New module 'imaxdiv'.

[gnulib.git] / lib / imaxdiv.c

diff --git a/lib/imaxdiv.c b/lib/imaxdiv.c
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+++ b/lib/imaxdiv.c
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+/* imaxdiv() function: division of 'intmax_t'.
+   Copyright (C) 2006 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+/* Specification.  */
+#include <inttypes.h>
+
+#include <stdlib.h>
+
+imaxdiv_t
+imaxdiv (intmax_t numer, intmax_t denom)
+{
+  imaxdiv_t result;
+
+  result.quot = numer / denom;
+  result.rem = numer % denom;
+
+  /* Verify the requirements of ISO C 99 section 6.5.5 paragraph 6:
+     "When integers are divided, the result of the / operator is the
+      algebraic quotient with any fractional part discarded.  (This is
+      often called "truncation toward zero".)  If the quotient a/b is
+      representable, the expression (a/b)*b + a%b shall equal a."  */
+  if (!(denom == 0
+       || (INTMAX_MIN + INTMAX_MAX < 0
+           && denom == -1
+           && numer < - INTMAX_MAX)))
+    {
+      if (!(result.quot * denom + result.rem == numer))
+       /* The compiler's implementation of / and % is broken.  */
+       abort ();
+      if (!(numer >= 0
+           ? result.rem >= 0
+             && (denom >= 0
+                 ? result.rem < denom
+                 : /* Don't write  result.rem < - denom,
+                      as it gives integer overflow if denom == INTMAX_MIN.  */
+                   - result.rem > denom)
+           : result.rem <= 0
+             && (denom >= 0
+                 ? result.rem > - denom
+                 : result.rem > denom)))
+       /* The compiler's implementation of / and % may be ok according to
+          C89, but not to C99.  Please report this to <bug-gnulib@ngu.org>.
+          This might be a big portability problem.  */
+       abort ();
+    }
+
+  return result;
+}