CSE 333 Exercise 2

• Write code that uses pointers and data representations.
• Examine the relationship between pointers and arrays.
• Use format specifiers to handle printing fixed-width integers.

As discussed in lecture, arrays and pointers are closely related:

• When used in an expression, an array name evaluates to a pointer.
• Array subscripting notation is actually pointer manipulation: ar[i] ↔ *(ar+i).
• An array argument and a pointer argument are functionally equivalent in that the function receives a copy of the pointer.

In addition, recall the topic of endianness:

• Endianness determines the ordering of the bytes when multibyte data is stored in memory — the least significant byte is stored at the littlest or biggest address.
  • This does not affect the address of the data, which is always that of the first/lowest byte.

Write a C program (ex2.c) that does the following:

• Contains a function called PrintBytes with prototype void PrintBytes(void* mem_addr, int num_bytes). The void pointer can be thought of as a generalized form of an array of bytes and num_bytes can be thought of as the length of the "array." This function should print out the length, the address passed in, and the bytes of memory as exactly two digits each in lowercase hexadecimal, e.g.,
  

  The 4 bytes starting at 0x7fff1081856c are: ff 01 30 4e

  • Recall that the address printed may vary from execution to execution due to security measures such as stack randomization.
  • For the case of num_bytes = 0, it's ok to have a space at the end of the output.
  • For the case of num_bytes > 0, there should not be a space at the end of the output.
• Contains a function called CopyAndSort that accepts, in order, two arrays of uint8_t's (i.e., two arrays of bytes) and an array length as arguments; you should assume the length of the two arrays are the same. The function should (1) call PrintBytes on the first array and its sizeof and (2) iterate through the entries of the first array and copy the entries into the second array in non-descending (i.e., ascending with duplicates allowed) sorted order.
  • You should not use any library functions that would perform the sort for you (e.g., qsort()), however you may use any type of sort. We would recommend using insertion sort.
• Completes the main function found below that sorts a local array {3, 2, 0, 8, 17, 6, 10, 7, 8, 1, 12} and dumps the bytes of the arrays along with some other variables using the two functions that you wrote. Your main should match the provided code exactly, with the exception of filling in the missing arguments:

  int main(int argc, char* argv[]) {
    int32_t int_val = 1;
    float   float_val = 1.0f;
    uint8_t arr_unsorted[] = {3, 2, 0, 8, 17, 6, 10, 7, 8, 1, 12};
    uint8_t arr_sorted[]   = {0, 0, 0, 0,  0, 0,  0, 0, 0, 0,  0};
  
    PrintBytes(&int_val, sizeof(int_val));
    PrintBytes(&float_val, sizeof(float_val));
    PrintBytes(arr_unsorted, _____);
    CopyAndSort(arr_unsorted, arr_sorted, _____);
    PrintBytes(arr_sorted, _____);
  
    return EXIT_SUCCESS;
  }
  

$ ./test_ex2
Expected output purposely not shown.

Output MATCHES expected (does not guarantee a full score; depends on your implementation)

General

For the sake of our autograder, make sure that your function names match the specifications exactly, including capitalization. You should write comments explaining the behavior and purpose of functions you define.

Program Layout

As with the previous exercise, make sure that you organize and comment your functions in such a way that follows the best C practices.

Format Specifiers

Utilize the correct format specifiers to avoid implicit casts and to increase the portability of your code.

Constants

Avoid "magic numbers" (i.e., unnamed numerical constants) where possible. Use predefined constants (e.g., EXIT_SUCCESS), if available, or use #define to define/name any integer constants that have a clear and specific use. Use sizeof to increase the portability of your code.

Submit the following file(s) by creating an ex2-submit tag in your repo before the assignment deadline. The file(s) should be located in the exact directory listed below (i.e., there should be a directory ex2 with the ex2.c file inside it), including capitalization:

• ex2/ex2.c

For full credit, your code must:

• Compile without errors or warnings on CSE Linux machines (lab workstations, attu, or CSE home VM).
• Have no runtime errors, memory leaks, or memory errors (gcc and valgrind).
• Be contained in the file listed above that compiles with the command:
  

  $ gcc -Wall -g -std=c17 -o ex2 ex2.c

• Have a comment at the top of your .c file with your name(s) and CSE or UW email address(es).
• Be pretty: the formatting, modularization, variable and function names, commenting, and so on should be consistent with class style guidelines. Additionally, the linter shouldn't have any complaints about your code (cpplint.py --clint).
• Be robust: your code should deal with hard-to-handle/edge cases and bogus user input (if there are any) gracefully.