Squashed 'src/minisketch/' content from commit 89629eb2c7

git-subtree-dir: src/minisketch
git-subtree-split: 89629eb2c7e262b39ba489b93b111760baded4b3

src/fields/generic_common_impl.h

@@ -0,0 +1,70 @@
+/**********************************************************************
+ * Copyright (c) 2018 Pieter Wuille, Greg Maxwell, Gleb Naumenko      *
+ * Distributed under the MIT software license, see the accompanying   *
+ * file LICENSE or http://www.opensource.org/licenses/mit-license.php.*
+ **********************************************************************/
+
+#ifndef _MINISKETCH_FIELDS_GENERIC_COMMON_IMPL_H_
+#define _MINISKETCH_FIELDS_GENERIC_COMMON_IMPL_H_ 1
+
+#include <stdint.h>
+
+#include "../int_utils.h"
+#include "../lintrans.h"
+
+namespace {
+
+/** Generic implementation for fields whose elements can be represented by an integer type. */
+template<typename I, int B, uint32_t MOD, typename F, typename T, const F* SQR, const F* QRT> class Field
+{
+    typedef BitsInt<I, B> O;
+    typedef LFSR<O, MOD> L;
+
+public:
+    typedef I Elem;
+    constexpr int Bits() const { return B; }
+
+    constexpr inline Elem Mul2(Elem val) const { return L::Call(val); }
+
+    class Multiplier
+    {
+        T table;
+    public:
+        explicit Multiplier(const Field&, Elem a) { table.template Build<L::Call>(a); }
+        constexpr inline Elem operator()(Elem a) const { return table.template Map<O>(a); }
+    };
+
+    Elem Mul(Elem a, Elem b) const { return GFMul<I, B, L, O>(a, b); }
+
+    /** Compute the square of a. */
+    inline constexpr Elem Sqr(Elem a) const { return SQR->template Map<O>(a); }
+
+    /** Compute x such that x^2 + x = a (undefined result if no solution exists). */
+    inline constexpr Elem Qrt(Elem a) const { return QRT->template Map<O>(a); }
+
+    /** Compute the inverse of x1. */
+    Elem Inv(Elem a) const { return InvExtGCD<I, O, B, MOD>(a); }
+
+    /** Generate a random field element. */
+    Elem FromSeed(uint64_t seed) const {
+        uint64_t k0 = 0x496e744669656c64ull; // "IntField"
+        uint64_t k1 = seed;
+        uint64_t count = ((uint64_t)B) << 32;
+        Elem ret;
+        do {
+            ret = O::Mask(I(SipHash(k0, k1, count++)));
+        } while(ret == 0);
+        return ret;
+    }
+
+    Elem Deserialize(BitReader& in) const { return in.template Read<B, I>(); }
+
+    void Serialize(BitWriter& out, Elem val) const { out.template Write<B, I>(val); }
+
+    constexpr Elem FromUint64(uint64_t x) const { return O::Mask(I(x)); }
+    constexpr uint64_t ToUint64(Elem val) const { return uint64_t(val); }
+};
+
+}
+
+#endif