diff --git a/stream/clients/io_stream.cpp b/stream/clients/io_stream.cpp
new file mode 100644
index 0000000000..5f1edc2217
--- /dev/null
+++ b/stream/clients/io_stream.cpp
@@ -0,0 +1,221 @@
+#include "io_stream.hpp"
+
+// This seems to work
+#ifndef EOF
+#define EOF -1
+#endif
+
+using namespace Mangle::Stream;
+
+#define BSIZE 1024
+
+// Streambuf for normal stream reading
+class _istreambuf : public std::streambuf
+{
+  StreamPtr client;
+  char buf[BSIZE];
+
+public:
+  _istreambuf(StreamPtr strm) : client(strm)
+  {
+    // Make sure we picked the right class
+    assert(client->isReadable);
+    assert(!client->hasPtr);
+
+    // Tell streambuf to delegate reading operations to underflow()
+    setg(NULL,NULL,NULL);
+
+    // Disallow writing
+    setp(NULL,NULL);
+  }
+
+  /* Underflow is called when there is no more info to read in the
+     input buffer. We need to refill buf with new data (if any), and
+     set up the internal pointers with setg() to reflect the new
+     state.
+  */
+  int underflow()
+  {
+    // Read some more data
+    size_t read = client->read(buf, BSIZE);
+    assert(read <= BSIZE);
+
+    // If we're out of data, then EOF
+    if(read == 0)
+      return EOF;
+
+    // Otherwise, set up input buffer
+    setg(buf, buf, buf+read);
+
+    // Return the first char
+    return *((unsigned char*)buf);
+  }
+
+  // Seek stream, if the source supports it. Ignores the second
+  // parameter as Mangle doesn't separate input and output pointers.
+  std::streampos seekpos(std::streampos pos, std::ios_base::openmode = std::ios_base::in)
+  {
+    // Does this stream know how to seek?
+    if(!client->isSeekable || !client->hasPosition)
+      // If not, signal an error.
+      return -1;
+
+    // Set stream position and reset the buffer.
+    client->seek(pos);
+    setg(NULL,NULL,NULL);
+
+    return client->tell();
+  }
+};
+
+// Streambuf optimized for pointer-based input streams
+class _ptrstreambuf : public std::streambuf
+{
+  StreamPtr client;
+
+public:
+  _ptrstreambuf(StreamPtr strm) : client(strm)
+  {
+    // Make sure we picked the right class
+    assert(client->isReadable);
+    assert(client->hasPtr);
+
+    // seekpos() does all the work
+    seekpos(0);
+  }
+
+  // Underflow is only called when we're at the end of the file
+  int underflow() { return EOF; }
+
+  // Seek to a new position within the memory stream. This bypasses
+  // client->seek() entirely so isSeekable doesn't have to be set.
+  std::streampos seekpos(std::streampos pos, std::ios_base::openmode = std::ios_base::in)
+  {
+    // All pointer streams need a size
+    assert(client->hasSize);
+
+    // Figure out how much will be left of the stream after seeking
+    size_t size = client->size() - pos;
+
+    // Get a pointer
+    char* ptr = (char*)client->getPtr(pos,size);
+
+    // And use it
+    setg(ptr,ptr,ptr+size);
+
+    return pos;
+  }
+};
+
+// Streambuf for stream writing
+class _ostreambuf : public std::streambuf
+{
+  StreamPtr client;
+  char buf[BSIZE];
+
+public:
+  _ostreambuf(StreamPtr strm) : client(strm)
+  {
+    // Make sure we picked the right class
+    assert(client->isWritable);
+
+    // Inform streambuf about our nice buffer
+    setp(buf, buf+BSIZE);
+
+    // Disallow reading
+    setg(NULL,NULL,NULL);
+  }
+
+  /* Sync means to flush (write) all current data to the output
+     stream. It will also set up the entire output buffer to be usable
+     again.
+  */
+  int sync()
+  {
+    // Get the number of bytes that streambuf wants us to write
+    int num = pptr() - pbase();
+    assert(num >= 0);
+
+    // Is there any work to do?
+    if(num == 0) return 0;
+
+    if((int)client->write(pbase(), num) != num)
+      // Inform caller that writing failed
+      return -1;
+
+    // Reset output buffer pointers
+    setp(buf, buf+BSIZE);
+
+    // No error
+    return 0;
+  }
+
+  /* Called whenever the output buffer is full.
+   */
+  int overflow(int c)
+  {
+    // First, write all existing data
+    if(sync()) return EOF;
+
+    // Put the requested character in the next round of output
+    if(c != EOF)
+      {
+        *pptr() = c;
+        pbump(1);
+      }
+
+    // No error
+    return 0;
+  }
+
+  // Seek stream, if the source supports it.
+  std::streampos seekpos(std::streampos pos, std::ios_base::openmode = std::ios_base::out)
+  {
+    if(!client->isSeekable || !client->hasPosition)
+      return -1;
+
+    // Flush data and reset buffers
+    sync();
+
+    // Set stream position
+    client->seek(pos);
+
+    return client->tell();
+  }
+};
+
+MangleIStream::MangleIStream(StreamPtr inp)
+  : std::istream(NULL)
+{
+  assert(inp->isReadable);
+
+  // Pick the right streambuf implementation based on whether the
+  // input supports pointers or not.
+  if(inp->hasPtr)
+    buf = new _ptrstreambuf(inp);
+  else
+    buf = new _istreambuf(inp);
+
+  rdbuf(buf);
+}
+
+MangleIStream::~MangleIStream()
+{
+  delete buf;
+}
+
+MangleOStream::MangleOStream(StreamPtr out)
+  : std::ostream(NULL)
+{
+  assert(out->isWritable);
+  buf = new _ostreambuf(out);
+
+  rdbuf(buf);
+}
+
+MangleOStream::~MangleOStream()
+{
+  // Make sure we don't have lingering data on exit
+  flush();
+  delete buf;
+}
diff --git a/stream/clients/io_stream.hpp b/stream/clients/io_stream.hpp
index 150f84cae2..98c6252ed2 100644
--- a/stream/clients/io_stream.hpp
+++ b/stream/clients/io_stream.hpp
@@ -4,173 +4,39 @@
 #include <assert.h>
 #include "../stream.hpp"
 #include <iostream>
-#include <vector>
-
-// This seems to work (TODO: test)
-#ifndef EOF
-#define EOF -1
-#endif
 
 namespace Mangle {
 namespace Stream {
 
   /** This file contains classes for wrapping an std::istream or
-      std::ostream around a Mangle::Stream. Not to be confused with
-      servers/std_(o)stream.hpp, which do the opposite (wrap a
-      Mangle::Stream around an std::istream/ostream.)
+      std::ostream around a Mangle::Stream.
 
       This allows you to use Mangle streams in places that require std
-      streams. The std::iostream interface is horrible and NOT
-      designed for easy subclassing. Defining your custom streams as
-      Mangle streams and then wrapping them here will usually be much
-      easier.
+      streams.
+
+      This is much easier than trying to make your own custom streams
+      into iostreams. The std::iostream interface is horrible and NOT
+      designed for easy subclassing. Create a Mangle::Stream instead,
+      and use this wrapper.
   */
-  class IOStreamBuffer : public std::streambuf
-  {
-    StreamPtr client;
-    std::vector<char> ibuf, obuf;
-
-  public:
-    IOStreamBuffer(StreamPtr strm) : client(strm)
-    {
-      // Set up input buffer
-      setg(NULL,NULL,NULL);
-      if(client->isReadable)
-        {
-          if(client->hasPtr)
-            {
-              assert(client->hasSize);
-
-              // If the client supports direct pointer reading, then
-              // this is really easy. No internal buffer is needed.
-              char *ptr = (char*) client->getPtr();
-
-              // Set up the entire file as the input buffer
-              setg(ptr,ptr,ptr+client->size());
-            }
-          else
-            {
-              // We need to do some manual slave labor. Set up an
-              // empty input buffer and let underflow() handle it.
-              ibuf.resize(1024);
-            }
-        }
-
-      // Only create output buffer if the stream is writable
-      if(client->isWritable)
-        {
-          obuf.resize(1024);
-          /* Set beginning and end pointers, tells streambuf to write
-             to this area and call overflow() when it's full.
-
-             Several examples use size-1, but the documentation for
-             streambuf clearly states that the end pointers is just
-             _past_ the last accessible position.
-          */
-          char *beg = &obuf[0];
-          setp(beg, beg+obuf.size());
-        }
-      else
-        // Writing not permitted
-        setp(NULL, NULL);
-    }
-
-    /* Underflow is called when there is no more info to read in the
-       input buffer. We need to refill ibuf with data (if any), and
-       set up the internal pointers with setg() to reflect the new
-       state.
-    */
-    int underflow()
-    {
-      assert(client->isReadable);
-
-      // If we've exhausted a pointer stream, then there's no more to
-      // be had.
-      if(client->hasPtr)
-        return EOF;
-
-      // Read some more data
-      assert(ibuf.size());
-      char *iptr = &ibuf[0];
-      size_t read = client->read(iptr, ibuf.size());
-
-      // If we're out of data, then EOF
-      if(read == 0)
-        return EOF;
-
-      // Otherwise, set up input buffer
-      setg(iptr, iptr, iptr+read);
-
-      // Return the first char
-      return *((unsigned char*)iptr);
-    }
-
-    /* Sync means to flush (write) all current data to the output
-       stream. It will also set up the entire output buffer to be
-       usable again.
-     */
-    int sync()
-    {
-      assert(client->isWritable);
-      assert(obuf.size() > 0);
-
-      // Get the number of bytes that streambuf wants us to write
-      int num = pptr() - pbase();
-      assert(num >= 0);
-
-      // Nothing to do
-      if(num == 0) return 0;
-
-      if((int)client->write(pbase(), num) != num)
-        return -1;
-
-      // Reset output buffer pointers
-      char *beg = &obuf[0];
-      setp(beg, beg+obuf.size());
-
-      return 0;
-    }
-
-    int overflow(int c=EOF)
-    {
-      // First, write all existing data
-      if(sync()) return EOF;
-
-      // Put the requested character in the output
-      if(c != EOF)
-        {
-          *pptr() = c;
-          pbump(1);
-        }
-
-      return 0;
-    }
-  };
 
+  // An istream wrapping a readable Mangle::Stream. Has extra
+  // optimizations for pointer-based streams.
   class MangleIStream : public std::istream
   {
-    IOStreamBuffer buf;
+    std::streambuf *buf;
   public:
-    MangleIStream(StreamPtr inp)
-      : std::istream(&buf)
-      , buf(inp)
-    {
-      assert(inp->isReadable);
-    }
+    MangleIStream(StreamPtr inp);
+    ~MangleIStream();
   };
 
+  // An ostream wrapping a writable Mangle::Stream.
   class MangleOStream : public std::ostream
   {
-    IOStreamBuffer buf;
+    std::streambuf *buf;
   public:
-    MangleOStream(StreamPtr inp)
-      : std::ostream(&buf)
-      , buf(inp)
-    {
-      assert(inp->isWritable);
-    }
-
-    ~MangleOStream() { flush(); }
+    MangleOStream(StreamPtr inp);
+    ~MangleOStream();
   };
 
 }} // namespaces
diff --git a/stream/tests/Makefile b/stream/tests/Makefile
index e4e32d1156..5f43978190 100644
--- a/stream/tests/Makefile
+++ b/stream/tests/Makefile
@@ -12,8 +12,8 @@ ogre_client_test: ogre_client_test.cpp ../stream.hpp ../clients/ogre_datastream.
 audiere_client_test: audiere_client_test.cpp ../stream.hpp ../clients/audiere_file.hpp ../clients/audiere_file.cpp
 	$(GCC) $< -o $@ ../clients/audiere_file.cpp $(L_AUDIERE)
 
-iostream_test: iostream_test.cpp ../clients/io_stream.hpp
-	$(GCC) $< -o $@
+iostream_test: iostream_test.cpp ../clients/io_stream.cpp
+	$(GCC) $^ -o $@
 
 file_server_test: file_server_test.cpp ../stream.hpp ../servers/file_stream.hpp ../servers/std_stream.hpp
 	$(GCC) $< -o $@
diff --git a/stream/tests/iostream_test.cpp b/stream/tests/iostream_test.cpp
index 7304e82fc7..6acebbbd61 100644
--- a/stream/tests/iostream_test.cpp
+++ b/stream/tests/iostream_test.cpp
@@ -46,7 +46,7 @@ public:
 
 void test2()
 {
-  cout << "Testing binary reading from non-memory:\n";
+  cout << "\nTesting binary reading from non-memory:\n";
 
   StreamPtr input(new Dummy);
   MangleIStream inp(input);
@@ -95,7 +95,7 @@ struct Dummy2 : Stream
 
 void test3()
 {
-  cout << "Writing to dummy stream:\n";
+  cout << "\nWriting to dummy stream:\n";
 
   cout << "  Pure dummy test:\n";
   StreamPtr output(new Dummy2);
@@ -123,10 +123,54 @@ void test3()
   out << "blah bleh blob";
 }
 
+struct Dummy3 : Stream
+{
+  int pos;
+
+  Dummy3() : pos(0)
+  {
+    hasPosition = true;
+    isSeekable = true;
+  }
+
+  size_t read(void*, size_t num)
+  {
+    cout << "    Reading " << num << " bytes from " << pos << endl;
+    pos += num;
+    return num;
+  }
+
+  void seek(size_t npos) { pos = npos; }
+  size_t tell() const { return pos; }
+};
+
+void test4()
+{
+  cout << "\nTesting seeking;\n";
+  StreamPtr input(new Dummy3);
+
+  cout << "  Direct reading:\n";
+  input->read(0,10);
+  input->read(0,5);
+
+  MangleIStream inp(input);
+
+  cout << "  Reading from istream:\n";
+  char buf[20];
+  inp.read(buf, 20);
+  inp.read(buf, 20);
+  inp.read(buf, 20);
+
+  cout << "  Seeking to 30 and reading again:\n";
+  inp.seekg(30);
+  inp.read(buf, 20);
+}
+
 int main()
 {
   test1();
   test2();
   test3();
+  test4();
   return 0;
 }
diff --git a/stream/tests/output/iostream_test.out b/stream/tests/output/iostream_test.out
index 9c28cade3f..b6da80c80d 100644
--- a/stream/tests/output/iostream_test.out
+++ b/stream/tests/output/iostream_test.out
@@ -3,8 +3,10 @@ Got: hello
 Got: you
 Got: world
 Got: you
+
 Testing binary reading from non-memory:
   Done
+
 Writing to dummy stream:
   Pure dummy test:
     Got: t e s t i n g 
@@ -19,3 +21,12 @@ Writing to dummy stream:
     Got: z 
   Writing some more and exiting:
     Got: b l a h   b l e h   b l o b 
+
+Testing seeking;
+  Direct reading:
+    Reading 10 bytes from 0
+    Reading 5 bytes from 10
+  Reading from istream:
+    Reading 1024 bytes from 15
+  Seeking to 30 and reading again:
+    Reading 1024 bytes from 30