fix: correct WAV RIFF length and padding (#1032)

* fix: correct WAV RIFF length and padding

Include the PCM payload in the RIFF chunk size and pad odd-length data chunks. Add regression coverage for empty, odd, even and larger payloads.

* chore: add comment explaning the wav padding byte

---------

Co-authored-by: Jan Laupetin <[email protected]>

test/ObjWritingTests/Sound/WavWriterTest.cpp

@@ -0,0 +1,40 @@
+#include "Sound/WavWriter.h"
+
+#include <catch2/catch_test_macros.hpp>
+#include <catch2/generators/catch_generators.hpp>
+#include <cstring>
+#include <sstream>
+#include <string>
+
+TEST_CASE("WavWriter: RIFF contains the complete PCM payload and alignment padding", "[sound][wav]")
+{
+    const auto size = GENERATE(0uz, 1uz, 2uz, 31uz, 2048uz);
+    const std::string samples(size, static_cast<char>(0x81));
+    std::ostringstream output(std::ios::binary);
+    const WavWriter writer(output);
+    writer.WritePcmHeader({1, 22050, 8}, samples.size());
+    writer.WritePcmData(samples.data(), samples.size());
+    const auto bytes = output.str();
+    REQUIRE(bytes.size() >= sizeof(WavHeader));
+    WavHeader header{};
+    std::memcpy(&header, bytes.data(), sizeof(header));
+    CHECK(header.chunkIdRiff == WAV_CHUNK_ID_RIFF);
+    CHECK(header.chunkIdSize == bytes.size() - 8u);
+    CHECK(header.format == WAV_WAVE_ID);
+    CHECK(header.chunkHeader.chunkID == WAV_CHUNK_ID_FMT);
+    CHECK(header.chunkHeader.chunkSize == sizeof(WavFormatChunkPcm));
+    CHECK(header.formatChunk.wFormatTag == WavFormat::PCM);
+    CHECK(header.formatChunk.nChannels == 1u);
+    CHECK(header.formatChunk.nSamplesPerSec == 22050u);
+    CHECK(header.formatChunk.nAvgBytesPerSec == 22050u);
+    CHECK(header.formatChunk.nBlockAlign == 1u);
+    CHECK(header.formatChunk.wBitsPerSample == 8u);
+    CHECK(header.subChunkHeader.chunkID == WAV_CHUNK_ID_DATA);
+    REQUIRE(header.subChunkHeader.chunkSize == samples.size());
+    CHECK(bytes.substr(sizeof(header), samples.size()) == samples);
+    CHECK(bytes.size() % 2u == 0u);
+    if (samples.size() & 1u)
+        CHECK(bytes.back() == '\0');
+    else
+        CHECK(bytes.size() == sizeof(header) + samples.size());
+}