ref: e42ad9964d9c9372ecb63c860ed2c91b09b373b2
parent: 0f459825a36dbd510a0a5975cba5af073fa42cbd
author: Runxi Yu <me@runxiyu.org>
date: Fri Feb 20 19:05:33 EST 2026
objectdb: Add Chain Not sure if it belongs here, we'll see in the future.
--- /dev/null
+++ b/objectdb/chain.go
@@ -1,0 +1,89 @@
+package objectdb
+
+import (
+ "errors"
+ "fmt"
+
+ "codeberg.org/lindenii/furgit/objectid"
+ "codeberg.org/lindenii/furgit/objecttype"
+)
+
+// Chain queries multiple object databases in order.
+type Chain struct {+ backends []ObjectDB
+}
+
+// NewChain creates an ordered object database chain.
+func NewChain(backends ...ObjectDB) *Chain {+ return &Chain{+ backends: append([]ObjectDB(nil), backends...),
+ }
+}
+
+// ReadBytesFull reads a full serialized object from the first backend that has it.
+func (chain *Chain) ReadBytesFull(id objectid.ObjectID) ([]byte, error) {+ for i, backend := range chain.backends {+ if backend == nil {+ continue
+ }
+ full, err := backend.ReadBytesFull(id)
+ if err == nil {+ return full, nil
+ }
+ if errors.Is(err, ErrObjectNotFound) {+ continue
+ }
+ return nil, fmt.Errorf("objectdb: backend %d read bytes full: %w", i, err)+ }
+ return nil, ErrObjectNotFound
+}
+
+// ReadBytesContent reads an object's type and content bytes from the first backend that has it.
+func (chain *Chain) ReadBytesContent(id objectid.ObjectID) (objecttype.Type, []byte, error) {+ for i, backend := range chain.backends {+ if backend == nil {+ continue
+ }
+ ty, content, err := backend.ReadBytesContent(id)
+ if err == nil {+ return ty, content, nil
+ }
+ if errors.Is(err, ErrObjectNotFound) {+ continue
+ }
+ return objecttype.TypeInvalid, nil, fmt.Errorf("objectdb: backend %d read bytes content: %w", i, err)+ }
+ return objecttype.TypeInvalid, nil, ErrObjectNotFound
+}
+
+// ReadHeader reads object header data from the first backend that has it.
+func (chain *Chain) ReadHeader(id objectid.ObjectID) (objecttype.Type, int64, error) {+ for i, backend := range chain.backends {+ if backend == nil {+ continue
+ }
+ ty, size, err := backend.ReadHeader(id)
+ if err == nil {+ return ty, size, nil
+ }
+ if errors.Is(err, ErrObjectNotFound) {+ continue
+ }
+ return objecttype.TypeInvalid, 0, fmt.Errorf("objectdb: backend %d read header: %w", i, err)+ }
+ return objecttype.TypeInvalid, 0, ErrObjectNotFound
+}
+
+// Close closes all backends and joins close errors.
+func (chain *Chain) Close() error {+ var errs []error
+ for _, backend := range chain.backends {+ if backend == nil {+ continue
+ }
+ if err := backend.Close(); err != nil {+ errs = append(errs, err)
+ }
+ }
+ return errors.Join(errs...)
+}
--
⑨