Do not truncate chunks that are not 100% written

index.js

@@ -5,6 +5,8 @@ const EventEmitter = require('events')
 const flatstr = require('flatstr')
 const inherits = require('util').inherits
 
+const maxWriteSize = 4096
+
 function openFile (file, sonic) {
   sonic._writing = true
   sonic.file = file
@@ -65,6 +67,13 @@ function SonicBoom (fd, minLength) {
       this.emit('error', err)
       return
     }
+
+    if (this._writingBuf.length !== n) {
+      this._writingBuf = this._writingBuf.slice(n)
+      fs.write(this.fd, this._writingBuf, 'utf8', this.release)
+      return
+    }
+
     this._writingBuf = ''
 
     if (this.destroyed) {
@@ -193,9 +202,9 @@ SonicBoom.prototype.destroy = function () {
 function actualWrite (sonic) {
   sonic._writing = true
   var buf = sonic._buf
-  if (buf.length >= 2048) {
-    buf = sonic._buf.slice(0, 2048)
-    sonic._buf = sonic._buf.slice(2048)
+  if (buf.length >= maxWriteSize) {
+    buf = sonic._buf.slice(0, maxWriteSize)
+    sonic._buf = sonic._buf.slice(maxWriteSize)
   } else {
     sonic._buf = ''
   }

test.js

@@ -433,3 +433,40 @@ test('chunk data accordingly', (t) => {
     t.is(code, 0)
   })
 })
+
+test('write buffers that are not totally written', (t) => {
+  t.plan(7)
+
+  const fakeFs = Object.create(fs)
+  fakeFs.write = function (fd, buf, enc, cb) {
+    t.pass('fake fs.write called')
+    fakeFs.write = fs.write
+    process.nextTick(cb, null, 0)
+  }
+  const SonicBoom = proxyquire('.', {
+    fs: fakeFs
+  })
+
+  const dest = file()
+  const fd = fs.openSync(dest, 'w')
+  const stream = new SonicBoom(fd)
+
+  stream.on('ready', () => {
+    t.pass('ready emitted')
+  })
+
+  t.ok(stream.write('hello world\n'))
+  t.ok(stream.write('something else\n'))
+
+  stream.end()
+
+  stream.on('finish', () => {
+    fs.readFile(dest, 'utf8', (err, data) => {
+      t.error(err)
+      t.equal(data, 'hello world\nsomething else\n')
+    })
+  })
+  stream.on('close', () => {
+    t.pass('close emitted')
+  })
+})