refactor(read): open the content file directly

lib/content/read.js

@@ -5,32 +5,21 @@ const Promise = require('bluebird')
 const checksumStream = require('checksum-stream')
 const contentPath = require('./path')
 const fs = require('graceful-fs')
-const pipe = require('mississippi').pipe
+const pipeline = require('mississippi').pipeline
 
 Promise.promisifyAll(fs)
 
 module.exports.readStream = readStream
 function readStream (cache, address, opts) {
   opts = opts || {}
-  const stream = checksumStream({
-    digest: address,
-    algorithm: opts.hashAlgorithm || 'sha512'
-  })
   const cpath = contentPath(cache, address, opts.hashAlgorithm || 'sha512')
-  hasContent(cache, address, opts.hashAlgorithm).then(exists => {
-    if (!exists) {
-      const err = new Error('content not found')
-      err.code = 'ENOENT'
-      err.cache = cache
-      err.digest = address
-      return stream.emit('error', err)
-    } else {
-      pipe(fs.createReadStream(cpath), stream)
-    }
-  }).catch(err => {
-    stream.emit('error', err)
-  })
-  return stream
+  return pipeline(
+    fs.createReadStream(cpath), checksumStream({
+      digest: address,
+      algorithm: opts.hashAlgorithm || 'sha512',
+      size: opts.size
+    })
+  )
 }
 
 module.exports.hasContent = hasContent