Add itoa() to stdlib.h

ncc/include/stdlib.h

@@ -2,6 +2,7 @@
 #define __STDLIB_H__
 
 #include <stddef.h>
+#include <assert.h>
 
 int abs(int n)
 {
@@ -15,6 +16,42 @@ void exit(int status)
     asm (status) -> void { exit; };
 }
 
+// Convert integer to string
+char* itoa(int value, char* str, int base)
+{
+    assert(base > 0 && base <= 16);
+
+    // Compute the number of digits
+    int num_digits = 0;
+    for (int n = value; n > 0; n = n / base)
+    {
+        int digit = value % base;
+        ++num_digits;
+    }
+
+    // The digits have to be written in reverse order
+    for (int i = num_digits - 1; i >= 0; --i)
+    {
+        int digit = value % base;
+        value = value / base;
+
+        char ch;
+        if (digit < 10)
+        {
+            ch = '0' + digit;
+        }
+        else
+        {
+            ch = 'A' + (digit - 10);
+        }
+
+        str[i] = ch;
+    }
+
+    // Write the null terminator
+    str[num_digits] = '\0';
+}
+
 // We define RAND_MAX to be the same as INT32_MAX
 #define RAND_MAX 0x7FFFFFFF
 

ncc/tests/stdlib.c

@@ -1,6 +1,8 @@
 #include <stdlib.h>
 #include <assert.h>
 
+char buf[32];
+
 void main()
 {
     assert(abs(-5) == 5);
@@ -16,13 +18,21 @@ void main()
     }
 
     // Check that at least one value is positive
-    while (true)
+    while (1)
     {
         int r = rand();
         if (r > 10)
             break;
     }
 
+    // Test itoa function
+    itoa(5, buf, 10);
+    assert(buf[0] == '5' && buf[1] == 0);
+    itoa(17, buf, 10);
+    assert(buf[0] == '1' && buf[1] == '7' && buf[2] == 0);
+    itoa(15, buf, 16);
+    assert(buf[0] == 'F' && buf[1] == 0);
+
     // Test the exit function
     exit(0);
 }