allow for all denominations up to TiB

main.c

@@ -1,28 +1,88 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <math.h>
+#include <string.h>
 #include <limits.h>
 
+#define KiB (unsigned long long int) 0x400
+#define MiB (unsigned long long int) 0x100000
+#define GiB (unsigned long long int) 0x40000000
+#define TiB (unsigned long long int) 0x10000000000
+
+#define LOADS TiB * 9999
+
+char* get_shorthand(unsigned long long int size) {
+        if (size < KiB) return 0;
+
+        if (size > LOADS) {
+                return ">9999 TiB";
+        }
+
+        char* buffer = malloc(sizeof(char) * 12);
+
+        if (size >= TiB) {
+                snprintf(buffer, 12, "%.2f TiB", (float) size / TiB);
+                return buffer;
+        }
+        if (size >= GiB) {
+                snprintf(buffer, 12, "%.2f GiB", (float) size / GiB);
+                return buffer;
+        }
+        if (size >= MiB) {
+                snprintf(buffer, 12, "%.2f MiB", (float) size / MiB);
+                return buffer;
+        }
+        if (size >= KiB) {
+                snprintf(buffer, 12, "%.2f KiB", (float) size / KiB);
+                return buffer;
+        }
+}
+
+unsigned long long int adjust_by_denomination(unsigned long long int size, char denomination) {
+        switch (denomination) {
+                case 'K':
+                        return size * KiB;
+                case 'M':
+                        return size * MiB;
+                case 'G':
+                        return size * GiB;
+                case 'T':
+                        return size * TiB;
+                default:
+                        return size;
+        }
+}
+
 int main() {
 
         unsigned long long int size = 0;
-        unsigned int gib = 0;
 
-        printf("please enter the number of gibibytes (GiB) you would like to allocate (1 GiB = 1073741824 bytes):\n> ");
+        printf("please enter the amount of memory you would like to allocate (\"1G\" = 1 GiB = 1073741824 bytes):\n> ");
         unsigned int digit = 0;
+        unsigned char last_char = 0;
         while (1) {
                 unsigned char input = getchar();
                 if (input == '\n') break;
+                last_char = input;
+
                 if (input < '0' || input > '9') continue;
 
-                if (digit > 0) gib = gib * 10;
+                if (digit > 0) size *= 10;
 
-                gib = gib + (unsigned int) input - 48;
+                size += (unsigned int) input - 48;
                 digit++;
         }
 
-        size = (unsigned long long int) gib * 1024 * 1024 * 1024;
+        size = adjust_by_denomination(size, last_char);
 
-        printf("you are about to allocate %d GiB (%llu bytes) of heap memory. are you sure? (y/n)\n> ", gib, size);
+        // even if the user doesn't specify a denomination, it still would be nice to display a truncated amount if available.
+        char* shorthand = get_shorthand(size);
+
+        if (shorthand) {
+                printf("you are about to allocate %s (%llu bytes) of heap memory. are you sure? (y/n)\n> ", shorthand, size);
+        } else {
+                printf("you are about to allocate %llu byte%c of heap memory. are you sure? (y/n)\n> ", size, size == 1 ? 0 : 's');
+        }
 
         unsigned char input = getchar();
         if (input != 'y') return 0;
@@ -42,7 +102,12 @@ int main() {
         }
         printf("\n");
 
-        printf("%d GiB (%llu bytes) of heap memory has been allocated. you are insane.\n", gib, size);
+        if (shorthand) {
+                printf("%s (%llu bytes) of heap memory has been allocated. you are insane.\n", shorthand, size);
+        } else {
+                printf("%llu byte%c of heap memory have been allocated. you are insane.\n", size, size == 1 ? 0 : 's');
+        }
+        free(shorthand);
         printf("press ENTER to release this memory, or CTRL+C to exit the program.\n");
 
         getchar();