Need help with the following Program in HLA: PROGRAM $14$: strlen Function

Write an HLA Assembly language program that implements the following function:

procedure strlen$($ baseStringAddress: dword $)$; @nodisplay; @noframe;

This function should return in AL the number of characters in the string parameter, passed by its base address. Here is a sample program dialogue:

Feed Me: asdfasdf

The String You Entered: asdfasdf Has Length $=8$

Feed Me: asdf

The String You Entered: asdf Has Length $=4$ NOTE THAT THERE IS AN IMPLEMENTATION OF STRINGS INPUT AND OUTPUT: In effect to assist you in working with strings, I authored the function gets and the procedure puts. As you can see from the example above, gets is used to read a string, while puts is used to write a string. These routines support the following syntax:

gets$($ baseStringAddress : dword; maxLength : uns$16)$;

puts$($ baseStringAddress : dword $)$;

Each routine needs to be passed a nicely allocated and null$-$terminated string by sending its base address $($that is$,$ index $0$ of the array$).$ In addition, gets takes a second parameter which tells it how many characters it can legally ramm into the array before it overwrites its allocated size.

Both of these routines are provided in the file: cs$17$string.hla. By stating in your program,

#include$("$cs$17$string.hla" $)$;

THIS IS THE FILE FOR cs$17$string.hla:

$//$ File: cs$17$string.hla

$//$ Provides the string manipulation functions puts and gets for students to use

$//$ this procedure prompts for a string, writing atmost maxLength bytes into a previously declared array

$//$ this maxLength should not include the terminating null in its count

$//$ the string parameter is being passed by its base address

procedure gets$($ baseStringAddress: dword; maxLength : uns$16)$; @nodisplay; @noframe;

$//$ uses the register DX$,$ DI$,$ ECX, EBX and EAX

static

dReturnAddress : dword;

wDIRegister : word :$=0$; $//$ preserve DI

wDXRegister : word :$=0$; $//$ preserve DX

dEAXRegister : dword :$=0$; $//$ preserve EAX

dEBXRegister : dword :$=0$; $//$ preserve EBX

dECXRegister : dword :$=0$; $//$ preserve ECX

$//$ I am trying to hide the datatype string for use by CS $17$

sData : string;

begin gets;

$//$ entry sequence

$//$ preserve registers

mov$($ EBX, dEBXRegister $)$;

mov$($ EAX, dEAXRegister $)$;

mov$($ DX$,$ wDXRegister $)$;

mov$($ DI$,$ wDIRegister $)$;

pop$($ dReturnAddress $)$; $//$ This is the return address

pop$($ DI $)$; $//$ This is the max length able to read

pop$($ EBX $)$; $//$ This is the base address of the string

$//$ push back the return address

push$($ dReturnAddress $)$;

$//$ preserve registers

push$($ wDIRegister $)$;

push$($ wDXRegister $)$;

push$($ dECXRegister $)$;

push$($ dEBXRegister $)$;

push$($ dEAXRegister $)$;

$//$ begin sub$-$task

$//$ prompt for a string

stdin.flushInput$()$;

stdin.a$\_$gets$()$; $//$ allocate and read string into EAX

mov$($ EAX, sData $)$; $//$ save address so it can be free'd later

$//$ copy data in sData over into starting at $[$EBX$]$

mov$(0,$ DX $)$; $//$ EBX will be the address of string$[$i$]$

mov$(0,$ ECX $)$;

getsRepeatLoop:

$//$ read no more than DI chars

cmp$($ DI$,0)$;

je getsEndLoop;

cmp$([$ EAX $+$ ECX $],$ DH $)$;

je getsEndLoop;

mov$([$ EAX $+$ ECX $],$ DL $)$; $//$ move character desired

mov$($ DL$,($type char $[$ EBX $]))$;

inc$($ ECX $)$;

inc$($ EBX $)$;

dec$($ DI $)$;

jmp getsRepeatLoop;

getsEndLoop:

$//$ set ending null

mov$($ DH$,($type char $[$ EBX $]))$;

$//$ release sData

strfree$($ sData $)$;

$//$ exit sequence

$//$ restore registers

pop$($ EAX $)$;

pop$($ EBX $)$;

pop$($ ECX $)$;

pop$($ DX $)$;

pop$($ DI $)$;

$//$ transfer control

ret$()$;

end gets;

$//$ this procedure prints the contents of a null$-$terminated string

$//$ the string parameter is being passed by its base address

procedure puts$($ baseStringAddress: dword $)$; @nodisplay; @noframe;

$//$ uses the register EBX

static

dReturnAddress : dword;

wDXRegister : word :$=0$; $//$ preserve DX

dEBXRegister : dword :$=0$; $//$ preserve EBX

begin puts;

$//$ entry sequence

$//$ preserve registers

mov$($ EBX, dEBXRegister $)$;

mov$($ DX$,$ wDXRegister $)$;

pop$($ dReturnAddress $)$; $//$ This is the return address

pop$($ EBX $)$; $//$ This is the base address of the string

$//$ push back the return address

push$($ dReturnAddress $)$;

$//$ preserve registers

push$($ dEBXRegister $)$;

push$($ wDXRegister $)$;

$//$ begin sub$-$task

$//$ print null$-$terminated string

mov$(0,$ DX $)$; $//$ EBX will be the address of string$[$i$]$

putsRepeatLoop:

cmp$([$ EBX $],$ DH $)$;

je putsEndLoop;

stdout.putc$([$ EBX $])$;

inc$($ EBX $)$;

jmp putsRepeatLoop;

putsEndLoop:

$//$ exit sequence

$//$ restore registers

pop$($ DX $)$;

pop$($ EBX $)$;

$//$ transfer control

ret$()$;