94 lines
2.4 KiB
Python
94 lines
2.4 KiB
Python
"""Preview generation worker subprocess.
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Two modes are supported:
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1) Legacy one-shot mode: argv has path/quality/maxsize/maxzoom.
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2) Long-lived mode: read JSONL commands from stdin and write framed responses.
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Framed response format:
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(blake3(packet))(uint32 json size)(uint32 payload size)(json)(binary payload)
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where packet = (uint32 json size)(uint32 payload size)(json)(binary payload).
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"""
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import logging
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import struct
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import sys
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from pathlib import Path
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import msgspec
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from blake3 import blake3
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class PreviewRequest(msgspec.Struct, omit_defaults=True):
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path: str
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quality: int
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maxsize: int
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maxzoom: float
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class PreviewResponse(msgspec.Struct, omit_defaults=True):
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ok: bool
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mime: str | None = None
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backend: str | None = None
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timings: list[float] | None = None
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error: str | None = None
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_enc = msgspec.json.Encoder()
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_dec_req = msgspec.json.Decoder(PreviewRequest)
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def _write_response(resp: PreviewResponse, payload: bytes) -> None:
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meta_bytes = _enc.encode(resp)
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packet = struct.pack("<II", len(meta_bytes), len(payload)) + meta_bytes + payload
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checksum = blake3(packet).digest()
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sys.stdout.buffer.write(checksum)
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sys.stdout.buffer.write(packet)
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sys.stdout.buffer.flush()
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def _run_once() -> None:
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if len(sys.argv) != 5:
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sys.stderr.write(f"Usage: {sys.argv[0]} <path> <quality> <maxsize> <maxzoom>\n")
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sys.exit(1)
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from cista.preview import dispatch
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path = Path(sys.argv[1])
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quality = int(sys.argv[2])
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maxsize = int(sys.argv[3])
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maxzoom = float(sys.argv[4])
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result, _ = dispatch(path, quality, maxsize, maxzoom)
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if result:
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sys.stdout.buffer.write(result)
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sys.stdout.buffer.flush()
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def _run_loop() -> None:
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from cista.preview import dispatch
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while True:
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line = sys.stdin.buffer.readline()
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if not line:
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return
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try:
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req = _dec_req.decode(line)
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result, resp = dispatch(
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Path(req.path), req.quality, req.maxsize, req.maxzoom
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)
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_write_response(resp, result or b"")
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except Exception as e:
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_write_response(PreviewResponse(ok=False, error=str(e)), b"")
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def main() -> None:
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# Configure all log output to stderr before any imports that may emit logs.
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logging.basicConfig(stream=sys.stderr, level=logging.INFO)
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if len(sys.argv) > 1:
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_run_once()
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return
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_run_loop()
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if __name__ == "__main__":
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main()
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