diff --git a/makefile b/makefile
index 02440476e0..df4a56c4bd 100644
--- a/makefile
+++ b/makefile
@@ -39,7 +39,7 @@ thread-lflags = -lpthread
 cflags = $(warnings) -fPIC -fno-rtti -fno-exceptions -fvisibility=hidden \
 	-I$(src) -I$(bld) $(thread-cflags) -D__STDC_LIMIT_MACROS
 
-lflags = $(thread-lflags) -ldl -lm
+lflags = $(thread-lflags) -ldl -lm -lz
 
 ifeq ($(mode),debug)
 cflags += -O0 -g3
diff --git a/src/builtin.cpp b/src/builtin.cpp
index 6020b759ce..482da77721 100644
--- a/src/builtin.cpp
+++ b/src/builtin.cpp
@@ -546,11 +546,11 @@ ResourceInputStream_open(Thread* t, jclass, jstring path)
 jint JNICALL
 ResourceInputStream_read(Thread*, jclass, jlong peer, jint position)
 {
-  Finder::Data* d = reinterpret_cast<Finder::Data*>(peer);
-  if (position >= static_cast<jint>(d->length())) {
+  System::Region* region = reinterpret_cast<System::Region*>(peer);
+  if (position >= static_cast<jint>(region->length())) {
     return -1;
   } else {
-    return d->start()[position];
+    return region->start()[position];
   }
 }
 
@@ -560,14 +560,14 @@ ResourceInputStream_read2(Thread* t, jclass, jlong peer, jint position,
 {
   if (length == 0) return 0;
   
-  Finder::Data* d = reinterpret_cast<Finder::Data*>(peer);
-  if (length > static_cast<jint>(d->length()) - position) {
-    length = static_cast<jint>(d->length()) - position;
+  System::Region* region = reinterpret_cast<System::Region*>(peer);
+  if (length > static_cast<jint>(region->length()) - position) {
+    length = static_cast<jint>(region->length()) - position;
   }
   if (length <= 0) {
     return -1;
   } else {
-    memcpy(&byteArrayBody(t, *b, offset), d->start() + position, length);
+    memcpy(&byteArrayBody(t, *b, offset), region->start() + position, length);
     return length;
   }
 }
@@ -575,7 +575,7 @@ ResourceInputStream_read2(Thread* t, jclass, jlong peer, jint position,
 void JNICALL
 ResourceInputStream_close(Thread*, jclass, jlong peer)
 {
-  reinterpret_cast<Finder::Data*>(peer)->dispose();
+  reinterpret_cast<System::Region*>(peer)->dispose();
 }
 
 } // namespace
diff --git a/src/common.h b/src/common.h
index c8ef37489b..3f0ba59894 100644
--- a/src/common.h
+++ b/src/common.h
@@ -128,6 +128,42 @@ mask(T* p)
   return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(p) & PointerMask);
 }
 
+inline uint32_t
+hash(const char* s)
+{
+  uint32_t h = 0;
+  for (unsigned i = 0; s[i]; ++i) {
+    h = (h * 31) + s[i];
+  }
+  return h;  
+}
+
+inline uint32_t
+hash(const uint8_t* s, unsigned length)
+{
+  uint32_t h = 0;
+  for (unsigned i = 0; i < length; ++i) {
+    h = (h * 31) + s[i];
+  }
+  return h;
+}
+
+inline uint32_t
+hash(const int8_t* s, unsigned length)
+{
+  return hash(reinterpret_cast<const uint8_t*>(s), length);
+}
+
+inline uint32_t
+hash(const uint16_t* s, unsigned length)
+{
+  uint32_t h = 0;
+  for (unsigned i = 0; i < length; ++i) {
+    h = (h * 31) + s[i];
+  }
+  return h;
+}
+
 } // namespace vm
 
 #endif//COMMON_H
diff --git a/src/finder.cpp b/src/finder.cpp
index ea4e980779..6078a21b3b 100644
--- a/src/finder.cpp
+++ b/src/finder.cpp
@@ -1,8 +1,4 @@
-#include "sys/mman.h"
-#include "sys/types.h"
-#include "sys/stat.h"
-#include "fcntl.h"
-
+#include "zlib.h"
 #include "system.h"
 #include "finder.h"
 
@@ -32,7 +28,341 @@ copy(System* s, const char* a)
   return p;
 }
 
-const char**
+bool
+equal(const void* a, unsigned al, const void* b, unsigned bl)
+{
+  if (al == bl) {
+    return memcmp(a, b, al) == 0;
+  } else {
+    return false;
+  }
+}
+
+class Element {
+ public:
+  Element(): next(0) { }
+  virtual ~Element() { }
+  virtual System::Region* find(const char* name) = 0;
+  virtual bool exists(const char* name) = 0;
+  virtual void dispose() = 0;
+
+  Element* next;
+};
+
+class DirectoryElement: public Element {
+ public:
+  DirectoryElement(System* s, const char* name):
+    s(s), name(name)
+  { }
+
+  virtual System::Region* find(const char* name) {
+    const char* file = append(s, this->name, "/", name);
+    System::Region* region;
+    System::Status status = s->map(&region, file);
+    s->free(file);
+
+    if (s->success(status)) {
+      return region;
+    } else {
+      return 0;
+    }
+  }
+
+  virtual bool exists(const char* name)  {
+    const char* file = append(s, this->name, "/", name);
+    System::FileType type = s->identify(file);
+    s->free(file);
+    return type != System::DoesNotExist;
+  }
+
+  virtual void dispose() {
+    s->free(name);
+    s->free(this);
+  }
+
+  System* s;
+  const char* name;
+};
+
+class PointerRegion: public System::Region {
+ public:
+  PointerRegion(System* s, const uint8_t* start, size_t length):
+    s(s),
+    start_(start),
+    length_(length)
+  { }
+
+  virtual const uint8_t* start() {
+    return start_;
+  }
+
+  virtual size_t length() {
+    return length_;
+  }
+
+  virtual void dispose() {
+    s->free(this);
+  }
+
+  System* s;
+  const uint8_t* start_;
+  size_t length_;
+};
+
+class DataRegion: public System::Region {
+ public:
+  DataRegion(System* s, size_t length):
+    s(s),
+    length_(length)
+  { }
+
+  virtual const uint8_t* start() {
+    return data;
+  }
+
+  virtual size_t length() {
+    return length_;
+  }
+
+  virtual void dispose() {
+    s->free(this);
+  }
+
+  System* s;
+  size_t length_;
+  uint8_t data[0];
+};
+
+class JarIndex {
+ public:
+  static const unsigned HeaderSize = 30;
+
+  enum CompressionMethod {
+    Stored = 0,
+    Deflated = 8
+  };
+
+  class Node {
+   public:
+    Node(uint32_t hash, const uint8_t* entry, Node* next):
+      hash(hash), entry(entry), next(next)
+    { }
+
+    uint32_t hash;
+    const uint8_t* entry;
+    Node* next;
+  };
+
+  JarIndex(System* s, unsigned capacity):
+    s(s),
+    capacity(capacity),
+    position(0),
+    nodes(static_cast<Node*>(s->allocate(sizeof(Node) * capacity))),
+    zStream(0)
+  {
+    memset(table, 0, sizeof(Node*) * capacity);
+  }
+
+  static uint16_t get2(const uint8_t* p) {
+    return
+      (static_cast<uint16_t>(p[1]) <<  8) |
+      (static_cast<uint16_t>(p[0])      );
+  }
+
+  static uint32_t get4(const uint8_t* p) {
+    return
+      (static_cast<uint32_t>(p[3]) << 24) |
+      (static_cast<uint32_t>(p[2]) << 16) |
+      (static_cast<uint32_t>(p[1]) <<  8) |
+      (static_cast<uint32_t>(p[0])      );
+  }
+
+  static uint32_t signature(const uint8_t* p) {
+    return get4(p);
+  }
+
+  static uint32_t compressionMethod(const uint8_t* p) {
+    return get4(p + 8);
+  }
+
+  static uint32_t compressedSize(const uint8_t* p) {
+    return get4(p + 18);
+  }
+
+  static uint32_t uncompressedSize(const uint8_t* p) {
+    return get4(p + 22);
+  }
+
+  static uint16_t fileNameLength(const uint8_t* p) {
+    return get2(p + 26);
+  }
+
+  static uint16_t extraFieldLength(const uint8_t* p) {
+    return get2(p + 28);
+  }
+
+  static const uint8_t* fileName(const uint8_t* p) {
+    return p + 30;
+  }
+
+  static JarIndex* make(System* s, unsigned capacity) {
+    return new
+      (s->allocate(sizeof(JarIndex) + (sizeof(Node*) * capacity)))
+      JarIndex(s, capacity);
+  }
+  
+  static JarIndex* open(System* s, System::Region* region) {
+    JarIndex* index = make(s, 32);
+
+    const uint8_t* p = region->start();
+    const uint8_t* end = p + region->length();
+    while (p < end) {
+      if (signature(p) == 0x04034b50) {
+        index = index->add(hash(fileName(p), fileNameLength(p)), p);
+
+        p += HeaderSize
+          + fileNameLength(p)
+          + extraFieldLength(p)
+          + compressedSize(p);
+      } else {
+        break;
+      }
+    }
+
+    return index;
+  }
+
+  JarIndex* add(uint32_t hash, const uint8_t* entry) {
+    if (position < capacity) {
+      unsigned i = hash & (capacity - 1);
+      table[i] = new (nodes + (position++)) Node(hash, entry, table[i]);
+      return this;
+    } else {
+      JarIndex* index = make(s, capacity * 2);
+      for (unsigned i = 0; i < capacity; ++i) {
+        index->add(nodes[i].hash, nodes[i].entry);
+      }
+      index->add(hash, entry);
+      dispose();
+      return index;
+    }
+  }
+
+  Node* findNode(const char* name) {
+    unsigned length = strlen(name);
+    unsigned i = hash(name) & (capacity - 1);
+    for (Node* n = table[i]; n; n = n->next) {
+      const uint8_t* p = n->entry;
+      if (equal(name, length, fileName(p), fileNameLength(p))) {
+        return n;
+      }
+    }
+    return 0;
+  }
+
+  System::Region* find(const char* name) {
+    Node* n = findNode(name);
+    if (n) {
+      const uint8_t* p = n->entry;
+      switch (compressionMethod(p)) {
+      case Stored: {
+        return new (s->allocate(sizeof(PointerRegion)))
+          PointerRegion(s, p + fileNameLength(p) + extraFieldLength(p),
+                        compressedSize(p));
+      } break;
+
+      case Deflated: {
+        DataRegion* region = new
+          (s->allocate(sizeof(DataRegion) + uncompressedSize(p)))
+          DataRegion(s, uncompressedSize(p));
+          
+        if (zStream == 0) {
+          zStream = static_cast<z_stream*>(s->allocate(sizeof(z_stream)));
+          memset(zStream, 0, sizeof(z_stream));
+          int r = inflateInit(zStream);
+          assert(s, r == Z_OK);
+        }
+
+        zStream->next_in = const_cast<uint8_t*>
+          (p + fileNameLength(p) + extraFieldLength(p));
+        zStream->avail_in = compressedSize(p);
+        zStream->next_out = region->data;
+        zStream->avail_out = region->length();
+
+        int r = inflate(zStream, Z_SYNC_FLUSH);
+        assert(s, r == Z_STREAM_END);
+      } break;
+
+      default:
+        abort(s);
+      }
+    }
+    return 0;
+  }
+
+  bool exists(const char* name) {
+    return findNode(name) != 0;
+  }
+
+  void dispose() {
+    if (zStream) {
+      inflateEnd(zStream);
+      s->free(zStream);
+    }
+    s->free(nodes);
+    s->free(this);
+  }
+
+  System* s;
+  unsigned capacity;
+  unsigned position;
+  Node* nodes;
+  z_stream* zStream;
+  Node* table[0];
+};
+
+class JarElement: public Element {
+ public:
+  JarElement(System* s, const char* name):
+    s(s), name(name) 
+  { }
+
+  void init() {
+    if (index == 0) {
+      System::Region* r;
+      if (s->success(s->map(&r, this->name))) {
+        region = r;
+        index = JarIndex::open(s, r);
+      }
+    }
+  }
+
+  virtual System::Region* find(const char* name) {
+    init();
+    return (index ? index->find(name) : 0);
+  }
+
+  virtual bool exists(const char* name)  {
+    init();
+    return (index ? index->exists(name) : 0);
+  }
+
+  virtual void dispose() {
+    s->free(name);
+    if (index) {
+      index->dispose();
+      region->dispose();
+    }
+    s->free(this);
+  }
+
+  System* s;
+  const char* name;
+  System::Region* region;
+  JarIndex* index;
+};
+
+Element*
 parsePath(System* s, const char* path)
 {
   class Tokenizer {
@@ -62,24 +392,43 @@ parsePath(System* s, const char* path)
     char delimiter;
   };
 
-  unsigned count = 0;
-  for (Tokenizer t(path, ':'); t.hasMore(); t.next()) ++ count;
-
-  const char** v = static_cast<const char**>
-    (s->allocate((count + 1) * sizeof(const char*)));
-
-  unsigned i = 0;
-  for (Tokenizer t(path, ':'); t.hasMore(); ++i) {
+  Element* first = 0;
+  Element* prev = 0;
+  for (Tokenizer t(path, ':'); t.hasMore();) {
     Tokenizer::Token token(t.next());
-    char* p = static_cast<char*>(s->allocate(token.length + 1));
-    memcpy(p, token.s, token.length);
-    p[token.length] = 0;
-    v[i] = p;
+    char* name = static_cast<char*>(s->allocate(token.length + 1));
+    memcpy(name, token.s, token.length);
+    name[token.length] = 0;
+
+    Element* e;
+    switch (s->identify(name)) {
+    case System::File: {
+      e = new (s->allocate(sizeof(JarElement)))
+        JarElement(s, name);
+    } break;
+
+    case System::Directory: {
+      e = new (s->allocate(sizeof(DirectoryElement)))
+        DirectoryElement(s, name);
+    } break;
+
+    default: {
+      s->free(name);
+      e = 0;
+    } break;
+    }
+
+    if (e) {
+      if (prev) {
+        prev->next = e;
+      } else {
+        first = e;
+      }
+      prev = e;
+    }
   }
 
-  v[i] = 0;
-
-  return v;
+  return first;
 }
 
 class MyFinder: public Finder {
@@ -90,67 +439,20 @@ class MyFinder: public Finder {
     pathString(copy(system, path))
   { }
 
-  class Data: public Finder::Data {
-   public:
-    Data(System* system, uint8_t* start, size_t length):
-      system(system),
-      start_(start),
-      length_(length)
-    { }
-
-    virtual const uint8_t* start() {
-      return start_;
-    }
-
-    virtual size_t length() {
-      return length_;
-    }
-
-    virtual void dispose() {
-      if (start_) {
-        munmap(start_, length_);
-      }
-      system->free(this);
-    }
-
-    System* system;
-    uint8_t* start_;
-    size_t length_;
-  };
-
-  virtual Data* find(const char* name) {
-    Data* d = new (system->allocate(sizeof(Data))) Data(system, 0, 0);
-
-    for (const char** p = path_; *p; ++p) {
-      const char* file = append(system, *p, "/", name);
-      int fd = open(file, O_RDONLY);
-      system->free(file);
-
-      if (fd != -1) {
-        struct stat s;
-        int r = fstat(fd, &s);
-        if (r != -1) {
-          void* data = mmap(0, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
-          if (data) {
-            d->start_ = static_cast<uint8_t*>(data);
-            d->length_ = s.st_size;
-            return d;
-          }
-        }
+  virtual System::Region* find(const char* name) {
+    for (Element* e = path_; e; e = e->next) {
+      System::Region* r = e->find(name);
+      if (r) {
+        return r;
       }
     }
     
-    system->free(d);
     return 0;
   }
 
   virtual bool exists(const char* name) {
-    for (const char** p = path_; *p; ++p) {
-      const char* file = append(system, *p, "/", name);
-      struct stat s;
-      int r = stat(file, &s);
-      system->free(file);
-      if (r == 0) {
+    for (Element* e = path_; e; e = e->next) {
+      if (e->exists(name)) {
         return true;
       }
     }
@@ -163,16 +465,17 @@ class MyFinder: public Finder {
   }
 
   virtual void dispose() {
-    for (const char** p = path_; *p; ++p) {
-      system->free(*p);
+    for (Element* e = path_; e;) {
+      Element* t = e;
+      e = e->next;
+      t->dispose();
     }
-    system->free(path_);
     system->free(pathString);
     system->free(this);
   }
 
   System* system;
-  const char** path_;
+  Element* path_;
   const char* pathString;
 };
 
diff --git a/src/finder.h b/src/finder.h
index 1caf1aa08b..8edf56d0ff 100644
--- a/src/finder.h
+++ b/src/finder.h
@@ -8,16 +8,8 @@ namespace vm {
 
 class Finder {
  public:
-  class Data {
-   public:
-    virtual ~Data() { }
-    virtual const uint8_t* start() = 0;
-    virtual size_t length() = 0;
-    virtual void dispose() = 0;
-  };
-
   virtual ~Finder() { }
-  virtual Data* find(const char* name) = 0;
+  virtual System::Region* find(const char* name) = 0;
   virtual bool exists(const char* name) = 0;
   virtual const char* path() = 0;
   virtual void dispose() = 0;
diff --git a/src/machine.cpp b/src/machine.cpp
index 66a7313eab..62dd0235aa 100644
--- a/src/machine.cpp
+++ b/src/machine.cpp
@@ -2285,16 +2285,16 @@ resolveClass(Thread* t, object spec)
       memcpy(file, &byteArrayBody(t, spec, 0), byteArrayLength(t, spec) - 1);
       memcpy(file + byteArrayLength(t, spec) - 1, ".class", 7);
 
-      Finder::Data* data = t->vm->finder->find(file);
+      System::Region* region = t->vm->finder->find(file);
 
-      if (data) {
+      if (region) {
         if (Verbose) {
           fprintf(stderr, "parsing %s\n", &byteArrayBody(t, spec, 0));
         }
 
         // parse class file
-        class_ = parseClass(t, data->start(), data->length());
-        data->dispose();
+        class_ = parseClass(t, region->start(), region->length());
+        region->dispose();
 
         if (LIKELY(t->exception == 0)) {
           if (Verbose) {
diff --git a/src/machine.h b/src/machine.h
index 068b47017d..34a660378d 100644
--- a/src/machine.h
+++ b/src/machine.h
@@ -1858,26 +1858,6 @@ makeTrace(Thread* t)
   return makeTrace(t, t->frame);
 }
 
-inline uint32_t
-hash(const int8_t* s, unsigned length)
-{
-  uint32_t h = 0;
-  for (unsigned i = 0; i < length; ++i) {
-    h = (h * 31) + static_cast<unsigned>(s[i]);
-  }
-  return h;  
-}
-
-inline uint32_t
-hash(const uint16_t* s, unsigned length)
-{
-  uint32_t h = 0;
-  for (unsigned i = 0; i < length; ++i) {
-    h = (h * 31) + s[i];
-  }
-  return h;  
-}
-
 inline unsigned
 baseSize(Thread* t, object o, object class_)
 {
diff --git a/src/system.cpp b/src/system.cpp
index 420dfe94bd..c6286fc836 100644
--- a/src/system.cpp
+++ b/src/system.cpp
@@ -6,6 +6,7 @@
 #include "fcntl.h"
 #include "dlfcn.h"
 #include "errno.h"
+#include "unistd.h"
 #include "pthread.h"
 #include "signal.h"
 #include "stdint.h"
@@ -376,6 +377,34 @@ class MySystem: public System {
     pthread_key_t key;
   };
 
+  class Region: public System::Region {
+   public:
+    Region(System* system, uint8_t* start, size_t length):
+      system(system),
+      start_(start),
+      length_(length)
+    { }
+
+    virtual const uint8_t* start() {
+      return start_;
+    }
+
+    virtual size_t length() {
+      return length_;
+    }
+
+    virtual void dispose() {
+      if (start_) {
+        munmap(start_, length_);
+      }
+      system->free(this);
+    }
+
+    System* system;
+    uint8_t* start_;
+    size_t length_;
+  };
+
   class Library: public System::Library {
    public:
     Library(System* s, void* p, const char* name, bool mapName,
@@ -517,6 +546,43 @@ class MySystem: public System {
     return dynamicCall(function, arguments, types, count, size, returnType);
   }
 
+  virtual Status map(System::Region** region, const char* name) {
+    Status status = 1;
+
+    int fd = open(name, O_RDONLY);
+    if (fd != -1) {
+      struct stat s;
+      int r = fstat(fd, &s);
+      if (r != -1) {
+        void* data = mmap(0, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+        if (data) {
+          *region = new (allocate(sizeof(Region)))
+            Region(this, static_cast<uint8_t*>(data), s.st_size);
+          status = 0;
+        }
+      }
+      close(fd);
+    }
+    
+    return status;
+  }
+
+  virtual FileType identify(const char* name) {
+    struct stat s;
+    int r = stat(name, &s);
+    if (r) {
+      if (S_ISREG(s.st_mode)) {
+        return File;
+      } else if (S_ISDIR(s.st_mode)) {
+        return Directory;
+      } else {
+        return Unknown;
+      }
+    } else {
+      return DoesNotExist;
+    }
+  }
+
   virtual Status load(System::Library** lib,
                       const char* name,
                       bool mapName,
diff --git a/src/system.h b/src/system.h
index 9002d772b4..1094dab57b 100644
--- a/src/system.h
+++ b/src/system.h
@@ -17,6 +17,13 @@ class System: public Allocator {
  public:
   typedef intptr_t Status;
 
+  enum FileType {
+    Unknown,
+    DoesNotExist,
+    File,
+    Directory
+  };
+
   class Thread {
    public:
     virtual ~Thread() { }
@@ -55,6 +62,14 @@ class System: public Allocator {
     virtual void dispose() = 0;
   };
 
+  class Region {
+   public:
+    virtual ~Region() { }
+    virtual const uint8_t* start() = 0;
+    virtual size_t length() = 0;
+    virtual void dispose() = 0;
+  };
+
   class Library {
    public:
     virtual ~Library() { }
@@ -74,6 +89,8 @@ class System: public Allocator {
   virtual uint64_t call(void* function, uintptr_t* arguments, uint8_t* types,
                         unsigned count, unsigned size,
                         unsigned returnType) = 0;
+  virtual Status map(Region**, const char* name) = 0;
+  virtual FileType identify(const char* name) = 0;
   virtual Status load(Library**, const char* name, bool mapName, Library* next)
   = 0;
   virtual void exit(int code) = 0;