From 21074bc355524ceb3675dc93579e219746c1b567 Mon Sep 17 00:00:00 2001
From: Will Scott <will@cypherpunk.email>
Date: Fri, 10 Sep 2021 06:38:47 -0700
Subject: [PATCH 1/3] add interface describing iteration

---
 v2/index/index.go | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/v2/index/index.go b/v2/index/index.go
index 071e8e6e..320751cc 100644
--- a/v2/index/index.go
+++ b/v2/index/index.go
@@ -8,6 +8,7 @@ import (
 	internalio "github.com/ipld/go-car/v2/internal/io"
 
 	"github.com/multiformats/go-multicodec"
+	"github.com/multiformats/go-multihash"
 
 	"github.com/multiformats/go-varint"
 
@@ -58,6 +59,20 @@ type (
 		// ErrNotFound is returned.
 		GetAll(cid.Cid, func(uint64) bool) error
 	}
+
+	// IterableIndex extends Index in cases where the Index is able to
+	// provide an iterator for getting the list of all entries in the
+	// index.
+	IterableIndex interface {
+		// ForEach takes a callback function that will be called
+		// on each entry in the index. The arguments to the callback are
+		// the multihash of the element, and the offset in the car file
+		// where the element appears.
+		//
+		// If the callback returns a non-nil error, the iteration is aborted,
+		// and the ForEach function returns the error to the user.
+		ForEach(func(multihash.Multihash, uint64) error) error
+	}
 )
 
 // GetFirst is a wrapper over Index.GetAll, returning the offset for the first

From 1f3b28b81666db275f70129b4b22597cca16afe6 Mon Sep 17 00:00:00 2001
From: Will Scott <will@cypherpunk.email>
Date: Fri, 10 Sep 2021 06:43:25 -0700
Subject: [PATCH 2/3] InterableIndex is superset of Index

---
 v2/index/index.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/v2/index/index.go b/v2/index/index.go
index 320751cc..8abd1d3a 100644
--- a/v2/index/index.go
+++ b/v2/index/index.go
@@ -64,6 +64,8 @@ type (
 	// provide an iterator for getting the list of all entries in the
 	// index.
 	IterableIndex interface {
+		Index
+
 		// ForEach takes a callback function that will be called
 		// on each entry in the index. The arguments to the callback are
 		// the multihash of the element, and the offset in the car file

From 2d2568297f2630e0954909fd8b5de5300934efc4 Mon Sep 17 00:00:00 2001
From: Will Scott <will@cypherpunk.email>
Date: Fri, 10 Sep 2021 06:47:12 -0700
Subject: [PATCH 3/3] assertion of new interface

---
 v2/index/mhindexsorted.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/v2/index/mhindexsorted.go b/v2/index/mhindexsorted.go
index 75d30971..15a731c8 100644
--- a/v2/index/mhindexsorted.go
+++ b/v2/index/mhindexsorted.go
@@ -11,6 +11,7 @@ import (
 )
 
 var _ Index = (*MultihashIndexSorted)(nil)
+var _ IterableIndex = (*MultihashIndexSorted)(nil)
 
 type (
 	// MultihashIndexSorted maps multihash code (i.e. hashing algorithm) to multiWidthCodedIndex.