TEST: tests for common/huffman.h

A few tests for the Huffman decoder.

The encoding is the example from Wikipedia.
This could be improved by someone more knowledgeable by
generating one at runtime or using multiple encodings
which would each contain one edge case.

test/common/huffman.h

@@ -0,0 +1,130 @@
+#include <cxxtest/TestSuite.h>
+#include "common/huffman.h"
+#include "common/bitstream.h"
+#include "common/memstream.h"
+
+class HuffmanTestSuite : public CxxTest::TestSuite
+{
+	public:
+	void test_get_with_full_symbols() {
+
+		/*
+		 * Testing the Huffman decoder.
+		 *
+		 * Encoding (arbitrary, for testing purpouses):
+		 * A=010
+		 * B=011
+		 * C=11
+		 * D=00
+		 * E=10
+		 */
+
+		uint32 codeCount = 5;
+		uint8 maxLength = 3;
+		const uint8 lengths[] = {3,3,2,2,2};
+		const uint32 codes[]  = {0x2, 0x3, 0x3, 0x0, 0x2};
+		const uint32 symbols[]  = {0xA, 0xB, 0xC, 0xD, 0xE};
+
+		Common::Huffman h (maxLength, codeCount, codes, lengths, symbols);
+
+		byte input[] = {0x4F, 0x20};
+		// Provided input...
+		uint32 expected[] = {0xA, 0xB, 0xC, 0xD, 0xE, 0xD, 0xD};
+		// ..and expected output.
+
+		/*
+		 * What should be going on:
+		 * 010 011 11 00 10 00 00 = A B C D E D D
+		 *  = 0100 1111 0010 0000 = 0x4F20
+		 */
+
+		Common::MemoryReadStream ms(input, sizeof(input));
+		Common::BitStream8MSB bs(ms);
+
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[0]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[1]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[2]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[3]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[4]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[5]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[6]);
+	}
+
+	void test_get_without_symbols() {
+
+		/*
+		 * This is basically the same as above, but
+		 * I pass minimal arguments.
+		 * Specifically, I avoid passing the symbols table, so that
+		 * array indices are used instead.
+		 *
+		 * Encoding becomes:
+		 *
+		 * 0=010
+		 * 1=011
+		 * 2=11
+		 * 3=00
+		 * 4=10
+		 */
+
+		uint32 codeCount = 5;
+		const uint8 lengths[] = {3,3,2,2,2};
+		const uint32 codes[]  = {0x2, 0x3, 0x3, 0x0, 0x2};
+
+		Common::Huffman h (0, codeCount, codes, lengths, 0);
+
+		byte input[] = {0x4F, 0x20};
+		uint32 expected[] = {0, 1, 2, 3, 4, 3 ,3};
+
+		Common::MemoryReadStream ms(input, sizeof(input));
+		Common::BitStream8MSB bs(ms);
+
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[0]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[1]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[2]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[3]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[4]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[5]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[6]);
+	}
+
+	void test_get_after_set_symbols() {
+
+		/*
+		 * Another variation of the above.
+		 * I use the setSymbols method to define, a posteriori,
+		 * an alphabet to be used in place of array indices
+		 */
+
+		uint32 codeCount = 5;
+		const uint8 lengths[] = {3,3,2,2,2};
+		const uint32 codes[]  = {0x2, 0x3, 0x3, 0x0, 0x2};
+
+		Common::Huffman h (0, codeCount, codes, lengths, 0);
+
+		const uint32 symbols[]  = {0xA, 0xB, 0xC, 0xD, 0xE};
+		h.setSymbols(symbols);
+
+		byte input[] = {0x4F, 0x20};
+		uint32 expected[] = {0xA, 0xB, 0xC, 0xD, 0xE, 0xD, 0xD};
+
+		Common::MemoryReadStream ms(input, sizeof(input));
+		Common::BitStream8MSB bs(ms);
+
+		/* New symbols:
+		 * A=010
+		 * B=011
+		 * C=11
+		 * D=00
+		 * E=10
+		 */
+
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[0]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[1]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[2]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[3]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[4]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[5]);
+		TS_ASSERT_EQUALS(h.getSymbol(bs), expected[6]);
+	}
+};