Merge pull request #5 from kaunta/i4

add basic text encoding and decoding

.gitignore

@@ -0,0 +1 @@
+rom

lttp/text.py

@@ -0,0 +1,160 @@
+from typing import NamedTuple, Sequence, Callable, Optional
+import itertools
+import string
+import unicodedata
+
+
+class Encoding(NamedTuple):
+    text: str
+    code: int
+
+
+_encoding_table: Sequence[Encoding] = [
+    *(
+        Encoding(text=x, code=y)
+        for x, y in itertools.chain(
+            zip(string.ascii_uppercase, range(0x0, 0x1A)),
+            zip(string.ascii_lowercase, range(0x1A, 0x34)),
+            zip(string.digits, range(0x34, 0x3E)),
+        )
+    ),
+    Encoding(text="!", code=0x3E),
+    Encoding(text="?", code=0x3F),
+    Encoding(text="-", code=0x40),
+    Encoding(text=".", code=0x41),
+    Encoding(text=",", code=0x42),
+    Encoding(text=unicodedata.lookup("HORIZONTAL ELLIPSIS"), code=0x43),
+    Encoding(text=unicodedata.lookup("RIGHTWARDS WHITE ARROW"), code=0x44),
+    Encoding(text="(", code=0x45),
+    Encoding(text=")", code=0x46),
+    Encoding(text=unicodedata.lookup("ANKH"), code=0x47),
+    Encoding(text=unicodedata.lookup("WATER WAVE"), code=0x48),
+    Encoding(text=unicodedata.lookup("SNAKE"), code=0x49),
+    # TODO: $4A: picture of Link's head in the kidnapper signs (left half)
+    # TODO: $4B: picture of Link's head in the kidnapper signs (right half)
+    Encoding(text=unicodedata.lookup("LEFT DOUBLE QUOTATION MARK"), code=0x4C),
+    Encoding(text=unicodedata.lookup("UPWARDS ARROW"), code=0x4D),
+    Encoding(text=unicodedata.lookup("DOWNWARDS ARROW"), code=0x4E),
+    Encoding(text=unicodedata.lookup("LEFTWARDS ARROW"), code=0x4F),
+    Encoding(text=unicodedata.lookup("RIGHTWARDS ARROW"), code=0x50),
+    Encoding(text="'", code=0x51),
+    # TODO: $52: heart piece upper left filled (just left side)
+    # TODO: $53: heart piece empty (just right side)
+    # TODO: $54: heart piece left filled (just left side)
+    # TODO: $55: heart piece 3/4 filled (just left side)
+    # TODO: $56: heart piece upper right filled (just right side)
+    # TODO: $57: heart piece all filled (just left side)
+    # TODO: $58: heart piece all filled (just right side),
+    Encoding(text=" ", code=0x59),
+    Encoding(text=unicodedata.lookup("LEFTWARDS WHITE ARROW"), code=0x5A),
+    Encoding(text=unicodedata.lookup("CIRCLED LATIN CAPITAL LETTER A"), code=0x5B),
+    Encoding(text=unicodedata.lookup("CIRCLED LATIN CAPITAL LETTER B"), code=0x5C),
+    Encoding(text=unicodedata.lookup("CIRCLED LATIN CAPITAL LETTER X"), code=0x5D),
+    Encoding(text=unicodedata.lookup("CIRCLED LATIN CAPITAL LETTER Y"), code=0x5E),
+    # TODO: $5F: alternate "l" or "I"? (apparently not used)
+    # TODO: $60: alternate "!" (apparently not used)
+    # TODO: $61: upside down "!" (apparently not used)
+    # TODO: $62 to $65: apparently tab characters or space characters? (apparently not used)
+    # TODO: $66: strange red and white '.' (apparently not used)
+    # Dictionary Commands
+    Encoding(text="on", code=0xC7),
+    Encoding(text="go", code=0xAC),
+    Encoding(text="in", code=0xB4),
+    Encoding(text="the", code=0xD8),
+    Encoding(text="be", code=0x97),
+    Encoding(text="do", code=0x9F),
+    Encoding(text="of", code=0xC6),
+    Encoding(text="ound", code=0xC4),
+    Encoding(text="ain", code=0x8F),
+    Encoding(text="en ", code=0xA0),
+    Encoding(text="hi", code=0xB0),
+    Encoding(text="and", code=0x90),
+    Encoding(text="re", code=0xCE),
+    Encoding(text="we", code=0xE0),
+    Encoding(text="ed ", code=0xA4),
+    Encoding(text="la", code=0xBA),
+    Encoding(text="so", code=0xD2),
+    Encoding(text="to", code=0xDA),
+    Encoding(text="an", code=0x93),
+    Encoding(text="en", code=0xA5),
+    Encoding(text="lo", code=0xBB),
+    Encoding(text="ev", code=0xA7),
+    Encoding(text="se", code=0xD0),
+    Encoding(text="er ", code=0xA1),
+    Encoding(text="me", code=0xBE),
+    Encoding(text="is", code=0xB5),
+    Encoding(text="and ", code=0x8C),
+    Encoding(text="for", code=0xA8),
+    Encoding(text="st", code=0xD3),
+    Encoding(text="ent", code=0xA3),
+    Encoding(text="tha", code=0xD7),
+    Encoding(text="ple", code=0xCA),
+    Encoding(text="pow", code=0xCB),
+    Encoding(text="fro", code=0xA9),
+    Encoding(text="wi", code=0xE2),
+    Encoding(text="at", code=0x94),
+    Encoding(text="ma", code=0xBD),
+    Encoding(text="all ", code=0x8E),
+    Encoding(text="wh", code=0xE1),
+    Encoding(text="ing ", code=0xB3),
+    Encoding(text="Tha", code=0xE5),
+    Encoding(text="sh", code=0xD1),
+    Encoding(text="have", code=0xAD),
+    Encoding(text="re ", code=0xCD),
+    Encoding(text="er", code=0xA6),
+    Encoding(text="know", code=0xB8),
+    Encoding(text="ter ", code=0xD4),
+    Encoding(text="des", code=0x9D),
+    Encoding(text="ear", code=0xA2),
+]
+
+
+def _ord(char: str) -> int:
+    """
+    Convert a character into the encoding byte.
+
+    """
+    for encoding in _encoding_table:
+        if encoding.text == char:
+            return encoding.code
+    raise ValueError(f"Unable to encode {char!r}")
+
+
+def _chr(ordinal: int) -> str:
+    """
+    Convert a encoded byte back into a character.
+
+    """
+    for encoding in _encoding_table:
+        if encoding.code == ordinal:
+            return encoding.text
+    raise ValueError(f"Unable to decode {ordinal!r}")
+
+
+def encode(s: str) -> bytes:
+    """
+    Encode a string into a series of bytes.
+
+    """
+    return bytes(map(_ord, s))
+
+
+def decode(b: bytes, *, on_fail: Optional[Callable[[int], str]] = None) -> str:
+    """
+    Decode a string from a series of bytes.
+
+    on_fail (if supplied) is called when a byte fails to decode. This can be
+    used to generate a fallback character.
+
+    """
+    chars = []
+    for x in b:
+        try:
+            char = _chr(x)
+        except ValueError:
+            if on_fail is None:
+                raise
+            else:
+                char = on_fail(x)
+        chars.append(char)
+    return "".join(chars)

script/beowulf.py

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+assert __name__ == "__main__"
+
+import argparse
+import pathlib
+
+import lttp.text
+
+parser = argparse.ArgumentParser()
+parser.add_argument("--input", required=True)
+parser.add_argument("--output", required=True)
+args = parser.parse_args()
+rom = bytearray(pathlib.Path(args.input).read_bytes())
+rom[940904:940924] = lttp.text.encode("LO, praise of the   ")
+rom[940925:940947] = lttp.text.encode("prowess of people-    ")
+rom[940948:940965] = lttp.text.encode("kings, of spear- ")
+rom[940968:940991] = lttp.text.encode("armed Danes, in days   ")
+pathlib.Path(args.output).write_bytes(rom)