mirror of
https://github.com/david-schmidt/Davex.git
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121 lines
3.5 KiB
Python
Executable File
121 lines
3.5 KiB
Python
Executable File
#!/usr/bin/python3
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# index create indexed.help <index-size-in-bytes>
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# index add indexed.help <text-file-to-add> [additional-entry-name-aliases-for-this-file]
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# Format of an indexed file is:
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#
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# +000 $00 DvxIdx $00
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# +008 Offset_to_text (4 bytes)
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# +012 Offset_to_index (4 bytes)
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# +016 Offset_to_free_index_space (4 bytes)
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# +020 <reserved, 32 bytes>
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# +052 start of index
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#
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# Index is:
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# length-pfx'd string, offset(4), uncompressed-length(4)
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# :
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# $00
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#
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# Text chunks are terminated by a $00. The data
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# is compressed, with 16 common characters using
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# only 5 bits (%1xxxx), and the remaining ones
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# using 8 bits (%0xxxxxxx).
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import sys, struct, os.path
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SixteenCommonBytes = " etoaisrn\x0dldhpcf" # Frozen for original format indexed.help files (see index.asm and shell main.asm)
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def Compress(ch):
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fourBits = SixteenCommonBytes.find(chr(ch))
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if fourBits != -1:
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return "{:0>5b}".format(16 + fourBits)
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return "{:0>8b}".format(ch)
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verb = sys.argv[1]
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indexFile = sys.argv[2]
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if verb == "create":
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indexSize = int(sys.argv[3])
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offsetToIndex = 52
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offsetOfText = offsetToIndex + indexSize
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outFile = open(indexFile, "wb")
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outFile.write(bytes("\x00DvxIdx\x00", "utf8"))
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outFile.write(struct.pack('i', offsetOfText))
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outFile.write(struct.pack('i', offsetToIndex))
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outFile.write(struct.pack('i', offsetToIndex)) # start of free space in index
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for pad in range(8):
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outFile.write(struct.pack('i', 0)) # 8 four-byte integers: reserved
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outFile.seek(offsetOfText - 1)
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outFile.write(struct.pack('B', 0))
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exit(0)
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if verb == "add":
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outFile = open(indexFile, "r+b")
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addFilePath = sys.argv[3]
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addFile = open (addFilePath, "r")
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addLines = addFile.readlines()
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addFileUncompressedSize = addFile.tell()
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addFile.close()
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# Read offsetOfText -- the index can't extend that far
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outFile.seek(8) # read offsetOfText from +008
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data = outFile.read(4)
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offsetOfText = int.from_bytes(data, "little")
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# End-of-file offset is where we will put the new chunk of compressed text.
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outFile.seek(0, 2) # end of file
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offsetToNewText = outFile.tell()
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# Seek to free index space
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outFile.seek(16)
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data = outFile.read(4)
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freeIndexSpace = int.from_bytes(data, "little")
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# Write new index entry: length-byte, string name, 4-byte offset to start of text, 4-byte length of (compressed?) text
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entryName = os.path.basename(addFilePath).lower()
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outFile.seek(freeIndexSpace)
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outFile.write(struct.pack('B', len(entryName)))
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outFile.write(bytes(entryName, "utf8"))
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outFile.write(struct.pack('i', offsetToNewText))
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outFile.write(struct.pack('i', addFileUncompressedSize))
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# Optionally write additional index entries for the same text we are adding.
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for extraName in sys.argv[4:]:
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outFile.write(struct.pack('B', len(extraName)))
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outFile.write(bytes(extraName, "utf8"))
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outFile.write(struct.pack('i', offsetToNewText))
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outFile.write(struct.pack('i', addFileUncompressedSize))
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# Update freeIndexSpace in file
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freeIndexSpace = outFile.tell()
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if freeIndexSpace >= offsetOfText:
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print("Error: Overflowed the available index space")
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exit(1)
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outFile.seek(16)
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outFile.write(struct.pack('i', freeIndexSpace))
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# Write the new text
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outFile.seek(offsetToNewText)
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outBinary = ""
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for line in addLines:
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for ch in line.rstrip():
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outBinary += Compress(ord(ch))
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outBinary += Compress(13) # carriage return
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outBinary += Compress(0)
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while len(outBinary) > 0:
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if len(outBinary) < 8:
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outBinary = (outBinary + "0000000")[0:8]
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byte = int(outBinary[0:8], 2)
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outBinary = outBinary[8:]
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outFile.write(struct.pack('B', byte))
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outFile.close()
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exit(0)
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print("Unknown verb: " + verb)
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exit(1)
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