Move /src to /subprojects

This will facilitate breaking up Nix into multiple packages for each
component with Meson.

subprojects/libstore/serve-protocol.hh

@@ -0,0 +1,193 @@
+#pragma once
+///@file
+
+#include "common-protocol.hh"
+
+namespace nix {
+
+#define SERVE_MAGIC_1 0x390c9deb
+#define SERVE_MAGIC_2 0x5452eecb
+
+#define SERVE_PROTOCOL_VERSION (2 << 8 | 7)
+#define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
+#define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
+
+
+struct StoreDirConfig;
+struct Source;
+
+// items being serialised
+struct BuildResult;
+struct UnkeyedValidPathInfo;
+
+
+/**
+ * The "serve protocol", used by ssh:// stores.
+ *
+ * This `struct` is basically just a `namespace`; We use a type rather
+ * than a namespace just so we can use it as a template argument.
+ */
+struct ServeProto
+{
+    /**
+     * Enumeration of all the request types for the protocol.
+     */
+    enum struct Command : uint64_t;
+
+    /**
+     * Version type for the protocol.
+     *
+     * @todo Convert to struct with separate major vs minor fields.
+     */
+    using Version = unsigned int;
+
+    /**
+     * A unidirectional read connection, to be used by the read half of the
+     * canonical serializers below.
+     */
+    struct ReadConn {
+        Source & from;
+        Version version;
+    };
+
+    /**
+     * A unidirectional write connection, to be used by the write half of the
+     * canonical serializers below.
+     */
+    struct WriteConn {
+        Sink & to;
+        Version version;
+    };
+
+    /**
+     * Stripped down serialization logic suitable for sharing with Hydra.
+     *
+     * @todo remove once Hydra uses Store abstraction consistently.
+     */
+    struct BasicClientConnection;
+    struct BasicServerConnection;
+
+    /**
+     * Data type for canonical pairs of serialisers for the serve protocol.
+     *
+     * See https://en.cppreference.com/w/cpp/language/adl for the broader
+     * concept of what is going on here.
+     */
+    template<typename T>
+    struct Serialise;
+    // This is the definition of `Serialise` we *want* to put here, but
+    // do not do so.
+    //
+    // See `worker-protocol.hh` for a longer explanation.
+#if 0
+    {
+        static T read(const StoreDirConfig & store, ReadConn conn);
+        static void write(const StoreDirConfig & store, WriteConn conn, const T & t);
+    };
+#endif
+
+    /**
+     * Wrapper function around `ServeProto::Serialise<T>::write` that allows us to
+     * infer the type instead of having to write it down explicitly.
+     */
+    template<typename T>
+    static void write(const StoreDirConfig & store, WriteConn conn, const T & t)
+    {
+        ServeProto::Serialise<T>::write(store, conn, t);
+    }
+
+    /**
+     * Options for building shared between
+     * `ServeProto::Command::BuildPaths` and
+     * `ServeProto::Command::BuildDerivation`.
+     */
+    struct BuildOptions;
+};
+
+enum struct ServeProto::Command : uint64_t
+{
+    QueryValidPaths = 1,
+    QueryPathInfos = 2,
+    DumpStorePath = 3,
+    ImportPaths = 4,
+    ExportPaths = 5,
+    BuildPaths = 6,
+    QueryClosure = 7,
+    BuildDerivation = 8,
+    AddToStoreNar = 9,
+};
+
+
+struct ServeProto::BuildOptions {
+    /**
+     * Default value in this and every other field is so tests pass when
+     * testing older deserialisers which do not set all the fields.
+     */
+    time_t maxSilentTime = -1;
+    time_t buildTimeout = -1;
+    size_t maxLogSize = -1;
+    size_t nrRepeats = -1;
+    bool enforceDeterminism = -1;
+    bool keepFailed = -1;
+
+    bool operator == (const ServeProto::BuildOptions &) const = default;
+};
+
+/**
+ * Convenience for sending operation codes.
+ *
+ * @todo Switch to using `ServeProto::Serialize` instead probably. But
+ * this was not done at this time so there would be less churn.
+ */
+inline Sink & operator << (Sink & sink, ServeProto::Command op)
+{
+    return sink << (uint64_t) op;
+}
+
+/**
+ * Convenience for debugging.
+ *
+ * @todo Perhaps render known opcodes more nicely.
+ */
+inline std::ostream & operator << (std::ostream & s, ServeProto::Command op)
+{
+    return s << (uint64_t) op;
+}
+
+/**
+ * Declare a canonical serialiser pair for the worker protocol.
+ *
+ * We specialise the struct merely to indicate that we are implementing
+ * the function for the given type.
+ *
+ * Some sort of `template<...>` must be used with the caller for this to
+ * be legal specialization syntax. See below for what that looks like in
+ * practice.
+ */
+#define DECLARE_SERVE_SERIALISER(T) \
+    struct ServeProto::Serialise< T > \
+    { \
+        static T read(const StoreDirConfig & store, ServeProto::ReadConn conn); \
+        static void write(const StoreDirConfig & store, ServeProto::WriteConn conn, const T & t); \
+    };
+
+template<>
+DECLARE_SERVE_SERIALISER(BuildResult);
+template<>
+DECLARE_SERVE_SERIALISER(UnkeyedValidPathInfo);
+template<>
+DECLARE_SERVE_SERIALISER(ServeProto::BuildOptions);
+
+template<typename T>
+DECLARE_SERVE_SERIALISER(std::vector<T>);
+template<typename T>
+DECLARE_SERVE_SERIALISER(std::set<T>);
+template<typename... Ts>
+DECLARE_SERVE_SERIALISER(std::tuple<Ts...>);
+
+#define COMMA_ ,
+template<typename K, typename V>
+DECLARE_SERVE_SERIALISER(std::map<K COMMA_ V>);
+#undef COMMA_
+
+}