implement block offset cache
parent
53e099e63b
commit
07fb196f30
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@ -6,7 +6,40 @@ import io
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class Blendfile(io.FileIO):
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class Blendfile(io.FileIO):
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def __init__(self, filename):
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def __init__(self, filename):
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super().__init__(filename, "rb")
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super().__init__(filename, "rb")
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# Offset of first file block header.
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self._block_start = 12
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self.read_header()
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self.read_header()
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# Offsets of each file block by code.
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self._block_offsets = self._read_block_offsets()
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# Looping through file block headers to find scene header
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for block_code, offset in self._block_offsets.items():
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if block_code.startswith("SC"):
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print(f"Found scene block at offset {offset}!")
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def _read_block_offsets(self):
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"""
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Cache the offset to each file block.
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"""
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block_offsets = {}
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self.seek(self._block_start)
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while True:
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# File block code; identifies type of data
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block_code = self.read(4).decode("utf-8")
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# Empty string indicates EOF.
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if block_code == "":
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break
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block_offsets[block_code] = self.tell()
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# Size of file block, after this header
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block_size = int.from_bytes(self.read(4), self.endianness)
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# Skip rest of file header.
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self.seek(self.pointer_size + 8, io.SEEK_CUR)
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# Skip to next file block.
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self.seek(block_size, io.SEEK_CUR)
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return block_offsets
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def read_header(self):
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def read_header(self):
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self.seek(0)
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self.seek(0)
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@ -21,27 +54,4 @@ class Blendfile(io.FileIO):
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self.endianness = "little" if self.read(1).decode("utf-8") == "v" else "big"
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self.endianness = "little" if self.read(1).decode("utf-8") == "v" else "big"
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# Blender version, 3-byte int; v2.93 is represented as 293, and so on
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# Blender version, 3-byte int; v2.93 is represented as 293, and so on
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self.version = int(self.read(3))
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self.version = int(self.read(3))
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# Looping through file block headers to find scene header
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# TODO: Implement proper error handling if the target file block does not exist.
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while True:
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# File block code; identifies type of data
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code = self.read(4).decode("utf-8")
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# Size of file block, after this header
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size = int.from_bytes(self.read(4), self.endianness)
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# Seeking to end of file block header
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self.seek(8+self.pointer_size+size, 1)
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# Scene file block codes will always begin with "SC"
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if code.startswith("SC"):
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# TODO: Acquire SDNA index of scene data, to be found in DNA1 file block
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# SDNA index occurs directly following file block size in header
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# and is pointer_size bytes long
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break
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# Seeking to the start of the next file block
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self.seek(8+self.pointer_size+size, 1)
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