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blendparse
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implement block offset cache

master
Josiah 2021-07-19 11:30:08 -05:00
parent 53e099e63b
commit 07fb196f30
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GPG Key ID: C7BB8573A4ABC4B9
1 changed files with 34 additions and 24 deletions
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blendparse.py
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@ -6,7 +6,40 @@ import io
class Blendfile(io.FileIO):
def __init__(self, filename):
super().__init__(filename, "rb")
# Offset of first file block header.
self._block_start = 12
self.read_header()
# Offsets of each file block by code.
self._block_offsets = self._read_block_offsets()
# Looping through file block headers to find scene header
for block_code, offset in self._block_offsets.items():
if block_code.startswith("SC"):
print(f"Found scene block at offset {offset}!")
def _read_block_offsets(self):
"""
Cache the offset to each file block.
"""
block_offsets = {}
self.seek(self._block_start)
while True:
# File block code; identifies type of data
block_code = self.read(4).decode("utf-8")
# Empty string indicates EOF.
if block_code == "":
break
block_offsets[block_code] = self.tell()
# Size of file block, after this header
block_size = int.from_bytes(self.read(4), self.endianness)
# Skip rest of file header.
self.seek(self.pointer_size + 8, io.SEEK_CUR)
# Skip to next file block.
self.seek(block_size, io.SEEK_CUR)
return block_offsets
def read_header(self):
self.seek(0)
@ -21,27 +54,4 @@ class Blendfile(io.FileIO):
self.endianness = "little" if self.read(1).decode("utf-8") == "v" else "big"
# Blender version, 3-byte int; v2.93 is represented as 293, and so on
self.version = int(self.read(3))
# Looping through file block headers to find scene header
# TODO: Implement proper error handling if the target file block does not exist.
while True:
# File block code; identifies type of data
code = self.read(4).decode("utf-8")
# Size of file block, after this header
size = int.from_bytes(self.read(4), self.endianness)
# Seeking to end of file block header
self.seek(8+self.pointer_size+size, 1)
# Scene file block codes will always begin with "SC"
if code.startswith("SC"):
# TODO: Acquire SDNA index of scene data, to be found in DNA1 file block
# SDNA index occurs directly following file block size in header
# and is pointer_size bytes long
break
# Seeking to the start of the next file block
self.seek(8+self.pointer_size+size, 1)
self.version = int(self.read(3))