override InputStream.available for FileInputStream and the instance returned by ZipFile.getInputStream

classpath/java/io/FileInputStream.java

@@ -16,6 +16,7 @@ public class FileInputStream extends InputStream {
   //   }
 
   private int fd;
+  private int remaining;
 
   public FileInputStream(FileDescriptor fd) {
     this.fd = fd.value;
@@ -23,12 +24,17 @@ public class FileInputStream extends InputStream {
 
   public FileInputStream(String path) throws IOException {
     fd = open(path);
+    remaining = (int) new File(path).length();
   }
 
   public FileInputStream(File file) throws IOException {
     this(file.getPath());
   }
 
+  public int available() throws IOException {
+    return remaining;
+  }
+
   private static native int open(String path) throws IOException;
 
   private static native int read(int fd) throws IOException;
@@ -39,7 +45,11 @@ public class FileInputStream extends InputStream {
   public static native void close(int fd) throws IOException;
 
   public int read() throws IOException {
-    return read(fd);
+    int c = read(fd);
+    if (c >= 0 && remaining > 0) {
+      -- remaining;
+    }
+    return c;
   }
 
   public int read(byte[] b, int offset, int length) throws IOException {
@@ -51,7 +61,11 @@ public class FileInputStream extends InputStream {
       throw new ArrayIndexOutOfBoundsException();
     }
 
-    return read(fd, b, offset, length);
+    int c = read(fd, b, offset, length);
+    if (c > 0 && remaining > 0) {
+      remaining -= c;
+    }
+    return c;
   }
 
   public void close() throws IOException {

classpath/java/util/zip/ZipFile.java

@@ -86,7 +86,7 @@ public class ZipFile {
   }
 
   public InputStream getInputStream(ZipEntry entry) throws IOException {
-    int pointer = ((MyEntry) entry).pointer();
+    final int pointer = ((MyEntry) entry).pointer();
     int method = compressionMethod(window, pointer);
     int size = compressedSize(window, pointer);
     InputStream in = new MyInputStream(file, fileData(window, pointer), size);
@@ -99,7 +99,35 @@ public class ZipFile {
       return in;
 
     case Deflated:
-      return new InflaterInputStream(in, new Inflater(true));
+      return new InflaterInputStream(in, new Inflater(true)) {
+        int remaining = uncompressedSize(window, pointer);
+
+        public int read() throws IOException {
+          int c = super.read();
+          if (c >= 0) {
+            -- remaining;
+          }
+          return c;
+        }
+
+        public int read(byte[] buffer) throws IOException {
+          return read(buffer, 0, buffer.length);
+        }
+
+        public int read(byte[] buffer, int offset, int length)
+          throws IOException
+        {
+          int c = super.read(buffer, offset, length);
+          if (c > 0) {
+            remaining -= c;
+          }
+          return c;
+        }
+
+        public int available() {
+          return remaining;
+        }
+      };
 
     default:
       throw new IOException();

test/Files.java

@@ -1,4 +1,6 @@
 import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
 
 public class Files {
   private static void expect(boolean v) {
@@ -46,6 +48,32 @@ public class Files {
       expect(! f.createNewFile());
       f.delete();
     }
+
+    { File f = new File("test.txt");
+      FileOutputStream out = new FileOutputStream(f);
+      try {
+        byte[] message = "hello, world!\n".getBytes();
+        out.write(message);
+        out.close();
+
+        FileInputStream in = new FileInputStream(f);
+        try {
+          expect(in.available() == message.length);
+          
+          for (int i = 0; i < message.length; ++i) {
+            in.read();
+            expect(in.available() == message.length - i - 1);
+          }
+          
+          expect(in.read() == -1);
+          expect(in.available() == 0);
+        } finally {
+          in.close();
+        }
+      } finally {
+        f.delete();
+      }
+    }
   }
 
 }