ref: 4e3357b476690e02945316519c7804e7f07ccb1b
parent: d585f0889eef41f1386abefe3daa2e617a21895e
author: Runxi Yu <me@runxiyu.org>
date: Wed Mar 4 09:36:33 EST 2026
objectstore/chain: Add an actual chain object store
--- /dev/null
+++ b/objectstore/chain/bytes.go
@@ -1,0 +1,54 @@
+package chain
+
+import (
+ "errors"
+ "fmt"
+
+ "codeberg.org/lindenii/furgit/objectid"
+ "codeberg.org/lindenii/furgit/objectstore"
+ "codeberg.org/lindenii/furgit/objecttype"
+)
+
+// 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, objectstore.ErrObjectNotFound) {+ continue
+ }
+
+ return nil, fmt.Errorf("objectstore: backend %d read bytes full: %w", i, err)+ }
+
+ return nil, objectstore.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, objectstore.ErrObjectNotFound) {+ continue
+ }
+
+ return objecttype.TypeInvalid, nil, fmt.Errorf("objectstore: backend %d read bytes content: %w", i, err)+ }
+
+ return objecttype.TypeInvalid, nil, objectstore.ErrObjectNotFound
+}
--- /dev/null
+++ b/objectstore/chain/chain.go
@@ -1,0 +1,11 @@
+// Package chain provides a wrapper object storage backend to query a chain of backends.
+package chain
+
+import (
+ "codeberg.org/lindenii/furgit/objectstore"
+)
+
+// Chain queries multiple object databases in order.
+type Chain struct {+ backends []objectstore.Store
+}
--- /dev/null
+++ b/objectstore/chain/close.go
@@ -1,0 +1,21 @@
+package chain
+
+import "errors"
+
+// 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
+ }
+
+ err := backend.Close()
+ if err != nil {+ errs = append(errs, err)
+ }
+ }
+
+ return errors.Join(errs...)
+}
--- /dev/null
+++ b/objectstore/chain/header.go
@@ -1,0 +1,32 @@
+package chain
+
+import (
+ "errors"
+ "fmt"
+
+ "codeberg.org/lindenii/furgit/objectid"
+ "codeberg.org/lindenii/furgit/objectstore"
+ "codeberg.org/lindenii/furgit/objecttype"
+)
+
+// 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, objectstore.ErrObjectNotFound) {+ continue
+ }
+
+ return objecttype.TypeInvalid, 0, fmt.Errorf("objectstore: backend %d read header: %w", i, err)+ }
+
+ return objecttype.TypeInvalid, 0, objectstore.ErrObjectNotFound
+}
--- /dev/null
+++ b/objectstore/chain/new.go
@@ -1,0 +1,10 @@
+package chain
+
+import "codeberg.org/lindenii/furgit/objectstore"
+
+// New creates an ordered object database chain.
+func New(backends ...objectstore.Store) *Chain {+ return &Chain{+ backends: append([]objectstore.Store(nil), backends...),
+ }
+}
--- /dev/null
+++ b/objectstore/chain/reader.go
@@ -1,0 +1,55 @@
+package chain
+
+import (
+ "errors"
+ "fmt"
+ "io"
+
+ "codeberg.org/lindenii/furgit/objectid"
+ "codeberg.org/lindenii/furgit/objectstore"
+ "codeberg.org/lindenii/furgit/objecttype"
+)
+
+// ReadReaderFull reads a full serialized object stream from the first backend that has it.
+func (chain *Chain) ReadReaderFull(id objectid.ObjectID) (io.ReadCloser, error) {+ for i, backend := range chain.backends {+ if backend == nil {+ continue
+ }
+
+ reader, err := backend.ReadReaderFull(id)
+ if err == nil {+ return reader, nil
+ }
+
+ if errors.Is(err, objectstore.ErrObjectNotFound) {+ continue
+ }
+
+ return nil, fmt.Errorf("objectstore: backend %d read reader full: %w", i, err)+ }
+
+ return nil, objectstore.ErrObjectNotFound
+}
+
+// ReadReaderContent reads an object's type, declared content length, and content stream from the first backend that has it.
+func (chain *Chain) ReadReaderContent(id objectid.ObjectID) (objecttype.Type, int64, io.ReadCloser, error) {+ for i, backend := range chain.backends {+ if backend == nil {+ continue
+ }
+
+ ty, size, reader, err := backend.ReadReaderContent(id)
+ if err == nil {+ return ty, size, reader, nil
+ }
+
+ if errors.Is(err, objectstore.ErrObjectNotFound) {+ continue
+ }
+
+ return objecttype.TypeInvalid, 0, nil, fmt.Errorf("objectstore: backend %d read reader content: %w", i, err)+ }
+
+ return objecttype.TypeInvalid, 0, nil, objectstore.ErrObjectNotFound
+}
--- /dev/null
+++ b/objectstore/chain/size.go
@@ -1,0 +1,31 @@
+package chain
+
+import (
+ "errors"
+ "fmt"
+
+ "codeberg.org/lindenii/furgit/objectid"
+ "codeberg.org/lindenii/furgit/objectstore"
+)
+
+// ReadSize reads object content length from the first backend that has it.
+func (chain *Chain) ReadSize(id objectid.ObjectID) (int64, error) {+ for i, backend := range chain.backends {+ if backend == nil {+ continue
+ }
+
+ size, err := backend.ReadSize(id)
+ if err == nil {+ return size, nil
+ }
+
+ if errors.Is(err, objectstore.ErrObjectNotFound) {+ continue
+ }
+
+ return 0, fmt.Errorf("objectstore: backend %d read size: %w", i, err)+ }
+
+ return 0, objectstore.ErrObjectNotFound
+}
--
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