CS360 LAB ASSIGNMENT #1 1. Submit a ZIP file of YOUR code and outputs to TA BEFORE DEMO time 2. Demo YOUR work to TA; TA will post demo schedule =========================== Part 1 ====================================== PART 1: myprintf Function Objective: I/O Function and Stack Usage Given: putchar(char c) of Linux, which prints a char. 1-1. Write YOUR own prints(char *s) fucntion to print a string. If you don't know how to do it, you BETTER attend my class lecture !!!! Given: The following printu() function print unsigned integer. typedef unsigned int u32; char *ctable = "0123456789ABCDEF"; int BASE = 10; int rpu(u32 x) { char c; if (x){ c = ctable[x % BASE]; rpu(x / BASE); putchar(c); } } int printu(u32 x) { (x==0)? putchar('0') : rpu(x); putchar(' '); } EXAMPLE: stack Assume u32 x = 123; ------ High 1st call to rpu(x): x=123; x%10 = 3 ===> c = ctable[3] = '3'; 2nd call to rpu(x): x=12; x%10 = 2 ===> c = ctable[2] = '2'; 3rd call : x=1; x%10 = 1 ===> c = ctable[1] = '1'; --------------------------------------------------------------- Low 4th call : x=0 => return ====> print '1'; retrun ====> print '2' retrun ====> print '3' 2-2. Write YOUR OWN fucntions int printx(u32 x) which print x in HEX (prefixed with 0x ) int printd(int x) which print an integer (x may be negative!!!) 3. REQUIREMENTS: ==================================================================== Write YOUR own myprintf(char *fmt, ...) function to print char by %c string by %s unsigned integer by %u unsigned integer in HEX by %x integer by %d Ignore field width and precision, just print the items as specified. 1-3. In the int main(int argc, char *argv[ ], char *env[ ]) function, use YOUR myprintf() to print argc value argv strings env strings Then, myprintf("char=%c string=%s dec=%u hex=%x neg=%d ", 'A', "this is a test", 100, 100, -100); /**** HELP INFO ******/ NOTE: This assignment is for 32-bit GCC, which passes parameters on stack. Use gcc -m32 t.c to compile your C source files. int myprintf(char *fmt, ...) // C compiler requires the 3 DOTs { Assume the call is myprintf(fmt, a,b,c,d); Upon entry, the following diagram shows the stack contents. char *cp -> "...%c ..%s ..%u .. %d " HIGH | LOW --------------------------- --|------------------------------------------ | d | c | b | a | fmt |retPC| ebp | locals ----------------|----------------|--------------------------------------- | | int *ip CPU.ebp 1. Let char *cp point at the format string: HOW? 2. Let int *ip point at the first item to be printed on stack: HOW? NOTE: In 32-bit mode, Every entry in the stack is 4-byte; for chars, they are in the lowest byte (of the 4-byte entry) for strings, they are POINTERs to the actual strings. *** ALGORITHM ****** Use cp to scan the format string: spit out each char that's NOT % for each , spit out an extra Upon seeing a %: get next char, which must be one of 'c','s','u','x','d' Then call YOUR putchar(*ip) for 'c'; prints(*ip) for 's'; printu(*ip) for 'u'; printx(*ip) for 'x'; printd(*ip) for 'd'; Advance ip to point to the next item on stack. After implementing your myprintf() function, write C program to test your myprintf() function first. Then use it in the assignment. SAMPLE Solution: ~samples/LAB1/myprintf # download and run it ===================== Part 2 ============================================ PART 2: Partition Table (This part is for general GCC, but you may use -m32) 2-1. OBJECTIVES Partition table, fdisk, structures in C, open-read files in Unix/Linux 2-2 Partition Table: A disk (floppy disk, hard disk, USB drive, SD cards, etc.) consists of 512-byte sectors, which are counted linearly as sector 0,1,2,3,.... A disk is usually divided into several partitions. The partitions are recorded in a partition table at the beginning (the 0th sector) of the disk, called the Master Boot Record (MBR). Inside the MBR, the partition table begins at the byte offset 0x1BE. The Partitin Table contains 4 entries, each 16 bytes long, defined in the following C structure.