Implement RetrieveBlockData as described by ADR 002

go.mod

@@ -24,9 +24,10 @@ require (
 	github.com/ipfs/interface-go-ipfs-core v0.4.0
 	github.com/lazyledger/lazyledger-core/p2p/ipld/plugin v0.0.0-20210219190522-0eccfb24e2aa
 	github.com/lazyledger/nmt v0.3.1
-	github.com/lazyledger/rsmt2d v0.1.1-0.20210327010029-ef1d6c54461e
+	github.com/lazyledger/rsmt2d v0.1.1-0.20210406153014-e1fd589bdb09
 	github.com/libp2p/go-buffer-pool v0.0.2
 	github.com/minio/highwayhash v1.0.1
+	github.com/multiformats/go-multihash v0.0.14
 	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
 	github.com/petermattis/goid v0.0.0-20180202154549-b0b1615b78e5 // indirect
 	github.com/pkg/errors v0.9.1
@@ -39,12 +40,11 @@ require (
 	github.com/spf13/viper v1.7.1
 	github.com/stretchr/testify v1.7.0
 	github.com/tendermint/tm-db v0.6.4
-	golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad
+	golang.org/x/crypto v0.0.0-20210322153248-0c34fe9e7dc2
 	golang.org/x/exp v0.0.0-20200331195152-e8c3332aa8e5 // indirect
-	golang.org/x/net v0.0.0-20201021035429-f5854403a974
+	golang.org/x/net v0.0.0-20210226172049-e18ecbb05110
 	google.golang.org/genproto v0.0.0-20201119123407-9b1e624d6bc4 // indirect
 	google.golang.org/grpc v1.35.0
-	gopkg.in/check.v1 v1.0.0-20200902074654-038fdea0a05b // indirect
 )
 
 replace (

go.sum

@@ -151,6 +151,7 @@ github.com/cpuguy83/go-md2man/v2 v2.0.0/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsr
 github.com/crackcomm/go-gitignore v0.0.0-20170627025303-887ab5e44cc3 h1:HVTnpeuvF6Owjd5mniCL8DEXo7uYXdQEmOP4FJbV5tg=
 github.com/crackcomm/go-gitignore v0.0.0-20170627025303-887ab5e44cc3/go.mod h1:p1d6YEZWvFzEh4KLyvBcVSnrfNDDvK2zfK/4x2v/4pE=
 github.com/creack/pty v1.1.7/go.mod h1:lj5s0c3V2DBrqTV7llrYr5NG6My20zk30Fl46Y7DoTY=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/cskr/pubsub v1.0.2 h1:vlOzMhl6PFn60gRlTQQsIfVwaPB/B/8MziK8FhEPt/0=
 github.com/cskr/pubsub v1.0.2/go.mod h1:/8MzYXk/NJAz782G8RPkFzXTZVu63VotefPnR9TIRis=
 github.com/davecgh/go-spew v0.0.0-20171005155431-ecdeabc65495/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -595,14 +596,20 @@ github.com/koron/go-ssdp v0.0.0-20191105050749-2e1c40ed0b5d/go.mod h1:5Ky9EC2xfo
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pretty v0.2.0/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
+github.com/kr/pretty v0.2.1 h1:Fmg33tUaq4/8ym9TJN1x7sLJnHVwhP33CNkpYV/7rwI=
+github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/pty v1.1.3/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/lazyledger/go-ipfs v0.8.0-lazypatch h1:8Dkw7Or6d0BmpFYFcxwgqWZ047BPGCsWtG7v9+H0ofk=
 github.com/lazyledger/go-ipfs v0.8.0-lazypatch/go.mod h1:CE4cJkjUmwW5LwJP26KKEAZ11ZED0DxzSryfv5RMf6E=
 github.com/lazyledger/go-leopard v0.0.0-20200604113236-298f93361181 h1:mUeCGuCgjZVadW4CzA2dMBq7p2BqaoCfpnKjxMmSaSE=
 github.com/lazyledger/go-leopard v0.0.0-20200604113236-298f93361181/go.mod h1:v1o1CRihQ9i7hizx23KK4aR79lxA6VDUIzUCfDva0XQ=
+github.com/lazyledger/go-leopard v0.0.0-20200724211609-50ec4b3fab41 h1:DTQODNWI71ZtqCT3wQg+RXl4K/zpu+hu5usISUhDq/E=
+github.com/lazyledger/go-leopard v0.0.0-20200724211609-50ec4b3fab41/go.mod h1:v1o1CRihQ9i7hizx23KK4aR79lxA6VDUIzUCfDva0XQ=
 github.com/lazyledger/go-verifcid v0.0.1-lazypatch h1:jAVwUw+DhuCzx5IcYpFh6d6HWxRRz8nhJ3rQo+vlFAc=
 github.com/lazyledger/go-verifcid v0.0.1-lazypatch/go.mod h1:kXPYu0XqTNUKWA1h3M95UHjUqBzDwXVVt/RXZDjKJmQ=
 github.com/lazyledger/merkletree v0.0.0-20201214195110-6901c4c3c75f h1:jbyPAH6o6hGte4RtZBaqWs2n4Fl6hS7qJGXX3qnjiy4=
@@ -611,6 +618,8 @@ github.com/lazyledger/nmt v0.3.1 h1:zP172RR33Es4dhb88GmUr9kBpAkH6Wcl7nQGJ3HQzu4=
 github.com/lazyledger/nmt v0.3.1/go.mod h1:tY7ypPX26Sbkt6F8EbPl3AT33B5N0BJe4OVPbq849YI=
 github.com/lazyledger/rsmt2d v0.1.1-0.20210327010029-ef1d6c54461e h1:3mwa4b4v9puYIFsfRN6TsXMbUagvhLtIzXWHN2GFHB4=
 github.com/lazyledger/rsmt2d v0.1.1-0.20210327010029-ef1d6c54461e/go.mod h1:ORR2U7THCNr1fpUhwYqZN7QCFJ20iR2uiIWfXKz3KJ4=
+github.com/lazyledger/rsmt2d v0.1.1-0.20210406153014-e1fd589bdb09 h1:5wpWhlalAm1vNpkR/L1BlWHyn8GT5XNieIZqTlKG9hc=
+github.com/lazyledger/rsmt2d v0.1.1-0.20210406153014-e1fd589bdb09/go.mod h1:EbB1gGbX51gBNm0hC5lMcbkgEyO3Wj2RYwba9mCUvPA=
 github.com/libp2p/go-addr-util v0.0.1/go.mod h1:4ac6O7n9rIAKB1dnd+s8IbbMXkt+oBpzX4/+RACcnlQ=
 github.com/libp2p/go-addr-util v0.0.2 h1:7cWK5cdA5x72jX0g8iLrQWm5TRJZ6CzGdPEhWj7plWU=
 github.com/libp2p/go-addr-util v0.0.2/go.mod h1:Ecd6Fb3yIuLzq4bD7VcywcVSBtefcAwnUISBM3WG15E=
@@ -1225,6 +1234,8 @@ github.com/viant/assertly v0.4.8/go.mod h1:aGifi++jvCrUaklKEKT0BU95igDNaqkvz+49u
 github.com/viant/toolbox v0.24.0/go.mod h1:OxMCG57V0PXuIP2HNQrtJf2CjqdmbrOx5EkMILuUhzM=
 github.com/vivint/infectious v0.0.0-20190108171102-2455b059135b h1:dLkqBELopfQNhe8S9ucnSf+HhiUCgK/hPIjVG0f9GlY=
 github.com/vivint/infectious v0.0.0-20190108171102-2455b059135b/go.mod h1:5oyMAv4hrBEKqBwORFsiqIrCNCmL2qcZLQTdJLYeYIc=
+github.com/vivint/infectious v0.0.0-20200605153912-25a574ae18a3 h1:zMsHhfK9+Wdl1F7sIKLyx3wrOFofpb3rWFbA4HgcK5k=
+github.com/vivint/infectious v0.0.0-20200605153912-25a574ae18a3/go.mod h1:R0Gbuw7ElaGSLOZUSwBm/GgVwMd30jWxBDdAyMOeTuc=
 github.com/warpfork/go-wish v0.0.0-20180510122957-5ad1f5abf436/go.mod h1:x6AKhvSSexNrVSrViXSHUEbICjmGXhtgABaHIySUSGw=
 github.com/warpfork/go-wish v0.0.0-20190328234359-8b3e70f8e830/go.mod h1:x6AKhvSSexNrVSrViXSHUEbICjmGXhtgABaHIySUSGw=
 github.com/warpfork/go-wish v0.0.0-20200122115046-b9ea61034e4a h1:G++j5e0OC488te356JvdhaM8YS6nMsjLAYF7JxCv07w=
@@ -1261,6 +1272,8 @@ github.com/yuin/goldmark v1.1.32/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9de
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 gitlab.com/NebulousLabs/errors v0.0.0-20171229012116-7ead97ef90b8 h1:gZfMjx7Jr6N8b7iJO4eUjDsn6xJqoyXg8D+ogdoAfKY=
 gitlab.com/NebulousLabs/errors v0.0.0-20171229012116-7ead97ef90b8/go.mod h1:ZkMZ0dpQyWwlENaeZVBiQRjhMEZvk6VTXquzl3FOFP8=
+gitlab.com/NebulousLabs/errors v0.0.0-20200929122200-06c536cf6975 h1:L/ENs/Ar1bFzUeKx6m3XjlmBgIUlykX9dzvp5k9NGxc=
+gitlab.com/NebulousLabs/errors v0.0.0-20200929122200-06c536cf6975/go.mod h1:ZkMZ0dpQyWwlENaeZVBiQRjhMEZvk6VTXquzl3FOFP8=
 gitlab.com/NebulousLabs/fastrand v0.0.0-20181126182046-603482d69e40 h1:dizWJqTWjwyD8KGcMOwgrkqu1JIkofYgKkmDeNE7oAs=
 gitlab.com/NebulousLabs/fastrand v0.0.0-20181126182046-603482d69e40/go.mod h1:rOnSnoRyxMI3fe/7KIbVcsHRGxe30OONv8dEgo+vCfA=
 go.etcd.io/bbolt v1.3.2/go.mod h1:IbVyRI1SCnLcuJnV2u8VeU0CEYM7e686BmAb1XKL+uU=
@@ -1338,6 +1351,8 @@ golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad h1:DN0cp81fZ3njFcrLCytUHRSUkqBjfTo4Tx9RJTWs0EY=
 golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad/go.mod h1:jdWPYTVW3xRLrWPugEBEK3UY2ZEsg3UU495nc5E+M+I=
+golang.org/x/crypto v0.0.0-20210322153248-0c34fe9e7dc2 h1:It14KIkyBFYkHkwZ7k45minvA9aorojkyjGk9KJ5B/w=
+golang.org/x/crypto v0.0.0-20210322153248-0c34fe9e7dc2/go.mod h1:T9bdIzuCu7OtxOm1hfPfRQxPLYneinmdGuTeoZ9dtd4=
 golang.org/x/exp v0.0.0-20180321215751-8460e604b9de/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20180807140117-3d87b88a115f/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
@@ -1414,6 +1429,8 @@ golang.org/x/net v0.0.0-20200707034311-ab3426394381/go.mod h1:/O7V0waA8r7cgGh81R
 golang.org/x/net v0.0.0-20200813134508-3edf25e44fcc/go.mod h1:/O7V0waA8r7cgGh81Ro3o1hOxt32SMVPicZroKQ2sZA=
 golang.org/x/net v0.0.0-20201021035429-f5854403a974 h1:IX6qOQeG5uLjB/hjjwjedwfjND0hgjPMMyO1RoIXQNI=
 golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwYZr8TS3Oi6o0r6Gce1SSxlDquU=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110 h1:qWPm9rbaAMKs8Bq/9LRpbMqxWRVUAQwMI9fVrssnTfw=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20181017192945-9dcd33a902f4/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20181203162652-d668ce993890/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
@@ -1489,7 +1506,11 @@ golang.org/x/sys v0.0.0-20200814200057-3d37ad5750ed/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211 h1:9UQO31fZ+0aKQOFldThf7BKPMJTiBfWycGh/u3UoO88=
 golang.org/x/sys v0.0.0-20201015000850-e3ed0017c211/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210403161142-5e06dd20ab57 h1:F5Gozwx4I1xtr/sr/8CFbb57iKi3297KFs0QDbGN60A=
+golang.org/x/sys v0.0.0-20210403161142-5e06dd20ab57/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/term v0.0.0-20201117132131-f5c789dd3221/go.mod h1:Nr5EML6q2oocZ2LXRh80K7BxOlk5/8JxuGnuhpl+muw=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -1631,6 +1652,8 @@ gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20200902074654-038fdea0a05b h1:QRR6H1YWRnHb4Y/HeNFCTJLFVxaq6wH4YuVdsUOr75U=
 gopkg.in/check.v1 v1.0.0-20200902074654-038fdea0a05b/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/cheggaaa/pb.v1 v1.0.25/go.mod h1:V/YB90LKu/1FcN3WVnfiiE5oMCibMjukxqG/qStrOgw=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=
@@ -1654,6 +1677,8 @@ gopkg.in/yaml.v2 v2.3.0 h1:clyUAQHOM3G0M3f5vQj7LuJrETvjVot3Z5el9nffUtU=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 grpc.go4.org v0.0.0-20170609214715-11d0a25b4919/go.mod h1:77eQGdRu53HpSqPFJFmuJdjuHRquDANNeA4x7B8WQ9o=
 honnef.co/go/tools v0.0.0-20180728063816-88497007e858/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

p2p/ipld/read.go

@@ -3,16 +3,215 @@ package ipld
 import (
 	"context"
 	"errors"
+	"fmt"
 	"math"
 
 	"github.com/ipfs/go-cid"
 	coreiface "github.com/ipfs/interface-go-ipfs-core"
 	"github.com/ipfs/interface-go-ipfs-core/path"
+	"github.com/lazyledger/lazyledger-core/p2p/ipld/plugin/nodes"
+	"github.com/lazyledger/lazyledger-core/types"
+	"github.com/lazyledger/rsmt2d"
 )
 
-// /////////////////////////////////////
+// //////////////////////////////////////
+//	Retrieve Block Data
+// ////////////////////////////////////
+
+const baseErrorMsg = "failure to retrieve block data:"
+
+var ErrEncounteredTooManyErrors = fmt.Errorf("%s %s", baseErrorMsg, "encountered too many errors")
+var ErrTimeout = fmt.Errorf("%s %s", baseErrorMsg, "timeout")
+
+// RetrieveBlockData asynchronously fetches block data until the underlying extended
+// data square can be restored and returned.
+func RetrieveBlockData(
+	ctx context.Context,
+	dah *types.DataAvailabilityHeader,
+	api coreiface.CoreAPI,
+	codec rsmt2d.CodecType,
+) (types.Data, error) {
+	edsWidth := uint32(len(dah.ColumnRoots))
+	originalSquareWidth := edsWidth / 2
+
+	// keep track of leaves using thread safe counter
+	sc := newshareCounter(ctx, edsWidth)
+
+	// convert the row and col roots into Cids
+	rowRoots := dah.RowsRoots.Bytes()
+	rowCids, err := rootsToCids(rowRoots)
+	if err != nil {
+		return types.Data{}, err
+	}
+
+	colRoots := dah.ColumnRoots.Bytes()
+	colCids, err := rootsToCids(colRoots)
+	if err != nil {
+		return types.Data{}, err
+	}
+
+	// async attempt to fetch each leaf
+	for axisIdx := uint32(0); axisIdx < uint32(len(rowCids)); axisIdx++ {
+		for idx := uint32(0); idx < edsWidth; idx++ {
+			go sc.retrieveShare(colCids[axisIdx], false, axisIdx, idx, api)
+			go sc.retrieveShare(rowCids[axisIdx], true, axisIdx, idx, api)
+		}
+	}
+
+	// wait until enough data has been collected, too many errors encountered,
+	// or the timeout is reached
+	err = sc.wait()
+
+	if err != nil {
+		return types.Data{}, err
+	}
+
+	// flatten the square
+	flattened := sc.flatten()
+
+	tree := NewErasuredNamespacedMerkleTree(uint64(originalSquareWidth))
+
+	// repair the square
+	eds, err := rsmt2d.RepairExtendedDataSquare(rowRoots, colRoots, flattened, codec, tree.Constructor)
+	if err != nil {
+		return types.Data{}, err
+	}
+
+	blockData, err := types.DataFromSquare(eds)
+	if err != nil {
+		return types.Data{}, err
+	}
+
+	return blockData, nil
+}
+
+type index struct {
+	row uint32
+	col uint32
+}
+
+type indexedShare struct {
+	data []byte
+	index
+}
+
+// shareCounter is a thread safe tallying mechanism for share retrieval
+type shareCounter struct {
+	// all shares
+	shares map[index][]byte
+	// number of shares successfully collected
+	counter uint32
+	// the width of the extended data square
+	edsWidth uint32
+	// the minimum shares needed to repair the extended data square
+	minSharesNeeded uint32
+
+	shareChan chan indexedShare
+	ctx       context.Context
+	cancel    context.CancelFunc
+	// any errors encountered when attempting to retrieve shares
+	errc      chan error
+	errCount  uint32
+	maxErrors uint32
+}
+
+func newshareCounter(parentCtx context.Context, edsWidth uint32) *shareCounter {
+	ctx, cancel := context.WithCancel(parentCtx)
+
+	// calculate the min number of shares needed to repair the square
+	originalSquareWidth := edsWidth / 2
+	minSharesNeeded := (edsWidth * edsWidth) - ((originalSquareWidth + 1) * (originalSquareWidth + 1))
+
+	maxErrors := edsWidth*edsWidth - minSharesNeeded
+
+	return &shareCounter{
+		shares:          make(map[index][]byte),
+		edsWidth:        edsWidth,
+		minSharesNeeded: minSharesNeeded,
+		shareChan:       make(chan indexedShare, 1),
+		errc:            make(chan error, 1),
+		maxErrors:       maxErrors,
+		ctx:             ctx,
+		cancel:          cancel,
+	}
+}
+
+// retrieveLeaf uses GetLeafData to fetch a single leaf and counts that leaf
+func (sc *shareCounter) retrieveShare(
+	rootCid cid.Cid,
+	isRow bool,
+	axisIdx uint32,
+	idx uint32,
+	api coreiface.CoreAPI,
+) {
+	data, err := GetLeafData(sc.ctx, rootCid, idx, sc.edsWidth, api)
+	if err != nil {
+		select {
+		case <-sc.ctx.Done():
+		case sc.errc <- err:
+		}
+	}
+
+	if len(data) < types.ShareSize {
+		return
+	}
+
+	// switch the row and col indexes if needed
+	rowIdx := idx
+	colIdx := axisIdx
+	if isRow {
+		rowIdx = axisIdx
+		colIdx = idx
+	}
+
+	select {
+	case <-sc.ctx.Done():
+	default:
+		sc.shareChan <- indexedShare{data: data[types.NamespaceSize:], index: index{row: rowIdx, col: colIdx}}
+	}
+}
+
+// wait until enough data has been collected, the timeout has been reached, or
+// too many errors are encountered
+func (sc *shareCounter) wait() error {
+	defer sc.cancel()
+
+	for {
+		select {
+		case <-sc.ctx.Done():
+			return ErrTimeout
+		case share := <-sc.shareChan:
+			_, has := sc.shares[share.index]
+			// add iff it does not already exists
+			if !has {
+				sc.shares[share.index] = share.data
+				sc.counter++
+				// check finishing condition
+				if sc.counter >= sc.minSharesNeeded {
+					return nil
+				}
+			}
+		case <-sc.errc:
+			sc.errCount++
+
+			if sc.errCount > sc.maxErrors {
+				return ErrEncounteredTooManyErrors
+			}
+		}
+	}
+}
+
+func (sc *shareCounter) flatten() [][]byte {
+	flattended := make([][]byte, sc.edsWidth*sc.edsWidth)
+	for index, data := range sc.shares {
+		flattended[(index.row*sc.edsWidth)+index.col] = data
+	}
+	return flattended
+}
+
+// //////////////////////////////////////
 //	Get Leaf Data
-// /////////////////////////////////////
+// ////////////////////////////////////
 
 // GetLeafData fetches and returns the data for leaf leafIndex of root rootCid.
 // It stops and returns an error if the provided context is cancelled before
@@ -94,3 +293,16 @@ func nextPowerOf2(v uint32) uint32 {
 	// return the next lowest power
 	return v / 2
 }
+
+// rootsToCids converts roots to cids
+func rootsToCids(roots [][]byte) ([]cid.Cid, error) {
+	cids := make([]cid.Cid, len(roots))
+	for i, root := range roots {
+		rootCid, err := nodes.CidFromNamespacedSha256(root)
+		if err != nil {
+			return nil, err
+		}
+		cids[i] = rootCid
+	}
+	return cids, nil
+}