feat: convert file manager into a plugin

plugins/file-manager/src/backend/transfer-segment-copy.ts

@@ -0,0 +1,40 @@
+export const SFTP_XFER_SEGMENT_SIZE = 256 * 1024 * 1024;
+export const DEFAULT_PARALLEL_SEGMENT_COUNT = 2;
+export const MAX_PARALLEL_SEGMENT_COUNT = 8;
+
+export interface SegmentCopyJob {
+  offset: number;
+  length: number;
+  segmentIndex: number;
+}
+
+export function clampParallelSegmentCount(value?: number): number {
+  const n = value ?? DEFAULT_PARALLEL_SEGMENT_COUNT;
+  return Math.max(1, Math.min(MAX_PARALLEL_SEGMENT_COUNT, Math.floor(n)));
+}
+
+export function buildSegmentCopyJobs(
+  fileSize: number,
+  initialOffset: number,
+  destResumeSize: number,
+): SegmentCopyJob[] {
+  const jobs: SegmentCopyJob[] = [];
+  for (
+    let offset = initialOffset;
+    offset < fileSize;
+    offset += SFTP_XFER_SEGMENT_SIZE
+  ) {
+    const length = Math.min(SFTP_XFER_SEGMENT_SIZE, fileSize - offset);
+    const segmentIndex = Math.floor(offset / SFTP_XFER_SEGMENT_SIZE);
+    if (destResumeSize >= offset + length) {
+      continue;
+    }
+    const start = destResumeSize > offset ? destResumeSize : offset;
+    jobs.push({
+      offset: start,
+      length: offset + length - start,
+      segmentIndex,
+    });
+  }
+  return jobs;
+}