Program 6

String Manipulation

Due: Monday, April 24

We will be using pointers in assembly language to manage dynamic structures.  We will use syscall 9 to acquire memory space from the heap at run time.  Read about the arguments and how to use syscall 9.  A dynamic string is dynamically allocated to be the proper size and ends in the null character (0)

Write an assembler language program with the following 4 functions:

• Length ($v0, $a0) - returns the length of the referenced string pointed to by $a0 in register $v0.
• Create ($v0, $a0) - returns a pointer in $v0 to the ASCII string that it dynamically allocates and copies the characters in the string pointed to by the pointer in $a0 into the new string created.
• Append ($v0, $a0, $a1) - returns a pointer in $v0 to the dynamic string that results from concatenating the two ASCII strings pointed to by $a0 and $a1.
• Print ($a0) - prints the string pointed to by the pointer in $a0.

The main will perform the following actions

1. Dynamically create a string (str1) containing "This is a test".  The value is passed via an asciiz string declared in the .data section
2. Create a string (str2) containing "of our string routines".  Same as above
3. Create a string (str3) by appending str1 to str2.
4. Print a title, followed by str1, str2 and str3; all properly labeled.

Write a second program that:

1. Reads a string from the first line of a file, reads a string from the next line, concatenates them (without new lines) and prints out the new string.