amend me: s3 chunked writer

odc/geo/cog/_s3.py

@@ -0,0 +1,149 @@
+"""
+S3 utils for COG to S3.
+"""
+from typing import Any, Callable, Dict, List, Optional, Tuple, Union
+
+SomeData = Union[bytes, bytearray]
+_5MB = 5 * (1 << 20)
+PartsWriter = Callable[[int, bytearray], Dict[str, Any]]
+
+
+class MPUChunk:
+    """
+    chunk cache and writer
+    """
+
+    # pylint: disable=too-many-arguments
+
+    __slots__ = (
+        "nextPartId",
+        "write_credits",
+        "data",
+        "left_data",
+        "parts",
+        "observed",
+        "eof",
+    )
+
+    def __init__(
+        self,
+        partId: int,
+        write_credits: int,
+        data: Optional[bytearray] = None,
+        left_data: Optional[bytearray] = None,
+        parts: Optional[List[Dict[str, Any]]] = None,
+        observed: Optional[List[Tuple[int, Any]]] = None,
+        eof: bool = False,
+    ) -> None:
+        assert partId >= 1
+        assert write_credits >= 0
+        assert partId + write_credits <= 10_000
+
+        self.nextPartId = partId
+        self.write_credits = write_credits
+        self.data = bytearray() if data is None else data
+        self.left_data = left_data
+        self.parts: List[Dict[str, Any]] = [] if parts is None else parts
+        self.observed: List[Tuple[int, Any]] = [] if observed is None else observed
+        self.eof = eof
+
+    def append(self, data: SomeData, chunk_id: Any = None):
+        sz = len(data)
+        self.observed.append((sz, chunk_id))
+        self.data += data
+
+    @property
+    def started_write(self) -> bool:
+        return len(self.parts) > 0
+
+    @staticmethod
+    def merge(lhs: "MPUChunk", rhs: "MPUChunk", write: PartsWriter) -> "MPUChunk":
+        if not rhs.started_write:
+            # no writes on the right
+            # Just append
+            assert rhs.left_data is None
+            assert len(rhs.parts) == 0
+
+            return MPUChunk(
+                lhs.nextPartId,
+                lhs.write_credits + rhs.write_credits,
+                lhs.data + rhs.data,
+                lhs.left_data,
+                lhs.parts,
+                lhs.observed + rhs.observed,
+                rhs.eof,
+            )
+
+        # Flush `lhs.data + rhs.left_data` if we can
+        #  or else move it into .left_data
+        lhs.final_flush(write, rhs.left_data)
+
+        return MPUChunk(
+            rhs.nextPartId,
+            rhs.write_credits,
+            rhs.data,
+            lhs.left_data,
+            lhs.parts + rhs.parts,
+            lhs.observed + rhs.observed,
+            rhs.eof,
+        )
+
+    def final_flush(
+        self, write: PartsWriter, extra_data: Optional[bytearray] = None
+    ) -> int:
+        data = self.data
+        if extra_data is not None:
+            data += extra_data
+
+        def _flush_data():
+            part = write(self.nextPartId, data)
+            self.parts.append(part)
+            self.data = bytearray()
+            self.nextPartId += 1
+            self.write_credits -= 1
+            return len(data)
+
+        # Have enough write credits
+        # AND (have enough bytes OR it's the last chunk)
+        can_flush = self.write_credits > 0 and (self.eof or len(data) >= _5MB)
+
+        if self.started_write:
+            assert can_flush is True
+            return _flush_data()
+
+        if can_flush:
+            return _flush_data()
+
+        assert self.left_data is None
+        self.left_data, self.data = data, bytearray()
+        return 0
+
+    def maybe_write(self, write: PartsWriter, min_sz: int) -> int:
+        # if not last section keep 5MB and 1 partId around after flush
+        bytes_to_keep, parts_to_keep = (0, 0) if self.eof else (_5MB, 1)
+
+        if self.write_credits - 1 < parts_to_keep:
+            return 0
+
+        bytes_to_write = len(self.data) - bytes_to_keep
+        if bytes_to_write < min_sz:
+            return 0
+
+        part = write(self.nextPartId, self.data[:bytes_to_write])
+
+        self.parts.append(part)
+        self.data = self.data[bytes_to_write:]
+        self.nextPartId += 1
+        self.write_credits -= 1
+
+        return bytes_to_write
+
+
+class MultiPartUpload:
+    """
+    Dask to S3 dumper.
+    """
+
+    def __init__(self, bucket: str, key: str):
+        self.bucket = bucket
+        self.key = key