From 6df19713e2d5d6beaa48dba84dc5eb0dde97cd41 Mon Sep 17 00:00:00 2001
From: Erik Elmore <erik@elmore.io>
Date: Wed, 12 Dec 2018 02:21:38 +0000
Subject: [PATCH] Add skipOverflow option

Also addresses surprising maxLength behavior described in mcollina/split2#23
---
 README.md |  6 ++++--
 index.js  | 21 ++++++++++++++++-----
 test.js   | 29 +++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index acb72a5..b87c796 100644
--- a/README.md
+++ b/README.md
@@ -28,8 +28,10 @@ is directly passed as a
 [Transform](https://nodejs.org/api/stream.html#stream_new_stream_transform_options)
 option.
 
-Additionally, the `.maxLength` option is implemented, which will make the split stream throw an error
-if the buffer size exceeds `.maxLength`.
+Additionally, the `.maxLength` and `.skipOverflow` options are implemented, which set limits on the internal
+buffer size and the stream's behavior when the limit is exceeded. There is no limit unless `maxLength` is set. When
+the internal buffer size exceeds `maxLength`, the stream emits an error by default. You may also set `skipOverflow` to
+true to suppress the error and instead skip past any lines that cause the internal buffer to exceed `maxLength`.
 
 Calling `.destroy` will make the stream emit `close`. Use this to perform cleanup logic
 
diff --git a/index.js b/index.js
index 57d76a4..2bb86cc 100644
--- a/index.js
+++ b/index.js
@@ -22,12 +22,19 @@ const kLast = Symbol('last')
 const kDecoder = Symbol('decoder')
 
 function transform (chunk, enc, cb) {
-  this[kLast] += this[kDecoder].write(chunk)
-  if (this[kLast].length > this.maxLength) {
-    return cb(new Error('maximum buffer reached'))
+  var list;
+  if (this.overflow) {
+    var buf = this[kDecoder].write(chunk)
+    list = buf.split(this.matcher)
+    if (list.length === 1) return cb()
+
+    list.shift()
+    this.overflow = false;
+  }
+  else {
+    this[kLast] += this[kDecoder].write(chunk)
+    list = this[kLast].split(this.matcher)
   }
-
-  var list = this[kLast].split(this.matcher)
 
   this[kLast] = list.pop()
 
@@ -35,6 +42,9 @@ function transform (chunk, enc, cb) {
     push(this, this.mapper(list[i]))
   }
 
+  this.overflow = this[kLast].length > this.maxLength
+  if (this.overflow && !this.skipOverflow) return cb(new Error('maximum buffer reached'))
+
   cb()
 }
 
@@ -103,6 +113,7 @@ function split (matcher, mapper, options) {
   stream.matcher = matcher
   stream.mapper = mapper
   stream.maxLength = options.maxLength
+  stream.skipOverflow = options.skipOverflow
 
   return stream
 }
diff --git a/test.js b/test.js
index 9715dfd..219d67f 100644
--- a/test.js
+++ b/test.js
@@ -302,3 +302,32 @@ test('readable highWaterMark', function (t) {
   t.equal(input._readableState.highWaterMark, 16)
   t.end()
 })
+
+test('maxLength < chunk size', function (t) {
+  t.plan(2)
+
+  var input = split({ maxLength: 2 })
+
+  input.pipe(strcb(function (err, list) {
+    t.error(err)
+    t.deepEqual(list, ['a', 'b'])
+  }))
+
+  input.end('a\nb')
+})
+
+test('maximum buffer limit w/skip', function (t) {
+  t.plan(2)
+
+  var input = split({ maxLength: 2, skipOverflow: true })
+
+  input.pipe(strcb(function (err, list) {
+    t.error(err)
+    t.deepEqual(list, ['a', 'b', 'c'])
+  }))
+
+  input.write('a\n123')
+  input.write('456')
+  input.write('789\nb\nc')
+  input.end()
+})