Merge pull request #9508 from ameerj/hle-ipc-buffer-span

hle_ipc: Use std::span to avoid heap allocations/copies when calling ReadBuffer

2 files changed, 35 insertions, 3 deletions

diff --git a/src/core/hle/kernel/hle_ipc.cpp b/src/core/hle/kernel/hle_ipc.cpp
index 738b6d0f1..494151eef 100644
--- a/src/core/hle/kernel/hle_ipc.cpp
+++ b/src/core/hle/kernel/hle_ipc.cpp
@@ -11,6 +11,7 @@
 #include "common/common_funcs.h"
 #include "common/common_types.h"
 #include "common/logging/log.h"
+#include "common/scratch_buffer.h"
 #include "core/hle/ipc_helpers.h"
 #include "core/hle/kernel/hle_ipc.h"
 #include "core/hle/kernel/k_auto_object.h"
@@ -325,7 +326,7 @@ Result HLERequestContext::WriteToOutgoingCommandBuffer(KThread& requesting_threa
     return ResultSuccess;
 }
 
-std::vector<u8> HLERequestContext::ReadBuffer(std::size_t buffer_index) const {
+std::vector<u8> HLERequestContext::ReadBufferCopy(std::size_t buffer_index) const {
     const bool is_buffer_a{BufferDescriptorA().size() > buffer_index &&
                            BufferDescriptorA()[buffer_index].Size()};
     if (is_buffer_a) {
@@ -345,6 +346,33 @@ std::vector<u8> HLERequestContext::ReadBuffer(std::size_t buffer_index) const {
     }
 }
 
+std::span<const u8> HLERequestContext::ReadBuffer(std::size_t buffer_index) const {
+    static thread_local std::array<Common::ScratchBuffer<u8>, 2> read_buffer_a;
+    static thread_local std::array<Common::ScratchBuffer<u8>, 2> read_buffer_x;
+
+    const bool is_buffer_a{BufferDescriptorA().size() > buffer_index &&
+                           BufferDescriptorA()[buffer_index].Size()};
+    if (is_buffer_a) {
+        ASSERT_OR_EXECUTE_MSG(
+            BufferDescriptorA().size() > buffer_index, { return {}; },
+            "BufferDescriptorA invalid buffer_index {}", buffer_index);
+        auto& read_buffer = read_buffer_a[buffer_index];
+        read_buffer.resize_destructive(BufferDescriptorA()[buffer_index].Size());
+        memory.ReadBlock(BufferDescriptorA()[buffer_index].Address(), read_buffer.data(),
+                         read_buffer.size());
+        return read_buffer;
+    } else {
+        ASSERT_OR_EXECUTE_MSG(
+            BufferDescriptorX().size() > buffer_index, { return {}; },
+            "BufferDescriptorX invalid buffer_index {}", buffer_index);
+        auto& read_buffer = read_buffer_x[buffer_index];
+        read_buffer.resize_destructive(BufferDescriptorX()[buffer_index].Size());
+        memory.ReadBlock(BufferDescriptorX()[buffer_index].Address(), read_buffer.data(),
+                         read_buffer.size());
+        return read_buffer;
+    }
+}
+
 std::size_t HLERequestContext::WriteBuffer(const void* buffer, std::size_t size,
                                            std::size_t buffer_index) const {
     if (size == 0) {
diff --git a/src/core/hle/kernel/hle_ipc.h b/src/core/hle/kernel/hle_ipc.h
index e252b5f4b..5bf4f171b 100644
--- a/src/core/hle/kernel/hle_ipc.h
+++ b/src/core/hle/kernel/hle_ipc.h
@@ -7,6 +7,7 @@
 #include <functional>
 #include <memory>
 #include <optional>
+#include <span>
 #include <string>
 #include <type_traits>
 #include <vector>
@@ -270,8 +271,11 @@ public:
         return domain_message_header.has_value();
     }
 
-    /// Helper function to read a buffer using the appropriate buffer descriptor
-    [[nodiscard]] std::vector<u8> ReadBuffer(std::size_t buffer_index = 0) const;
+    /// Helper function to get a span of a buffer using the appropriate buffer descriptor
+    [[nodiscard]] std::span<const u8> ReadBuffer(std::size_t buffer_index = 0) const;
+
+    /// Helper function to read a copy of a buffer using the appropriate buffer descriptor
+    [[nodiscard]] std::vector<u8> ReadBufferCopy(std::size_t buffer_index = 0) const;
 
     /// Helper function to write a buffer using the appropriate buffer descriptor
     std::size_t WriteBuffer(const void* buffer, std::size_t size,