Method Copy

src/bccore/txapi.go:162–233

(ctx context.Context, txh blobcache.Handle, srcTxns []blobcache.Handle, cids []blobcache.CID, out *blobcache.BitMap)

}

func (sys *System) Copy(ctx context.Context, txh blobcache.Handle, srcTxns []blobcache.Handle, cids []blobcache.CID, out *blobcache.BitMap) error {
	logctx.Debug(ctx, "begin", zap.String("method", "Copy"), zap.Stringer("oid", txh.OID))
	defer logctx.Debug(ctx, "done", zap.String("method", "Copy"), zap.Stringer("oid", txh.OID))
	dstTx, err := sys.resolveTx(txh, true, blobcache.Action_TX_COPY_TO)
	if err != nil {
		return err
	}
	if p := dstTx.backend.Params(); !p.Modify {
		return blobcache.ErrTxReadOnly{Tx: txh.OID, Op: "COPY"}
	}

	type srcTxn struct {
		oid blobcache.OID
		tx  transaction
	}
	resolvedSrcs := make([]srcTxn, len(srcTxns))
	for i, srcH := range srcTxns {
		src, err := sys.resolveTx(srcH, true, blobcache.Action_TX_COPY_FROM)
		if err != nil {
			return err
		}
		resolvedSrcs[i] = srcTxn{oid: srcH.OID, tx: src}
	}

	var buf []byte
	var exists blobcache.BitMap
	for i, cid := range cids {
		if len(resolvedSrcs) == 0 {
			continue
		}
		start := int(cid[0]) % len(resolvedSrcs)
		for j := range resolvedSrcs {
			src := resolvedSrcs[(start+j)%len(resolvedSrcs)]
			exists = exists[:0]
			if err := src.tx.backend.Exists(ctx, []blobcache.CID{cid}, &exists); err != nil {
				return fmt.Errorf("copy from tx %v: %w", src.oid, err)
			}
			if !exists.IsSet(0) {
				continue
			}
			srcMax := src.tx.backend.MaxSize()
			if cap(buf) < srcMax {
				buf = make([]byte, srcMax)
			}
			n, err := src.tx.backend.Get(ctx, cid, buf[:srcMax], blobcache.GetOpts{})
			if err != nil {
				if blobcache.IsErrNotFound(err) {
					continue
				}
				return fmt.Errorf("copy from tx %v: %w", src.oid, err)
			}
			data := buf[:n]
			if dstTx.backend.HashAlgo().Hash(data) != cid {
				continue
			}
			cid2, err := dstTx.backend.Post(ctx, data, blobcache.PostOpts{})
			if err != nil {
				var eTooLarge blobcache.ErrTooLarge