mirror of
https://github.com/protomaps/PMTiles.git
synced 2026-02-04 10:51:07 +00:00
86 lines
2.8 KiB
Python
86 lines
2.8 KiB
Python
import json
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import mmap
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from contextlib import contextmanager
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@contextmanager
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def read(fname):
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r = Reader(fname)
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try:
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yield r
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finally:
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r.close()
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class Reader:
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def __init__(self, fname):
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self.f = open(fname, "r+b")
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self.mmap = mmap.mmap(self.f.fileno(), 0)
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assert int.from_bytes(self.mmap[0:2], byteorder="little") == 0x4D50
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first_entry_idx = 10 + self.metadata_len
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self.root_dir, self.leaves = self.load_directory(
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first_entry_idx, self.root_entries
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)
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def load_directory(self, offset, num_entries):
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directory = {}
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leaves = {}
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for i in range(offset, offset + num_entries * 17, 17):
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z = int.from_bytes(self.mmap[i : i + 1], byteorder="little")
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x = int.from_bytes(self.mmap[i + 1 : i + 4], byteorder="little")
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y = int.from_bytes(self.mmap[i + 4 : i + 7], byteorder="little")
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tile_off = int.from_bytes(self.mmap[i + 7 : i + 13], byteorder="little")
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tile_len = int.from_bytes(self.mmap[i + 13 : i + 17], byteorder="little")
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if z & 0b10000000:
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leaves[(z & 0b01111111, x, y)] = (tile_off, tile_len)
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else:
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directory[(z, x, y)] = (tile_off, tile_len)
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return (directory, leaves)
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def close(self):
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self.f.close()
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@property
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def metadata_len(self):
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return int.from_bytes(self.mmap[4:8], byteorder="little")
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@property
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def metadata(self):
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s = self.mmap[10 : 10 + self.metadata_len]
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return json.loads(s)
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@property
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def version(self):
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return int.from_bytes(self.mmap[2:4], byteorder="little")
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@property
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def root_entries(self):
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return int.from_bytes(self.mmap[8:10], byteorder="little")
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@property
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def leaf_level(self):
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return next(iter(self.leaves))[0]
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def get(self, z, x, y):
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val = self.root_dir.get((z, x, y))
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if val:
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return self.mmap[val[0] : val[0] + val[1]]
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else:
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if len(self.leaves) > 0:
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level_diff = z - self.leaf_level
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leaf = (self.leaf_level, x // (1 << level_diff), y // (1 << level_diff))
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val = self.leaves.get(leaf)
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if val:
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directory, _ = self.load_directory(val[0], val[1] // 17)
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val = directory.get((z, x, y))
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if val:
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return self.mmap[val[0] : val[0] + val[1]]
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def tiles(self):
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for k, v in self.root_dir.items():
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yield (k, self.mmap[v[0] : v[0] + v[1]])
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for val in self.leaves.values():
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leaf_dir, _ = self.load_directory(val[0], val[1] // 17)
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for k, v in leaf_dir.items():
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yield (k, self.mmap[v[0] : v[0] + v[1]])
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