Initial commit (Clean history)

path/to/venv/lib/python3.12/site-packages/docx/image/helpers.py

@@ -0,0 +1,86 @@
+from struct import Struct
+
+from .exceptions import UnexpectedEndOfFileError
+
+BIG_ENDIAN = ">"
+LITTLE_ENDIAN = "<"
+
+
+class StreamReader:
+    """Wraps a file-like object to provide access to structured data from a binary file.
+
+    Byte-order is configurable. `base_offset` is added to any base value provided to
+    calculate actual location for reads.
+    """
+
+    def __init__(self, stream, byte_order, base_offset=0):
+        super(StreamReader, self).__init__()
+        self._stream = stream
+        self._byte_order = LITTLE_ENDIAN if byte_order == LITTLE_ENDIAN else BIG_ENDIAN
+        self._base_offset = base_offset
+
+    def read(self, count):
+        """Allow pass-through read() call."""
+        return self._stream.read(count)
+
+    def read_byte(self, base, offset=0):
+        """Return the int value of the byte at the file position defined by
+        self._base_offset + `base` + `offset`.
+
+        If `base` is None, the byte is read from the current position in the stream.
+        """
+        fmt = "B"
+        return self._read_int(fmt, base, offset)
+
+    def read_long(self, base, offset=0):
+        """Return the int value of the four bytes at the file position defined by
+        self._base_offset + `base` + `offset`.
+
+        If `base` is None, the long is read from the current position in the stream. The
+        endian setting of this instance is used to interpret the byte layout of the
+        long.
+        """
+        fmt = "<L" if self._byte_order is LITTLE_ENDIAN else ">L"
+        return self._read_int(fmt, base, offset)
+
+    def read_short(self, base, offset=0):
+        """Return the int value of the two bytes at the file position determined by
+        `base` and `offset`, similarly to ``read_long()`` above."""
+        fmt = b"<H" if self._byte_order is LITTLE_ENDIAN else b">H"
+        return self._read_int(fmt, base, offset)
+
+    def read_str(self, char_count, base, offset=0):
+        """Return a string containing the `char_count` bytes at the file position
+        determined by self._base_offset + `base` + `offset`."""
+
+        def str_struct(char_count):
+            format_ = "%ds" % char_count
+            return Struct(format_)
+
+        struct = str_struct(char_count)
+        chars = self._unpack_item(struct, base, offset)
+        unicode_str = chars.decode("UTF-8")
+        return unicode_str
+
+    def seek(self, base, offset=0):
+        location = self._base_offset + base + offset
+        self._stream.seek(location)
+
+    def tell(self):
+        """Allow pass-through tell() call."""
+        return self._stream.tell()
+
+    def _read_bytes(self, byte_count, base, offset):
+        self.seek(base, offset)
+        bytes_ = self._stream.read(byte_count)
+        if len(bytes_) < byte_count:
+            raise UnexpectedEndOfFileError
+        return bytes_
+
+    def _read_int(self, fmt, base, offset):
+        struct = Struct(fmt)
+        return self._unpack_item(struct, base, offset)
+
+    def _unpack_item(self, struct, base, offset):
+        bytes_ = self._read_bytes(struct.size, base, offset)
+        return struct.unpack(bytes_)[0]