Checkpoint the party/runtime stack before share-program and malicious-mode work.

Ship the TLS mesh, composer, Beaver/Yao/leaf MPC, prep/online paths, apps, and docs so the tree is pushable before elevating share_expr, security_mode, and prep resume.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/dpf/fixed_share.hpp

@@ -0,0 +1,87 @@
+/// @file dpf/fixed_share.hpp
+/// @brief Fixed-point arithmetic shares: `fixed<IntBits, FracBits>`.
+#ifndef LIBDPF_INCLUDE_DPF_FIXED_SHARE_HPP__
+#define LIBDPF_INCLUDE_DPF_FIXED_SHARE_HPP__
+
+#include <cstddef>
+#include <cstdint>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "hedley/hedley.h"
+
+#include "dpf/share_vec.hpp"
+#include "dpf/trunc.hpp"
+
+namespace dpf
+{
+
+template <unsigned IntBits, unsigned FracBits>
+struct fixed
+{
+    static constexpr unsigned int_bits = IntBits;
+    static constexpr unsigned frac_bits = FracBits;
+    static constexpr unsigned width = IntBits + FracBits;
+    static_assert(width > 0 && width <= 128, "fixed width 1..128");
+
+    using ring = std::conditional_t<(width > 64), unsigned __int128, std::uint64_t>;
+
+    ring raw{};
+
+    fixed() = default;
+    explicit fixed(ring v) : raw(v) {}
+
+    static fixed from_integer(ring i)
+    {
+        return fixed{static_cast<ring>(i << FracBits)};
+    }
+
+    static fixed mul_clear(fixed a, fixed b)
+    {
+        const ring prod = static_cast<ring>(a.raw * b.raw);
+        return fixed{static_cast<ring>(prod >> FracBits)};
+    }
+
+    friend fixed operator+(fixed a, fixed b)
+    {
+        return fixed{static_cast<ring>(a.raw + b.raw)};
+    }
+
+    friend fixed operator-(fixed a, fixed b)
+    {
+        return fixed{static_cast<ring>(a.raw - b.raw)};
+    }
+};
+
+template <unsigned IntBits, unsigned FracBits>
+using fixed_vec = share_vec<typename fixed<IntBits, FracBits>::ring>;
+
+/// @brief Fixed-point product via mul_trunc by FracBits (Beaver, both parties).
+template <unsigned IntBits, unsigned FracBits>
+HEDLEY_WARN_UNUSED_RESULT
+std::pair<fixed_vec<IntBits, FracBits>, fixed_vec<IntBits, FracBits>>
+fixed_mul_share(const fixed_vec<IntBits, FracBits> & x0,
+    const fixed_vec<IntBits, FracBits> & x1,
+    const fixed_vec<IntBits, FracBits> & y0,
+    const fixed_vec<IntBits, FracBits> & y1)
+{
+    if (x0.size() != x1.size() || x0.size() != y0.size()
+        || y0.size() != y1.size())
+        throw std::invalid_argument("fixed_mul_share size");
+    fixed_vec<IntBits, FracBits> z0(x0.size(), protocol::domain::a, 0);
+    fixed_vec<IntBits, FracBits> z1(x0.size(), protocol::domain::a, 1);
+    for (std::size_t i = 0; i < x0.size(); ++i)
+    {
+        // Widen so IntBits+FracBits products do not wrap before the shift.
+        auto mt = trunc::mul_exact_trunc(x0[i], x1[i], y0[i], y1[i], FracBits);
+        z0[i] = mt.z0;
+        z1[i] = mt.z1;
+    }
+    return {std::move(z0), std::move(z1)};
+}
+
+}  // namespace dpf
+
+#endif  // LIBDPF_INCLUDE_DPF_FIXED_SHARE_HPP__