From 65a18ed669d64dc7a6f85baeda0de8e38e7add07 Mon Sep 17 00:00:00 2001
From: Lucas Molas <schomatis@gmail.com>
Date: Wed, 11 Jul 2018 12:24:37 -0300
Subject: [PATCH] unixfs: fix `dagTruncate` to preserve node type

Extract the original `FSNode` passed inside the `ipld.Node` argument and modify
its `Blocksizes` (removing all of them and re-adding the ones that were not
truncated). In contrast, the replaced code was creating a new `FSNode` that was
not preserving some of the features of the original one.

Change `TRUNC_HASH` values in `sharness` that were created with the bug to the
correct values.

License: MIT
Signed-off-by: Lucas Molas <schomatis@gmail.com>
---
 test/sharness/t0250-files-api.sh |  8 ++++----
 unixfs/mod/dagmodifier.go        | 12 +++++++++---
 unixfs/unixfs.go                 |  6 ++++++
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/test/sharness/t0250-files-api.sh b/test/sharness/t0250-files-api.sh
index 61f52c2bf..5499ab3d4 100755
--- a/test/sharness/t0250-files-api.sh
+++ b/test/sharness/t0250-files-api.sh
@@ -613,7 +613,7 @@ tests_for_files_api() {
   ROOT_HASH=QmcwKfTMCT7AaeiD92hWjnZn9b6eh9NxnhfSzN5x2vnDpt
   CATS_HASH=Qma88m8ErTGkZHbBWGqy1C7VmEmX8wwNDWNpGyCaNmEgwC
   FILE_HASH=QmQdQt9qooenjeaNhiKHF3hBvmNteB4MQBtgu3jxgf9c7i
-  TRUNC_HASH=QmdaQZbLwK5ykweGdCVovNnvBom7QhikovDUVqTPHQG4L8
+  TRUNC_HASH=QmPVnT9gocPbqzN4G6SMp8vAPyzcjDbUJrNdKgzQquuDg4
   test_files_api "($EXTRA)"
 
   test_expect_success "can create some files for testing with raw-leaves ($EXTRA)" '
@@ -629,13 +629,13 @@ tests_for_files_api() {
   ROOT_HASH=QmW3dMSU6VNd1mEdpk9S3ZYRuR1YwwoXjGaZhkyK6ru9YU
   CATS_HASH=QmPqWDEg7NoWRX8Y4vvYjZtmdg5umbfsTQ9zwNr12JoLmt
   FILE_HASH=QmRCgHeoKxCqK2Es6M6nPUDVWz19yNQPnsXGsXeuTkSKpN
-  TRUNC_HASH=QmRFJEKWF5A5FyFYZgNhusLw2UziW9zBKYr4huyHjzcB6o
+  TRUNC_HASH=QmckstrVxJuecVD1FHUiURJiU9aPURZWJieeBVHJPACj8L
   test_files_api "($EXTRA, raw-leaves)" '' --raw-leaves
 
   ROOT_HASH=QmageRWxC7wWjPv5p36NeAgBAiFdBHaNfxAehBSwzNech2
   CATS_HASH=zdj7WkEzPLNAr5TYJSQC8CFcBjLvWFfGdx6kaBrJXnBguwWeX
   FILE_HASH=zdj7WYHvf5sBRgSBjYnq64QFr449CCbgupXfBvoYL3aHC1DzJ
-  TRUNC_HASH=zdj7WYLYbka6Ydg8gZUJRLKnFBVehCADhQKBsFbNiMxZSB5Gj
+  TRUNC_HASH=zdj7Wjr8GHZonPFVCWvz2SLLo9H6MmqBxyeB34ArHfyCbmdJG
   if [ "$EXTRA" = "offline" ]; then
     test_files_api "($EXTRA, cidv1)" --cid-version=1
   fi
@@ -660,7 +660,7 @@ tests_for_files_api() {
     ROOT_HASH=zDMZof1kxEsAwSgCZsGQRVcHCMtHLjkUQoiZUbZ87erpPQJGUeW8
     CATS_HASH=zDMZof1kuAhr3zBkxq48V7o9HJZCTVyu1Wd9wnZtVcPJLW8xnGft
     FILE_HASH=zDMZof1kxbB9CvxgRioBzESbGnZUxtSCsZ18H1EUkxDdWt1DYEkK
-    TRUNC_HASH=zDMZof1kxXqKdVsVo231qVdN3hCTF5a34UuQZpzmm5K7CbRJ4u2S
+    TRUNC_HASH=zDMZof1kpH1vxK3k2TeYc8w59atCbzMzrhZonsztMWSptVro2zQa
     test_files_api "($EXTRA, blake2b-256 root)"
   fi
 
diff --git a/unixfs/mod/dagmodifier.go b/unixfs/mod/dagmodifier.go
index 28de7228d..f8aa5ce63 100644
--- a/unixfs/mod/dagmodifier.go
+++ b/unixfs/mod/dagmodifier.go
@@ -529,7 +529,13 @@ func dagTruncate(ctx context.Context, n ipld.Node, size uint64, ds ipld.DAGServi
 	var cur uint64
 	end := 0
 	var modified ipld.Node
-	ndata := ft.NewFSNode(ft.TRaw)
+	ndata, err := ft.FSNodeFromBytes(nd.Data())
+	if err != nil {
+		return nil, err
+	}
+	// Reset the block sizes of the node to adjust them
+	// with the new values of the truncated children.
+	ndata.RemoveAllBlockSizes()
 	for i, lnk := range nd.Links() {
 		child, err := lnk.GetNode(ctx, ds)
 		if err != nil {
@@ -558,7 +564,7 @@ func dagTruncate(ctx context.Context, n ipld.Node, size uint64, ds ipld.DAGServi
 		ndata.AddBlockSize(childsize)
 	}
 
-	err := ds.Add(ctx, modified)
+	err = ds.Add(ctx, modified)
 	if err != nil {
 		return nil, err
 	}
@@ -573,7 +579,7 @@ func dagTruncate(ctx context.Context, n ipld.Node, size uint64, ds ipld.DAGServi
 	if err != nil {
 		return nil, err
 	}
-
+	// Save the new block sizes to the original node.
 	nd.SetData(d)
 
 	// invalidate cache and recompute serialized data
diff --git a/unixfs/unixfs.go b/unixfs/unixfs.go
index 9cd9731ed..d048c422b 100644
--- a/unixfs/unixfs.go
+++ b/unixfs/unixfs.go
@@ -201,6 +201,12 @@ func (n *FSNode) BlockSize(i int) uint64 {
 	return n.format.Blocksizes[i]
 }
 
+// RemoveAllBlockSizes removes all the child block sizes of this node.
+func (n *FSNode) RemoveAllBlockSizes() {
+	n.format.Blocksizes = []uint64{}
+	n.format.Filesize = proto.Uint64(uint64(len(n.Data())))
+}
+
 // GetBytes marshals this node as a protobuf message.
 func (n *FSNode) GetBytes() ([]byte, error) {
 	return proto.Marshal(&n.format)