reorganization

itoa.c

@@ -0,0 +1,43 @@
+/* Convert the integer D to a string and save the string in BUF. If
+   BASE is equal to 'd', interpret that D is decimal, and if BASE is
+   equal to 'x', interpret that D is hexadecimal. */
+void itoa(char *buf, int base, int d)
+{
+  char *p = buf;
+  char *p1, *p2;
+  unsigned long ud = d;
+  int divisor = 10;
+
+  /* If %d is specified and D is minus, put `-' in the head. */
+  if (base == 'd' && d < 0)
+  {
+    *p++ = '-';
+    ++buf;
+    ud = -d;
+  }
+  else if (base == 'x')
+    divisor = 16;
+
+  /* Divide UD by DIVISOR until UD == 0. */
+  do
+  {
+    int remainder = ud % divisor;
+    *p++ = (remainder < 10) ? remainder + '0' : remainder + 'a' - 10;
+  }
+  while (ud /= divisor);
+
+  /* Terminate BUF. */
+  *p = 0;
+
+  /* Reverse BUF. */
+  p1 = buf;
+  p2 = p - 1;
+  while (p1 < p2)
+  {
+    char tmp = *p1;
+    *p1 = *p2;
+    *p2 = tmp;
+    p1++;
+    p2--;
+  }
+}