned version of
|
|||
**LISTING 22.7 L22-7.ASM**
|
||||
|
||||
```nasm
|
||||
ClearS procnear
|
||||
pop dx ;get the return address
|
||||
pop ax ;put fill char into AL
|
||||
pop bx ;get the attribute
|
||||
mov ah,bh ;put attribute into AH
|
||||
pop cx ;get the buffer size
|
||||
pop di ;get the offset of the buffer origin
|
||||
pop es ;get the segment of the buffer origin
|
||||
mov bx,es ;put the segment where we can test it
|
||||
or bx,di ;null pointer?
|
||||
je Bye ;yes, so we're done
|
||||
cld ;make STOSW count up
|
||||
rep stosw ;do the string store
|
||||
ClearS proc near
|
||||
pop dx ;get the return address
|
||||
pop ax ;put fill char into AL
|
||||
pop bx ;get the attribute
|
||||
mov ah,bh ;put attribute into AH
|
||||
pop cx ;get the buffer size
|
||||
pop di ;get the offset of the buffer origin
|
||||
pop es ;get the segment of the buffer origin
|
||||
mov bx,es ;put the segment where we can test it
|
||||
or bx,di ;null pointer?
|
||||
je Bye ;yes, so we're done
|
||||
cld ;make STOSW count up
|
||||
rep stosw ;do the string store
|
||||
Bye:
|
||||
jmp dx ;return to the calling code
|
||||
ClearS endp
|
||||
jmp dx ;return to the calling code
|
||||
ClearS endp
|
||||
```
|
||||
|
||||
At long last, we're down to the bare metal. This version of `ClearS`
|
||||
|
|
|
|||
Loading…
Reference in a new issue