Updated boost to v1.55.0

[rsem.git] / boost / random / detail / large_arithmetic.hpp

diff --git a/boost/random/detail/large_arithmetic.hpp b/boost/random/detail/large_arithmetic.hpp
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+++ b/boost/random/detail/large_arithmetic.hpp
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+/* boost random/detail/large_arithmetic.hpp header file
+ *
+ * Copyright Steven Watanabe 2011
+ * Distributed under the Boost Software License, Version 1.0. (See
+ * accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * See http://www.boost.org for most recent version including documentation.
+ *
+ * $Id: large_arithmetic.hpp 71018 2011-04-05 21:27:52Z steven_watanabe $
+ */
+
+#ifndef BOOST_RANDOM_DETAIL_LARGE_ARITHMETIC_HPP
+#define BOOST_RANDOM_DETAIL_LARGE_ARITHMETIC_HPP
+
+#include <boost/cstdint.hpp>
+#include <boost/integer.hpp>
+#include <boost/limits.hpp>
+#include <boost/random/detail/integer_log2.hpp>
+
+#include <boost/random/detail/disable_warnings.hpp>
+
+namespace boost {
+namespace random {
+namespace detail {
+
+struct div_t {
+    boost::uintmax_t quotient;
+    boost::uintmax_t remainder;
+};
+
+inline div_t muldivmod(boost::uintmax_t a, boost::uintmax_t b, boost::uintmax_t m)
+{
+    static const int bits =
+        ::std::numeric_limits< ::boost::uintmax_t>::digits / 2;
+    static const ::boost::uintmax_t mask = (::boost::uintmax_t(1) << bits) - 1;
+    typedef ::boost::uint_t<bits>::fast digit_t;
+
+    int shift = std::numeric_limits< ::boost::uintmax_t>::digits - 1
+        - detail::integer_log2(m);
+
+    a <<= shift;
+    m <<= shift;
+
+    digit_t product[4] = { 0, 0, 0, 0 };
+    digit_t a_[2] = { digit_t(a & mask), digit_t((a >> bits) & mask) };
+    digit_t b_[2] = { digit_t(b & mask), digit_t((b >> bits) & mask) };
+    digit_t m_[2] = { digit_t(m & mask), digit_t((m >> bits) & mask) };
+
+    // multiply a * b
+    for(int i = 0; i < 2; ++i) {
+        digit_t carry = 0;
+        for(int j = 0; j < 2; ++j) {
+            ::boost::uint64_t temp = ::boost::uintmax_t(a_[i]) * b_[j] +
+                carry + product[i + j];
+            product[i + j] = digit_t(temp & mask);
+            carry = digit_t(temp >> bits);
+        }
+        if(carry != 0) {
+            product[i + 2] += carry;
+        }
+    }
+
+    digit_t quotient[2];
+
+    if(m == 0) {
+        div_t result = {
+            ((::boost::uintmax_t(product[3]) << bits) | product[2]),
+            ((::boost::uintmax_t(product[1]) << bits) | product[0]) >> shift,
+        };
+        return result;
+    }
+
+    // divide product / m
+    for(int i = 3; i >= 2; --i) {
+        ::boost::uintmax_t temp =
+            ::boost::uintmax_t(product[i]) << bits | product[i - 1];
+
+        digit_t q = digit_t((product[i] == m_[1]) ? mask : temp / m_[1]);
+
+        ::boost::uintmax_t rem =
+            ((temp - ::boost::uintmax_t(q) * m_[1]) << bits) + product[i - 2];
+
+        ::boost::uintmax_t diff = m_[0] * ::boost::uintmax_t(q);
+
+        int error = 0;
+        if(diff > rem) {
+            if(diff - rem > m) {
+                error = 2;
+            } else {
+                error = 1;
+            }
+        }
+        q -= error;
+        rem = rem + error * m - diff;
+
+        quotient[i - 2] = q;
+        product[i] = 0;
+        product[i-1] = (rem >> bits) & mask;
+        product[i-2] = rem & mask;
+    }
+
+    div_t result = {
+        ((::boost::uintmax_t(quotient[1]) << bits) | quotient[0]),
+        ((::boost::uintmax_t(product[1]) << bits) | product[0]) >> shift,
+    };
+    return result;
+}
+
+inline boost::uintmax_t muldiv(boost::uintmax_t a, boost::uintmax_t b, boost::uintmax_t m)
+{ return detail::muldivmod(a, b, m).quotient; }
+
+inline boost::uintmax_t mulmod(boost::uintmax_t a, boost::uintmax_t b, boost::uintmax_t m)
+{ return detail::muldivmod(a, b, m).remainder; }
+
+} // namespace detail
+} // namespace random
+} // namespace boost
+
+#include <boost/random/detail/enable_warnings.hpp>
+
+#endif // BOOST_RANDOM_DETAIL_LARGE_ARITHMETIC_HPP