Codes

1. Float Format (f)

Add format f to interpret the next 4 bytes as a 32-bit floating-point number.

case 'f': {
  float fv = *(float *)p;
  // xv6 printf usually requires doubles for float args
  printf("%f\n", (double)fv); 
  p += 4;
  break;
}

2. Octal Format (o)

Add format o to print the next 4 bytes as an octal (base-8) integer.

case 'o': {
  int v = *(int *)p;
  printf("%o\n", v);
  p += sizeof(int);
  break;
}

3. Binary Format (b)

Add format b to print the next 1 byte as 8 bits of binary (e.g., 01010101).

case 'b': {
  unsigned char v = *p;
  for (int j = 7; j >= 0; j--) {
    // Shift bit to the right and mask the last bit
    printf("%d", (v >> j) & 1);
  }
  printf("\n");
  p += 1;
  break;
}

4. Hex without Prefix (x)

Add format x to print 4 bytes in hexadecimal without the standard 0x prefix.

case 'x': {
  unsigned int v = *(unsigned int *)p;
  printf("%x\n", v);
  p += sizeof(unsigned int);
  break;
}

5. Truncated String Pointer (s)

Modify the s (pointer) format to truncate and only print the first 8 characters of the string.

case 's': {
  char *sp = *(char **)p;
  // Use the precision specifier .8 to limit characters
  printf("%.8s\n", sp);
  p += sizeof(char *);
  break;
}

6. Address Tracking (A)

Add a format character A that prints the hex memory address of the current data pointer.

case 'A': {
  printf("%p\n", p);
  // Note: We don't increment 'p' because no data was consumed
  break;
}

7. Skip Logic (k)

Implement a "skip" character k that advances the data pointer by 4 bytes without printing anything.

case 'k': {
  p += 4; // Advance pointer without output
  break;
}

8. Item Delimiter

Modify memdump to print a custom delimiter (like a vertical bar |) between every parsed item.

// End of switch(fmt[i]) block
if (fmt[i+1] != 0 && fmt[i] != 'S') {
    printf(" | ");
}
// End of for loop

9. Big-Endian Integer

Change the integer format i to print the 4 bytes in Big-Endian order instead of Little-Endian.

case 'i': {
  unsigned char *b = (unsigned char *)p;
  // Shift bytes: [0] is most significant, [3] is least significant
  int v = (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3];
  printf("%d\n", v);
  p += 4;
  break;
}

10. String Length Tracking (S)

Change format S (inline string) to print the string length in parentheses after the text.

case 'S': {
  char *sp = p;
  printf("%s (%d)\n", sp, strlen(sp));
  // Since 'S' is usually the end of a format, we return
  return; 
}