PrototypeChooser support (#305)

* complete reads of lazy nodes in walks

v2/go.mod

@@ -9,10 +9,11 @@ require (
 	github.com/ipfs/go-ipld-cbor v0.0.5
 	github.com/ipfs/go-ipld-format v0.3.0
 	github.com/ipfs/go-merkledag v0.6.0
+	github.com/ipfs/go-unixfsnode v1.4.0
 	github.com/ipld/go-codec-dagpb v1.3.1
 	github.com/ipld/go-ipld-prime v0.16.0
 	github.com/ipld/go-ipld-prime/storage/bsadapter v0.0.0-20211210234204-ce2a1c70cd73
-	github.com/multiformats/go-multicodec v0.3.1-0.20210902112759-1539a079fd61
+	github.com/multiformats/go-multicodec v0.5.0
 	github.com/multiformats/go-multihash v0.1.0
 	github.com/multiformats/go-varint v0.0.6
 	github.com/petar/GoLLRB v0.0.0-20210522233825-ae3b015fd3e9
@@ -22,13 +23,16 @@ require (
 )
 
 require (
+	github.com/Stebalien/go-bitfield v0.0.1 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/google/uuid v1.2.0 // indirect
 	github.com/hashicorp/golang-lru v0.5.4 // indirect
 	github.com/ipfs/bbloom v0.0.4 // indirect
+	github.com/ipfs/go-bitfield v1.0.0 // indirect
 	github.com/ipfs/go-blockservice v0.3.0 // indirect
 	github.com/ipfs/go-datastore v0.5.0 // indirect
+	github.com/ipfs/go-ipfs-chunker v0.0.1 // indirect
 	github.com/ipfs/go-ipfs-ds-help v1.1.0 // indirect
 	github.com/ipfs/go-ipfs-exchange-interface v0.1.0 // indirect
 	github.com/ipfs/go-ipfs-exchange-offline v0.2.0 // indirect
@@ -40,6 +44,7 @@ require (
 	github.com/ipfs/go-verifcid v0.0.1 // indirect
 	github.com/jbenet/goprocess v0.1.4 // indirect
 	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
+	github.com/libp2p/go-buffer-pool v0.0.2 // indirect
 	github.com/mattn/go-isatty v0.0.13 // indirect
 	github.com/minio/blake2b-simd v0.0.0-20160723061019-3f5f724cb5b1 // indirect
 	github.com/minio/sha256-simd v1.0.0 // indirect
@@ -52,6 +57,7 @@ require (
 	github.com/polydawn/refmt v0.0.0-20201211092308-30ac6d18308e // indirect
 	github.com/spaolacci/murmur3 v1.1.0 // indirect
 	github.com/whyrusleeping/cbor-gen v0.0.0-20200123233031-1cdf64d27158 // indirect
+	github.com/whyrusleeping/chunker v0.0.0-20181014151217-fe64bd25879f // indirect
 	go.uber.org/atomic v1.7.0 // indirect
 	go.uber.org/multierr v1.7.0 // indirect
 	go.uber.org/zap v1.16.0 // indirect

v2/go.sum

@@ -18,6 +18,8 @@ github.com/Kubuxu/go-os-helper v0.0.1/go.mod h1:N8B+I7vPCT80IcP58r50u4+gEEcsZETF
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
 github.com/Shopify/sarama v1.19.0/go.mod h1:FVkBWblsNy7DGZRfXLU0O9RCGt5g3g3yEuWXgklEdEo=
 github.com/Shopify/toxiproxy v2.1.4+incompatible/go.mod h1:OXgGpZ6Cli1/URJOF1DMxUHB2q5Ap20/P/eIdh4G0pI=
+github.com/Stebalien/go-bitfield v0.0.1 h1:X3kbSSPUaJK60wV2hjOPZwmpljr6VGCqdq4cBLhbQBo=
+github.com/Stebalien/go-bitfield v0.0.1/go.mod h1:GNjFpasyUVkHMsfEOk8EFLJ9syQ6SI+XWrX9Wf2XH0s=
 github.com/VividCortex/gohistogram v1.0.0/go.mod h1:Pf5mBqqDxYaXu3hDrrU+w6nw50o/4+TcAqDqk/vUH7g=
 github.com/aead/siphash v1.0.1/go.mod h1:Nywa3cDsYNNK3gaciGTWPwHt0wlpNV15vwmswBAUSII=
 github.com/afex/hystrix-go v0.0.0-20180502004556-fa1af6a1f4f5/go.mod h1:SkGFH1ia65gfNATL8TAiHDNxPzPdmEL5uirI2Uyuz6c=
@@ -26,6 +28,7 @@ github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751/go.mod h1:LOuy
 github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
 github.com/alecthomas/units v0.0.0-20190717042225-c3de453c63f4/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
 github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d/go.mod h1:rBZYJk541a8SKzHPHnH3zbiI+7dagKZ0cgpgrD7Fyho=
+github.com/alecthomas/units v0.0.0-20210927113745-59d0afb8317a/go.mod h1:OMCwj8VM1Kc9e19TLln2VL61YJF0x1XFtfdL4JdbSyE=
 github.com/anmitsu/go-shlex v0.0.0-20161002113705-648efa622239/go.mod h1:2FmKhYUyUczH0OGQWaF5ceTx0UBShxjsH6f8oGKYe2c=
 github.com/apache/thrift v0.12.0/go.mod h1:cp2SuWMxlEZw2r+iP2GNCdIi4C1qmUzdZFSVb+bacwQ=
 github.com/apache/thrift v0.13.0/go.mod h1:cp2SuWMxlEZw2r+iP2GNCdIi4C1qmUzdZFSVb+bacwQ=
@@ -120,6 +123,7 @@ github.com/francoispqt/gojay v1.2.13/go.mod h1:ehT5mTG4ua4581f1++1WLG0vPdaA9HaiD
 github.com/franela/goblin v0.0.0-20200105215937-c9ffbefa60db/go.mod h1:7dvUGVsVBjqR7JHJk0brhHOZYGmfBYOrK0ZhYMEtBr4=
 github.com/franela/goreq v0.0.0-20171204163338-bcd34c9993f8/go.mod h1:ZhphrRTfi2rbfLwlschooIH4+wKKDR4Pdxhh+TRoA20=
 github.com/frankban/quicktest v1.11.3/go.mod h1:wRf/ReqHper53s+kmmSZizM8NamnL3IM0I9ntUbOk+k=
+github.com/frankban/quicktest v1.14.0/go.mod h1:NeW+ay9A/U67EYXNFA1nPE8e/tnQv/09mUdL/ijj8og=
 github.com/frankban/quicktest v1.14.2 h1:SPb1KFFmM+ybpEjPUhCCkZOM5xlovT5UbrMvWnXyBns=
 github.com/frankban/quicktest v1.14.2/go.mod h1:mgiwOwqx65TmIk1wJ6Q7wvnVMocbUorkibMOrVTHZps=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
@@ -181,6 +185,7 @@ github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/google/go-cmp v0.5.3/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.4/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.6/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.7 h1:81/ik6ipDQS2aGcBfIN5dHDB36BwrStyeAQquSYCV4o=
 github.com/google/go-cmp v0.5.7/go.mod h1:n+brtR0CgQNWTVd5ZUFpTBC8YFBDLK/h/bpaJ8/DtOE=
 github.com/google/go-github v17.0.0+incompatible/go.mod h1:zLgOLi98H3fifZn+44m+umXrS52loVEgC2AApnigrVQ=
@@ -246,11 +251,15 @@ github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANyt
 github.com/influxdata/influxdb1-client v0.0.0-20191209144304-8bf82d3c094d/go.mod h1:qj24IKcXYK6Iy9ceXlo3Tc+vtHo9lIhSX5JddghvEPo=
 github.com/ipfs/bbloom v0.0.4 h1:Gi+8EGJ2y5qiD5FbsbpX/TMNcJw8gSqr7eyjHa4Fhvs=
 github.com/ipfs/bbloom v0.0.4/go.mod h1:cS9YprKXpoZ9lT0n/Mw/a6/aFV6DTjTLYHeA+gyqMG0=
+github.com/ipfs/go-bitfield v1.0.0 h1:y/XHm2GEmD9wKngheWNNCNL0pzrWXZwCdQGv1ikXknQ=
+github.com/ipfs/go-bitfield v1.0.0/go.mod h1:N/UiujQy+K+ceU1EF5EkVd1TNqevLrCQMIcAEPrdtus=
+github.com/ipfs/go-bitswap v0.5.1/go.mod h1:P+ckC87ri1xFLvk74NlXdP0Kj9RmWAh4+H78sC6Qopo=
 github.com/ipfs/go-bitswap v0.6.0 h1:f2rc6GZtoSFhEIzQmddgGiel9xntj02Dg0ZNf2hSC+w=
 github.com/ipfs/go-bitswap v0.6.0/go.mod h1:Hj3ZXdOC5wBJvENtdqsixmzzRukqd8EHLxZLZc3mzRA=
 github.com/ipfs/go-block-format v0.0.2/go.mod h1:AWR46JfpcObNfg3ok2JHDUfdiHRgWhJgCQF+KIgOPJY=
 github.com/ipfs/go-block-format v0.0.3 h1:r8t66QstRp/pd/or4dpnbVfXT5Gt7lOqRvC+/dDTpMc=
 github.com/ipfs/go-block-format v0.0.3/go.mod h1:4LmD4ZUw0mhO+JSKdpWwrzATiEfM7WWgQ8H5l6P8MVk=
+github.com/ipfs/go-blockservice v0.2.1/go.mod h1:k6SiwmgyYgs4M/qt+ww6amPeUH9EISLRBnvUurKJhi8=
 github.com/ipfs/go-blockservice v0.3.0 h1:cDgcZ+0P0Ih3sl8+qjFr2sVaMdysg/YZpLj5WJ8kiiw=
 github.com/ipfs/go-blockservice v0.3.0/go.mod h1:P5ppi8IHDC7O+pA0AlGTF09jruB2h+oP3wVVaZl8sfk=
 github.com/ipfs/go-cid v0.0.1/go.mod h1:GHWU/WuQdMPmIosc4Yn1bcCT7dSeX4lBafM7iqUPQvM=
@@ -279,11 +288,14 @@ github.com/ipfs/go-ds-badger v0.2.3/go.mod h1:pEYw0rgg3FIrywKKnL+Snr+w/LjJZVMTBR
 github.com/ipfs/go-ds-leveldb v0.0.1/go.mod h1:feO8V3kubwsEF22n0YRQCffeb79OOYIykR4L04tMOYc=
 github.com/ipfs/go-ds-leveldb v0.4.1/go.mod h1:jpbku/YqBSsBc1qgME8BkWS4AxzF2cEu1Ii2r79Hh9s=
 github.com/ipfs/go-ds-leveldb v0.4.2/go.mod h1:jpbku/YqBSsBc1qgME8BkWS4AxzF2cEu1Ii2r79Hh9s=
+github.com/ipfs/go-ipfs-blockstore v0.2.1/go.mod h1:jGesd8EtCM3/zPgx+qr0/feTXGUeRai6adgwC+Q+JvE=
 github.com/ipfs/go-ipfs-blockstore v1.1.2/go.mod h1:w51tNR9y5+QXB0wkNcHt4O2aSZjTdqaEWaQdSxEyUOY=
 github.com/ipfs/go-ipfs-blockstore v1.2.0 h1:n3WTeJ4LdICWs/0VSfjHrlqpPpl6MZ+ySd3j8qz0ykw=
 github.com/ipfs/go-ipfs-blockstore v1.2.0/go.mod h1:eh8eTFLiINYNSNawfZOC7HOxNTxpB1PFuA5E1m/7exE=
 github.com/ipfs/go-ipfs-blocksutil v0.0.1 h1:Eh/H4pc1hsvhzsQoMEP3Bke/aW5P5rVM1IWFJMcGIPQ=
 github.com/ipfs/go-ipfs-blocksutil v0.0.1/go.mod h1:Yq4M86uIOmxmGPUHv/uI7uKqZNtLb449gwKqXjIsnRk=
+github.com/ipfs/go-ipfs-chunker v0.0.1 h1:cHUUxKFQ99pozdahi+uSC/3Y6HeRpi9oTeUHbE27SEw=
+github.com/ipfs/go-ipfs-chunker v0.0.1/go.mod h1:tWewYK0we3+rMbOh7pPFGDyypCtvGcBFymgY4rSDLAw=
 github.com/ipfs/go-ipfs-delay v0.0.0-20181109222059-70721b86a9a8/go.mod h1:8SP1YXK1M1kXuc4KJZINY3TQQ03J2rwBG9QfXmbRPrw=
 github.com/ipfs/go-ipfs-delay v0.0.1 h1:r/UXYyRcddO6thwOnhiznIAiSvxMECGgtv35Xs1IeRQ=
 github.com/ipfs/go-ipfs-delay v0.0.1/go.mod h1:8SP1YXK1M1kXuc4KJZINY3TQQ03J2rwBG9QfXmbRPrw=
@@ -292,8 +304,11 @@ github.com/ipfs/go-ipfs-ds-help v1.1.0 h1:yLE2w9RAsl31LtfMt91tRZcrx+e61O5mDxFRR9
 github.com/ipfs/go-ipfs-ds-help v1.1.0/go.mod h1:YR5+6EaebOhfcqVCyqemItCLthrpVNot+rsOU/5IatU=
 github.com/ipfs/go-ipfs-exchange-interface v0.1.0 h1:TiMekCrOGQuWYtZO3mf4YJXDIdNgnKWZ9IE3fGlnWfo=
 github.com/ipfs/go-ipfs-exchange-interface v0.1.0/go.mod h1:ych7WPlyHqFvCi/uQI48zLZuAWVP5iTQPXEfVaw5WEI=
+github.com/ipfs/go-ipfs-exchange-offline v0.1.1/go.mod h1:vTiBRIbzSwDD0OWm+i3xeT0mO7jG2cbJYatp3HPk5XY=
 github.com/ipfs/go-ipfs-exchange-offline v0.2.0 h1:2PF4o4A7W656rC0RxuhUace997FTcDTcIQ6NoEtyjAI=
 github.com/ipfs/go-ipfs-exchange-offline v0.2.0/go.mod h1:HjwBeW0dvZvfOMwDP0TSKXIHf2s+ksdP4E3MLDRtLKY=
+github.com/ipfs/go-ipfs-files v0.0.3/go.mod h1:INEFm0LL2LWXBhNJ2PMIIb2w45hpXgPjNoE7yA8Y1d4=
+github.com/ipfs/go-ipfs-posinfo v0.0.1/go.mod h1:SwyeVP+jCwiDu0C313l/8jg6ZxM0qqtlt2a0vILTc1A=
 github.com/ipfs/go-ipfs-pq v0.0.2 h1:e1vOOW6MuOwG2lqxcLA+wEn93i/9laCY8sXAw76jFOY=
 github.com/ipfs/go-ipfs-pq v0.0.2/go.mod h1:LWIqQpqfRG3fNc5XsnIhz/wQ2XXGyugQwls7BgUmUfY=
 github.com/ipfs/go-ipfs-routing v0.2.1 h1:E+whHWhJkdN9YeoHZNj5itzc+OR292AJ2uE9FFiW0BY=
@@ -322,19 +337,26 @@ github.com/ipfs/go-log/v2 v2.1.1/go.mod h1:2v2nsGfZsvvAJz13SyFzf9ObaqwHiHxsPLEHn
 github.com/ipfs/go-log/v2 v2.1.3/go.mod h1:/8d0SH3Su5Ooc31QlL1WysJhvyOTDCjcCZ9Axpmri6g=
 github.com/ipfs/go-log/v2 v2.3.0 h1:31Re/cPqFHpsRHgyVwjWADPoF0otB1WrjTy8ZFYwEZU=
 github.com/ipfs/go-log/v2 v2.3.0/go.mod h1:QqGoj30OTpnKaG/LKTGTxoP2mmQtjVMEnK72gynbe/g=
+github.com/ipfs/go-merkledag v0.5.1/go.mod h1:cLMZXx8J08idkp5+id62iVftUQV+HlYJ3PIhDfZsjA4=
 github.com/ipfs/go-merkledag v0.6.0 h1:oV5WT2321tS4YQVOPgIrWHvJ0lJobRTerU+i9nmUCuA=
 github.com/ipfs/go-merkledag v0.6.0/go.mod h1:9HSEwRd5sV+lbykiYP+2NC/3o6MZbKNaa4hfNcH5iH0=
 github.com/ipfs/go-metrics-interface v0.0.1 h1:j+cpbjYvu4R8zbleSs36gvB7jR+wsL2fGD6n0jO4kdg=
 github.com/ipfs/go-metrics-interface v0.0.1/go.mod h1:6s6euYU4zowdslK0GKHmqaIZ3j/b/tL7HTWtJ4VPgWY=
 github.com/ipfs/go-peertaskqueue v0.7.0 h1:VyO6G4sbzX80K58N60cCaHsSsypbUNs1GjO5seGNsQ0=
 github.com/ipfs/go-peertaskqueue v0.7.0/go.mod h1:M/akTIE/z1jGNXMU7kFB4TeSEFvj68ow0Rrb04donIU=
+github.com/ipfs/go-unixfs v0.3.1 h1:LrfED0OGfG98ZEegO4/xiprx2O+yS+krCMQSp7zLVv8=
+github.com/ipfs/go-unixfs v0.3.1/go.mod h1:h4qfQYzghiIc8ZNFKiLMFWOTzrWIAtzYQ59W/pCFf1o=
+github.com/ipfs/go-unixfsnode v1.4.0 h1:9BUxHBXrbNi8mWHc6j+5C580WJqtVw9uoeEKn4tMhwA=
+github.com/ipfs/go-unixfsnode v1.4.0/go.mod h1:qc7YFFZ8tABc58p62HnIYbUMwj9chhUuFWmxSokfePo=
 github.com/ipfs/go-verifcid v0.0.1 h1:m2HI7zIuR5TFyQ1b79Da5N9dnnCP1vcu2QqawmWlK2E=
 github.com/ipfs/go-verifcid v0.0.1/go.mod h1:5Hrva5KBeIog4A+UpqlaIU+DEstipcJYQQZc0g37pY0=
+github.com/ipld/go-car/v2 v2.1.1/go.mod h1:+2Yvf0Z3wzkv7NeI69i8tuZ+ft7jyjPYIWZzeVNeFcI=
 github.com/ipld/go-codec-dagpb v1.3.0/go.mod h1:ga4JTU3abYApDC3pZ00BC2RSvC3qfBb9MSJkMLSwnhA=
 github.com/ipld/go-codec-dagpb v1.3.1 h1:yVNlWRQexCa54ln3MSIiUN++ItH7pdhBFhh0hSgZu1w=
 github.com/ipld/go-codec-dagpb v1.3.1/go.mod h1:ErNNglIi5KMur/MfFE/svtgQthzVvf+43MrzLbpcIZY=
 github.com/ipld/go-ipld-prime v0.9.1-0.20210324083106-dc342a9917db/go.mod h1:KvBLMr4PX1gWptgkzRjVZCrLmSGcZCb/jioOQwCqZN8=
 github.com/ipld/go-ipld-prime v0.11.0/go.mod h1:+WIAkokurHmZ/KwzDOMUuoeJgaRQktHtEaLglS3ZeV8=
+github.com/ipld/go-ipld-prime v0.14.0/go.mod h1:9ASQLwUFLptCov6lIYc70GRB4V7UTyLD0IJtrDJe6ZM=
 github.com/ipld/go-ipld-prime v0.16.0 h1:RS5hhjB/mcpeEPJvfyj0qbOj/QL+/j05heZ0qa97dVo=
 github.com/ipld/go-ipld-prime v0.16.0/go.mod h1:axSCuOCBPqrH+gvXr2w9uAOulJqBPhHPT2PjoiiU1qA=
 github.com/ipld/go-ipld-prime/storage/bsadapter v0.0.0-20211210234204-ce2a1c70cd73 h1:TsyATB2ZRRQGTwafJdgEUQkmjOExRV0DNokcihZxbnQ=
@@ -659,8 +681,10 @@ github.com/multiformats/go-multibase v0.0.1/go.mod h1:bja2MqRZ3ggyXtZSEDKpl0uO/g
 github.com/multiformats/go-multibase v0.0.3 h1:l/B6bJDQjvQ5G52jw4QGSYeOTZoAwIO77RblWplfIqk=
 github.com/multiformats/go-multibase v0.0.3/go.mod h1:5+1R4eQrT3PkYZ24C3W2Ue2tPwIdYQD509ZjSb5y9Oc=
 github.com/multiformats/go-multicodec v0.3.0/go.mod h1:qGGaQmioCDh+TeFOnxrbU0DaIPw8yFgAZgFG0V7p1qQ=
-github.com/multiformats/go-multicodec v0.3.1-0.20210902112759-1539a079fd61 h1:ZrUuMKNgJ52qHPoQ+bx0h0uBfcWmN7Px+4uKSZeesiI=
 github.com/multiformats/go-multicodec v0.3.1-0.20210902112759-1539a079fd61/go.mod h1:1Hj/eHRaVWSXiSNNfcEPcwZleTmdNP81xlxDLnWU9GQ=
+github.com/multiformats/go-multicodec v0.3.1-0.20211210143421-a526f306ed2c/go.mod h1:1Hj/eHRaVWSXiSNNfcEPcwZleTmdNP81xlxDLnWU9GQ=
+github.com/multiformats/go-multicodec v0.5.0 h1:EgU6cBe/D7WRwQb1KmnBvU7lrcFGMggZVTPtOW9dDHs=
+github.com/multiformats/go-multicodec v0.5.0/go.mod h1:DiY2HFaEp5EhEXb/iYzVAunmyX/aSFMxq2KMKfWEues=
 github.com/multiformats/go-multihash v0.0.1/go.mod h1:w/5tugSrLEbWqlcgJabL3oHFKTwfvkofsjW2Qa1ct4U=
 github.com/multiformats/go-multihash v0.0.5/go.mod h1:lt/HCbqlQwlPBz7lv0sQCdtfcMtlJvakRUn/0Ual8po=
 github.com/multiformats/go-multihash v0.0.8/go.mod h1:YSLudS+Pi8NHE7o6tb3D8vrpKa63epEDmG8nTduyAew=
@@ -860,6 +884,8 @@ github.com/whyrusleeping/cbor v0.0.0-20171005072247-63513f603b11 h1:5HZfQkwe0mIf
 github.com/whyrusleeping/cbor v0.0.0-20171005072247-63513f603b11/go.mod h1:Wlo/SzPmxVp6vXpGt/zaXhHH0fn4IxgqZc82aKg6bpQ=
 github.com/whyrusleeping/cbor-gen v0.0.0-20200123233031-1cdf64d27158 h1:WXhVOwj2USAXB5oMDwRl3piOux2XMV9TANaYxXHdkoE=
 github.com/whyrusleeping/cbor-gen v0.0.0-20200123233031-1cdf64d27158/go.mod h1:Xj/M2wWU+QdTdRbu/L/1dIZY8/Wb2K9pAhtroQuxJJI=
+github.com/whyrusleeping/chunker v0.0.0-20181014151217-fe64bd25879f h1:jQa4QT2UP9WYv2nzyawpKMOCl+Z/jW7djv2/J50lj9E=
+github.com/whyrusleeping/chunker v0.0.0-20181014151217-fe64bd25879f/go.mod h1:p9UJB6dDgdPgMJZs7UjUOdulKyRr9fqkS+6JKAInPy8=
 github.com/whyrusleeping/go-keyspace v0.0.0-20160322163242-5b898ac5add1/go.mod h1:8UvriyWtv5Q5EOgjHaSseUEdkQfvwFv1I/In/O2M9gc=
 github.com/whyrusleeping/go-logging v0.0.0-20170515211332-0457bb6b88fc/go.mod h1:bopw91TMyo8J3tvftk8xmU2kPmlrt4nScJQZU2hE5EM=
 github.com/whyrusleeping/go-logging v0.0.1/go.mod h1:lDPYj54zutzG1XYfHAhcc7oNXEburHQBn+Iqd4yS4vE=
@@ -1009,6 +1035,7 @@ golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20200317015054-43a5402ce75a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -1024,6 +1051,7 @@ golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/sys v0.0.0-20190219092855-153ac476189d/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190228124157-a34e9553db1e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190302025703-b6889370fb10/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190316082340-a2f829d7f35f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190405154228-4b34438f7a67/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

v2/internal/loader/writing_loader.go

@@ -16,7 +16,7 @@ type writerOutput struct {
 	w     io.Writer
 	size  uint64
 	code  multicodec.Code
-	rcrds []index.Record
+	rcrds map[cid.Cid]index.Record
 }
 
 func (w *writerOutput) Size() uint64 {
@@ -28,7 +28,11 @@ func (w *writerOutput) Index() (index.Index, error) {
 	if err != nil {
 		return nil, err
 	}
-	if err := idx.Load(w.rcrds); err != nil {
+	rcrds := make([]index.Record, 0, len(w.rcrds))
+	for _, r := range w.rcrds {
+		rcrds = append(rcrds, r)
+	}
+	if err := idx.Load(rcrds); err != nil {
 		return nil, err
 	}
 
@@ -63,17 +67,13 @@ func (w *writingReader) Read(p []byte) (int, error) {
 		if _, err := cpy.WriteTo(w.wo.w); err != nil {
 			return 0, err
 		}
-
-		// maybe write the index.
-		if w.wo.code != index.CarIndexNone {
-			_, c, err := cid.CidFromBytes([]byte(w.cid))
-			if err != nil {
-				return 0, err
-			}
-			w.wo.rcrds = append(w.wo.rcrds, index.Record{
-				Cid:    c,
-				Offset: w.wo.size,
-			})
+		_, c, err := cid.CidFromBytes([]byte(w.cid))
+		if err != nil {
+			return 0, err
+		}
+		w.wo.rcrds[c] = index.Record{
+			Cid:    c,
+			Offset: w.wo.size,
 		}
 		w.wo.size += uint64(w.len) + uint64(len(size)+len(w.cid))
 
@@ -94,11 +94,21 @@ func TeeingLinkSystem(ls ipld.LinkSystem, w io.Writer, initialOffset uint64, ind
 		w:     w,
 		size:  initialOffset,
 		code:  indexCodec,
-		rcrds: make([]index.Record, 0),
+		rcrds: make(map[cid.Cid]index.Record),
 	}
 
 	tls := ls
 	tls.StorageReadOpener = func(lc linking.LinkContext, l ipld.Link) (io.Reader, error) {
+		_, c, err := cid.CidFromBytes([]byte(l.Binary()))
+		if err != nil {
+			return nil, err
+		}
+
+		// if we've already read this cid in this session, don't re-write it.
+		if _, ok := wo.rcrds[c]; ok {
+			return ls.StorageReadOpener(lc, l)
+		}
+
 		r, err := ls.StorageReadOpener(lc, l)
 		if err != nil {
 			return nil, err

v2/options.go

@@ -4,6 +4,7 @@ import (
 	"math"
 
 	"github.com/ipld/go-car/v2/index"
+	"github.com/ipld/go-ipld-prime/traversal"
 	"github.com/multiformats/go-multicodec"
 )
 
@@ -40,6 +41,7 @@ type Options struct {
 	BlockstoreUseWholeCIDs       bool
 	MaxTraversalLinks            uint64
 	WriteAsCarV1                 bool
+	TraversalPrototypeChooser    traversal.LinkTargetNodePrototypeChooser
 }
 
 // ApplyOptions applies given opts and returns the resulting Options.
@@ -118,3 +120,11 @@ func MaxIndexCidSize(s uint64) Option {
 		o.MaxIndexCidSize = s
 	}
 }
+
+// WithTraversalPrototypeChooser specifies the prototype chooser that should be used
+// when performing traversals in writes from a linksystem.
+func WithTraversalPrototypeChooser(t traversal.LinkTargetNodePrototypeChooser) Option {
+	return func(o *Options) {
+		o.TraversalPrototypeChooser = t
+	}
+}