diff --git a/src/main/php/io/streams/SpooledInputStream.class.php b/src/main/php/io/streams/SpooledInputStream.class.php
new file mode 100755
index 000000000..1b7ac8aab
--- /dev/null
+++ b/src/main/php/io/streams/SpooledInputStream.class.php
@@ -0,0 +1,114 @@
+<?php namespace io\streams;
+
+use io\IOException;
+use lang\Environment;
+
+/**
+ * Seekable input stream which spools to a temporary file
+ *
+ * @test  io.unittest.SpooledInputStreamTest
+ */
+class SpooledInputStream implements InputStream, Seekable {
+  const PREFIX= 'spooled-';
+
+  private $in, $buffer;
+  private $end= null;
+
+  /**
+   * Creates a new spooled input stream
+   * 
+   * @param  io.streams.InputStream $in
+   * @param  ?string|io.Path|io.Folder|io.File|io.streams.Buffer $temp
+   */
+  public function __construct(InputStream $in, $temp= null) {
+    $this->in= $in;
+    $this->buffer= $temp instanceof Buffer ? $temp : new Buffer($temp ?? Environment::tempDir(), 0);
+  }
+
+  /** @return int */
+  public function available() {
+    return null === $this->end
+      ? $this->in->available() + $this->buffer->size() - $this->buffer->tell()
+      : $this->end - $this->buffer->tell()
+    ;
+  }
+
+  /**
+   * Reads, spooling the data to the file
+   *
+   * @param  int $limit
+   * @return string
+   */
+  public function read($limit= 8192) {
+
+    // Read from the underlying stream if we're at the end of the file
+    if (null === $this->end && $this->buffer->tell() >= $this->buffer->size()) {
+      $chunk= $this->in->read($limit);
+      if ('' === $chunk) {
+        $this->end= $this->buffer->tell();
+      } else {
+        $this->buffer->write($chunk);
+      }
+    } else {
+      $chunk= $this->buffer->read($limit);
+    }
+
+    return $chunk;
+  }
+
+  /** @return int */
+  private function drain() {
+    $this->buffer->seek(0, SEEK_END);
+    while ('' !== ($chunk= $this->in->read())) {
+      $this->buffer->write($chunk);
+    }
+    return $this->buffer->tell();
+  }
+
+  /**
+   * Seeks to a given offset
+   *
+   * @param  int $offset
+   * @param  int $whence SEEK_SET, SEEK_CUR or SEEK_END
+   * @return void
+   * @throws io.IOException
+   */
+  public function seek($offset, $whence= SEEK_SET) {
+    switch ($whence) {
+      case SEEK_SET: $position= $offset; break;
+      case SEEK_CUR: $position= $this->buffer->tell() + $offset; break;
+      case SEEK_END: $position= ($this->end??= $this->drain()) + $offset; break;
+      default: $position= -1; break;
+    }
+
+    if ($position < 0) {
+      throw new IOException("Seek error, position {$offset} in mode {$whence}");
+    }
+
+    // Read from underlying stream when seeking forward, clamping on EOF.
+    if (null === $this->end && ($fill= ($position - $this->buffer->size())) > 0) {
+      $this->buffer->seek(0, SEEK_END);
+      while ($fill > 0 && $this->in->available()) {
+        $chunk= $this->in->read($fill);
+        $this->buffer->write($chunk);
+        $fill-= strlen($chunk);
+      }
+      $fill && $this->end= $this->buffer->tell();
+    }
+
+    $this->buffer->seek(min($this->end ?? $this->buffer->size(), $position), SEEK_SET);
+  }
+
+  /** @return int */
+  public function tell() { return $this->buffer->tell(); }
+
+  /** @return void */
+  public function close() {
+    $this->buffer->close();
+  }
+
+  /** Ensures close() is called */
+  public function __destruct() {
+    $this->close();
+  }
+}
\ No newline at end of file
diff --git a/src/test/php/io/unittest/SpooledInputStreamTest.class.php b/src/test/php/io/unittest/SpooledInputStreamTest.class.php
new file mode 100755
index 000000000..3593136a4
--- /dev/null
+++ b/src/test/php/io/unittest/SpooledInputStreamTest.class.php
@@ -0,0 +1,183 @@
+<?php namespace io\unittest;
+
+use io\streams\{SpooledInputStream, MemoryInputStream, Streams};
+use io\{TempFile, Folder, Path, IOException};
+use lang\Environment;
+use test\{Assert, Expect, Test, Values};
+
+class SpooledInputStreamTest {
+  const BYTES= 'Test success';
+
+  /** @param ?string|io.Path|io.Folder|io.File $temp */
+  private function newFixture($temp= null): SpooledInputStream {
+    return new SpooledInputStream(new MemoryInputStream(self::BYTES), $temp);
+  }
+
+  #[Test]
+  public function can_create() {
+    $this->newFixture();
+  }
+
+  #[Test]
+  public function reading() {
+    $stream= $this->newFixture();
+
+    Assert::equals(0, $stream->tell());
+    Assert::equals(strlen(self::BYTES), $stream->available());
+    Assert::equals(self::BYTES, Streams::readAll($stream));
+  }
+
+  #[Test]
+  public function reading_after_seeking() {
+    $stream= $this->newFixture();
+    $stream->seek(5);
+    $stream->seek(0);
+
+    Assert::equals(0, $stream->tell());
+    Assert::equals(strlen(self::BYTES), $stream->available());
+    Assert::equals(self::BYTES, Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, 1, 5])]
+  public function seeking_forward($offset) {
+    $stream= $this->newFixture();
+    $stream->seek($offset, SEEK_SET);
+
+    Assert::equals($offset, $stream->tell());
+    Assert::equals(strlen(self::BYTES) - $offset, $stream->available());
+    Assert::equals(substr(self::BYTES, $offset), Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, -1, -5])]
+  public function seeking_to_end($offset) {
+    $stream= $this->newFixture();
+    $stream->seek($offset, SEEK_END);
+
+    Assert::equals(strlen(self::BYTES) + $offset, $stream->tell());
+    Assert::equals(-$offset, $stream->available());
+    Assert::equals(substr(self::BYTES, strlen(self::BYTES) + $offset), Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, 1, -1])]
+  public function seeking_relative($offset) {
+    $stream= $this->newFixture();
+    $stream->seek(5, SEEK_SET);
+    $stream->seek($offset, SEEK_CUR);
+
+    Assert::equals(5 + $offset, $stream->tell());
+    Assert::equals(strlen(self::BYTES) - 5 - $offset, $stream->available());
+    Assert::equals(substr(self::BYTES, 5 + $offset), Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, 1, 5])]
+  public function seeking_forward_set($offset) {
+    $stream= $this->newFixture();
+    $stream->seek($offset, SEEK_SET);
+
+    Assert::equals($offset, $stream->tell());
+    Assert::equals(strlen(self::BYTES) - $offset, $stream->available());
+    Assert::equals(substr(self::BYTES, $offset), Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, 1, 5])]
+  public function seeking_forward_cur($offset) {
+    $stream= $this->newFixture();
+    $stream->seek(strlen(self::BYTES), SEEK_SET);
+    $stream->seek(-$offset, SEEK_CUR);
+
+    Assert::equals(strlen(self::BYTES) - $offset, $stream->tell());
+    Assert::equals($offset, $stream->available());
+    Assert::equals(substr(self::BYTES, strlen(self::BYTES) - $offset), Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, 1, 5])]
+  public function seeking_forward_triggers_read($offset) {
+    $stream= $this->newFixture();
+    $stream->seek(5, SEEK_SET);
+    $stream->seek(strlen(self::BYTES) - $offset, SEEK_SET);
+
+    Assert::equals(strlen(self::BYTES) - $offset, $stream->tell());
+    Assert::equals($offset, $stream->available());
+    Assert::equals(substr(self::BYTES, strlen(self::BYTES) - $offset), Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, 1, 5])]
+  public function seeking_back_to_offset_after_reading_until_end($offset) {
+    $stream= $this->newFixture();
+    while ($stream->available()) {
+      $stream->read();
+    }
+    $stream->seek($offset, SEEK_SET);
+
+    Assert::equals($offset, $stream->tell());
+    Assert::equals(strlen(self::BYTES) - $offset, $stream->available());
+    Assert::equals(substr(self::BYTES, $offset), Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, -1, -5])]
+  public function seeking_to_end_after_reading_until_end($offset) {
+    $stream= $this->newFixture();
+    while ($stream->available()) {
+      $stream->read();
+    }
+    $stream->seek($offset, SEEK_END);
+
+    Assert::equals(strlen(self::BYTES) + $offset, $stream->tell());
+    Assert::equals(-$offset, $stream->available());
+    Assert::equals(substr(self::BYTES, strlen(self::BYTES) + $offset), Streams::readAll($stream));
+  }
+
+  #[Test, Values([0, -1, -5])]
+  public function seeking_to_end_after_seeking_relative($offset) {
+    $stream= $this->newFixture();
+    $stream->seek(5, SEEK_SET);
+    $stream->seek($offset, SEEK_END);
+
+    Assert::equals(strlen(self::BYTES) + $offset, $stream->tell());
+    Assert::equals(-$offset, $stream->available());
+    Assert::equals(substr(self::BYTES, strlen(self::BYTES) + $offset), Streams::readAll($stream));
+  }
+
+  #[Test]
+  public function close_can_be_called_twice() {
+    $stream= $this->newFixture();
+
+    $stream->close();
+    $stream->close();
+  }
+
+  #[Test, Expect(IOException::class), Values([SEEK_SET, SEEK_CUR])]
+  public function cannot_seek_before_beginning_of_file($whence) {
+    $this->newFixture()->seek(-1, $whence);
+  }
+
+  #[Test, Expect(IOException::class)]
+  public function cannot_seek_with_invalid_whence() {
+    $this->newFixture()->seek(0, 6100);
+  }
+
+  #[Test]
+  public function position_after_seek_error() {
+    $stream= $this->newFixture();
+    $stream->read(4);
+
+    Assert::throws(IOException::class, fn() => $stream->seek(-1));
+    Assert::equals(4, $stream->tell());
+  }
+
+  #[Test]
+  public function position_after_seek_set_past_end() {
+    $stream= $this->newFixture();
+    $stream->seek(strlen(self::BYTES) + 1, SEEK_SET);
+
+    Assert::equals(strlen(self::BYTES), $stream->tell());
+  }
+
+  #[Test]
+  public function position_after_seek_end_past_end() {
+    $stream= $this->newFixture();
+    $stream->seek(1, SEEK_END);
+
+    Assert::equals(strlen(self::BYTES), $stream->tell());
+  }
+}
\ No newline at end of file