diff --git a/.coveralls.yml b/.coveralls.yml
new file mode 100644
index 0000000..f3ba4db
--- /dev/null
+++ b/.coveralls.yml
@@ -0,0 +1,4 @@
+src_dir: src
+coverage_clover: build/logs/clover.xml
+json_path: build/logs/coveralls-upload.json
+service_name: travis-ci
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..8ce09ce
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,10 @@
+/vendor
+composer.phar
+composer.lock
+*.iml
+.idea
+.env.*.php
+.env.php
+.DS_Store
+.vagrant
+Thumbs.db
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..af0b37b
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,21 @@
+language: php
+
+php:
+  - 5.4
+  - 5.5
+  - 5.6
+
+matrix:
+  allow_failures:
+    - php: 5.6
+
+before_script:
+  - composer self-update
+  - composer install
+
+script:
+  - mkdir -p build/logs
+  - phpunit --coverage-clover build/logs/clover.xml -c test/
+
+after_script:
+  - php vendor/bin/coveralls -v
\ No newline at end of file
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..9888268
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,19 @@
+Copyright (c) 2014 ada-u
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is furnished
+to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..7e05486
--- /dev/null
+++ b/README.md
@@ -0,0 +1,45 @@
+# PHP IdGen
+
+### 64bit ID Generator for PHP
+
+`PHP IdGen` is an implementation of twitter Snowflake concept. This provides generating IDs based on time in a distributed environment.
+
+### ID Specification
+
+The IDs consist of four elements:
+
+ - timestamp
+ - region id
+ - server id
+ - sequence
+
+You can specify any bit length to each element.
+
+## Usage
+
+### Prerequisites
+
+ - PHP 5.4 or later
+
+### Installation
+
+### Sample
+
+```php
+
+// example:
+// 41 bit for timestamp
+// 5  bit for region id
+// 5  bit for server id
+// 12 bit for sequence per milliseconds
+// 1414334507356 - service start epoch (unix timestamp)
+$config = new IdValueConfig(41, 5, 5, 12, 1414334507356);
+
+$service = new IdGenService($config);
+
+$worker = $service->createIdWorker(new RegionId(1), new ServerId(1));
+
+$id = $worker->generate();
+// string(10) "4194439168"
+
+```
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..b3dc477
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,24 @@
+{
+  "name": "ada-u/php-idgen",
+  "type": "library",
+  "description": "Id Generator for PHP",
+  "keywords": [ "php-idgen", "id", "generator" ],
+  "homepage": "https://github.com/ada-u/php-idgen",
+  "authors": [
+    { "name": "ada-u", "email": "ada-u@ada-u.com" }
+  ],
+  "license": "MIT",
+  "require-dev": {
+    "phpunit/phpunit": "4.4.*",
+    "mockery/mockery": "0.9.*",
+    "satooshi/php-coveralls": "dev-master"
+  },
+  "require": {
+    "php": ">=5.4.0"
+  },
+  "autoload": {
+    "psr-4": {
+      "Adachi\\IdGen\\": "src/IdGen/"
+    }
+  }
+}
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
new file mode 100644
index 0000000..2344527
--- /dev/null
+++ b/phpunit.xml.dist
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<phpunit backupGlobals="false"
+         backupStaticAttributes="false"
+         colors="true"
+         convertErrorsToExceptions="true"
+         convertNoticesToExceptions="true"
+         convertWarningsToExceptions="true"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://raw.github.com/sebastianbergmann/phpunit/master/phpunit.xsd"
+         bootstrap="./tests/bootstrap.php"
+        >
+    <testsuites>
+        <testsuite name="tests">
+            <directory>./tests/</directory>
+        </testsuite>
+    </testsuites>
+    <logging>
+        <log type="coverage-clover" target="../build/logs/clover.xml"/>
+    </logging>
+</phpunit>
\ No newline at end of file
diff --git a/src/IdGen/Foundation/IdValue/Element/RegionId.php b/src/IdGen/Foundation/IdValue/Element/RegionId.php
new file mode 100644
index 0000000..ecc077a
--- /dev/null
+++ b/src/IdGen/Foundation/IdValue/Element/RegionId.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace Adachi\IdGen\Foundation\IdValue\Element;
+
+/**
+ * Class RegionId
+ *
+ * @package Adachi\IdGen\Foundation\IdValue\Element
+ */
+class RegionId
+{
+    /**
+     * @var int
+     */
+    public $value;
+
+    /**
+     * @param int $value
+     */
+    public function __construct($value)
+    {
+        $this->value = $value;
+    }
+
+    /**
+     * @param RegionId $target
+     * @return bool
+     */
+    public function equals(RegionId $target)
+    {
+        return $this->value === $target->value;
+    }
+
+    /**
+     * @return string
+     */
+    public function __toString()
+    {
+        return (String) $this->value;
+    }
+}
diff --git a/src/IdGen/Foundation/IdValue/Element/ServerId.php b/src/IdGen/Foundation/IdValue/Element/ServerId.php
new file mode 100644
index 0000000..f4328a8
--- /dev/null
+++ b/src/IdGen/Foundation/IdValue/Element/ServerId.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace Adachi\IdGen\Foundation\IdValue\Element;
+
+/**
+ * Class ServerId
+ *
+ * @package Adachi\IdGen\Foundation\IdValue\Element
+ */
+class ServerId
+{
+    /**
+     * @var int
+     */
+    public $value;
+
+    /**
+     * @param int $value
+     */
+    public function __construct($value)
+    {
+        $this->value = $value;
+    }
+
+    /**
+     * @param ServerId $target
+     * @return bool
+     */
+    public function equals(ServerId $target)
+    {
+        return $this->value === $target->value;
+    }
+
+    /**
+     * @return string
+     */
+    public function __toString()
+    {
+        return (String) $this->value;
+    }
+}
diff --git a/src/IdGen/Foundation/IdValue/Element/Timestamp.php b/src/IdGen/Foundation/IdValue/Element/Timestamp.php
new file mode 100644
index 0000000..54a563b
--- /dev/null
+++ b/src/IdGen/Foundation/IdValue/Element/Timestamp.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace Adachi\IdGen\Foundation\IdValue\Element;
+
+/**
+ * Class Timestamp
+ *
+ * @package Adachi\IdGen\Foundation\IdValue\Element
+ */
+class Timestamp
+{
+    /**
+     * @var int
+     */
+    public $value;
+
+    /**
+     * @param int $value
+     */
+    public function __construct($value)
+    {
+        $this->value = $value;
+    }
+
+    /**
+     * @param Timestamp $target
+     * @return bool
+     */
+    public function equals(Timestamp $target)
+    {
+        return $this->value === $target->value;
+    }
+
+    /**
+     * @return string
+     */
+    public function __toString()
+    {
+        return (String) $this->value;
+    }
+}
\ No newline at end of file
diff --git a/src/IdGen/Foundation/IdValue/IdValue.php b/src/IdGen/Foundation/IdValue/IdValue.php
new file mode 100644
index 0000000..d1c0e7d
--- /dev/null
+++ b/src/IdGen/Foundation/IdValue/IdValue.php
@@ -0,0 +1,81 @@
+<?php
+
+namespace Adachi\IdGen\Foundation\IdValue;
+
+use Adachi\IdGen\Foundation\IdValue\Element\ServerId;
+use Adachi\IdGen\Foundation\IdValue\Element\Timestamp;
+use Adachi\IdGen\Foundation\IdValue\Element\RegionId;
+
+/**
+ * Class IdValue
+ *
+ * @package Adachi\IdGen\Foundation\IdValue
+ */
+class IdValue
+{
+
+    /**
+     * @var \Adachi\IdGen\Foundation\IdValue\Element\Timestamp
+     */
+    public $timestamp;
+
+    /**
+     * @var \Adachi\IdGen\Foundation\IdValue\Element\RegionId
+     */
+    public $regionId;
+
+    /**
+     * @var \Adachi\IdGen\Foundation\IdValue\Element\ServerId
+     */
+    public $serverId;
+
+    /**
+     * @var int
+     */
+    public $sequence;
+
+    /**
+     * @var int
+     */
+    protected $value;
+
+    /**
+     * @param Timestamp $timestamp
+     * @param RegionId $regionId
+     * @param ServerId $serverId
+     * @param int $sequence
+     * @param int $value
+     */
+    public function __construct(Timestamp $timestamp, RegionId $regionId, ServerId $serverId, $sequence, $value)
+    {
+        $this->timestamp = $timestamp;
+        $this->regionId = $regionId;
+        $this->serverId = $serverId;
+        $this->sequence = $sequence;
+        $this->value = $value;
+    }
+
+    /**
+     * @return int
+     */
+    public function toInt()
+    {
+        return $this->value;
+    }
+
+    /**
+     * @return string
+     */
+    public function asString()
+    {
+        return (string) $this->value;
+    }
+
+    /**
+     * @return string
+     */
+    public function __toString()
+    {
+        return $this->asString();
+    }
+}
\ No newline at end of file
diff --git a/src/IdGen/Foundation/IdValue/IdValueConfig.php b/src/IdGen/Foundation/IdValue/IdValueConfig.php
new file mode 100644
index 0000000..d8af637
--- /dev/null
+++ b/src/IdGen/Foundation/IdValue/IdValueConfig.php
@@ -0,0 +1,122 @@
+<?php
+
+namespace Adachi\IdGen\Foundation\IdValue;
+
+/**
+ * Class IdValueConfig
+ *
+ * @package Adachi\IdGen\Foundation\IdValueConfig
+ */
+class IdValueConfig
+{
+    /**
+     * @var int
+     */
+    public $timestampBitLength;
+
+    /**
+     * @var int
+     */
+    public $regionIdBitLength;
+
+    /**
+     * @var int
+     */
+    public $serverIdBitLength;
+
+    /**
+     * @var int
+     */
+    public $sequenceBitLength;
+
+    /**
+     * @var int
+     */
+    public $maxTimestamp;
+
+    /**
+     * @var int
+     */
+    public $maxRegionId;
+
+    /**
+     * @var int
+     */
+    public $maxServerId;
+
+    /**
+     * @var int
+     */
+    public $maxSequence;
+
+    /**
+     * @var int
+     */
+    public $timestampBitShift;
+
+    /**
+     * @var int
+     */
+    public $regionIdBitShift;
+
+    /**
+     * @var int
+     */
+    public $serverIdBitShift;
+
+    /**
+     * @var int
+     */
+    public $timestampMask;
+
+    /**
+     * @var int
+     */
+    public $regionIdMask;
+
+    /**
+     * @var int
+     */
+    public $serverIdMask;
+
+    /**
+     * @var int
+     */
+    public $sequenceMask;
+
+    /**
+     * @var int
+     */
+    public $epoch;
+
+    /**
+     * @param int $timestampBitLength
+     * @param int $regionIdBitLength
+     * @param int $serverIdBitLength
+     * @param int $sequenceBitLength
+     * @param int $epochOffset
+     */
+    public function __construct($timestampBitLength, $regionIdBitLength, $serverIdBitLength, $sequenceBitLength, $epochOffset)
+    {
+        $this->timestampBitLength = $timestampBitLength;
+        $this->regionIdBitLength = $regionIdBitLength;
+        $this->serverIdBitLength = $serverIdBitLength;
+        $this->sequenceBitLength = $sequenceBitLength;
+        $this->epoch = $epochOffset;
+
+        $this->maxTimestamp = -1 ^ (-1 << $this->timestampBitLength);
+        $this->maxRegionId = -1 ^ (-1 << $this->regionIdBitLength);
+        $this->maxServerId = -1 ^ (-1 << $this->serverIdBitLength);
+        $this->maxSequence = -1 ^ (-1 << $this->sequenceBitLength);
+
+        $this->serverIdBitShift = $this->sequenceBitLength;
+        $this->regionIdBitShift = $this->serverIdBitShift + $this->serverIdBitLength;
+        $this->timestampBitShift = $this->regionIdBitShift + $this->regionIdBitLength;
+
+        $this->timestampMask = -1 ^ (-1 << ($this->timestampBitLength + $this->timestampBitShift));
+        $this->regionIdMask = -1 ^ (-1 << ($this->regionIdBitLength + $this->regionIdBitShift));
+        $this->serverIdMask = -1 ^ (-1 << ($this->serverIdBitLength + $this->serverIdBitShift));
+        $this->sequenceMask = -1 ^ (-1 << $this->sequenceBitLength);
+    }
+
+}
\ No newline at end of file
diff --git a/src/IdGen/Foundation/IdWorker/IdWorker.php b/src/IdGen/Foundation/IdWorker/IdWorker.php
new file mode 100644
index 0000000..7deecec
--- /dev/null
+++ b/src/IdGen/Foundation/IdWorker/IdWorker.php
@@ -0,0 +1,189 @@
+<?php
+
+namespace Adachi\IdGen\Foundation\IdWorker;
+
+use Adachi\IdGen\Foundation\IdValue\Element\RegionId;
+use Adachi\IdGen\Foundation\IdValue\Element\ServerId;
+use Adachi\IdGen\Foundation\IdValue\Element\Timestamp;
+use Adachi\IdGen\Foundation\IdValue\IdValueConfig;
+use Adachi\IdGen\Foundation\IdValue\IdValue;
+
+/**
+ * Class IdWorker
+ *
+ * @package Adachi\IdGen\Foundation\IdWorker
+ */
+class IdWorker
+{
+    /**
+     * @var \Adachi\IdGen\Foundation\IdValue\IdValueConfig
+     */
+    protected $config;
+
+    /**
+     * @var \Adachi\IdGen\Foundation\IdValue\Element\RegionId
+     */
+    protected $regionId;
+
+    /**
+     * @var \Adachi\IdGen\Foundation\IdValue\Element\ServerId
+     */
+    protected $serverId;
+
+    /**
+     * (mutable)
+     *
+     * @var \Adachi\IdGen\Foundation\IdValue\Element\Timestamp
+     */
+    protected $lastTimestamp = null;
+
+    /**
+     * @var int
+     * @fixme refactor
+     */
+    private $semaphoreId;
+
+    /**
+     * Key name of shared memory block
+     * @fixme refactor
+     */
+    const SHM_KEY = 12345;
+
+    /**
+     * Key name of shared memory segment
+     * @fixme refactor
+     */
+    const SHM_SEQUENCE = 54321;
+
+    /**
+     * @param IdValueConfig $config
+     * @param RegionId $regionId
+     * @param ServerId $serverId
+     * @param int $semaphoreId
+     */
+    public function __construct(IdValueConfig $config, RegionId $regionId, ServerId $serverId, $semaphoreId = 45454)
+    {
+        $this->config = $config;
+        $this->regionId = $regionId;
+        $this->serverId = $serverId;
+        $this->semaphoreId = $semaphoreId;
+    }
+
+
+    /**
+     * @param IdValue $value
+     * @return int
+     * @throws \RuntimeException
+     */
+    public function write(IdValue $value)
+    {
+        if ($value->timestamp->value <= $this->config->maxTimestamp &&
+            $value->regionId->value <= $this->config->maxRegionId &&
+            $value->serverId->value <= $this->config->maxServerId &&
+            $value->sequence <= $this->config->maxSequence)
+        {
+            return  $this->calculateValue($value->timestamp, $value->regionId, $value->serverId, $value->sequence);
+        }
+        else
+        {
+            throw new \RuntimeException("IdValue Specification is not satisfied");
+        }
+    }
+
+    /**
+     * @param $value
+     * @return IdValue
+     * @throws \RuntimeException
+     */
+    public function read($value)
+    {
+        $timestamp = new Timestamp(($value & $this->config->timestampMask) >> $this->config->timestampBitShift);
+        $regionId = new RegionId(($value & $this->config->regionIdMask) >> $this->config->regionIdBitShift);
+        $serverId = new ServerId(($value & $this->config->serverIdMask) >> $this->config->serverIdBitShift);
+        $sequence = ($value & $this->config->sequenceMask);
+
+        if ($timestamp->value <= $this->config->maxTimestamp &&
+            $regionId->value <= $this->config->maxRegionId &&
+            $serverId->value <= $this->config->maxServerId &&
+            $sequence <= $this->config->maxSequence)
+        {
+            return new IdValue($timestamp, $regionId, $serverId, $sequence, $this->calculateValue($timestamp, $regionId, $serverId, $sequence));
+        }
+        else
+        {
+            throw new \RuntimeException("IdValue Specification is not satisfied");
+        }
+    }
+
+    /**
+     * @return IdValue
+     */
+    public function generate()
+    {
+        $timestamp = $this->generateTimestamp();
+
+        // Acquire semaphore
+        $semaphore = sem_get($this->semaphoreId);
+        sem_acquire($semaphore);
+
+        // Attach shared memory
+        $memory = shm_attach(self::SHM_KEY);
+
+        $sequence = 0;
+
+        if ( ! is_null($this->lastTimestamp) && $timestamp->equals($this->lastTimestamp))
+        {
+            // Increment sequence
+            $sequence = (shm_get_var($memory, self::SHM_SEQUENCE) + 1) & $this->config->sequenceMask;
+            shm_put_var($memory, self::SHM_SEQUENCE, $sequence);
+
+            if ($sequence === 0)
+            {
+                usleep(1000);
+                $timestamp = $this->generateTimestamp();
+            }
+        }
+        else
+        {
+            // Reset sequence if timestamp is different from last one.
+            $sequence = 0;
+            shm_put_var($memory, self::SHM_SEQUENCE, $sequence);
+        }
+
+        // Detach shared memory
+        shm_detach($memory);
+
+        // Release semaphore
+        sem_release($semaphore);
+
+        // Update lastTimestamp
+        $this->lastTimestamp = $timestamp;
+
+        return new IdValue($timestamp, $this->regionId, $this->serverId, $sequence, $this->calculateValue($timestamp, $this->regionId, $this->serverId, $sequence));
+    }
+
+    /**
+     * @todo make this protected, but it'll be difficult to test. any ideas?
+     * @return Timestamp
+     */
+    public function generateTimestamp()
+    {
+        $stamp = (int) round(microtime(true) * 1000);
+        return new Timestamp($stamp - $this->config->epoch);
+    }
+
+    /**
+     * @param Timestamp $timestamp
+     * @param RegionId $regionId
+     * @param ServerId $serverId
+     * @param $sequence
+     * @return int
+     */
+    protected function calculateValue(Timestamp $timestamp, RegionId $regionId, ServerId $serverId, $sequence)
+    {
+        return ($timestamp->value << $this->config->timestampBitShift) |
+               ($regionId->value << $this->config->regionIdBitShift)   |
+               ($serverId->value << $this->config->serverIdBitShift)   |
+               ($sequence);
+    }
+}
\ No newline at end of file
diff --git a/src/IdGen/Service/IdGenService.php b/src/IdGen/Service/IdGenService.php
new file mode 100644
index 0000000..28e7fbe
--- /dev/null
+++ b/src/IdGen/Service/IdGenService.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace Adachi\IdGen\Service;
+
+use Adachi\IdGen\Foundation\IdValue\Element\RegionId;
+use Adachi\IdGen\Foundation\IdValue\Element\ServerId;
+use Adachi\IdGen\Foundation\IdValue\IdValueConfig;
+use Adachi\IdGen\Foundation\IdWorker\IdWorker;
+
+/**
+ * Class IdGenService
+ *
+ * @package Adachi\IdGen\Service
+ */
+class IdGenerateService {
+
+    /**
+     * @var \Adachi\IdGen\Foundation\IdValue\IdValueConfig
+     */
+    protected $config;
+
+    /**
+     * @param IdValueConfig $config
+     */
+    public function __construct(IdValueConfig $config)
+    {
+        $this->config = $config;
+    }
+
+    /**
+     * @param RegionId $regionId
+     * @param ServerId $serverId
+     * @return IdWorker
+     */
+    public function createIdWorker(RegionId $regionId, ServerId $serverId)
+    {
+        return new IdWorker($this->config, $regionId, $serverId);
+    }
+}
\ No newline at end of file
diff --git a/tests/Tests/IdGen/Foundation/IdWorker/IdWorkerTest.php b/tests/Tests/IdGen/Foundation/IdWorker/IdWorkerTest.php
new file mode 100644
index 0000000..b1bbb9b
--- /dev/null
+++ b/tests/Tests/IdGen/Foundation/IdWorker/IdWorkerTest.php
@@ -0,0 +1,47 @@
+<?php
+
+use Adachi\IdGen\Foundation\IdValue\Element\RegionId;
+use Adachi\IdGen\Foundation\IdValue\Element\ServerId;
+use Adachi\IdGen\Foundation\IdValue\Element\Timestamp;
+use Adachi\IdGen\Foundation\IdValue\IdValueConfig;
+
+/**
+ * Class IdWorkerTest
+ */
+class IdWorkerTest extends PHPUnit_Framework_TestCase
+{
+
+    /**
+     * @var \Adachi\IdGen\Foundation\IdWorker\IdWorker|Mockery\Mock
+     */
+    private $idWorker;
+
+    protected function setUp()
+    {
+        $config = new IdValueConfig(41, 5, 5, 12, 1414334507356);
+        $this->idWorker = Mockery::mock('\Adachi\IdGen\Foundation\IdWorker\IdWorker[generateTimestamp]', [$config, new RegionId(1), new ServerId(1)]);
+        $this->idWorker->shouldReceive('generateTimestamp')
+            ->andReturn(new Timestamp(1000));
+    }
+
+    /**
+     * @test
+     */
+    public function createIdValue()
+    {
+        $id = $this->idWorker->generate();
+        // Timestamp(1000) | RegionId(1) | ServerId(1) | Sequence(0)
+        // 1111101000 00001 00001 000000000000
+        $this->assertSame(sprintf('%b', $this->idWorker->write($id)), '11111010000000100001000000000000');
+    }
+
+    /**
+     * @test
+     */
+    public function convertIdValueToIntValue()
+    {
+        $id = $this->idWorker->generate();
+        $intValue = $this->idWorker->write($id);
+        $this->assertEquals($id, $this->idWorker->read($intValue));
+    }
+}
\ No newline at end of file
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
new file mode 100644
index 0000000..c0d757a
--- /dev/null
+++ b/tests/bootstrap.php
@@ -0,0 +1,3 @@
+<?php
+$loader = require __DIR__ . '/../vendor/autoload.php';
+$loader->set('Tests', __DIR__);
\ No newline at end of file