demo: Add special tests for v1 format

While v1 is not finalized yet, hopefully the only changes that will
happen here are going to be to the vertex number, and/or channel
encoding.

To make sure we can decode the data in all cases this adds two tests,
one with a normal v1 stream encoded at level 3, which does not exercise
all format features, and a specially crafted stream that exercises all
bitgroup widths, all control modes and all channel modes to encode the
same data.

demo/tests.cpp

@@ -58,6 +58,27 @@ static const unsigned char kVertexDataV0[] = {
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // clang-format :-/
 };
 
+static const unsigned char kVertexDataV1[] = {
+    0xae, 0xee, 0xaa, 0xee, 0x00, 0x4b, 0x4b, 0x4b, 0x00, 0x00, 0x4b, 0x00, 0x00, 0x7d, 0x7d,
+    0x7d, 0x00, 0x00, 0x7d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x62, 0x00, 0x62, // clang-format :-/
+};
+
+// This binary blob is a valid v1 encoding of vertex buffer but it used a custom version of
+// the encoder that exercised all features of the format; because of this it is much larger
+// and will never be produced by the encoder itself.
+static const unsigned char kVertexDataV1Custom[] = {
+    0xae, 0xd4, 0x94, 0xd4, 0x01, 0x0e, 0x00, 0x58, 0x57, 0x58, 0x02, 0x02, 0x12, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x58, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00,
+    0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x0e, 0x00, 0x7d, 0x7d, 0x7d, 0x01, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x7d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x01, 0x62, // clang-format :-/
+};
+
 static void decodeIndexV0()
 {
 	const size_t index_count = sizeof(kIndexBuffer) / sizeof(kIndexBuffer[0]);
@@ -358,6 +379,28 @@ static void decodeVertexV0()
 	assert(memcmp(decoded, kVertexBuffer, sizeof(kVertexBuffer)) == 0);
 }
 
+static void decodeVertexV1()
+{
+	const size_t vertex_count = sizeof(kVertexBuffer) / sizeof(kVertexBuffer[0]);
+
+	std::vector<unsigned char> buffer(kVertexDataV1, kVertexDataV1 + sizeof(kVertexDataV1));
+
+	PV decoded[vertex_count];
+	assert(meshopt_decodeVertexBuffer(decoded, vertex_count, sizeof(PV), &buffer[0], buffer.size()) == 0);
+	assert(memcmp(decoded, kVertexBuffer, sizeof(kVertexBuffer)) == 0);
+}
+
+static void decodeVertexV1Custom()
+{
+	const size_t vertex_count = sizeof(kVertexBuffer) / sizeof(kVertexBuffer[0]);
+
+	std::vector<unsigned char> buffer(kVertexDataV1Custom, kVertexDataV1Custom + sizeof(kVertexDataV1Custom));
+
+	PV decoded[vertex_count];
+	assert(meshopt_decodeVertexBuffer(decoded, vertex_count, sizeof(PV), &buffer[0], buffer.size()) == 0);
+	assert(memcmp(decoded, kVertexBuffer, sizeof(kVertexBuffer)) == 0);
+}
+
 static void encodeVertexMemorySafe()
 {
 	const size_t vertex_count = sizeof(kVertexBuffer) / sizeof(kVertexBuffer[0]);
@@ -2024,6 +2067,9 @@ void runTests()
 	decodeVertexRejectExtraBytes();
 	decodeVertexRejectMalformedHeaders();
 
+	decodeVertexV1();
+	decodeVertexV1Custom();
+
 	for (int version = 0; version <= 1; ++version)
 	{
 		meshopt_encodeVertexVersion(version == 1 ? 0xe : version);