page ,132 title strcat - concatenate (append) one string to another;***;strcat.asm - contains strcat() and strcpy() routines;; Copyright (c) 1985-1997, Microsoft Corporation. All rights reserved.;;Purpose:; STRCAT concatenates (appends) a copy of the source string to the; end of the destination string, returning the destination string.;;******************************************************************************* .xlist include cruntime.inc .listpage;***;char *strcat(dst, src) - concatenate (append) one string to another;;Purpose:; Concatenates src onto the end of dest. Assumes enough; space in dest.;; Algorithm:; char * strcat (char * dst, char * src); {; char * cp = dst;;; while( *cp ); ++cp; /* Find end of dst */; while( *cp++ = *src++ ); ; /* Copy src to end of dst */; return( dst );; };;Entry:; char *dst - string to which "src" is to be appended; const char *src - string to be appended to the end of "dst";;Exit:; The address of "dst" in EAX;;Uses:; EAX, ECX;;Exceptions:;;*******************************************************************************page;***;char *strcpy(dst, src) - copy one string over another;;Purpose:; Copies the string src into the spot specified by; dest; assumes enough room.;; Algorithm:; char * strcpy (char * dst, char * src); {; char * cp = dst;;; while( *cp++ = *src++ ); ; /* Copy src over dst */; return( dst );; };;Entry:; char * dst - string over which "src" is to be copied; const char * src - string to be copied over "dst";;Exit:; The address of "dst" in EAX;;Uses:; EAX, ECX;;Exceptions:;******************************************************************************* CODESEG% public strcat, strcpy ; make both functions availablestrcpy proc push edi ; preserve edi mov edi,[esp+8] ; edi points to dest string 堆栈 jmp short copy_startstrcpy endp align 16strcat proc .FPO ( 0, 2, 0, 0, 0, 0 ) mov ecx,[esp+4] ; ecx -> dest string push edi ; preserve edi test ecx,3 ; test if string is aligned on 32 bits je short find_end_of_dest_string_loopdest_misaligned: ; simple byte loop until string is aligned mov al,byte ptr [ecx] inc ecx test al,al je short start_byte_3 test ecx,3 jne short dest_misaligned align 4find_end_of_dest_string_loop: mov eax,dword ptr [ecx] ; read 4 bytes mov edx,7efefeffh add edx,eax xor eax,-1 xor eax,edx add ecx,4 test eax,81010100h je short find_end_of_dest_string_loop ; found zero byte in the loop mov eax,[ecx - 4] test al,al ; is it byte 0 je short start_byte_0 test ah,ah ; is it byte 1 je short start_byte_1 test eax,00ff0000h ; is it byte 2 je short start_byte_2 test eax,0ff000000h ; is it byte 3 je short start_byte_3 jmp short find_end_of_dest_string_loop ; taken if bits 24-30 are clear and bit ; 31 is setstart_byte_3: lea edi,[ecx - 1] jmp short copy_startstart_byte_2: lea edi,[ecx - 2] jmp short copy_startstart_byte_1: lea edi,[ecx - 3] jmp short copy_startstart_byte_0: lea edi,[ecx - 4]; jmp short copy_start; edi points to the end of dest string.copy_start:: mov ecx,[esp+0ch] ; ecx -> sorc string test ecx,3 ; test if string is aligned on 32 bits je short main_loop_entrancesrc_misaligned: ; simple byte loop until string is aligned mov dl,byte ptr [ecx] inc ecx test dl,dl je short byte_0 mov [edi],dl inc edi test ecx,3 jne short src_misaligned ;continue aligned loop jmp short main_loop_entrancemain_loop: ; edx contains first dword of sorc string mov [edi],edx ; store one more dword add edi,4 ; kick dest pointermain_loop_entrance: mov edx,7efefeffh mov eax,dword ptr [ecx] ; read 4 bytes add edx,eax ; plus edx magic_bits xor eax,-1 ; eax = ~eax xor eax,edx ; mov edx,[ecx] ; it's in cache now add ecx,4 ; kick dest pointer test eax,81010100h je short main_loop ; found zero byte in the loop; main_loop_end: test dl,dl ; is it byte 0 je short byte_0 test dh,dh ; is it byte 1 je short byte_1 test edx,00ff0000h ; is it byte 2 je short byte_2 test edx,0ff000000h ; is it byte 3 je short byte_3 jmp short main_loop ; taken if bits 24-30 are clear and bit ; 31 is setbyte_3: mov [edi],edx mov eax,[esp+8] ; return in eax pointer to dest string pop edi retbyte_2: mov [edi],dx mov eax,[esp+8] ; return in eax pointer to dest string mov byte ptr [edi+2],0 pop edi retbyte_1: mov [edi],dx mov eax,[esp+8] ; return in eax pointer to dest string pop edi retbyte_0: mov [edi],dl mov eax,[esp+8] ; return in eax pointer to dest string pop edi retstrcat endp end
char* strcpy(char*pdest,const char*psrc){const char *char_psrc;const ulong *longword_psrc,*longword_pdest;register ulong longword, magic_bits;char *char_pest=pdest;for (char_psrc = psrc; //初始位置((ulong)char_src& (sizeof(ulong) - 1)) != 0; //边界对齐判断 //地址的size以下全部是0*char_pdest++ = *char_psrc++) //copy...{if (*char_psrc == '\0') //结束...{*char_pdest='\0';return pdest;}}longword_psrc = (ulong*)char_psrc; //从自然边界开始longword_pdest = (ulong*)char_pdest;magic_bits = 0x7efefeffL;while (1){longword = *longword_psrc++;if ((((longword + magic_bits) ^ ~longword) & ~magic_bits) != 0){const char *cp = (const char*)(longword_psrc - 1);if (cp[0] == 0) {*(char*)longword_pdest = '\0';return pdest;}if (cp[1] == 0){*(WORD*)longword_pdest = *(WORD*)longword_word;return pdest;}if (cp[2] == 0) {*(WORD*)longword_pdest = *(WORD*)longword_word;*((char*)longword_pdest+2) = '\0';return pdest;} if (cp[3] == 0) {*longword_pdest = *longword_word;return pdest;}}*longword_pdest++ = *longword;}}char* strcat(char*pdest,const char*psrc){const char *char_psrc;const ulong *longword_psrc,*longword_pdest;register ulong longword, magic_bits;char *char_pest=pdest;while(1) //查找源字符串终止位置{longword = *longword_psrc++;if ((((longword + magic_bits) ^ ~longword) & ~magic_bits) != 0){const char *cp = (const char*)(longword_psrc - 1);if (cp[0] == 0){char_pdest = (char*)longword;break;}if (cp[1] == 0){char_pdest = (char*)longword + 1;break;}if (cp[2] == 0){char_pdest = (char*)longword + 2;break;}if (cp[3] == 0){char_pdest = (char*)longword + 3;break;}}}//strcpyfor (char_psrc = psrc;((ulong)char_src& (sizeof(ulong) - 1)) != 0;*char_pdest++ = *char_psrc++){if (*char_psrc == '\0'){*char_pdest='\0';return pdest;}}//对齐后的strcpylongword_psrc = (ulong*)char_psrc;longword_pdest = (ulong*)char_pdest;magic_bits = 0x7efefeffL;while (1){longword = *longword_psrc++;if ((((longword + magic_bits) ^ ~longword) & ~magic_bits) != 0){//判断是否有0const char *cp = (const char*)(longword_psrc - 1);if (cp[0] == 0){*(char*)longword_pdest = '\0';return pdest;}if (cp[1] == 0){*(WORD*)longword_pdest = *(WORD*)longword_word;return pdest;}if (cp[2] == 0){*(WORD*)longword_pdest = *(WORD*)longword_word;*((char*)longword_pdest+2) = '\0';return pdest;}if (cp[3] == 0){*longword_pdest = *longword_word;return pdest;}}*longword_pdest++ = *longword;}}
