Data commit

Task/Non-decimal-radices-Convert/C/non-decimal-radices-convert.c

@@ -0,0 +1,48 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdint.h>
+
+char *to_base(int64_t num, int base)
+{
+  char *tbl = "0123456789abcdefghijklmnopqrstuvwxyz";
+  char buf[66] = {'\0'};
+  char *out;
+  uint64_t n;
+  int i, len = 0, neg = 0;
+  if (base > 36) {
+    fprintf(stderr, "base %d too large\n", base);
+    return 0;
+  }
+
+  /* safe against most negative integer */
+  n = ((neg = num < 0)) ? (~num) + 1 : num;
+
+  do { buf[len++] = tbl[n % base]; } while(n /= base);
+
+  out = malloc(len + neg + 1);
+  for (i = neg; len > 0; i++) out[i] = buf[--len];
+  if (neg) out[0] = '-';
+
+  return out;
+}
+
+long from_base(const char *num_str, int base)
+{
+  char *endptr;
+  /* there is also strtoul() for parsing into an unsigned long */
+  /* in C99, there is also strtoll() and strtoull() for parsing into long long and
+   * unsigned long long, respectively */
+  int result = strtol(num_str, &endptr, base);
+  return result;
+}
+
+int main()
+{
+  int64_t x;
+  x = ~(1LL << 63) + 1;
+  printf("%lld in base 2: %s\n", x, to_base(x, 2));
+  x = 383;
+  printf("%lld in base 16: %s\n", x, to_base(x, 16));
+  return 0;
+}