From d6b72e4514f6829a6d5a2efd636a5c486353a3a4 Mon Sep 17 00:00:00 2001
From: Andreas Lind <andreas@one.com>
Date: Mon, 22 Sep 2014 12:59:26 +0200
Subject: [PATCH] Don't childProcess.spawn until the first .write call.

---
 lib/PngQuant.js | 88 +++++++++++++++++++++++++++++--------------------
 1 file changed, 53 insertions(+), 35 deletions(-)

diff --git a/lib/PngQuant.js b/lib/PngQuant.js
index 8ef0fb2..bce6850 100644
--- a/lib/PngQuant.js
+++ b/lib/PngQuant.js
@@ -12,46 +12,17 @@ var binPath = pngQuantBin ? pngQuantBin.path : 'pngquant';
 function PngQuant(pngQuantArgs) {
     Stream.call(this);
 
-    if (!pngQuantArgs || pngQuantArgs.length === 0) {
-        pngQuantArgs = [256];
+    this.pngQuantArgs = pngQuantArgs;
+
+    if (!this.pngQuantArgs || this.pngQuantArgs.length === 0) {
+        this.pngQuantArgs = [256];
     }
 
     this.writable = this.readable = true;
     this.commandLine = binPath + (pngQuantArgs ? ' ' + pngQuantArgs.join(' ') : ''); // For debugging
-    this.pngQuantProcess = childProcess.spawn(binPath, pngQuantArgs);
 
     this.hasEnded = false;
     this.seenDataOnStdout = false;
-
-    this.pngQuantProcess.on('error', this._reportError.bind(this));
-
-    this.pngQuantProcess.stderr.on('data', function (data) {
-        if (!this.hasEnded) {
-            this._reportError(new Error('Saw pngquant output on stderr: ' + data.toString('ascii')));
-            this.hasEnded = true;
-        }
-    }.bind(this));
-
-    this.pngQuantProcess.on('exit', function (exitCode) {
-        if (exitCode > 0 && !this.hasEnded) {
-            this._reportError(new Error('The pngquant process exited with a non-zero exit code: ' + exitCode));
-            this.hasEnded = true;
-        }
-    }.bind(this));
-
-    this.pngQuantProcess.stdout.on('data', function (chunk) {
-        this.seenDataOnStdout = true;
-        this.emit('data', chunk);
-    }.bind(this)).on('end', function () {
-        if (!this.hasEnded) {
-            if (this.seenDataOnStdout) {
-                this.emit('end');
-            } else {
-                this._reportError(new Error('PngQuant: The stdout stream ended without emitting any data'));
-            }
-            this.hasEnded = true;
-        }
-    }.bind(this));
 }
 
 util.inherits(PngQuant, Stream);
@@ -64,22 +35,69 @@ PngQuant.prototype._reportError = function (err) {
 };
 
 PngQuant.prototype.write = function (chunk) {
+    if (!this.pngQuantProcess) {
+        this.pngQuantProcess = childProcess.spawn(binPath, this.pngQuantArgs);
+        this.pngQuantProcess.on('error', this._reportError.bind(this));
+
+        this.pngQuantProcess.stderr.on('data', function (data) {
+            if (!this.hasEnded) {
+                this._reportError(new Error('Saw pngquant output on stderr: ' + data.toString('ascii')));
+                this.hasEnded = true;
+            }
+        }.bind(this));
+
+        this.pngQuantProcess.on('exit', function (exitCode) {
+            if (exitCode > 0 && !this.hasEnded) {
+                this._reportError(new Error('The pngquant process exited with a non-zero exit code: ' + exitCode));
+                this.hasEnded = true;
+            }
+        }.bind(this));
+
+        this.pngQuantProcess.stdout.on('data', function (chunk) {
+            this.seenDataOnStdout = true;
+            this.emit('data', chunk);
+        }.bind(this)).on('end', function () {
+            if (!this.hasEnded) {
+                if (this.seenDataOnStdout) {
+                    this.emit('end');
+                } else {
+                    this._reportError(new Error('PngQuant: The stdout stream ended without emitting any data'));
+                }
+                this.hasEnded = true;
+            }
+        }.bind(this));
+
+        if (this.pauseStdoutOfPngQuantProcessAfterStartingIt) {
+            this.pngQuantProcess.stdout.pause();
+        }
+    }
     this.pngQuantProcess.stdin.write(chunk);
 };
 
 PngQuant.prototype.end = function (chunk) {
     if (chunk) {
         this.write(chunk);
+    } else if (!this.pngQuantProcess) {
+        // No chunks have been rewritten. Write an empty one to make sure there's pngquant process.
+        this.write(new Buffer(0));
     }
     this.pngQuantProcess.stdin.end();
 };
 
 PngQuant.prototype.pause = function () {
-    this.pngQuantProcess.stdout.pause();
+    if (this.pngQuantProcess) {
+        this.pngQuantProcess.stdout.pause();
+    } else {
+        this.pauseStdoutOfPngQuantProcessAfterStartingIt = true;
+    }
 };
 
 PngQuant.prototype.resume = function () {
-    this.pngQuantProcess.stdout.resume();
+    if (this.pngQuantProcess) {
+        this.pngQuantProcess.stdout.resume();
+    } else {
+        this.pauseStdoutOfPngQuantProcessAfterStartingIt = false;
+    }
 };
 
 module.exports = PngQuant;