Initial commit of Roster

2025-06-28 01:12:46 -05:00
commit c23d3a7676
4367 changed files with 890519 additions and 0 deletions
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+"""Python implementation of ASCII85/ASCIIHex decoder (Adobe version)."""
+
+import re
+from base64 import a85decode
+from binascii import unhexlify
+
+start_re = re.compile(rb"^\s*<?\s*~\s*")
+end_re = re.compile(rb"\s*~\s*>?\s*$")
+
+
+def ascii85decode(data: bytes) -> bytes:
+    """In ASCII85 encoding, every four bytes are encoded with five ASCII
+    letters, using 85 different types of characters (as 256**4 < 85**5).
+    When the length of the original bytes is not a multiple of 4, a special
+    rule is used for round up.
+
+    Adobe's ASCII85 implementation expects the input to be terminated
+    by `b"~>"`, and (though this is absent from the PDF spec) it can
+    also begin with `b"<~"`.  We can't reliably expect this to be the
+    case, and there can be off-by-one errors in stream lengths which
+    mean we only see `~` at the end.  Worse yet, `<` and `>` are
+    ASCII85 digits, so we can't strip them.  We settle on a compromise
+    where we strip leading `<~` or `~` and trailing `~` or `~>`.
+    """
+    data = start_re.sub(b"", data)
+    data = end_re.sub(b"", data)
+    return a85decode(data)
+
+
+bws_re = re.compile(rb"\s")
+
+
+def asciihexdecode(data: bytes) -> bytes:
+    """ASCIIHexDecode filter: PDFReference v1.4 section 3.3.1
+    For each pair of ASCII hexadecimal digits (0-9 and A-F or a-f), the
+    ASCIIHexDecode filter produces one byte of binary data. All white-space
+    characters are ignored. A right angle bracket character (>) indicates
+    EOD. Any other characters will cause an error. If the filter encounters
+    the EOD marker after reading an odd number of hexadecimal digits, it
+    will behave as if a 0 followed the last digit.
+    """
+    data = bws_re.sub(b"", data)
+    idx = data.find(b">")
+    if idx != -1:
+        data = data[:idx]
+        if idx % 2 == 1:
+            data += b"0"
+    return unhexlify(data)