Add udpardGather #sonar

libudpard/udpard.c

@@ -1651,3 +1651,27 @@ int_fast8_t udpardRxSubscriptionInit(struct UdpardRxSubscription* const   self,
     (void) &rxPortFree;
     return 0;
 }
+
+// =====================================================================================================================
+// ====================================================    MISC    =====================================================
+// =====================================================================================================================
+
+size_t udpardGather(const struct UdpardFragment head, const size_t destination_size, void* const destination)
+{
+    size_t offset = 0;
+    if (NULL != destination)
+    {
+        const struct UdpardFragment* frag = &head;
+        while ((frag != NULL) && (offset < destination_size))
+        {
+            UDPARD_ASSERT(frag->view.data != NULL);
+            const size_t frag_size = smaller(frag->view.size, destination_size - offset);
+            // NOLINTNEXTLINE(clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling)
+            (void) memmove(((byte_t*) destination) + offset, frag->view.data, frag_size);
+            offset += frag_size;
+            UDPARD_ASSERT(offset <= destination_size);
+            frag = frag->next;
+        }
+    }
+    return offset;
+}

libudpard/udpard.h

@@ -1021,6 +1021,22 @@ int_fast8_t udpardRxRPCDispatcherReceive(struct UdpardRxRPCDispatcher* const sel
                                          const uint_fast8_t                  redundant_iface_index,
                                          struct UdpardRxRPCTransfer* const   out_transfer);
 
+// =====================================================================================================================
+// ====================================================    MISC    =====================================================
+// =====================================================================================================================
+
+/// This helper function takes the head of a fragmented buffer list and copies the data into the contiguous buffer
+/// provided by the user. If the total size of all fragments combined exceeds the size of the user-provided buffer,
+/// copying will stop early after the buffer is filled, thus truncating the fragmented data short.
+///
+/// The source list is not modified. Do not forget to free its memory afterward if it was dynamically allocated.
+///
+/// The function has no effect and returns zero if the destination buffer is NULL.
+/// The data pointers in the fragment list shall be valid, otherwise the behavior is undefined.
+///
+/// Returns the number of bytes copied into the contiguous destination buffer.
+size_t udpardGather(const struct UdpardFragment head, const size_t destination_size, void* const destination);
+
 #ifdef __cplusplus
 }
 #endif

tests/CMakeLists.txt

@@ -86,6 +86,7 @@ endfunction()
 gen_test_matrix(test_helpers "src/test_helpers.c")
 gen_test_matrix(test_cavl "src/test_cavl.cpp")
 gen_test_matrix(test_tx "${library_dir}/udpard.c;src/test_tx.cpp")
+gen_test_matrix(test_misc "${library_dir}/udpard.c;src/test_misc.cpp")
 gen_test_matrix(test_intrusive_crc "src/test_intrusive_crc.c")
 gen_test_matrix(test_intrusive_tx "src/test_intrusive_tx.c")
 gen_test_matrix(test_intrusive_rx "src/test_intrusive_rx.c")

tests/src/test_misc.cpp

@@ -0,0 +1,79 @@
+/// This software is distributed under the terms of the MIT License.
+/// Copyright (C) OpenCyphal Development Team  <opencyphal.org>
+/// Copyright Amazon.com Inc. or its affiliates.
+/// SPDX-License-Identifier: MIT
+
+#include <udpard.h>
+#include "hexdump.hpp"
+#include <unity.h>
+#include <iostream>
+#include <array>
+#include <algorithm>
+
+namespace
+{
+void testGather()
+{
+    const std::string_view payload =
+        "It's very simple. The attacker must first transform themselves into life forms that can survive in a "
+        "low-dimensional universe. For instance, a four-dimensional species can transform itself into "
+        "three-dimensional creatures, or a three-dimensional species can transform itself into two-dimensional life. "
+        "After the entire civilization has entered a lower dimension, they can initiate a dimensional strike against "
+        "the enemy without concern for the consequences.";
+
+    std::array<UdpardFragment, 4> frags{{}};
+    frags.at(0).next = &frags.at(1);
+    frags.at(1).next = &frags.at(2);
+    frags.at(2).next = &frags.at(3);
+    frags.at(3).next = nullptr;
+
+    frags.at(0).view.data = payload.data();
+    frags.at(0).view.size = 100;
+
+    frags.at(1).view.data = payload.data() + frags.at(0).view.size;
+    frags.at(1).view.size = 100;
+
+    frags.at(2).view.data = payload.data() + frags.at(1).view.size + frags.at(0).view.size;
+    frags.at(2).view.size = 0;  // Edge case.
+
+    frags.at(3).view.data = payload.data() + frags.at(2).view.size + frags.at(1).view.size + frags.at(0).view.size;
+    frags.at(3).view.size = payload.size() - frags.at(2).view.size - frags.at(1).view.size - frags.at(0).view.size;
+
+    std::array<std::uint8_t, 1024> mono{};
+
+    // Copy full size payload.
+    std::generate(mono.begin(), mono.end(), [] { return std::rand() % 256; });
+    TEST_ASSERT_EQUAL(payload.size(), udpardGather(frags.at(0), mono.size(), mono.data()));
+    TEST_ASSERT_EQUAL_MEMORY(payload.data(), mono.data(), payload.size());
+
+    // Truncation mid-fragment.
+    std::generate(mono.begin(), mono.end(), [] { return std::rand() % 256; });
+    TEST_ASSERT_EQUAL(150, udpardGather(frags.at(0), 150, mono.data()));
+    TEST_ASSERT_EQUAL_MEMORY(payload.data(), mono.data(), 150);
+
+    // Truncation at the fragment boundary.
+    std::generate(mono.begin(), mono.end(), [] { return std::rand() % 256; });
+    TEST_ASSERT_EQUAL(200, udpardGather(frags.at(0), 200, mono.data()));
+    TEST_ASSERT_EQUAL_MEMORY(payload.data(), mono.data(), 200);
+
+    // Empty destination.
+    mono.fill(0xA5);
+    TEST_ASSERT_EQUAL(0, udpardGather(frags.at(0), 0, mono.data()));
+    TEST_ASSERT_EQUAL(0, std::count_if(mono.begin(), mono.end(), [](const auto x) { return x != 0xA5; }));
+
+    // Edge cases.
+    TEST_ASSERT_EQUAL(0, udpardGather(frags.at(0), 0, nullptr));
+    TEST_ASSERT_EQUAL(0, udpardGather(frags.at(0), 100, nullptr));
+}
+}  // namespace
+
+void setUp() {}
+
+void tearDown() {}
+
+int main()
+{
+    UNITY_BEGIN();
+    RUN_TEST(testGather);
+    return UNITY_END();
+}