;---------------------------------------------- ;StrNCpyAsm - copy zero terminated string2 to zero terminated string1, ; but copy no more than count (parameter) characters ; or the length of string2, whichever comes first ; entry: - str1Add contains the address of string1 ; - str2Add contains the address of string2 ; - count contains the max number of characters to copy ; exit: NONE (no return value so do not use edi to return an address) ; ; Note: StrNCpyAsm does not zero terminate the copied string ; unless the 0 is within count characters copied. ; ; example1: char str1[]= {'h','e','l','l','o',' ','w','o','r','l','d',0}; ; char str2[]= {'G','o','o','d','-','b','y','e',0}; ; StrNCpyAsm(str1,str2,4);//terminating 0 not copied since only 4 characters copied ; ;//and terminating 0 not within the 4 characters ; after copy str1 contains: 'G','o','o','d','o',' ','w','o','r','l','d',0 ; ; example2: use str1 and str2 from example1 ; ; StrNCpyAsm(str1,str2,9); //terminating 0 copied since terminating 0 ; //within 9 characters copied ; str1 contains: 'G','o','o','d','-','b','y','e',0,'l','d',0 ; ; example3: use str1 and str2 from example1 ; ; StrNCpyAsm(str1,str2,15);//copy 15 characters upto and including 0, ; //whichever comes first ; //only 9 characters including 0 copied ; after copy str1 contains: 'G','o','o','d','-','b','y','e',0,'l','d',0 ; ; The above is how you would call StrNCpyAsm from C++. ; ; To call StrNCpyAsm from an asm function use: ; ; push 20 ;max num of characters to copy ; push str2Add ;address of string 2 ; push str1Add ;address of string 1 ; call StrNCpyAsm ; ;no add esp, 12 needed because stack cleaup automatically done ; ; ; hint1: use StrLenAsm to get the number of characters in str2 ; hint2: the length returned by StrLenAsm does not include terminating 0 ; hint3: copy the lesser of the length of the string (including terminating 0) ; or count characters ;copy to ecx the lesser of count or the length of string2 (including terminating 0) ; Please note for the above, you need the length of string2 including terminating 0. ; StrLenAsm returns the length not including terminating 0 ;populate esi and edi with the correct values ;clear the direction flag ; ;Do not use a loop in this function. use rep and movsb to copy ; ; Note: the parameters below (str1Add and str2Add) contain the address of the ; strings you want to work with. To transfer those addesses to a register ; just use mov reg, str1Add ; Do not use mov reg, offset str1Add and ; do not use lea reg, str1Add ; StrNCpyAsm PROC uses eax esi edi ecx , ;save registers used str1Add:DWORD, ;address of string1 str2Add:DWORD, ;address of string2 count:DWORD ;max chars to copy mov edi, str1Add mov esi, str2Add mov ecx, count ;Student code here ( you may change or delete any of the above 3 lines of code for efficiency if necessary) ;If you use the above 3 lines, you must comment them ret ;return to caller StrNCpyAsm ENDP ;-------------------------------------------- ;StrCatAsm - append 0 terminated string2 to 0 terminated string1 ; entry: str1Add contains the address of string1 ; str2Add contains the address of string2 ; exit: NONE ; note: StrCatAsm puts in terminating 0 ; ; example: char str1[] = {'h','e','l','l','o',0}; ; char str2[] = {'w','o','r','l','d',0}; ; after StrCatAsm(str1,str2) ; string1 = 'h','e','l','l','o','w','o','r','l','d',0 ; ; The above is how you would call StrCatAsm from C++. ; ; To call StrCatAsm from another asm function use: ; ; To call StrCatAsm from an asm function use: ; ; push str2Add ;address of string 2 ; push str1Add ;address of string 1 ; call StrCatAsm ; ;no add esp, 8 needed because stack cleaup automatically done ; ; Do not use a loop in this function. ; Do not call StrLenAsm in this function. ; StrCatAsm should zero terminate the concatenated string which is done by StrCpyAsm ; when you call it to copy str2 to the end of str1. ; ; Choose 2 instructions from the following string instructions to use: ; rep, repe, repne, movsb,stosb,cmpsb,scasb ; ;populate ecx with MAX_LEN defined at the top of this file ;get to the end of str1 using two string instructions ;then call StrCpyAsm to copy str2 to end of str1. ; ; Note: the parameters below (str1Add and str2Add) contain the address of the ; strings you want to work with. To transfer those addesses to a register ; just use mov reg, str1Add ; Do not use mov reg, offset str1Add and ; do not use lea reg, str1Add StrCatAsm PROC uses eax edi ecx esi , ;save registers used str1Add:DWORD, ;address of string1 str2Add:DWORD ;address of string2 mov edi, str1Add mov esi, str2Add ;Student code here( you may change or delete any of the above 2 lines of code for efficiency if necessary) ;If you use the above 2 lines, you must comment them ret ;return to caller StrCatAsm ENDP ;StrRemove - Remove count characters from str1 starting at location ; ; entry: - addStr contains the address of the string to remove characters from ; - location contains the location in the string to start removing characters from ; - count contains the max number of characters to remove ; exit: NONE (no return value) ; ; Note: location starts at 0 and counting starts on the left. ; ; For example: ; ; location 0123 ; str1 = "Be my friend" location = 3 ('m') count = 3 ; after StrRemove(strAdd,3,3) str1 = "Be friend" ; ; hint1: setup source to the address of location + count ; hint2: setup destination to the address of location. ; hint3: copy source to destination (think StrCpyAsm) ; ; Do not use a loop and you don't even need to use the ; string instructions, just use StrCpyAsm ; ; To call StrRemove from C++ use: ; StrRemove(str1,4,8); ; ; The above means remove 8 chars from str1 starting at location 4 ; ; Note: the parameter below (addStr) contains the address of the ; strings you want to work with. To transfer that addess to a register ; just use mov reg, str1Add ; Do not use mov reg, offset str1Add and ; do not use lea reg, str1Add StrRemove PROC uses edi esi ebx ecx, ;save registers used strAdd:DWORD, ;address of string to remove chars from location:DWORD, ;location in string to start removing chars from count:DWORD ;number of chars to remove mov esi, strAdd mov ebx, location mov ecx, count ;student code here ( you may change or delete any of the above 3 lines of code for efficiency if necessary) ;If you use the above 3 lines, you must comment them ret ;return to caller StrRemove ENDP ;*************Extra Credit - StrInsertEC************************ ;For extra credit code StrInsertEC below ;See the program 8 specifications document (pdf file) ;on the class web site for full instructions about ;implementing StrInsertEC below. ;StrInsertEC - Insert str2 into str1 at position ; ; entry: - str1 contains the address of string1 ; - str2 contains the address of string2 ; - position contains the position in string 1 to insert string 2 at. ; exit: NONE (no return value) ; ; Note: position starts at 0 and counting starts on the left. ; ; For example: ; ; position 0123456 ; str1 = "Be my friend today" and str2 = "good " position = 6 ('f') ; after StrInsert(str1,str2,6) str1 = "Be my good friend today" ; ; Note: No checking is done to make sure str1 is big enough to ; accomodate the insert. ; ;In the extra credit version do not copy part of string 1 to a ;buffer so there will be no need for a local variable. ;Just work within string 1 and copy part of str1(from position ;to the end of str1) towards the end of the str1 to make ;room for the string to insert (str2). ; ;You should not use a loop. ; ;You should use string instructions to copy string 1 down within itself. ;You can use StrNCpyAsm to copy str2 into str1 starting at position. ; ; To call StrInsertEC from C++ use: ; StrInsertEC(str1,str2,12); ; ; The above means insert str2 into str1 starting at position 12 in str1. ; ; Note: the parameters below (str1Add and str2Add) contain the address of the ; strings you want to work with. To transfer those addesses to a register ; just use mov reg, str1Add ; Do not use mov reg, offset str1Add and ; do not use lea reg, str1Add StrInsertEC PROC str1Add:DWORD , ;string 1 address str2Add:DWORD, ;string 2 address position:DWORD ;position to insert at in str1 mov edi, str1Add mov esi, str2Add mov ecx, position ;Student code here( you may change or delete any of the above 3 lines of code for efficiency if necessary) ;If you use the above 3 lines, you must comment them ret StrInsertEC ENDP END