From 39de6ea2cfd621aaecb60185677449cd6e527aaa Mon Sep 17 00:00:00 2001
From: Daniel Lowrey <rdlowrey@php.net>
Date: Fri, 10 Jul 2015 21:59:39 -0400
Subject: [PATCH] [WIP] initial code commit

---
 .gitignore                      |   2 +
 .php_cs                         |  15 ++
 CONTRIBUTING.md                 |  33 ++++
 README.md                       |  25 +++
 composer.json                   |  45 +++++
 lib/BlockingDescriptor.php      |  90 +++++++++
 lib/BlockingFilesystem.php      | 169 ++++++++++++++++
 lib/Descriptor.php              |  49 +++++
 lib/Filesystem.php              | 146 ++++++++++++++
 lib/UvDescriptor.php            | 130 ++++++++++++
 lib/UvFilesystem.php            | 340 ++++++++++++++++++++++++++++++++
 lib/functions.php               |  30 +++
 phpunit.xml                     |  35 ++++
 test/BlockingDescriptorTest.php |  15 ++
 test/BlockingFilesystemTest.php |  15 ++
 test/DescriptorTest.php         |  86 ++++++++
 test/FilesystemTest.php         | 129 ++++++++++++
 test/UvDescriptorTest.php       |  15 ++
 test/UvFilesystemTest.php       |  19 ++
 test/fixture/small.txt          |   1 +
 20 files changed, 1389 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 .php_cs
 create mode 100644 CONTRIBUTING.md
 create mode 100644 README.md
 create mode 100644 composer.json
 create mode 100644 lib/BlockingDescriptor.php
 create mode 100644 lib/BlockingFilesystem.php
 create mode 100644 lib/Descriptor.php
 create mode 100644 lib/Filesystem.php
 create mode 100644 lib/UvDescriptor.php
 create mode 100644 lib/UvFilesystem.php
 create mode 100644 lib/functions.php
 create mode 100644 phpunit.xml
 create mode 100644 test/BlockingDescriptorTest.php
 create mode 100644 test/BlockingFilesystemTest.php
 create mode 100644 test/DescriptorTest.php
 create mode 100644 test/FilesystemTest.php
 create mode 100644 test/UvDescriptorTest.php
 create mode 100644 test/UvFilesystemTest.php
 create mode 100644 test/fixture/small.txt

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..d8a7996
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+composer.lock
+vendor/
diff --git a/.php_cs b/.php_cs
new file mode 100644
index 0000000..d1a2e36
--- /dev/null
+++ b/.php_cs
@@ -0,0 +1,15 @@
+<?php
+
+return Symfony\CS\Config\Config::create()
+    ->level(Symfony\CS\FixerInterface::NONE_LEVEL)
+    ->fixers([
+        "psr2",
+        "-braces",
+        "-psr0",
+    ])
+	->finder(
+		Symfony\CS\Finder\DefaultFinder::create()
+			->in(__DIR__ . "/lib")
+			->in(__DIR__ . "/test")
+	)
+;
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..b8bcb32
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,33 @@
+## Submitting useful bug reports
+
+Please search existing issues first to make sure this is not a duplicate.
+Every issue report has a cost for the developers required to field it; be
+respectful of others' time and ensure your report isn't spurious prior to
+submission. Additionally, please do us all a favor by adhering to the
+principles of sound bug reporting laid out by Simon Tatham here:
+
+http://www.chiark.greenend.org.uk/~sgtatham/bugs.html
+
+## Development ideology
+
+Truths which we believe to be self-evident:
+
+- **It's an asynchronous world.**  Be wary of anything that undermines
+   async principles.
+
+- **The answer is not more options.**  If you feel compelled to expose
+   new preferences to the user it's very possible you've made a wrong
+   turn somewhere.
+
+- **There are no power users.** The idea that some users "understand"
+   concepts better than others has proven to be, for the most part, false.
+   If anything, "power users" are more dangerous than the rest, and we
+   should avoid exposing dangerous functionality to them.
+
+## Code style
+
+The amphp project adheres to the PSR-2 style guide with the exception that
+opening braces for classes and methods must appear on the same line as
+the declaration:
+
+https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..99afa41
--- /dev/null
+++ b/README.md
@@ -0,0 +1,25 @@
+# amp/fs [![Build Status](https://travis-ci.org/amphp/fs.svg?branch=master)](https://travis-ci.org/amphp/fs)
+
+`amp/fs` is a non-blocking filesystem manipulation library for use with the
+[amp concurrency framework](https://github.com/amphp/amp).
+
+**Dependencies**
+
+- PHP 5.5+
+- [php-uv](https://github.com/chobie/php-uv) (optional)
+- [eio](https://pecl.php.net/package/eio) (optional)
+
+`amp/fs` works out of the box without any PHP extensions. However, it does so
+in a blocking manner. This capability only exists to simplify development across
+environments where extensions may not be present. Using this library in
+production without either the php-uv or eio extension is **NOT** reccommended.
+
+**Current Version**
+
+ - v0.1.0
+
+**Installation**
+
+```bash
+$ composer require amphp/fs: ~0.1
+```
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..40007f8
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,45 @@
+{
+    "name": "amphp/fs",
+    "homepage": "https://github.com/amphp/fs",
+    "description": "Non-blocking filesystem tools for amp applications",
+    "keywords": [
+        "filesystem",
+        "static",
+        "async",
+        "non-blocking",
+        "amp",
+        "amphp"
+    ],
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "Daniel Lowrey",
+            "email": "rdlowrey@php.net",
+            "role": "Creator / Lead Developer"
+        }
+    ],
+    "require": {
+        "php": ">=7.0.0-dev",
+        "amphp/amp": "dev-master"
+    },
+    "require-dev": {
+        "phpunit/phpunit": "~4.4.0",
+        "fabpot/php-cs-fixer": "~1.9"
+    },
+    "autoload": {
+        "psr-4": {
+            "Amp\\Fs\\": "lib"
+        },
+        "files": ["lib/functions.php"]
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "Amp\\Fs\\Test\\": "test/"
+        }
+    },
+    "extra": {
+        "branch-alias": {
+            "dev-master": "0.1.0-dev"
+        }
+    }
+}
diff --git a/lib/BlockingDescriptor.php b/lib/BlockingDescriptor.php
new file mode 100644
index 0000000..44bb410
--- /dev/null
+++ b/lib/BlockingDescriptor.php
@@ -0,0 +1,90 @@
+<?php
+
+namespace Amp\Fs;
+
+use Amp\{ Promise, Success, Failure };
+
+class BlockingDescriptor implements Descriptor {
+    private $fh;
+
+    /**
+     * @param resource $fh An open uv filesystem descriptor
+     */
+    public function __construct($fh, string $path) {
+        $this->fh = $fh;
+        $this->path = $path;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function read(int $offset, int $len): Promise {
+        \fseek($this->fh, $offset);
+        $data = \fread($this->fh, $len);
+
+        if ($data !== false) {
+            return new Success($data);
+        } else {
+            return new Failure(new \RuntimeException(
+                "Failed reading from file handle"
+            ));
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function write(int $offset, string $data): Promise {
+        \fseek($this->fh, $offset);
+        $len = \fwrite($this->fh, $data);
+
+        if ($len !== false) {
+            return new Success($data);
+        } else {
+            return new Failure(new \RuntimeException(
+                "Failed writing to file handle"
+            ));
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function truncate(int $length = 0): Promise {
+        if (ftruncate($this->fh, $length)) {
+            return new Success;
+        } else {
+            return new Failure(new \RuntimeException(
+                "Failed truncating file handle"
+            ));
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function stat(): Promise {
+        if ($stat = fstat($this->fh)) {
+            $stat["isfile"] = (bool) is_file($this->path);
+            $stat["isdir"] = empty($stat["isfile"]);
+            return new Success($stat);
+        } else {
+            return new Failure(new \RuntimeException(
+                "File handle stat failed"
+            ));
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function close(): Promise {
+        if (\fclose($this->fh)) {
+            return new Success;
+        } else {
+            return new Failure(new \RuntimeException(
+                "Failed closing file handle"
+            ));
+        }
+    }
+}
diff --git a/lib/BlockingFilesystem.php b/lib/BlockingFilesystem.php
new file mode 100644
index 0000000..cacef9d
--- /dev/null
+++ b/lib/BlockingFilesystem.php
@@ -0,0 +1,169 @@
+<?php
+
+namespace Amp\Fs;
+
+use Amp\{ Reactor, function reactor, Promise, Success, Failure };
+
+class BlockingFilesystem implements Filesystem {
+    private $reactor;
+
+    public function __construct(Reactor $reactor = null) {
+        $this->reactor = $reactor ?: reactor();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function open(string $path, int $mode = self::READ): Promise {
+        $openMode = 0;
+
+        if ($mode & self::READ && $mode & self::WRITE) {
+            $openMode = ($mode & self::CREATE) ? "c+" : "r+";
+        } elseif ($mode & self::READ) {
+            $openMode = "r";
+        } elseif ($mode & self::WRITE) {
+            $openMode = "c";
+        } else {
+            return new Failure(new \InvalidArgumentException(
+                "Invalid file open mode: Filesystem::READ or Filesystem::WRITE or both required"
+            ));
+        }
+
+        if ($fh = @fopen($path, $openMode)) {
+            $descriptor = new BlockingDescriptor($fh, $path);
+            return new Success($descriptor);
+        } else {
+            return new Failure(new \RuntimeException(
+                "Failed opening file handle"
+            ));
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function stat(string $path): Promise {
+        if ($stat = @stat($path)) {
+            $stat["isfile"] = (bool) is_file($path);
+            $stat["isdir"] = empty($stat["isfile"]);
+            clearstatcache(true, $path);
+        } else {
+            $stat = null;
+        }
+
+        return new Success($stat);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function lstat(string $path): Promise {
+        if ($stat = @lstat($path)) {
+            $stat["isfile"] = (bool) is_file($path);
+            $stat["isdir"] = empty($stat["isfile"]);
+            clearstatcache(true, $path);
+        } else {
+            $stat = null;
+        }
+
+        return new Success($stat);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function symlink(string $target, string $link): Promise {
+        return new Success((bool) symlink($target, $link));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function rename(string $from, string $to): Promise {
+        return new Success((bool) rename($from, $to));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function unlink(string $path): Promise {
+        return new Success((bool) unlink($path));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function mkdir(string $path, int $mode = 0644): Promise {
+        return new Success((bool) mkdir($path, $mode));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function rmdir(string $path): Promise {
+        return new Success((bool) rmdir($path));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function scandir(string $path): Promise {
+        if ($arr = scandir($path)) {
+            $arr = array_values(array_filter($arr, function($el) {
+                return !($el === "." || $el === "..");
+            }));
+            clearstatcache(true, $path);
+            return new Success($arr);
+        } else {
+            return new Failure(new \RuntimeException(
+                "Failed reading contents from {$path}"
+            ));
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function chmod(string $path, int $mode): Promise {
+        return new Success((bool) chmod($path, $mode));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function chown(string $path, int $uid, int $gid): Promise {
+        if (!@chown($path, $uid)) {
+            return new Failure(new \RuntimeException(
+                error_get_last()["message"]
+            ));
+        } elseif (!@chgrp($path, $gid)) {
+            return new Failure(new \RuntimeException(
+                error_get_last()["message"]
+            ));
+        } else {
+            return new Success;
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get(string $path): Promise {
+        $result = @file_get_contents($path);
+        return ($result === false)
+            ? new Failure(new \RuntimeException(error_get_last()["message"]))
+            : new Success($result)
+        ;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function put(string $path, string $contents): Promise {
+        $result = @file_put_contents($path, $contents);
+        return ($result === false)
+            ? new Failure(new \RuntimeException(error_get_last()["message"]))
+            : new Success($result)
+        ;
+    }
+}
diff --git a/lib/Descriptor.php b/lib/Descriptor.php
new file mode 100644
index 0000000..6cd70eb
--- /dev/null
+++ b/lib/Descriptor.php
@@ -0,0 +1,49 @@
+<?php
+
+namespace Amp\Fs;
+
+use Amp\Promise;
+
+interface Descriptor {
+    /**
+     * Read $len bytes from the open file handle starting at $offset
+     *
+     * @param int $offset
+     * @param int $len
+     * @return \Amp\Promise
+     */
+    public function read(int $offset, int $len): Promise;
+
+    /**
+     * Write $data to the open file handle starting at $offset
+     *
+     * @param int $offset
+     * @param string $data
+     * @return \Amp\Promise
+     */
+    public function write(int $offset, string $data): Promise;
+
+    /**
+     * Truncate the file to the specified $length
+     *
+     * Note: The descriptor must be opened for writing
+     *
+     * @param int $length
+     * @return \Amp\Promise
+     */
+    public function truncate(int $length = 0): Promise;
+
+    /**
+     * Retrieve the filesystem stat array for the current descriptor
+     *
+     * @return \Amp\Promise
+     */
+    public function stat(): Promise;
+
+    /**
+     * Close the file handle
+     *
+     * @return \Amp\Promise
+     */
+    public function close(): Promise;
+}
diff --git a/lib/Filesystem.php b/lib/Filesystem.php
new file mode 100644
index 0000000..f7fcae5
--- /dev/null
+++ b/lib/Filesystem.php
@@ -0,0 +1,146 @@
+<?php
+
+namespace Amp\Fs;
+
+use Amp\Promise;
+
+interface Filesystem {
+    const READ   = 0b001;
+    const WRITE  = 0b010;
+    const CREATE = 0b100;
+
+    /**
+     * Open a file handle for reading and/or writing
+     *
+     * At least READ or WRITE is required in the mode bitmask. If the file does not exist the
+     * CREATE flag is necessary in READ mode or the operation will fail. When WRITE mode is
+     * specified in the bitmask the file will always be created if it does not already exist.
+     *
+     * Example:
+     *
+     *     <?php
+     *     use function Amp\Fs\fs();
+     *     use Amp\Fs\{ Filesystem, Descriptor };
+     *
+     *     function() {
+     *         $fs = fs();
+     *         $mode = Filesystem::READ | Filesystem::WRITE;
+     *         $fh = yield $fs->open("/path/to/file", $mode);
+     *         assert($fh instanceof Descriptor);
+     *
+     *
+     * NOTE: This operation is only valid for files (not directories).
+     *
+     * @param string $path The filesystem path to open
+     * @param int $mode A flag bitmask: [Filesystem::READ | Filesystem::WRITE | Filesystem::CREATE]
+     * @return \Amp\Promise
+     */
+    public function open(string $path, int $mode = self::READ): Promise;
+
+    /**
+     * Execute a file stat operation
+     *
+     * If the requested path does not exist the resulting Promise will resolve to NULL.
+     *
+     * @param string $path The file system path to stat
+     * @return \Amp\Promise A promise resolving to an associative array upon successful resolution
+     */
+    public function stat(string $path): Promise;
+
+    /**
+     * Same as stat() except if the path is a link then the link's data is returned
+     *
+     * @param string $path The file system path to stat
+     * @return \Amp\Promise A promise resolving to an associative array upon successful resolution
+     */
+    public function lstat(string $path): Promise;
+
+    /**
+     * Create a symlink $link pointing to the file/directory located at $target
+     *
+     * @param string $target
+     * @param string $link
+     * @return \Amp\Promise
+     */
+    public function symlink(string $target, string $link): Promise;
+
+    /**
+     * Rename a file or directory
+     *
+     * @param string $from
+     * @param string $to
+     * @return \Amp\Promise
+     */
+    public function rename(string $from, string $to): Promise;
+
+    /**
+     * Delete a file
+     *
+     * @param string $path
+     * @return \Amp\Promise
+     */
+    public function unlink(string $path): Promise;
+
+    /**
+     * Create a director
+     *
+     * @param string $path
+     * @param int $mode
+     * @return \Amp\Promise
+     */
+    public function mkdir(string $path, int $mode = 0644): Promise;
+
+    /**
+     * Delete a directory
+     *
+     * @param string $path
+     * @return \Amp\Promise
+     */
+    public function rmdir(string $path): Promise;
+
+    /**
+     * Retrieve an array of files and directories inside the specified path
+     *
+     * Dot entries are not included in the resulting array (i.e. "." and "..").
+     *
+     * @param string $path
+     * @return \Amp\Promise
+     */
+    public function scandir(string $path): Promise;
+
+    /**
+     * chmod a file or directory
+     *
+     * @param string $path
+     * @param int $mode
+     * @return \Amp\Promise
+     */
+    public function chmod(string $path, int $mode): Promise;
+
+    /**
+     * chown a file or directory
+     *
+     * @param string $path
+     * @param int $uid
+     * @param int $gid
+     * @return \Amp\Promise
+     */
+    public function chown(string $path, int $uid, int $gid): Promise;
+
+    /**
+     * Buffer the specified file's contents
+     *
+     * @param string $path The file path from which to buffer contents
+     * @return \Amp\Promise A promise resolving to a string upon successful resolution
+     */
+    public function get(string $path): Promise;
+
+    /**
+     * Write the contents string to the specified path.
+     *
+     * @param string $path The file path to which to $contents should be written
+     * @param string $contents The data to write to the specified $path
+     * @return \Amp\Promise A promise resolving to the integer length written upon success
+     */
+    public function put(string $path, string $contents): Promise;
+}
diff --git a/lib/UvDescriptor.php b/lib/UvDescriptor.php
new file mode 100644
index 0000000..09a98a0
--- /dev/null
+++ b/lib/UvDescriptor.php
@@ -0,0 +1,130 @@
+<?php
+
+namespace Amp\Fs;
+
+use Amp\{ Promise, Deferred, UvReactor };
+
+class UvDescriptor implements Descriptor {
+    private $reactor;
+    private $fh;
+    private $loop;
+    private $isCloseInitialized = false;
+
+    /**
+     * @param \Amp\UvReactor $reactor
+     * @param resource $fh An open uv filesystem descriptor
+     */
+    public function __construct(UvReactor $reactor, $fh) {
+        $this->reactor = $reactor;
+        $this->fh = $fh;
+        $this->loop = $reactor->getUnderlyingLoop();
+    }
+
+    public function __destruct() {
+        if (empty($this->isCloseInitialized)) {
+            $this->close();
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function read(int $offset, int $len): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        uv_fs_read($this->loop, $this->fh, $offset, $len, function($fh, $result, $buf) use ($promisor) {
+            $this->reactor->delRef();
+            if ($result < 0) {
+                $promisor->fail(new \RuntimeException(
+                    "Failed reading from file handle: " . \uv_strerror($result)
+                ));
+            } else {
+                $promisor->succeed($buf);
+            }
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function write(int $offset, string $data): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        uv_fs_write($this->loop, $this->fh, $data, $offset, function($fh, $result) use ($promisor) {
+            $this->reactor->delRef();
+            if ($result < 0) {
+                $promisor->fail(new \RuntimeException(
+                    "Failed writing to file handle: " . \uv_strerror($result)
+                ));
+            } else {
+                $promisor->succeed($result);
+            }
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function truncate(int $length = 0): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        uv_fs_ftruncate($this->loop, $this->fh, $length, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            if (empty($fh)) {
+                $promisor->fail(new \RuntimeException(
+                    "Failed truncating file handle"
+                ));
+            } else {
+                $promisor->succeed();
+            }
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function stat(): Promise {
+        // @TODO Pull result from stat cache if it exists
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_fstat($this->loop, $this->fh, function($fh, $stat) use ($promisor) {
+            if ($fh) {
+                $stat["isdir"] = (bool) ($stat["mode"] & \UV::S_IFDIR);
+                $stat["isfile"] = empty($stat["isdir"]);
+            } else {
+                $stat = null;
+            }
+            $this->reactor->delRef();
+            $promisor->succeed($stat);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function close(): Promise {
+        $this->isCloseInitialized = true;
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        uv_fs_close($this->loop, $this->fh, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            if (empty($fh)) {
+                $promisor->fail(new \RuntimeException(
+                    "Failed closing file handle"
+                ));
+            } else {
+                $promisor->succeed();
+            }
+        });
+
+        return $promisor->promise();
+    }
+}
diff --git a/lib/UvFilesystem.php b/lib/UvFilesystem.php
new file mode 100644
index 0000000..c4989b4
--- /dev/null
+++ b/lib/UvFilesystem.php
@@ -0,0 +1,340 @@
+<?php
+
+namespace Amp\Fs;
+
+use Amp\{ UvReactor, Promise, Failure, Deferred };
+use function Amp\{ resolve, reactor };
+
+class UvFilesystem implements Filesystem {
+    private $reactor;
+    private $loop;
+
+    /**
+     * @param \Amp\UvReactor $reactor
+     */
+    public function __construct(UvReactor $reactor) {
+        $this->reactor = $reactor;
+        $this->loop = $this->reactor->getUnderlyingLoop();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function open(string $path, int $mode = self::READ): Promise {
+        $openFlags = 0;
+        $fileChmod = 0;
+
+        if ($mode & self::READ && $mode & self::WRITE) {
+            $openFlags = \UV::O_RDWR;
+            $mode |= self::CREATE;
+        } elseif ($mode & self::READ) {
+            $openFlags = \UV::O_RDONLY;
+        } elseif ($mode & self::WRITE) {
+            $openFlags = \UV::O_WRONLY;
+            $mode |= self::CREATE;
+        } else {
+            return new Failure(new \InvalidArgumentException(
+                "Invalid file open mode: Filesystem::READ or Filesystem::WRITE or both required"
+            ));
+        }
+
+        if ($mode & self::CREATE) {
+            $openFlags |= \UV::O_CREAT;
+            $fileChmod = 0644;
+        }
+
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_open($this->loop, $path, $openFlags, $fileChmod, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            if ($fh) {
+                $descriptor = new UvDescriptor($this->reactor, $fh);
+                $promisor->succeed($descriptor);
+            } else {
+                $promisor->fail(new \RuntimeException(
+                    "Failed opening file handle"
+                ));
+            }
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function stat(string $path): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_stat($this->loop, $path, function($fh, $stat) use ($promisor) {
+            if ($fh) {
+                $stat["isdir"] = (bool) ($stat["mode"] & \UV::S_IFDIR);
+                $stat["isfile"] = empty($stat["isdir"]);
+            } else {
+                $stat = null;
+            }
+            $this->reactor->delRef();
+            $promisor->succeed($stat);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function lstat(string $path): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_lstat($this->loop, $path, function($fh, $stat) use ($promisor) {
+            if ($fh) {
+                $stat["isdir"] = (bool) ($stat["mode"] & \UV::S_IFDIR);
+                $stat["isfile"] = empty($stat["isdir"]);
+            } else {
+                $stat = null;
+            }
+            $this->reactor->delRef();
+            $promisor->succeed($stat);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function symlink(string $target, string $link): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        uv_fs_symlink($this->loop, $target, $link, \UV::S_IRWXU | \UV::S_IRUSR, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            $promisor->succeed((bool)$fh);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function rename(string $from, string $to): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_rename($this->loop, $from, $to, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            $promisor->succeed((bool)$fh);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function unlink(string $path): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_unlink($this->loop, $path, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            $promisor->succeed((bool)$fh);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function mkdir(string $path, int $mode = 0644): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_mkdir($this->loop, $path, $mode, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            $promisor->succeed((bool)$fh);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function rmdir(string $path): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_rmdir($this->loop, $path, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            $promisor->succeed((bool)$fh);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function scandir(string $path): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        uv_fs_readdir($this->loop, $path, 0, function($fh, $data) use ($promisor, $path) {
+            $this->reactor->delRef();
+            if (empty($fh)) {
+                $promisor->fail(new \RuntimeException(
+                    "Failed reading contents from {$path}"
+                ));
+            } else {
+                $promisor->succeed($data);
+            }
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function chmod(string $path, int $mode): Promise {
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_chmod($this->loop, $path, $mode, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            $promisor->succeed((bool)$fh);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function chown(string $path, int $uid, int $gid): Promise {
+        // @TODO Return a failure in windows environments
+        $this->reactor->addRef();
+        $promisor = new Deferred;
+        \uv_fs_chown($this->loop, $path, $uid, $gid, function($fh) use ($promisor) {
+            $this->reactor->delRef();
+            $promisor->succeed((bool)$fh);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get(string $path): Promise {
+        return resolve($this->doGet($path), $this->reactor);
+    }
+
+    private function doGet(string $path): \Generator {
+        $this->reactor->addRef();
+        if (!$fh = yield $this->doFsOpen($path, $flags = \UV::O_RDONLY, $mode = 0)) {
+            $this->reactor->delRef();
+            throw new \RuntimeException(
+                "Failed opening file handle: {$path}"
+            );
+        }
+
+        $promisor = new Deferred;
+        $stat = yield $this->doFsStat($fh);
+        if (empty($stat)) {
+            $this->reactor->delRef();
+            $promisor->fail(new \RuntimeException(
+                "stat operation failed on open file handle"
+            ));
+        } elseif (!$stat["isfile"]) {
+            \uv_fs_close($this->loop, $fh, function() use ($promisor) {
+                $this->reactor->delRef();
+                $promisor->fail(new \RuntimeException(
+                    "cannot buffer contents: path is not a file"
+                ));
+            });
+        } else {
+            $buffer = yield $this->doFsRead($fh, $offset = 0, $stat["size"]);
+            if ($buffer === false ) {
+                \uv_fs_close($this->loop, $fh, function() use ($promisor) {
+                    $this->reactor->delRef();
+                    $promisor->fail(new \RuntimeException(
+                        "read operation failed on open file handle"
+                    ));
+                });
+            } else {
+                \uv_fs_close($this->loop, $fh, function() use ($promisor, $buffer) {
+                    $this->reactor->delRef();
+                    $promisor->succeed($buffer);
+                });
+            }
+        }
+
+        return yield $promisor->promise();
+    }
+
+    private function doFsOpen(string $path, int $flags, int $mode): Promise {
+        $promisor = new Deferred;
+        \uv_fs_open($this->loop, $path, $flags, $mode, function($fh) use ($promisor, $path) {
+            $promisor->succeed($fh);
+        });
+
+        return $promisor->promise();
+    }
+
+    private function doFsStat($fh): Promise {
+        $promisor = new Deferred;
+        \uv_fs_fstat($this->loop, $fh, function($fh, $stat) use ($promisor) {
+            if ($fh) {
+                $stat["isdir"] = (bool) ($stat["mode"] & \UV::S_IFDIR);
+                $stat["isfile"] = !$stat["isdir"];
+                $promisor->succeed($stat);
+            } else {
+                $promisor->succeed();
+            }
+        });
+
+        return $promisor->promise();
+    }
+
+    private function doFsRead($fh, int $offset, int $len): Promise {
+        $promisor = new Deferred;
+        \uv_fs_read($this->loop, $fh, $offset, $len, function($fh, $nread, $buffer) use ($promisor) {
+            $promisor->succeed(($nread < 0) ? false : $buffer);
+        });
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function put(string $path, string $contents): Promise {
+        return resolve($this->doPut($path, $contents), $this->reactor);
+    }
+
+    private function doPut(string $path, string $contents): \Generator {
+        $flags = \UV::O_WRONLY | \UV::O_CREAT;
+        $mode = \UV::S_IRWXU | \UV::S_IRUSR;
+        $this->reactor->addRef();
+        if (!$fh = yield $this->doFsOpen($path, $flags, $mode)) {
+            $this->reactor->delRef();
+            throw new \RuntimeException(
+                "Failed opening write file handle"
+            );
+        }
+
+        $promisor = new Deferred;
+        $len = strlen($contents);
+        \uv_fs_write($this->loop, $fh, $contents, $offset = 0, function($fh, $result) use ($promisor, $len) {
+            \uv_fs_close($this->loop, $fh, function() use ($promisor, $result, $len) {
+                $this->reactor->delRef();
+                if ($result < 0) {
+                    $promisor->fail(new \RuntimeException(
+                        uv_strerror($result)
+                    ));
+                } else {
+                    $promisor->succeed($len);
+                }
+            });
+        });
+
+        return yield $promisor->promise();
+    }
+}
diff --git a/lib/functions.php b/lib/functions.php
new file mode 100644
index 0000000..a565e29
--- /dev/null
+++ b/lib/functions.php
@@ -0,0 +1,30 @@
+<?php
+
+namespace Amp\Fs;
+
+use function Amp\reactor;
+
+/**
+ * Get the global default filesystem instance
+ *
+ * @param \Amp\Fs\Filesystem $assign Optionally specify a new default filesystem instance
+ * @return \Amp\Fs\Filesystem Returns the default filesystem instance
+ */
+function fs(Filesystem $assign = null): Filesystem {
+    static $filesystem;
+    if ($assign) {
+        return ($filesystem = $assign);
+    } elseif ($filesystem) {
+        return $filesystem;
+    } elseif (\extension_loaded('uv')) {
+        return ($filesystem = new UvFilesystem(reactor()));
+    /*
+    // @TODO
+    } elseif (\extension_loaded("eio") {
+        return ($filesystem = new EioFilesystem);
+    }
+    */
+    } else {
+        return ($filesystem = new BlockingFilesystem(reactor()));
+    }
+}
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..5bc65ab
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<phpunit bootstrap="./vendor/autoload.php" colors="true">
+    <testsuites>
+        <testsuite name="Tests">
+            <directory>./test</directory>
+        </testsuite>
+    </testsuites>
+    <filter>
+        <whitelist addUncoveredFilesFromWhitelist="true">
+            <directory>./lib</directory>
+        </whitelist>
+    </filter>
+
+    <logging>
+<!--
+        <log
+            type="coverage-html"
+            target="./test/coverage"
+            charset="UTF-8"
+            yui="true"
+            lowUpperBound="35"
+            highLowerBound="70"
+            showUncoveredFiles="true"
+        />
+-->
+        <log
+            type="coverage-text"
+            target="php://stdout"
+            lowUpperBound="35"
+            highLowerBound="70"
+        />
+
+    </logging>
+</phpunit>
diff --git a/test/BlockingDescriptorTest.php b/test/BlockingDescriptorTest.php
new file mode 100644
index 0000000..85e78ff
--- /dev/null
+++ b/test/BlockingDescriptorTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Amp\Fs\Test;
+
+use Amp\{ Reactor, NativeReactor };
+use Amp\Fs\{ Filesystem, BlockingFilesystem };
+
+class BlockingDescriptorTest extends DescriptorTest {
+    protected function getReactor(): Reactor {
+        return new NativeReactor;
+    }
+    protected function getFilesystem(Reactor $reactor): Filesystem {
+        return new BlockingFilesystem($reactor);
+    }
+}
diff --git a/test/BlockingFilesystemTest.php b/test/BlockingFilesystemTest.php
new file mode 100644
index 0000000..310558d
--- /dev/null
+++ b/test/BlockingFilesystemTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Amp\Fs\Test;
+
+use Amp\{ Reactor, NativeReactor };
+use Amp\Fs\{ Filesystem, BlockingFilesystem };
+
+class BlockingFilesystemTest extends FilesystemTest {
+    protected function getReactor(): Reactor {
+        return new NativeReactor;
+    }
+    protected function getFilesystem(Reactor $reactor): Filesystem {
+        return new BlockingFilesystem($reactor);
+    }
+}
diff --git a/test/DescriptorTest.php b/test/DescriptorTest.php
new file mode 100644
index 0000000..a31a5c1
--- /dev/null
+++ b/test/DescriptorTest.php
@@ -0,0 +1,86 @@
+<?php
+
+namespace Amp\Fs\Test;
+
+use Amp\Reactor;
+use Amp\Fs\Filesystem;
+
+abstract class DescriptorTest extends \PHPUnit_Framework_TestCase {
+    abstract protected function getReactor(): Reactor;
+    abstract protected function getFilesystem(Reactor $reactor): Filesystem;
+
+    public function testReadWriteCreate() {
+        ($this->getReactor())->run(function($reactor) {
+            $path = __DIR__ . "/fixture/new.txt";
+            $fs = $this->getFilesystem($reactor);
+            $flags = Filesystem::READ | Filesystem::WRITE | Filesystem::CREATE;
+            $fh = yield $fs->open($path, $flags);
+            yield $fh->write(0, "test");
+            $data = yield $fh->read(0, 8192);
+            $this->assertSame("test", $data);
+            yield $fh->close();
+            yield $fs->unlink($path);
+        });
+    }
+
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testWriteFailsOnDirectory() {
+        ($this->getReactor())->run(function($reactor) {
+            $path = __DIR__ . "/fixture/dir";
+            $fs = $this->getFilesystem($reactor);
+            $flags = Filesystem::READ | Filesystem::WRITE | Filesystem::CREATE;
+            $fh = yield $fs->open($path, $flags);
+            yield $fh->write(0, "should fail because this is a directory");
+        });
+    }
+
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testReadFailsOnDirectory() {
+        ($this->getReactor())->run(function($reactor) {
+            $path = __DIR__ . "/fixture/dir";
+            $fs = $this->getFilesystem($reactor);
+            $flags = Filesystem::READ | Filesystem::WRITE | Filesystem::CREATE;
+            $fh = yield $fs->open($path, $flags);
+            yield $fh->read(0, 8192);
+        });
+    }
+
+    public function testTruncate() {
+        ($this->getReactor())->run(function($reactor) {
+            $path = __DIR__ . "/fixture/truncate.txt";
+            $fs = $this->getFilesystem($reactor);
+            $flags = Filesystem::READ | Filesystem::WRITE | Filesystem::CREATE;
+            $fh = yield $fs->open($path, $flags);
+            yield $fh->write(0, "test");
+            $data = yield $fh->read(0, 8192);
+            $this->assertSame("test", $data);
+            yield $fh->truncate();
+            yield $fh->close();
+
+            $this->assertEquals(0, (yield $fs->stat($path))["size"]);
+            yield $fs->unlink($path);
+        });
+    }
+    
+    public function testStat() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+
+            // file
+            $fh = yield $fs->open(__DIR__ . "/fixture/small.txt");
+            $stat = yield $fh->stat();
+            $this->assertTrue($stat["isfile"]);
+            $this->assertFalse($stat["isdir"]);
+
+            // directory
+            $fh = yield $fs->open(__DIR__ . "/fixture/dir");
+            $stat = yield $fh->stat();
+            $this->assertFalse($stat["isfile"]);
+            $this->assertTrue($stat["isdir"]);
+        });
+    }
+}
diff --git a/test/FilesystemTest.php b/test/FilesystemTest.php
new file mode 100644
index 0000000..e707daf
--- /dev/null
+++ b/test/FilesystemTest.php
@@ -0,0 +1,129 @@
+<?php
+
+namespace Amp\Fs\Test;
+
+use Amp\Reactor;
+use Amp\Fs\Filesystem;
+
+abstract class FilesystemTest extends \PHPUnit_Framework_TestCase {
+    abstract protected function getReactor(): Reactor;
+    abstract protected function getFilesystem(Reactor $reactor): Filesystem;
+
+    public function testOpen() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+            $descriptor = yield $fs->open(__DIR__ . "/fixture/small.txt", Filesystem::READ);
+            $this->assertInstanceOf("Amp\Fs\Descriptor", $descriptor);
+        });
+    }
+
+    public function testScandir() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+            $actual = yield $fs->scandir(__DIR__ . "/fixture");
+            $expected = ["dir", "small.txt"];
+            $this->assertSame($expected, $actual);
+        });
+    }
+
+    public function testSymlink() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+
+            $target = __DIR__ . "/fixture/small.txt";
+            $link = __DIR__ . "/fixture/symlink.txt";
+            $this->assertTrue(yield $fs->symlink($target, $link));
+            $this->assertTrue(is_link($link));
+            yield $fs->unlink($link);
+        });
+    }
+
+    public function testLstat() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+
+            $target = __DIR__ . "/fixture/small.txt";
+            $link = __DIR__ . "/fixture/symlink.txt";
+            $this->assertTrue(yield $fs->symlink($target, $link));
+            $this->assertTrue(is_array(yield $fs->lstat($link)));
+            yield $fs->unlink($link);
+        });
+    }
+
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testOpenFailsOnNonexistentFile() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+            $descriptor = yield $fs->open(__DIR__ . "/fixture/nonexistent", Filesystem::READ);
+            $this->assertInstanceOf("Amp\Fs\Descriptor", $descriptor);
+        });
+    }
+
+    public function testStat() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+
+            // file
+            $stat = yield $fs->stat(__DIR__ . "/fixture/small.txt");
+            $this->assertTrue($stat["isfile"]);
+            $this->assertFalse($stat["isdir"]);
+
+            // directory
+            $stat = yield $fs->stat(__DIR__ . "/fixture/dir");
+            $this->assertFalse($stat["isfile"]);
+            $this->assertTrue($stat["isdir"]);
+
+            // nonexistent
+            $stat = yield $fs->stat(__DIR__ . "/fixture/nonexistent");
+            $this->assertNull($stat);
+        });
+    }
+
+    public function testRename() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+
+            $contents1 = "rename test";
+            $old = __DIR__ . "/fixture/rename1.txt";
+            $new = __DIR__ . "/fixture/rename2.txt";
+
+            yield $fs->put($old, $contents1);
+            yield $fs->rename($old, $new);
+            $contents2 = yield $fs->get($new);
+            yield $fs->unlink($new);
+
+            $this->assertSame($contents1, $contents2);
+        });
+    }
+
+    public function testUnlink() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+
+            $toUnlink = __DIR__ . "/fixture/unlink";
+
+            yield $fs->put($toUnlink, "");
+            $this->assertTrue((bool) yield $fs->stat($toUnlink));
+            yield $fs->unlink($toUnlink);
+            $this->assertNull(yield $fs->stat($toUnlink));
+        });
+    }
+
+    public function testMkdirRmdir() {
+        ($this->getReactor())->run(function($reactor) {
+            $fs = $this->getFilesystem($reactor);
+
+            $dir = __DIR__ . "/fixture/newdir";
+
+            yield $fs->mkdir($dir);
+            $stat = yield $fs->stat($dir);
+            $this->assertTrue($stat["isdir"]);
+            $this->assertFalse($stat["isfile"]);
+            yield $fs->rmdir($dir);
+            $this->assertNull(yield $fs->stat($dir));
+        });
+    }
+
+}
diff --git a/test/UvDescriptorTest.php b/test/UvDescriptorTest.php
new file mode 100644
index 0000000..2542642
--- /dev/null
+++ b/test/UvDescriptorTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Amp\Fs\Test;
+
+use Amp\{ Reactor, UvReactor };
+use Amp\Fs\{ Filesystem, UvFilesystem };
+
+class UvDescriptorTest extends DescriptorTest {
+    protected function getReactor(): Reactor {
+        return new UvReactor;
+    }
+    protected function getFilesystem(Reactor $reactor): Filesystem {
+        return new UvFilesystem($reactor);
+    }
+}
diff --git a/test/UvFilesystemTest.php b/test/UvFilesystemTest.php
new file mode 100644
index 0000000..5be75d4
--- /dev/null
+++ b/test/UvFilesystemTest.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Amp\Fs\Test;
+
+use Amp\{ Reactor, UvReactor };
+use Amp\Fs\{ Filesystem, UvFilesystem };
+
+class UvFilesystemTest extends FilesystemTest {
+    protected function getReactor(): Reactor {
+        return new UvReactor;
+    }
+    protected function getFilesystem(Reactor $reactor): Filesystem {
+        return new UvFilesystem($reactor);
+    }
+    
+    public function testScandir() {
+        $this->markTestSkipped("currently crashes php");
+    }
+}
diff --git a/test/fixture/small.txt b/test/fixture/small.txt
new file mode 100644
index 0000000..64c3ecd
--- /dev/null
+++ b/test/fixture/small.txt
@@ -0,0 +1 @@
+small
\ No newline at end of file