--- /dev/null
+/* -*-c-*-
+ *
+ * Program to find appropriate types for multiprecision integer stuff.
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <limits.h>
+#if __STDC_VERSION__ >= 199900l
+# include <stdint.h>
+#endif
+
+/* --- Hack for GCC --- *
+ *
+ * WG14 in their infinite wisdom decided not to use the GCC constant name.
+ */
+
+#if defined(ULONG_LONG_MAX) && !defined(ULLONG_MAX)
+# define ULLONG_MAX ULONG_LONG_MAX
+#endif
+
+/* --- Choose the largest integer type --- */
+
+#if defined(UINTMAX_MAX)
+ typedef uintmax_t umax;
+# define P_UMAX PRIuMAX
+#elif defined(ULLONG_MAX)
+ typedef unsigned long long umax;
+# define P_UMAX "%llu"
+#else
+ typedef unsigned long umax;
+# define P_UMAX "%lu"
+#endif
+
+/* --- Table of interesting types --- *
+ *
+ * These are in preference order.
+ */
+
+enum {
+ f_stdint
+};
+
+struct itype {
+ const char *name;
+ umax max;
+ unsigned flags;
+ unsigned bits;
+} tytab[] = {
+ { "unsigned int", UINT_MAX, 0 },
+ { "unsigned short", USHRT_MAX, 0 },
+ { "unsigned long", ULONG_MAX, 0 },
+#ifdef ULLONG_MAX
+ { "unsigned long long", ULLONG_MAX, 0 },
+#endif
+#ifdef UINTMAX_MAX
+ { "uintmax_t", UINTMAX_MAX, f_stdint },
+#endif
+ { 0, 0 },
+};
+
+typedef struct itype itype;
+
+/* --- Main program --- */
+
+int main(int argc, char *argv[])
+{
+ itype *i;
+ itype *largest, *mpw, *mpd;
+
+ /* --- Find the bitcounts --- */
+
+ for (i = tytab; i->name; i++) {
+ unsigned bits;
+ umax u = i->max;
+ for (bits = 0; u; bits++)
+ u >>= 1;
+ i->bits = bits;
+ }
+
+ /* --- Now try to find the interesting types --- *
+ *
+ * The first thing to do is to find the largest type. Then I find the
+ * `best' type which is less than half that size, and then the `best' type
+ * which is twice as big as that one.
+ */
+
+ largest = tytab;
+ for (i = tytab; i->name; i++) {
+ if (i->bits > largest->bits)
+ largest = i;
+ }
+ for (mpw = 0, i = tytab; i->name; i++) {
+ if (i->bits * 2 <= largest->bits && (!mpw || i->bits > mpw->bits))
+ mpw = i;
+ }
+ if (!mpw)
+ mpw = tytab;
+ for (mpd = 0, i = tytab; i->name; i++) {
+ if (i->bits >= mpw->bits * 2 && (!mpd || i->bits < mpd->bits))
+ mpd = i;
+ }
+ if (!mpd) {
+ static itype w, d;
+ d = w = *mpw;
+ w.bits /= 2; w.max = ~(~((umax)0) << w.bits);
+ d.bits = w.bits * 2; d.max = ~(~((umax)0) << d.bits);
+ mpw = &w; mpd = &d;
+ }
+
+ /* --- Output time --- */
+
+ puts("\
+/* -*-c-*-\n\
+ *\n\
+ * mptypes.h [generated]\n\
+ */\n\
+\n\
+#ifndef MPTYPES_H\n\
+#define MPTYPES_H\n\
+");
+ if ((mpd->flags | mpw->flags) & f_stdint) {
+ puts("\
+#if __STDC_VERSION__ >= 199900l\n\
+# include <stdint.h>\n\
+#endif\n\
+");
+ }
+ printf("\
+typedef %s mpw;\n\
+#define MPW_BITS %u\n\
+#define MPW_MAX " P_UMAX "\n\
+\n\
+typedef %s mpd;\n\
+#define MPD_BITS %u\n\
+#define MPD_MAX " P_UMAX "\n\
+\n\
+#endif\n\
+",
+ mpw->name, mpw->bits, mpw->max,
+ mpd->name, mpd->bits, mpd->max);
+
+ return (0);
+}