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231 lines
6.3 KiB
231 lines
6.3 KiB
page ,132 |
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title strcat - concatenate (append) one string to another |
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;*** |
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;strcat.asm - contains strcat() and strcpy() routines |
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; |
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; Copyright (c) Microsoft Corporation. All rights reserved. |
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; |
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;Purpose: |
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; STRCAT concatenates (appends) a copy of the source string to the |
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; end of the destination string, returning the destination string. |
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; |
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;******************************************************************************* |
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.xlist |
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include cruntime.inc |
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.list |
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page |
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;*** |
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;char *strcat(dst, src) - concatenate (append) one string to another |
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; |
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;Purpose: |
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; Concatenates src onto the end of dest. Assumes enough |
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; space in dest. |
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; |
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; Algorithm: |
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; char * strcat (char * dst, char * src) |
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; { |
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; char * cp = dst; |
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; |
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; while( *cp ) |
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; ++cp; /* Find end of dst */ |
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; while( *cp++ = *src++ ) |
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; ; /* Copy src to end of dst */ |
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; return( dst ); |
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; } |
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; |
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;Entry: |
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; char *dst - string to which "src" is to be appended |
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; const char *src - string to be appended to the end of "dst" |
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; |
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;Exit: |
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; The address of "dst" in EAX |
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; |
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;Uses: |
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; EAX, ECX |
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; |
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;Exceptions: |
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; |
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;******************************************************************************* |
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page |
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;*** |
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;char *strcpy(dst, src) - copy one string over another |
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; |
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;Purpose: |
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; Copies the string src into the spot specified by |
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; dest; assumes enough room. |
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; |
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; Algorithm: |
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; char * strcpy (char * dst, char * src) |
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; { |
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; char * cp = dst; |
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; |
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; while( *cp++ = *src++ ) |
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; ; /* Copy src over dst */ |
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; return( dst ); |
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; } |
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; |
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;Entry: |
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; char * dst - string over which "src" is to be copied |
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; const char * src - string to be copied over "dst" |
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; |
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;Exit: |
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; The address of "dst" in EAX |
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; |
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;Uses: |
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; EAX, ECX |
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; |
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;Exceptions: |
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;******************************************************************************* |
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CODESEG |
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% public strcat, strcpy ; make both functions available |
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strcpy proc \ |
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dst:ptr byte, \ |
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src:ptr byte |
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OPTION PROLOGUE:NONE, EPILOGUE:NONE |
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push edi ; preserve edi |
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mov edi,[esp+8] ; edi points to dest string |
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jmp short copy_start |
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strcpy endp |
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align 16 |
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strcat proc \ |
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dst:ptr byte, \ |
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src:ptr byte |
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OPTION PROLOGUE:NONE, EPILOGUE:NONE |
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.FPO ( 0, 2, 0, 0, 0, 0 ) |
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mov ecx,[esp+4] ; ecx -> dest string |
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push edi ; preserve edi |
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test ecx,3 ; test if string is aligned on 32 bits |
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je short find_end_of_dest_string_loop |
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dest_misaligned: ; simple byte loop until string is aligned |
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mov al,byte ptr [ecx] |
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add ecx,1 |
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test al,al |
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je short start_byte_3 |
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test ecx,3 |
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jne short dest_misaligned |
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align 4 |
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find_end_of_dest_string_loop: |
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mov eax,dword ptr [ecx] ; read 4 bytes |
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mov edx,7efefeffh |
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add edx,eax |
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xor eax,-1 |
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xor eax,edx |
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add ecx,4 |
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test eax,81010100h |
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je short find_end_of_dest_string_loop |
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; found zero byte in the loop |
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mov eax,[ecx - 4] |
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test al,al ; is it byte 0 |
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je short start_byte_0 |
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test ah,ah ; is it byte 1 |
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je short start_byte_1 |
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test eax,00ff0000h ; is it byte 2 |
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je short start_byte_2 |
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test eax,0ff000000h ; is it byte 3 |
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je short start_byte_3 |
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jmp short find_end_of_dest_string_loop |
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; taken if bits 24-30 are clear and bit |
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; 31 is set |
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start_byte_3: |
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lea edi,[ecx - 1] |
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jmp short copy_start |
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start_byte_2: |
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lea edi,[ecx - 2] |
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jmp short copy_start |
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start_byte_1: |
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lea edi,[ecx - 3] |
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jmp short copy_start |
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start_byte_0: |
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lea edi,[ecx - 4] |
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; jmp short copy_start |
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; edi points to the end of dest string. |
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copy_start:: |
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mov ecx,[esp+0ch] ; ecx -> sorc string |
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test ecx,3 ; test if string is aligned on 32 bits |
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je short main_loop_entrance |
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src_misaligned: ; simple byte loop until string is aligned |
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mov dl,byte ptr [ecx] |
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add ecx,1 |
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test dl,dl |
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je short byte_0 |
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mov [edi],dl |
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add edi,1 |
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test ecx,3 |
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jne short src_misaligned |
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jmp short main_loop_entrance |
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main_loop: ; edx contains first dword of sorc string |
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mov [edi],edx ; store one more dword |
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add edi,4 ; kick dest pointer |
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main_loop_entrance: |
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mov edx,7efefeffh |
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mov eax,dword ptr [ecx] ; read 4 bytes |
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add edx,eax |
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xor eax,-1 |
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xor eax,edx |
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mov edx,[ecx] ; it's in cache now |
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add ecx,4 ; kick dest pointer |
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test eax,81010100h |
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je short main_loop |
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; found zero byte in the loop |
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; main_loop_end: |
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test dl,dl ; is it byte 0 |
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je short byte_0 |
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test dh,dh ; is it byte 1 |
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je short byte_1 |
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test edx,00ff0000h ; is it byte 2 |
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je short byte_2 |
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test edx,0ff000000h ; is it byte 3 |
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je short byte_3 |
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jmp short main_loop ; taken if bits 24-30 are clear and bit |
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; 31 is set |
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byte_3: |
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mov [edi],edx |
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mov eax,[esp+8] ; return in eax pointer to dest string |
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pop edi |
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ret |
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byte_2: |
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mov [edi],dx |
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mov eax,[esp+8] ; return in eax pointer to dest string |
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mov byte ptr [edi+2],0 |
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pop edi |
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ret |
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byte_1: |
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mov [edi],dx |
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mov eax,[esp+8] ; return in eax pointer to dest string |
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pop edi |
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ret |
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byte_0: |
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mov [edi],dl |
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mov eax,[esp+8] ; return in eax pointer to dest string |
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pop edi |
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ret |
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strcat endp |
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end |
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