fix: support count as well as length

fixes #21

Some userland applications switch between go and js implementations
at will.  Go prefers `offset`/`count`, the interface spec says it
should be `offset`/`length`. Bend like a reed in the wind and
support both.

License: MIT
Signed-off-by: achingbrain <[email protected]>

src/core/read-pull-stream.js

@@ -22,6 +22,9 @@ module.exports = (context) => {
   return function mfsReadPullStream (path, options = {}) {
     options = Object.assign({}, defaultOptions, options)
 
+    // support legacy go arguments
+    options.length = options.length || options.count
+
     log(`Reading ${path}`)
 
     const deferred = defer.source()

src/http/read.js

@@ -17,12 +17,14 @@ const mfsRead = (api) => {
         const {
           arg,
           offset,
-          length
+          length,
+          count
         } = request.query
 
         const stream = ipfs.files.readReadableStream(arg, {
           offset,
-          length
+          length,
+          count
         })
 
         if (!stream._read) {

test/read.spec.js

@@ -128,6 +128,25 @@ describe('read', function () {
           .then((buffer) => expect(buffer).to.deep.equal(data.slice(0, length)))
       })
 
+      it('reads a file with a legacy count argument', () => {
+        const path = `/some-file-${Math.random()}.txt`
+        let data = Buffer.alloc(0)
+        const length = 10
+
+        return mfs.write(path, bufferStream(100, {
+          collector: (bytes) => {
+            data = Buffer.concat([data, bytes])
+          }
+        }), {
+          create: true
+        })
+          .then(() => method.read(path, {
+            count: length
+          }))
+          .then((result) => method.collect(result))
+          .then((buffer) => expect(buffer).to.deep.equal(data.slice(0, length)))
+      })
+
       it('reads a file with an offset and a length', () => {
         const path = `/some-file-${Math.random()}.txt`
         let data = Buffer.alloc(0)
@@ -149,6 +168,27 @@ describe('read', function () {
           .then((buffer) => expect(buffer).to.deep.equal(data.slice(offset, offset + length)))
       })
 
+      it('reads a file with an offset and a legacy count argument', () => {
+        const path = `/some-file-${Math.random()}.txt`
+        let data = Buffer.alloc(0)
+        const offset = 10
+        const length = 10
+
+        return mfs.write(path, bufferStream(100, {
+          collector: (bytes) => {
+            data = Buffer.concat([data, bytes])
+          }
+        }), {
+          create: true
+        })
+          .then(() => method.read(path, {
+            offset,
+            count: length
+          }))
+          .then((result) => method.collect(result))
+          .then((buffer) => expect(buffer).to.deep.equal(data.slice(offset, offset + length)))
+      })
+
       it('refuses to read a directory', () => {
         const path = '/'