1 files changed, 91 insertions, 0 deletions
diff --git a/tools/compressed_data_extractor.py b/tools/compressed_data_extractor.py
new file mode 100644
index 0000000..9756c02
--- /dev/null
+++ b/tools/compressed_data_extractor.py
@@ -0,0 +1,91 @@
+import argparse
+import mmap
+from math import floor as floor
+
+parser = argparse.ArgumentParser(description='Extracts compressed data.')
+parser.add_argument('offsets', metavar='offsets', type=str, nargs='+',
+                    help='start offset(s) of the compressed data')
+parser.add_argument('-s', metavar='suffix', dest='suffix', type=str, nargs=1, default=[],
+                    help='suffix for output file names')
+
+args = parser.parse_args()
+
+def getByteString(offset, len):
+    with open('baserom.gbc') as rom:
+        romMap = mmap.mmap(rom.fileno(), 0, access=mmap.ACCESS_READ)
+        return romMap[offset : offset + len]
+
+def getByte(offset):
+    return getByteString(offset, 1)[0]
+
+def convertOffset(ptrBytes, offset):
+    bank = floor(offset / 0x4000)
+    return (ptrBytes[0] + (ptrBytes[1] << 8)) + bank * 0x4000 - 0x4000
+
+def getFormattedOffset(offset):
+    return '{:0x}'.format(offset)
+
+def convertWordToInt(byteArr):
+    assert(len(byteArr) == 2)
+    return byteArr[1] * 0x100 + byteArr[0]
+
+def getCompressedData(offset):
+    data = []
+    pos = offset # init current position
+    repeatToggle = False
+    lenByte = 0x00
+
+    size = convertWordToInt(getByteString(pos, 2))
+    #data.extend(getByteString(pos, 2)) don't append size bytes to output
+    pos += 2
+
+    while (size > 0):
+        cmdByte = getByte(pos)
+        pos += 1
+        data.append(cmdByte)
+
+        for b in range(8):
+            if (cmdByte & (1 << (7 - b)) != 0):
+                # copy one byte literally
+                data.append(getByte(pos))
+                pos += 1
+                size -= 1
+            else:
+                # copy previous sequence
+                data.append(getByte(pos))
+                pos += 1
+
+                repeatToggle = not repeatToggle
+                if (repeatToggle):
+                    # sequence length
+                    lenByte = getByte(pos)
+                    data.append(lenByte)
+                    pos += 1
+                    size -= (lenByte >> 4) + 2
+                else:
+                    # no sequence length byte if toggle is off
+                    size -= (lenByte & 0x0f) + 2
+
+            assert(size >= 0)
+
+            # the decompression might finish while still
+            # reading command bits, so break early when this happens
+            if (size == 0):
+                break
+
+    return bytes(data)
+
+def outputData(offset, filename):
+    with open(filename + '.bin', 'wb') as outFile:
+        outFile.write(getCompressedData(offset))
+
+n = 1
+for offsetStr in args.offsets:
+    offset = int(offsetStr, 16)
+    filename = 'compressed_data_' + getFormattedOffset(offset)
+    if (args.suffix):
+        filename = args.suffix[0]
+        if (len(args.offsets) > 1):
+            filename = filename + str(n)
+    outputData(offset, filename)
+    n += 1