use readStream instead of readFile

src/parser.coffee

@@ -1,11 +1,10 @@
 {EventEmitter} = require 'events'
 Header = require './header'
 fs = require 'fs'
-iconv = require 'iconv-lite'
 
 class Parser extends EventEmitter
 
-    constructor: (@filename, @encoding = 'utf-8') ->
+    constructor: (@filename) ->
 
     parse: =>
         @emit 'start', @
@@ -16,17 +15,57 @@ class Parser extends EventEmitter
             @emit 'header', @header
 
             sequenceNumber = 0
-
-            fs.readFile @filename, (err, buffer) =>
-                throw err if err
-
-                loc = @header.start
-                while loc < (@header.start + @header.numberOfRecords * @header.recordLength) and loc < buffer.length
-                    @emit 'record', @parseRecord ++sequenceNumber, buffer.slice loc, loc += @header.recordLength
-
-                @emit 'end', @
+
+            loc = @header.start
+            bufLoc = @header.start
+            overflow = null
+            @paused = false
+
+            stream = fs.createReadStream @filename
+
+            @readBuf = =>
+
+                if @paused
+
+                    @emit 'paused'
+
+                    return
+
+                while buffer = stream.read()
+
+                    if bufLoc isnt @header.start then bufLoc = 0
+
+                    if overflow isnt null then buffer = overflow + buffer
+
+                    while loc < (@header.start + @header.numberOfRecords * @header.recordLength) && (bufLoc + @header.recordLength) <= buffer.length
+
+                        @emit 'record', @parseRecord ++sequenceNumber, buffer.slice bufLoc, bufLoc += @header.recordLength
+
+                    loc += bufLoc
+
+                    if bufLoc < buffer.length then overflow = buffer.slice bufLoc, buffer.length else overflow = null
+
+                    return @
+
+            stream.on 'readable',@readBuf
+
+            stream.on 'end', () =>
+
+                @emit 'end'
 
         return @
+
+    pause: =>
+
+        @paused = true
+
+    resume: =>
+
+        @paused = false
+
+        @emit 'resuming'
+
+        do @readBuf
 
     parseRecord: (sequenceNumber, buffer) =>
         record = {
@@ -42,10 +81,10 @@ class Parser extends EventEmitter
         return record
 
     parseField: (field, buffer) =>
-        value = (iconv.decode buffer, @encoding).trim()
+        value = (buffer.toString 'utf-8').replace /^\x20+|\x20+$/g, ''
 
         if field.type is 'N' then value = parseInt value, 10
 
         return value
 
-module.exports = Parser
+module.exports = Parser