1 files changed, 77 insertions, 0 deletions
diff --git a/scripts/LOMHash.c b/scripts/LOMHash.c
new file mode 100644
index 0000000..b3b97c3
--- /dev/null
+++ b/scripts/LOMHash.c
@@ -0,0 +1,77 @@
+#include <stdio.h>
+typedef unsigned short UINT16;
+typedef unsigned char BYTE;
+static UINT16 HuffCodeLOM[] = { 0x0001, 0x0000, 0x0002, 0x0009, 0x0006, 0x0005, 0x000d, 0x000b,
+	                            0x0003, 0x001b, 0x0007, 0x0017, 0x0037, 0x000f, 0x004f, 0x006f,
+	                            0x002f, 0x00ef, 0x001f, 0x005f, 0x015f, 0x009f, 0x00df, 0x01df,
+	                            0x003f, 0x013f, 0x00bf, 0x01bf, 0x007f, 0x017f, 0x00ff, 0x01ff };
+
+UINT16 HashTable[32] = { [0 ... 31] = 0xffff };
+
+BYTE tab[4] = { 0, 4, 10, 19 };
+
+UINT16 hash(UINT16 key)
+{
+	return ((key & 0x1f) ^ (key >> 5) ^ (key >> 9));
+}
+
+BYTE minihash(UINT16 key)
+{
+	BYTE h;
+	h = (key >> 4) & 0xf;
+	return ((h ^ (h >> 2) ^ (h >> 3)) & 0x3);
+}
+
+void buildhashtable(void)
+{
+	for (int i = 0; i < 32; i++)
+	{
+		UINT16 h = hash(HuffCodeLOM[i]);
+
+		if (HashTable[h] != 0xffff)
+		{
+			HashTable[h] ^= (HuffCodeLOM[i] & 0xfe0) ^ 0xfe0;
+			HashTable[tab[minihash(HuffCodeLOM[i])]] = i;
+		}
+		else
+		{
+			HashTable[h] = i;
+			HashTable[h] ^= 0xfe0;
+		}
+
+		printf("at %d %" PRIu16 "=0x%" PRIx16 "\n", i, h, HashTable[h]);
+	}
+}
+
+BYTE getvalue(UINT16 huff)
+{
+	UINT16 h = HashTable[hash(huff)];
+
+	if ((h ^ huff) >> 5)
+	{
+		return h & 0x1f;
+	}
+	else
+		return HashTable[tab[minihash(huff)]];
+}
+
+main()
+{
+	buildhashtable();
+	printf("static UINT16 HuffIndexLOM[32] = {\n");
+
+	for (int i = 0; i < 32; i++)
+	{
+		if (i == 31)
+			printf("0x%" PRIx16 " };\n", HashTable[i]);
+		else
+			printf("0x%" PRIx16 ", ", HashTable[i]);
+	}
+
+	for (int i = 0; i < 32; i++)
+		if (i != getvalue(HuffCodeLOM[i]))
+			printf("Fail :( at %d : 0x%04" PRIx16 " got %" PRIu8 "\n", i, HuffCodeLOM[i],
+			       getvalue(HuffCodeLOM[i]));
+
+	return 0;
+}