More efficient filesystem implementation

classlib/src/main/java/org/teavm/classlib/fs/VirtualFileAccessor.java

@@ -18,9 +18,15 @@ package org.teavm.classlib.fs;
 import java.io.IOException;
 
 public interface VirtualFileAccessor {
-    int read(int pos, byte[] buffer, int offset, int limit) throws IOException;
+    int read(byte[] buffer, int offset, int limit) throws IOException;
 
-    void write(int pos, byte[] buffer, int offset, int limit) throws IOException;
+    void write(byte[] buffer, int offset, int limit) throws IOException;
+
+    int tell() throws IOException;
+
+    void seek(int target) throws IOException;
+
+    void skip(int amount) throws IOException;
 
     int size() throws IOException;
 

classlib/src/main/java/org/teavm/classlib/fs/c/CVirtualFile.java

@@ -100,7 +100,7 @@ public class CVirtualFile implements VirtualFile {
         if (file == 0) {
             return null;
         }
-        return new CVirtualFileAccessor(file, append ? -1 : 0);
+        return new CVirtualFileAccessor(file);
     }
 
     @Override

classlib/src/main/java/org/teavm/classlib/fs/c/CVirtualFileAccessor.java

@@ -20,38 +20,50 @@ import org.teavm.classlib.fs.VirtualFileAccessor;
 
 public class CVirtualFileAccessor implements VirtualFileAccessor {
     private long file;
-    private int position;
 
-    public CVirtualFileAccessor(long file, int position) {
+    public CVirtualFileAccessor(long file) {
         this.file = file;
-        this.position = position;
     }
 
     @Override
-    public int read(int pos, byte[] buffer, int offset, int limit) throws IOException {
+    public int read(byte[] buffer, int offset, int limit) throws IOException {
-        ensurePosition(pos);
+        return CFileSystem.read(file, buffer, offset, limit);
-        int bytesRead = CFileSystem.read(file, buffer, offset, limit);
-        position += bytesRead;
-        return bytesRead;
     }
 
     @Override
-    public void write(int pos, byte[] buffer, int offset, int limit) throws IOException {
+    public void write(byte[] buffer, int offset, int limit) throws IOException {
-        ensurePosition(pos);
         int bytesWritten = CFileSystem.write(file, buffer, offset, limit);
         if (bytesWritten < limit) {
             throw new IOException();
         }
-        position += bytesWritten;
+    }
+
+    @Override
+    public int tell() throws IOException {
+        return CFileSystem.tell(file);
+    }
+
+    @Override
+    public void skip(int amount) throws IOException {
+        CFileSystem.seek(file, 0, amount);
+    }
+
+    @Override
+    public void seek(int target) throws IOException {
+        CFileSystem.seek(file, 0, target);
     }
 
     @Override
     public int size() throws IOException {
+        int current = CFileSystem.tell(file);
         if (!CFileSystem.seek(file, 2, 0)) {
             throw new IOException();
         }
-        position = CFileSystem.tell(file);
+        int result = CFileSystem.tell(file);
-        return position;
+        if (!CFileSystem.seek(file, 0, current)) {
+            throw new IOException();
+        }
+        return result;
     }
 
     @Override
@@ -59,11 +71,13 @@ public class CVirtualFileAccessor implements VirtualFileAccessor {
         if (!CFileSystem.seek(file, 2, 0)) {
             throw new IOException();
         }
-        position = CFileSystem.tell(file);
+        int position = CFileSystem.tell(file);
         if (position < size) {
             byte[] zeros = new byte[4096];
             while (position < size) {
-                write(position, zeros, 0, Math.min(zeros.length, size - position));
+                int bytesToWrite = Math.min(zeros.length, size - position);
+                write(zeros, 0, bytesToWrite);
+                position += bytesToWrite;
             }
         }
     }
@@ -83,13 +97,4 @@ public class CVirtualFileAccessor implements VirtualFileAccessor {
             throw new IOException();
         }
     }
-
-    private void ensurePosition(int pos) throws IOException {
-        if (position != pos) {
-            if (!CFileSystem.seek(file, 0, pos)) {
-                throw new IOException();
-            }
-            position = pos;
-        }
-    }
 }

classlib/src/main/java/org/teavm/classlib/fs/memory/InMemoryVirtualFile.java

@@ -58,21 +58,50 @@ public class InMemoryVirtualFile extends AbstractInMemoryVirtualFile {
         }
 
         return new VirtualFileAccessor() {
+            private int pos;
+
+            {
+                if (append) {
+                    pos = size;
+                }
+            }
+
             @Override
-            public int read(int pos, byte[] buffer, int offset, int limit) {
+            public int read(byte[] buffer, int offset, int limit) {
                 limit = Math.max(0, Math.min(size - pos, limit));
-                System.arraycopy(data, pos, buffer, offset, limit);
+                if (limit > 0) {
+                    System.arraycopy(data, pos, buffer, offset, limit);
+                    pos += limit;
+                }
                 return limit;
             }
 
             @Override
-            public void write(int pos, byte[] buffer, int offset, int limit) {
+            public void write(byte[] buffer, int offset, int limit) {
                 expandData(pos + limit);
                 System.arraycopy(buffer, offset, data, pos, limit);
-                size = pos + limit;
+                pos += limit;
+                if (pos > size) {
+                    size = pos;
+                }
                 modify();
             }
 
+            @Override
+            public int tell() throws IOException {
+                return pos;
+            }
+
+            @Override
+            public void seek(int target) throws IOException {
+                pos = target;
+            }
+
+            @Override
+            public void skip(int amount) throws IOException {
+                pos += amount;
+            }
+
             @Override
             public int size() {
                 return size;

classlib/src/main/java/org/teavm/classlib/java/io/TFileInputStream.java

@@ -23,9 +23,8 @@ import org.teavm.classlib.fs.VirtualFile;
 import org.teavm.classlib.fs.VirtualFileAccessor;
 
 public class TFileInputStream extends InputStream {
+    private static final byte[] ONE_BYTE_BUFFER = new byte[1];
     private VirtualFileAccessor accessor;
-    private int pos;
-    private boolean eof;
 
     public TFileInputStream(TFile file) throws FileNotFoundException {
         VirtualFile virtualFile = file.findVirtualFile();
@@ -52,16 +51,9 @@ public class TFileInputStream extends InputStream {
         if (len == 0) {
             return 0;
         }
-        if (eof) {
-            return -1;
-        }
         ensureOpened();
-        int result = accessor.read(pos, b, off, len);
+        int result = accessor.read(b, off, len);
-        pos += result;
+        return result > 0 ? result : -1;
-        if (pos == accessor.size()) {
-            eof = true;
-        }
-        return result;
     }
 
     @Override
@@ -70,25 +62,20 @@ public class TFileInputStream extends InputStream {
             throw new IOException("Value must be positive: " + n);
         }
         ensureOpened();
-        if (eof) {
+        int last = accessor.tell();
-            return 0;
+        accessor.skip((int) n - 1);
+        if (accessor.read(ONE_BYTE_BUFFER, 0, 1) < 1) {
+            int position = accessor.size();
+            accessor.seek(position);
+            return position - last;
         }
-        int newPos = Math.max(pos, Math.min(accessor.size(), pos + (int) n));
+        return n;
-        int result = newPos - pos;
-        pos = newPos;
-        if (result == 0) {
-            eof = true;
-        }
-        return result;
     }
 
     @Override
     public int available() throws IOException {
         ensureOpened();
-        if (eof) {
+        return Math.max(0, accessor.size() - accessor.tell());
-            return 0;
-        }
-        return Math.max(0, accessor.size() - pos);
     }
 
     @Override
@@ -102,17 +89,9 @@ public class TFileInputStream extends InputStream {
     @Override
     public int read() throws IOException {
         ensureOpened();
-        if (eof) {
+        byte[] buffer = ONE_BYTE_BUFFER;
-            return -1;
+        int read = accessor.read(buffer, 0, 1);
-        }
+        return read != 0 ? buffer[0] : -1;
-        byte[] buffer = new byte[1];
-        int read = accessor.read(pos, buffer, 0, 1);
-        if (read == 0) {
-            eof = true;
-        } else {
-            pos++;
-        }
-        return !eof ? buffer[0] : -1;
     }
 
     private void ensureOpened() throws IOException {

classlib/src/main/java/org/teavm/classlib/java/io/TFileOutputStream.java

@@ -24,8 +24,8 @@ import org.teavm.classlib.fs.VirtualFile;
 import org.teavm.classlib.fs.VirtualFileAccessor;
 
 public class TFileOutputStream extends OutputStream {
+    private static byte[] ONE_BYTE_BUFER = new byte[1];
     private VirtualFileAccessor accessor;
-    private int pos;
 
     public TFileOutputStream(TFile file) throws FileNotFoundException {
         this(file, false);
@@ -57,10 +57,6 @@ public class TFileOutputStream extends OutputStream {
         if (accessor == null) {
             throw new FileNotFoundException();
         }
-
-        if (append) {
-            pos = -1;
-        }
     }
 
     @Override
@@ -69,9 +65,8 @@ public class TFileOutputStream extends OutputStream {
         if (off < 0 || len < 0 || off > b.length - len) {
             throw new IndexOutOfBoundsException();
         }
-        ensurePos();
+        ensureOpened();
-        accessor.write(pos, b, off, len);
+        accessor.write(b, off, len);
-        pos += len;
     }
 
     @Override
@@ -90,10 +85,10 @@ public class TFileOutputStream extends OutputStream {
 
     @Override
     public void write(int b) throws IOException {
-        ensurePos();
+        ensureOpened();
-        byte[] buffer = { (byte) b };
+        byte[] buffer = ONE_BYTE_BUFER;
-        accessor.write(pos, buffer, 0, 1);
+        buffer[0] = (byte) b;
-        pos++;
+        accessor.write(buffer, 0, 1);
     }
 
     private void ensureOpened() throws IOException {
@@ -101,11 +96,4 @@ public class TFileOutputStream extends OutputStream {
             throw new IOException("This stream is already closed");
         }
     }
-
-    private void ensurePos() throws IOException {
-        ensureOpened();
-        if (pos < 0) {
-            pos = accessor.size();
-        }
-    }
 }

classlib/src/main/java/org/teavm/classlib/java/io/TRandomAccessFile.java

@@ -29,10 +29,10 @@ import org.teavm.classlib.java.lang.TIndexOutOfBoundsException;
 import org.teavm.classlib.java.lang.TNullPointerException;
 
 public class TRandomAccessFile implements DataInput, DataOutput, Closeable {
+    private static final byte[] ONE_BYTE_BUFFER = new byte[1];
     private boolean readOnly;
     private boolean autoFlush;
     private VirtualFileAccessor accessor;
-    private int pos;
     private byte[] buff;
 
     public TRandomAccessFile(String name, String mode) throws FileNotFoundException {
@@ -76,13 +76,9 @@ public class TRandomAccessFile implements DataInput, DataOutput, Closeable {
         if (off < 0 || len < 0 || off + len > b.length) {
             throw new IndexOutOfBoundsException();
         }
-        if (pos >= accessor.size()) {
-            return -1;
-        }
         ensureOpened();
-        int result = accessor.read(pos, b, off, len);
+        int result = accessor.read(b, off, len);
-        pos += result;
+        return result >  0 ? result : -1;
-        return result;
     }
 
     public int read(byte[] b) throws IOException {
@@ -92,8 +88,7 @@ public class TRandomAccessFile implements DataInput, DataOutput, Closeable {
     public int read() throws IOException {
         ensureOpened();
         byte[] buffer = new byte[1];
-        int read = accessor.read(pos, buffer, 0, 1);
+        int read = accessor.read(buffer, 0, 1);
-        pos += read;
         return read > 0 ? buffer[0] : -1;
     }
 
@@ -134,20 +129,24 @@ public class TRandomAccessFile implements DataInput, DataOutput, Closeable {
     public int skipBytes(int n) throws IOException {
         ensureOpened();
 
-        int newPos = Math.max(pos, Math.min(accessor.size(), pos));
+        int last = accessor.tell();
-        int result = newPos - pos;
+        accessor.skip(n - 1);
-        pos = newPos;
+        if (accessor.read(ONE_BYTE_BUFFER, 0, 1) < 1) {
-        return result;
+            int position = accessor.size();
+            accessor.seek(position);
+            return position - last;
+        }
+        return n;
     }
 
     public long getFilePointer() throws IOException {
         ensureOpened();
-        return pos;
+        return accessor.tell();
     }
 
     public void seek(long pos) throws IOException {
         ensureOpened();
-        this.pos = (int) pos;
+        accessor.seek((int) pos);
     }
 
     public long length() throws IOException {
@@ -287,11 +286,10 @@ public class TRandomAccessFile implements DataInput, DataOutput, Closeable {
     public void write(int b) throws IOException {
         ensureOpened();
         byte[] buffer = { (byte) b };
-        accessor.write(pos, buffer, 0, 1);
+        accessor.write(buffer, 0, 1);
         if (autoFlush) {
             accessor.flush();
         }
-        pos++;
     }
 
     @Override
@@ -306,11 +304,10 @@ public class TRandomAccessFile implements DataInput, DataOutput, Closeable {
             throw new IndexOutOfBoundsException();
         }
         ensureOpened();
-        accessor.write(pos, b, off, len);
+        accessor.write(b, off, len);
         if (autoFlush) {
             accessor.flush();
         }
-        pos += len;
     }
 
     @Override

core/src/main/resources/org/teavm/backend/c/file.c

@@ -566,7 +566,7 @@ int32_t teavm_file_flush(int64_t file) {
 }
 
 int32_t teavm_file_seek(int64_t file, int32_t where, int32_t offset) {
-  return SetFilePointer((HANDLE) file, offset, 0, where);
+  return SetFilePointer((HANDLE) file, offset, 0, where) != INVALID_SET_FILE_POINTER;
 }
 
 int32_t teavm_file_tell(int64_t file) {