3 files changed, 43 insertions, 8 deletions

diff --git a/lib/app.js b/lib/app.js
index 1daf064..8ef859f 100644
--- a/lib/app.js
+++ b/lib/app.js
@@ -177,10 +177,7 @@ App.prototype.addBlob = function (cb) {
   done(function (err, hash, add) {
     cb(err, hash)
   })
-  return pull(
-    hasher(hashCb),
-    this.sbot.blobs.add(addCb)
-  )
+  return sink
 }
 
 App.prototype.pushBlob = function (id, cb) {
@@ -188,15 +185,25 @@ App.prototype.pushBlob = function (id, cb) {
   this.sbot.blobs.push(id, cb)
 }
 
-App.prototype.readBlob = function (link, opts) {
+App.prototype.readBlob = function (link) {
   link = u.toLink(link)
-  opts = opts || {}
   return this.sbot.blobs.get({
     hash: link.link,
     size: link.size,
+  })
+}
+
+App.prototype.readBlobSlice = function (link, opts) {
+  if (this.sbot.blobs.getSlice) return this.sbot.blobs.getSlice({
+    hash: link.link,
+    size: link.size,
     start: opts.start,
     end: opts.end,
   })
+  return pull(
+    this.readBlob(link),
+    u.pullSlice(opts.start, opts.end)
+  )
 }
 
 App.prototype.ensureHasBlobs = function (links, cb) {
diff --git a/lib/git.js b/lib/git.js
index 07061e2..1360a6f 100644
--- a/lib/git.js
+++ b/lib/git.js
@@ -82,7 +82,7 @@ Git.prototype.openObject = function (opts, cb) {
 
 Git.prototype.readObject = function (obj) {
   return pull(
-    this.app.readBlob(obj.packLink, {start: obj.offset, end: obj.next}),
+    this.app.readBlobSlice(obj.packLink, {start: obj.offset, end: obj.next}),
     this.decodeObject({
       type: obj.type,
       length: obj.length,
@@ -310,7 +310,7 @@ Git.prototype.decodeObject = function (opts) {
             if (!offset) return cb(null, 'missing source object ' +
               sourcehash.toString('hex'))
             var readSource = pull(
-              self.app.readBlob(opts.packLink, {
+              self.app.readBlobSlice(opts.packLink, {
                 start: offset.offset,
                 end: offset.next
               }),
diff --git a/lib/util.js b/lib/util.js
index e8fc435..d25ecaf 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -141,3 +141,31 @@ u.escapeHTML = function (html) {
     .replace(/</g, '&lt;')
     .replace(/>/g, '&gt;')
 }
+
+u.pullSlice = function (start, end) {
+  if (end == null) end = Infinity
+  var offset = 0
+  return function (read) {
+    return function (abort, cb) {
+      if (abort) read(abort, cb)
+      else if (offset >= end) read(true, function (err) {
+        cb(err || true)
+      })
+      else if (offset < start) read(null, function next(err, data) {
+        if (err) return cb(err)
+        offset += data.length
+        if (offset <= start) read(null, next)
+        else if (offset < end) cb(null,
+          data.slice(data.length - (offset - start)))
+        else cb(null, data.slice(data.length - (offset - start),
+          data.length - (offset - end)))
+      })
+      else read(null, function (err, data) {
+        if (err) return cb(err)
+        offset += data.length
+        if (offset <= end) cb(null, data)
+          else cb(null, data.slice(0, data.length - (offset - end)))
+      })
+    }
+  }
+}