htc: implement much of worker receive logic

libraries/libstratosphere/source/htclow/mux/htclow_mux_ring_buffer.cpp

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2018-2020 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <stratosphere.hpp>
+#include "htclow_mux_ring_buffer.hpp"
+
+namespace ams::htclow::mux {
+
+    Result RingBuffer::Write(const void *data, size_t size) {
+        /* Validate pre-conditions. */
+        AMS_ASSERT(!m_is_read_only);
+
+        /* Check that our buffer can hold the data. */
+        R_UNLESS(m_buffer != nullptr,                 htclow::ResultChannelBufferOverflow());
+        R_UNLESS(m_data_size + size <= m_buffer_size, htclow::ResultChannelBufferOverflow());
+
+        /* Determine position and copy sizes. */
+        const size_t  pos = (m_data_size + m_offset) % m_buffer_size;
+        const size_t left = m_buffer_size - pos;
+        const size_t over = size - left;
+
+        /* Copy. */
+        if (left != 0) {
+            std::memcpy(static_cast<u8 *>(m_buffer) + pos, data, left);
+        }
+        if (over != 0) {
+            std::memcpy(m_buffer, static_cast<const u8 *>(data) + left, over);
+        }
+
+        /* Update our data size. */
+        m_data_size += size;
+
+        return ResultSuccess();
+    }
+
+}