java.nio: partial Path/Files/FileSystem/InputStream implementation

Makefile

@@ -10,7 +10,7 @@ CFLAGS += -Wall -Werror -Wfatal-errors -Wno-error=unused-variable -fstack-protec
 CFLAGS += -I$(MAKEFILE_PATH)/
 CFLAGS += -I$(MAKEFILE_PATH)/c
 CFLAGS += -DDEBUG
-CFLAGS += -DDEBUG_PRINT
+#CFLAGS += -DDEBUG_PRINT
 LDFLAGS = -lm
 OPT ?= -O0
 DEPFLAGS = -MMD -MP

c/backtrace.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include "native_types.h"
-#include "frame.h"
+#include "vm.h"
 
 struct backtrace_entry {
   struct class_file * class_file;

c/class_resolver.c

@@ -13,7 +13,6 @@
 #include "fatal.h"
 #include "parse_type.h"
 #include "find_attribute.h"
-#include "frame.h"
 #include "native_types_allocate.h"
 #include "vm_instance.h"
 

c/class_resolver.h

@@ -5,53 +5,7 @@
 #include "class_file.h"
 #include "hash_table.h"
 #include "native_types.h"
-
-enum initialization_state {
-  CLASS_UNINITIALIZED,
-  CLASS_INITIALIZING,
-  CLASS_INITIALIZED,
-};
-
-struct method_entry {
-  struct class_entry * class_entry;
-  struct method_info * method_info;
-  struct Code_attribute * code_attribute;
-};
-
-union attribute_entry {
-  struct class_entry * class_entry;
-  struct method_entry * method_entry;
-  struct field_entry * field_entry;
-  struct objectref * string_objectref;
-};
-
-struct field_entry {
-  struct class_entry * class_entry;
-  struct field_info * field_info;
-  union {
-    int32_t instance_index;
-    int32_t static_index;
-  };
-};
-
-struct class_entry {
-  struct class_file * class_file;
-  enum initialization_state initialization_state;
-  union attribute_entry * attribute_entry;
-  int32_t static_fields_count;
-  int32_t * static_fields;
-  int32_t instance_fields_count;
-
-  struct {
-    int length;
-    struct hash_table_entry * entry;
-  } fields;
-
-  struct {
-    int length;
-    struct hash_table_entry * entry;
-  } methods;
-};
+#include "vm.h"
 
 struct hash_table_entry * class_resolver_load_from_buffers(const uint8_t ** buffers,
                                                            int length,
@@ -94,3 +48,7 @@ bool class_resolver_instanceof(int class_hash_table_length,
                                struct class_entry * origin_class_entry,
                                const int class_index,
                                struct objectref * objectref);
+
+struct objectref * class_resolver_lookup_string(struct vm * vm,
+                                                struct class_entry * class_entry,
+                                                const int string_index);

c/decode.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "frame.h"
+#include "vm.h"
 
 uint32_t decode_print_instruction(const uint8_t * code, uint32_t pc);
 void decode_execute_instruction(struct vm * vm, const uint8_t * code, uint32_t pc);

c/execute.h

@@ -2,7 +2,7 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void op_aaload(struct vm * vm);
 void op_aastore(struct vm * vm);

c/execute_helper.h

@@ -1,8 +1,3 @@
-// declared here due to circular frame.h include in class_resolver.h
-struct objectref * class_resolver_lookup_string(struct vm * vm,
-                                                struct class_entry * class_entry,
-                                                const int string_index);
-
 static inline struct field_entry * field_entry_from_constant_index(int class_hash_table_length,
                                                                    struct hash_table_entry * class_hash_table,
                                                                    struct class_entry * origin_class_entry,

c/frame_stack.h

@@ -1,9 +1,56 @@
 #pragma once
 
+#include <stdint.h>
+
+#include "vm.h"
 #include "assert.h"
-#include "class_file.h"
-#include "class_resolver.h"
-#include "native_types.h"
+
+enum initialization_state {
+  CLASS_UNINITIALIZED,
+  CLASS_INITIALIZING,
+  CLASS_INITIALIZED,
+};
+
+struct method_entry {
+  struct class_entry * class_entry;
+  struct method_info * method_info;
+  struct Code_attribute * code_attribute;
+};
+
+union attribute_entry {
+  struct class_entry * class_entry;
+  struct method_entry * method_entry;
+  struct field_entry * field_entry;
+  struct objectref * string_objectref;
+};
+
+struct field_entry {
+  struct class_entry * class_entry;
+  struct field_info * field_info;
+  union {
+    int32_t instance_index;
+    int32_t static_index;
+  };
+};
+
+struct class_entry {
+  struct class_file * class_file;
+  enum initialization_state initialization_state;
+  union attribute_entry * attribute_entry;
+  int32_t static_fields_count;
+  int32_t * static_fields;
+  int32_t instance_fields_count;
+
+  struct {
+    int length;
+    struct hash_table_entry * entry;
+  } fields;
+
+  struct {
+    int length;
+    struct hash_table_entry * entry;
+  } methods;
+};
 
 struct frame {
   struct class_entry * class_entry;
@@ -27,20 +74,6 @@ struct stack {
   int32_t capacity;
 };
 
-struct vm {
-  struct stack frame_stack;
-  struct stack data_stack;
-  struct frame * current_frame;
-  struct {
-    int length;
-    struct hash_table_entry * entry;
-  } class_hash_table;
-  struct {
-    int length;
-    struct hash_table_entry * entry;
-  } native_hash_table;
-};
-
 static inline struct frame * stack_push_frame(struct stack * stack, int num_frames)
 {
   struct frame * frame = &stack->frame[stack->ix];
@@ -182,17 +215,3 @@ static inline double operand_stack_pop_f64(struct frame * frame)
   double f = *((double *)&value);
   return f;
 }
-
-bool vm_initialize_class(struct vm * vm, struct class_entry * class_entry);
-void vm_special_method_call(struct vm * vm, struct class_entry * class_entry, struct method_entry * method_entry);
-void vm_static_method_call(struct vm * vm, struct class_entry * class_entry, struct method_entry * method_entry);
-void vm_method_return(struct vm * vm);
-void vm_execute(struct vm * vm);
-struct vm * vm_start(int class_hash_table_length,
-                     struct hash_table_entry * class_hash_table,
-                     int native_hash_table_length,
-                     struct hash_table_entry * native_hash_table,
-                     const uint8_t * main_class_name,
-                     int main_class_name_length);
-int descriptor_nargs(struct constant * descriptor_constant, uint8_t * return_type);
-void vm_exception(struct vm * vm, struct objectref * objectref);

c/gc.c

@@ -1,6 +1,8 @@
-#include "frame.h"
+#include "gc.h"
 #include "memory_allocator.h"
 #include "printf.h"
+#include "hash_table.h"
+#include "native_types.h"
 
 static void walk_address(void * address);
 

c/gc.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "frame.h"
+#include "vm.h"
 
 void gc_mark(struct vm * vm);
 void gc_sweep();

c/native.c

@@ -4,6 +4,7 @@
 #include "printf.h"
 #include "native.h"
 #include "native/class.h"
+#include "native/libcinputstream.h"
 #include "native/loader.h"
 #include "native/math.h"
 #include "native/memory.h"
@@ -160,6 +161,26 @@ const static struct native_method native_method[] = {
     .method_descriptor = "(Ljava/lang/Object;)I",
     .func = native_java_lang_system_hashcode_1,
   },
+#if !defined(__dreamcast__)
+  {
+    .class_name = "jvm/internal/LibcInputStream",
+    .method_name = "_open",
+    .method_descriptor = "([B)I",
+    .func = native_jvm_internal_libcinputstream_open_1,
+  },
+  {
+    .class_name = "jvm/internal/LibcInputStream",
+    .method_name = "_close",
+    .method_descriptor = "(I)V",
+    .func = native_jvm_internal_libcinputstream_close_1,
+  },
+  {
+    .class_name = "jvm/internal/LibcInputStream",
+    .method_name = "_read",
+    .method_descriptor = "(I)I",
+    .func = native_jvm_internal_libcinputstream_read_1,
+  },
+#endif
 };
 
 struct hash_table_entry * native_init_hash_table(int * hash_table_length)

c/native.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "frame.h"
+#include "vm.h"
 
 void native_method_call(struct vm * vm,
                         struct constant * class_name_constant,

c/native/class.c

@@ -1,6 +1,7 @@
 #include "class.h"
 #include "printf.h"
 #include "vm_instance.h"
+#include "class_resolver.h"
 
 void native_java_lang_class_getname_1(struct vm * vm, uint32_t * args)
 {

c/native/class.h

@@ -2,7 +2,7 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void native_java_lang_class_getname_1(struct vm * vm, uint32_t * args);
 void native_java_lang_class_getsuperclass_1(struct vm * vm, uint32_t * args);

c/native/libcinputstream.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+
+#include "libcinputstream.h"
+#include "assert.h"
+#include "native_types.h"
+
+void native_jvm_internal_libcinputstream_open_1(struct vm * vm, uint32_t * args)
+{
+  struct arrayref * arrayref = (struct arrayref *)args[0];
+  assert(arrayref != nullptr);
+  assert(arrayref->length > 0);
+  assert(arrayref->u8[arrayref->length - 1] == 0);
+  FILE * file = fopen((const char *)arrayref->u8, "rb");
+  assert(file != nullptr);
+
+  operand_stack_push_u32(vm->current_frame, (uint32_t)file);
+}
+
+void native_jvm_internal_libcinputstream_close_1(struct vm * vm, uint32_t * args)
+{
+  FILE * file = (FILE *)args[0];
+  assert(file != nullptr);
+  int ret = fclose(file);
+  assert(ret == 0);
+}
+
+void native_jvm_internal_libcinputstream_read_1(struct vm * vm, uint32_t * args)
+{
+  FILE * file = (FILE *)args[0];
+  assert(file != nullptr);
+
+  uint8_t buf[1];
+  int32_t size = fread(buf, 1, 1, file);
+  if (size == 0)
+    operand_stack_push_u32(vm->current_frame, (uint32_t)-1);
+  else
+    operand_stack_push_u32(vm->current_frame, (uint32_t)buf[0]);
+}

c/native/libcinputstream.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <stdint.h>
+
+#include "vm.h"
+
+void native_jvm_internal_libcinputstream_open_1(struct vm * vm, uint32_t * args);
+void native_jvm_internal_libcinputstream_close_1(struct vm * vm, uint32_t * args);
+void native_jvm_internal_libcinputstream_read_1(struct vm * vm, uint32_t * args);

c/native/loader.c

@@ -4,6 +4,7 @@
 #include "malloc.h"
 #include "loader.h"
 #include "native.h"
+#include "class_resolver.h"
 
 static uint8_t loader_buffer[0x100000] __attribute__ ((aligned (32)));
 

c/native/loader.h

@@ -2,7 +2,7 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void native_jvm_internal_loader_getbuffer_0(struct vm * vm, uint32_t * args);
 void native_jvm_internal_loader_load_2(struct vm * vm, uint32_t * args);

c/native/math.h

@@ -2,7 +2,7 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void native_java_lang_math_sin_1(struct vm * vm, uint32_t * args);
 void native_java_lang_math_cos_1(struct vm * vm, uint32_t * args);

c/native/memory.h

@@ -2,7 +2,7 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void native_java_misc_memory_putU4_2(struct vm * vm, uint32_t * args);
 void native_java_misc_memory_putU2_2(struct vm * vm, uint32_t * args);

c/native/object.c

@@ -1,5 +1,6 @@
 #include "object.h"
 #include "vm_instance.h"
+#include "native_types.h"
 
 void native_java_lang_object_getclass_1(struct vm * vm, uint32_t * args)
 {

c/native/object.h

@@ -2,6 +2,6 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void native_java_lang_object_getclass_1(struct vm * vm, uint32_t * args);

c/native/printstream.c

@@ -5,18 +5,22 @@
 void native_java_io_printstream_write_ba_1(struct vm * vm, uint32_t * args)
 {
   struct arrayref * arrayref = (struct arrayref *)args[0];
+  assert(arrayref != nullptr);
   print_bytes(arrayref->u8, arrayref->length);
 }
 
 void native_java_io_printstream_write_ca_1(struct vm * vm, uint32_t * args)
 {
   struct arrayref * arrayref = (struct arrayref *)args[0];
+  assert(arrayref != nullptr);
   print_chars(arrayref->u16, arrayref->length);
 }
 
 void native_java_io_printstream_write_s_1(struct vm * vm, uint32_t * args)
 {
   struct objectref * objectref = (struct objectref *)args[0];
+  assert(objectref != nullptr);
   struct arrayref * arrayref = objectref->aref[0];
+  assert(arrayref != nullptr);
   print_chars(arrayref->u16, arrayref->length);
 }

c/native/printstream.h

@@ -2,7 +2,7 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void native_java_io_printstream_write_ba_1(struct vm * vm, uint32_t * args);
 void native_java_io_printstream_write_ca_1(struct vm * vm, uint32_t * args);

c/native/runtime.h

@@ -2,7 +2,7 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void native_java_lang_runtime_freememory_0(struct vm * vm, uint32_t * args);
 void native_java_lang_runtime_gc_0(struct vm * vm, uint32_t * args);

c/native/system.h

@@ -2,6 +2,6 @@
 
 #include <stdint.h>
 
-#include "frame.h"
+#include "vm.h"
 
 void native_java_lang_system_hashcode_1(struct vm * vm, uint32_t * args);

c/native_types.h

@@ -3,7 +3,6 @@
 #include <stdint.h>
 
 #include "assert.h"
-#include "class_resolver.h"
 #include "memory_allocator.h"
 
 enum tag_type {

c/native_types_allocate.h

@@ -1,8 +1,9 @@
 #pragma once
 
 #include "native_types.h"
-#include "frame.h"
 #include "gc.h"
+#include "vm.h"
+#include "memory_allocator.h"
 
 static inline void * gc_memory_allocate(struct vm * vm, int size)
 {

c/vm.c

@@ -4,7 +4,6 @@
 #include "class_file.h"
 #include "bytes.h"
 #include "decode.h"
-#include "frame.h"
 #include "class_resolver.h"
 #include "printf.h"
 #include "string.h"
@@ -104,20 +103,26 @@ bool vm_initialize_class(struct vm * vm, struct class_entry * class_entry)
 
       for (int j = 0; j < field_info->attributes_count; j++) {
         if (field_info->attributes[j].attribute_name_index == constantvalue_name_index) {
-          struct attribute_info * attribute = &field_info->attributes[j];
-          struct constant * constantvalue = &class_file->constant_pool[attribute->constantvalue->constantvalue_index - 1];
-          assert(constantvalue->tag == CONSTANT_Integer); // also need to support CONSTANT_String
-
           struct constant * name_constant = &class_file->constant_pool[field_info->name_index - 1];
           assert(name_constant->tag == CONSTANT_Utf8);
-
           struct field_entry * field_entry = class_resolver_lookup_field(class_entry->fields.length,
                                                                          class_entry->fields.entry,
                                                                          name_constant->utf8.bytes,
                                                                          name_constant->utf8.length);
           assert(field_entry != nullptr);
-          class_entry->static_fields[field_entry->static_index] = constantvalue->integer.bytes;
-          debugf("  constantvalue: %d\n", constantvalue->integer.bytes);
+
+          struct attribute_info * attribute = &field_info->attributes[j];
+          struct constant * constantvalue = &class_file->constant_pool[attribute->constantvalue->constantvalue_index - 1];
+          if (constantvalue->tag == CONSTANT_Integer) {
+            class_entry->static_fields[field_entry->static_index] = constantvalue->integer.bytes;
+          } else if (constantvalue->tag == CONSTANT_String) {
+            struct objectref * objectref = class_resolver_lookup_string(vm,
+                                                                        class_entry,
+                                                                        attribute->constantvalue->constantvalue_index);
+            class_entry->static_fields[field_entry->static_index] = (int32_t)objectref;
+          } else {
+            assert(!"invalid constantvalue tag");
+          }
           break;
 
         }

c/vm.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#include "frame_stack.h"
+#include "class_file.h"
+
+struct vm {
+  struct stack frame_stack;
+  struct stack data_stack;
+  struct frame * current_frame;
+  struct {
+    int length;
+    struct hash_table_entry * entry;
+  } class_hash_table;
+  struct {
+    int length;
+    struct hash_table_entry * entry;
+  } native_hash_table;
+};
+
+bool vm_initialize_class(struct vm * vm, struct class_entry * class_entry);
+void vm_special_method_call(struct vm * vm, struct class_entry * class_entry, struct method_entry * method_entry);
+void vm_static_method_call(struct vm * vm, struct class_entry * class_entry, struct method_entry * method_entry);
+void vm_method_return(struct vm * vm);
+void vm_execute(struct vm * vm);
+struct vm * vm_start(int class_hash_table_length,
+                     struct hash_table_entry * class_hash_table,
+                     int native_hash_table_length,
+                     struct hash_table_entry * native_hash_table,
+                     const uint8_t * main_class_name,
+                     int main_class_name_length);
+int descriptor_nargs(struct constant * descriptor_constant, uint8_t * return_type);
+void vm_exception(struct vm * vm, struct objectref * objectref);

c/vm_instance.c

@@ -1,6 +1,7 @@
 #include "string.h"
 #include "native_types_allocate.h"
 #include "vm_instance.h"
+#include "class_resolver.h"
 
 struct objectref * vm_instance_create(struct vm * vm, const char * class_name)
 {

c/vm_instance.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "frame.h"
+#include "vm.h"
 
 struct objectref * vm_instance_create(struct vm * vm, const char * class_name);
 struct objectref * vm_instance_string_from_constant(struct vm * vm, struct constant * constant);

classes/java/io/Closeable.java

@@ -0,0 +1,7 @@
+package java.io;
+
+public interface Closeable
+    extends AutoCloseable {
+
+    void close() throws IOException;
+}

classes/java/io/IOException.java

@@ -0,0 +1,4 @@
+package java.io;
+
+public class IOException extends Exception {
+}

classes/java/io/InputStream.java

@@ -0,0 +1,72 @@
+package java.io;
+
+public abstract class InputStream
+    implements Closeable {
+
+    public InputStream() {
+    }
+
+    public int available() throws IOException {
+        return 0;
+    }
+
+    public void close() throws IOException {
+    }
+
+    public void mark(int readlimit) {
+    }
+
+    public abstract int read() throws IOException;
+
+    public int read(byte[] b) throws IOException {
+        return read(b, 0, b.length);
+    }
+
+    public int read(byte[] b,
+                    int off,
+                    int len) throws IOException {
+        if (off < 0 || len < 0 || len > b.length - off)
+            throw new IndexOutOfBoundsException();
+
+        if (b == null)
+            throw new NullPointerException();
+
+        for (int i = 0; i < len; i++) {
+            try {
+                int c = read();
+                boolean endOfStream = c == -1;
+                if (endOfStream) {
+                    if (i == 0)
+                        return -1;
+                    else
+                        return i;
+                }
+                b[off + i] = (byte)c;
+            } catch (IOException e) {
+                if (i == 0)
+                    throw e;
+                else
+                    return i;
+            }
+        }
+
+        return len;
+    }
+
+    public void reset() throws IOException {
+        throw new IOException();
+    }
+
+    public long skip(long n)
+        throws IOException {
+
+        long ni = n;
+        while (ni > 0L) {
+            int b = read();
+            if (b < 0)
+                break;
+            ni -= 1;
+        }
+        return n - ni;
+    }
+}

classes/java/lang/Class.java

@@ -1,7 +1,7 @@
 package java.lang;
 
 public final class Class<T> {
-    private Object klass; // struct class_entry *
+    private int class_entry; // is actually struct class_entry *
     private String name;
 
     private Class() {

classes/java/nio/file/FileSystem.java

@@ -0,0 +1,26 @@
+package java.nio.file;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.nio.file.spi.FileSystemProvider;
+
+public abstract class FileSystem
+    implements Closeable {
+
+    protected FileSystem() {
+    }
+
+    public abstract void close()
+        throws IOException;
+
+    public abstract Path getPath(String first,
+                                 String... more);
+
+    public abstract String getSeparator();
+
+    public abstract boolean isOpen();
+
+    public abstract boolean isReadOnly();
+
+    public abstract FileSystemProvider provider();
+}

classes/java/nio/file/FileSystems.java

@@ -0,0 +1,12 @@
+package java.nio.file;
+
+import jvm.internal.LibcFileSystem;
+
+public final class FileSystems {
+    private FileSystems() {
+    }
+
+    public static FileSystem getDefault() {
+        return LibcFileSystem.getLibcFileSystem();
+    }
+}

classes/java/nio/file/Files.java

@@ -0,0 +1,15 @@
+package java.nio.file;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+public final class Files {
+
+
+    public static InputStream newInputStream(Path path,
+                                             OpenOption... options)
+        throws IOException {
+
+        return path.getFileSystem().provider().newInputStream(path, options);
+    }
+}

classes/java/nio/file/OpenOption.java

@@ -0,0 +1,4 @@
+package java.nio.file;
+
+public interface OpenOption {
+}

classes/java/nio/file/Path.java

@@ -0,0 +1,7 @@
+package java.nio.file;
+
+public interface Path
+//    extends Comparable<Path>, Iterable<Path>
+{
+    FileSystem getFileSystem();
+}

classes/java/nio/file/spi/FileSystemProvider.java

@@ -0,0 +1,18 @@
+package java.nio.file.spi;
+
+import java.nio.file.Path;
+import java.nio.file.OpenOption;
+import java.io.InputStream;
+import java.io.IOException;
+
+public abstract class FileSystemProvider {
+    protected FileSystemProvider() {
+    }
+
+    public InputStream newInputStream(Path path,
+                                      OpenOption... options)
+        throws IOException {
+
+        throw new IOException();
+    }
+}

classes/jvm/internal/LibcFileSystem.java

@@ -0,0 +1,43 @@
+package jvm.internal;
+
+import java.nio.file.FileSystem;
+import java.nio.file.Path;
+import java.nio.file.spi.FileSystemProvider;
+
+public class LibcFileSystem extends FileSystem {
+    private static final String separator = "/";
+
+    private static LibcFileSystem libcFileSystem = new LibcFileSystem();
+
+    public static LibcFileSystem getLibcFileSystem() {
+        return libcFileSystem;
+    }
+
+    private LibcFileSystem() {
+        super();
+    }
+
+    public void close() {
+        // do nothing
+    }
+
+    public Path getPath(String first, String ... more) {
+        return LibcPath.fromString(first, more);
+    }
+
+    public String getSeparator() {
+        return LibcFileSystem.separator;
+    }
+
+    public boolean isOpen() {
+        return true;
+    }
+
+    public boolean isReadOnly() {
+        return false;
+    }
+
+    public FileSystemProvider provider() {
+        return LibcFileSystemProvider.getLibcFileSystemProvider();
+    }
+}

classes/jvm/internal/LibcFileSystemProvider.java

@@ -0,0 +1,26 @@
+package jvm.internal;
+
+import java.nio.file.Path;
+import java.nio.file.OpenOption;
+import java.nio.file.FileSystem;
+import java.nio.file.spi.FileSystemProvider;
+import java.io.InputStream;
+import java.io.IOException;
+
+public class LibcFileSystemProvider extends FileSystemProvider {
+    private static LibcFileSystemProvider libcFileSystemProvider = new LibcFileSystemProvider();
+
+    private LibcFileSystemProvider() {
+        super();
+    }
+
+    public static LibcFileSystemProvider getLibcFileSystemProvider() {
+        return libcFileSystemProvider;
+    }
+
+    public InputStream newInputStream(Path path,
+                                      OpenOption... options)
+        throws IOException {
+        return new LibcInputStream((LibcPath)path);
+    }
+}

classes/jvm/internal/LibcInputStream.java

@@ -0,0 +1,25 @@
+package jvm.internal;
+
+import java.io.InputStream;
+
+public class LibcInputStream extends InputStream {
+    private int file; // is actually FILE *
+
+    private static native int _open(byte[] path);
+
+    public LibcInputStream(LibcPath path) {
+        file = _open(path.path);
+    }
+
+    private static native void _close(int file);
+
+    public void close() {
+        _close(file);
+    }
+
+    private static native int _read(int file);
+
+    public int read() {
+        return _read(file);
+    }
+}

classes/jvm/internal/LibcPath.java

@@ -0,0 +1,43 @@
+package jvm.internal;
+
+import java.nio.file.Path;
+import java.nio.file.FileSystem;
+
+public class LibcPath implements Path {
+    public byte[] path;
+
+    public LibcPath(byte[] path) {
+        this.path = path;
+    }
+
+    private static int copyInto(byte[] dest, int offset, String s) {
+        int length = s.length();
+        for (int i = 0; i < length; i++) {
+            dest[offset + i] = (byte)s.charAt(i);
+        }
+        return offset + length;
+    }
+
+    public static LibcPath fromString(String first, String... more) {
+        int length = first.length();
+        for (int i = 0; i < more.length; i++) {
+            length += more[i].length();
+        }
+        length += more.length + 1; // including C string null terminator
+
+        byte[] path = new byte[length];
+        int offset = 0;
+        offset = copyInto(path, offset, first);
+        byte sep = (byte)'/';
+        for (int i = 0; i < more.length; i++) {
+            path[offset++] = sep;
+            offset = copyInto(path, offset, more[i]);
+        }
+
+        return new LibcPath(path);
+    }
+
+    public FileSystem getFileSystem() {
+        return LibcFileSystem.getLibcFileSystem();
+    }
+}

classes/test/TestInputStream.java

@@ -0,0 +1,16 @@
+package test;
+
+import java.nio.file.FileSystems;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.io.InputStream;
+import java.io.IOException;
+
+class TestInputStream {
+    public static void main() throws IOException {
+        Path path = FileSystems.getDefault().getPath("/home/bilbo/source.txt");
+        InputStream is = Files.newInputStream(path);
+        char c = (char)is.read();
+        System.out.println(c);
+    }
+}

java.mk

@@ -15,7 +15,7 @@ OBJ = \
 	c/execute.o \
 	c/fatal.o \
 	c/find_attribute.o \
-	c/frame.o \
+	c/vm.o \
 	c/gc.o \
 	c/hash_table.o \
 	c/malloc.o \
@@ -42,6 +42,7 @@ MAIN_DREAMCAST_OBJ = \
 
 MAIN_HOSTED_OBJ = \
 	c/file.o \
+	c/native/libcinputstream.o \
 	c/main_hosted.o
 
 PRINT_CLASS_OBJ = \