--- SheepShaver/src/rom_patches.cpp	2002/02/04 16:58:13	1.1
+++ SheepShaver/src/rom_patches.cpp	2003/05/14 22:11:59	1.3
@@ -74,6 +74,130 @@ static bool patch_nanokernel(void);
 static bool patch_68k(void);
 
 
+// Decode LZSS data
+static void decode_lzss(const uint8 *src, uint8 *dest, int size)
+{
+	char dict[0x1000];
+	int run_mask = 0, dict_idx = 0xfee;
+	for (;;) {
+		if (run_mask < 0x100) {
+			// Start new run
+			if (--size < 0)
+				break;
+			run_mask = *src++ | 0xff00;
+		}
+		bool bit = run_mask & 1;
+		run_mask >>= 1;
+		if (bit) {
+			// Verbatim copy
+			if (--size < 0)
+				break;
+			int c = *src++;
+			dict[dict_idx++] = c;
+			*dest++ = c;
+			dict_idx &= 0xfff;
+		} else {
+			// Copy from dictionary
+			if (--size < 0)
+				break;
+			int idx = *src++;
+			if (--size < 0)
+				break;
+			int cnt = *src++;
+			idx |= (cnt << 4) & 0xf00;
+			cnt = (cnt & 0x0f) + 3;
+			while (cnt--) {
+				char c = dict[idx++];
+				dict[dict_idx++] = c;
+				*dest++ = c;
+				idx &= 0xfff;
+				dict_idx &= 0xfff;
+			}
+		}
+	}
+}
+
+// Decode parcels of ROM image (MacOS 9.X and even earlier)
+void decode_parcels(const uint8 *src, uint8 *dest, int size)
+{
+	uint32 parcel_offset = 0x14;
+	D(bug("Offset   Type Name\n"));
+	while (parcel_offset != 0) {
+		const uint32 *parcel_data = (uint32 *)(src + parcel_offset);
+		uint32 next_offset = ntohl(parcel_data[0]);
+		uint32 parcel_type = ntohl(parcel_data[1]);
+		D(bug("%08x %c%c%c%c %s\n", parcel_offset,
+			  (parcel_type >> 24) & 0xff, (parcel_type >> 16) & 0xff,
+			  (parcel_type >> 8) & 0xff, parcel_type & 0xff, &parcel_data[6]));
+		if (parcel_type == FOURCC('r','o','m',' ')) {
+			uint32 lzss_offset  = ntohl(parcel_data[2]);
+			uint32 lzss_size = ((uint32)src + parcel_offset) - ((uint32)parcel_data + lzss_offset);
+			decode_lzss((uint8 *)parcel_data + lzss_offset, dest, lzss_size);
+		}
+		parcel_offset = next_offset;
+	}
+}
+
+
+/*
+ *  Decode ROM image, 4 MB plain images or NewWorld images
+ */
+
+bool DecodeROM(uint8 *data, uint32 size)
+{
+	if (size == ROM_SIZE) {
+		// Plain ROM image
+		memcpy((void *)ROM_BASE, data, ROM_SIZE);
+		return true;
+	}
+	else if (strncmp((char *)data, "<CHRP-BOOT>", 11) == 0) {
+		// CHRP compressed ROM image
+		uint32 image_offset, image_size;
+		bool decode_info_ok = false;
+		
+		char *s = strstr((char *)data, "constant lzss-offset");
+		if (s != NULL) {
+			// Probably a plain LZSS compressed ROM image
+			if (sscanf(s - 7, "%06x", &image_offset) == 1) {
+				s = strstr((char *)data, "constant lzss-size");
+				if (s != NULL && (sscanf(s - 7, "%06x", &image_size) == 1))
+					decode_info_ok = true;
+			}
+		}
+		else {
+			// Probably a MacOS 9.2.x ROM image
+			s = strstr((char *)data, "constant parcels-offset");
+			if (s != NULL) {
+				if (sscanf(s - 7, "%06x", &image_offset) == 1) {
+					s = strstr((char *)data, "constant parcels-size");
+					if (s != NULL && (sscanf(s - 7, "%06x", &image_size) == 1))
+						decode_info_ok = true;
+				}
+			}
+		}
+		
+		// No valid information to decode the ROM found?
+		if (!decode_info_ok)
+			return false;
+		
+		// Check signature, this could be a parcels-based ROM image
+		uint32 rom_signature = ntohl(*(uint32 *)(data + image_offset));
+		if (rom_signature == FOURCC('p','r','c','l')) {
+			D(bug("Offset of parcels data: %08x\n", image_offset));
+			D(bug("Size of parcels data: %08x\n", image_size));
+			decode_parcels(data + image_offset, (uint8 *)ROM_BASE, image_size);
+		}
+		else {
+			D(bug("Offset of compressed data: %08x\n", image_offset));
+			D(bug("Size of compressed data: %08x\n", image_size));
+			decode_lzss(data + image_offset, (uint8 *)ROM_BASE, image_size);
+		}
+		return true;
+	}
+	return false;
+}
+
+
 /*
  *  Search ROM for byte string, return ROM offset (or 0)
  */