def prepare_truncate(manifest: LocalFileManifest,
size: int) -> Tuple[LocalFileManifest, Set[BlockID]]:
# Prepare
block, remainder = locate(size, manifest.blocksize)
removed_ids = chunk_id_set(manifest.blocks[block])
# Truncate buffers
blocks = manifest.blocks[:block]
if remainder:
chunks = manifest.blocks[block]
stop_index = index_of_chunk_after_stop(chunks, size)
last_chunk = chunks[stop_index - 1]
chunks = chunks[:stop_index - 1]
chunks += (last_chunk.evolve(stop=size), )
blocks += (chunks, )
removed_ids -= chunk_id_set(chunks)
# Clean up
for chunks in manifest.blocks[block + 1:]:
removed_ids |= chunk_id_set(chunks)
# Craft new manifest
new_manifest = manifest.evolve_and_mark_updated(size=size, blocks=blocks)
# Return truncate result
return new_manifest, removed_ids
def prepare_write(
manifest: LocalFileManifest, size: int, offset: int, timestamp: DateTime
) -> Tuple[LocalFileManifest, WriteOperationList, ChunkIDSet]:
# Prepare
padding = 0
removed_ids: ChunkIDSet = set()
write_operations: WriteOperationList = []
# Padding
if offset > manifest.size:
padding = offset - manifest.size
size += padding
offset = manifest.size
# Copy buffers
blocks = list(manifest.blocks)
# Loop over blocks
for block, subsize, start, content_offset in split_write(
size, offset, manifest.blocksize):
# Prepare new chunk
new_chunk = Chunk.new(start, start + subsize)
write_operations.append((new_chunk, content_offset - padding))
# Lazy block write
chunks = manifest.get_chunks(block)
new_chunks, more_removed_ids = block_write(chunks, subsize, start,
new_chunk)
# Update data structures
removed_ids |= more_removed_ids
if len(blocks) == block:
blocks.append(new_chunks)
else:
blocks[block] = new_chunks
# Evolve manifest
new_size = max(manifest.size, offset + size)
new_manifest = manifest.evolve_and_mark_updated(size=new_size,
blocks=tuple(blocks),
timestamp=timestamp)
# Return write result
return new_manifest, write_operations, removed_ids
