libos: Add os::LocalClient

libos/CMakeLists.txt

@@ -15,6 +15,7 @@ set(SOURCES
     src/Prompt.cpp
     src/Security.cpp
     src/LocalServer.cpp
+    src/LocalClient.cpp
 )
 
 add_library(os ${SOURCES})

libos/include/os/LocalClient.h

@@ -0,0 +1,90 @@
+#pragma once
+#include <luna/SharedPtr.h>
+#include <luna/StringView.h>
+
+namespace os
+{
+    /**
+     * @brief A client used to connect to a local server socket.
+     */
+    class LocalClient : public Shareable
+    {
+      public:
+        /**
+         * @brief Create a new client object and connect it to a local server.
+         *
+         * @param path The path of the server socket to connect to.
+         * @param blocking Whether the client should block if no data is available and recv() is called.
+         * @return Result<SharedPtr<LocalClient>> An error, or a new client object.
+         */
+        static Result<SharedPtr<LocalClient>> connect(StringView path, bool blocking);
+
+        /**
+         * @brief Return the underlying socket file descriptor used by this object.
+         *
+         * @return int The file descriptor.
+         */
+        int fd() const
+        {
+            return m_fd;
+        }
+
+        /**
+         * @brief Read arbitrary data from the server. The call will block if there is no data and this object has not
+         * been created as non-blocking.
+         *
+         * @param buf The buffer to read data into.
+         * @param length The maximum amount of bytes to read.
+         * @return Result<usize> An error, or the number of bytes read.
+         */
+        Result<usize> recv(u8* buf, usize length);
+
+        /**
+         * @brief Read an object from the server. The call will block if there is no data and this object has not been
+         * created as non-blocking.
+         *
+         * @tparam T The type of the object.
+         * @param out A reference to the object to read data into.
+         * @return Result<void> Whether the operation succeded.
+         */
+        template <typename T> Result<void> recv_typed(T& out)
+        {
+            TRY(recv((u8*)&out, sizeof(T)));
+            return {};
+        }
+
+        /**
+         * @brief Send arbitrary data to the server.
+         *
+         * @param buf The buffer to send data from.
+         * @param length The amount of bytes to send.
+         * @return Result<usize> An error, or the number of bytes actually sent.
+         */
+        Result<usize> send(const u8* buf, usize length);
+
+        /**
+         * @brief Send an object to the server.
+         *
+         * @tparam T The type of the object.
+         * @param out A reference to the object to send data from.
+         * @return Result<void> Whether the operation succeded.
+         */
+        template <typename T> Result<void> send_typed(const T& out)
+        {
+            TRY(send((const u8*)&out, sizeof(T)));
+            return {};
+        }
+
+        /**
+         * @brief Disconnect from the attached server.
+         *
+         * This will make any further reads on this connection return ECONNRESET, and will make this object invalid.
+         */
+        void disconnect();
+
+        ~LocalClient();
+
+      private:
+        int m_fd;
+    };
+}

libos/src/LocalClient.cpp

@@ -0,0 +1,59 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <os/LocalClient.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+namespace os
+{
+    Result<SharedPtr<LocalClient>> LocalClient::connect(StringView path, bool blocking)
+    {
+        auto client = TRY(make_shared<LocalClient>());
+
+        int sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
+        if (sockfd < 0) return err(errno);
+
+        struct sockaddr_un un;
+        un.sun_family = AF_UNIX;
+        strncpy(un.sun_path, path.chars(), sizeof(un.sun_path));
+
+        if (::connect(sockfd, (struct sockaddr*)&un, sizeof(un)) < 0)
+        {
+            close(sockfd);
+            return err(errno);
+        }
+
+        if (!blocking) { fcntl(sockfd, F_SETFL, O_NONBLOCK); }
+
+        fcntl(sockfd, F_SETFD, FD_CLOEXEC);
+
+        client->m_fd = sockfd;
+        return client;
+    }
+
+    LocalClient::~LocalClient()
+    {
+        close(m_fd);
+    }
+
+    Result<usize> LocalClient::recv(u8* buf, usize length)
+    {
+        ssize_t nread = read(m_fd, buf, length);
+        if (nread < 0) return err(errno);
+        return nread;
+    }
+
+    Result<usize> LocalClient::send(const u8* buf, usize length)
+    {
+        ssize_t nwrite = write(m_fd, buf, length);
+        if (nwrite < 0) return err(errno);
+        return nwrite;
+    }
+
+    void LocalClient::disconnect()
+    {
+        close(m_fd);
+        m_fd = -1;
+    }
+}