The skip method may, for a variety of
* reasons, end up skipping over some smaller number of bytes,
- * possibly 0. If n is negative, an
- * IOException is thrown, even though the skip
- * method of the {@link InputStream} superclass does nothing in this case.
- * The actual number of bytes skipped is returned.
+ * possibly 0. If n is negative, the method
+ * will try to skip backwards. In case the backing file does not support
+ * backward skip at its current position, an IOException is
+ * thrown. The actual number of bytes skipped is returned. If it skips
+ * forwards, it returns a positive value. If it skips backwards, it
+ * returns a negative value.
*
- *
This method may skip more bytes than are remaining in the backing - * file. This produces no exception and the number of bytes skipped + *
This method may skip more bytes than what are remaining in the + * backing file. This produces no exception and the number of bytes skipped * may include some number of bytes that were beyond the EOF of the * backing file. Attempting to read from the stream after skipping past * the end will result in -1 indicating the end of the file. @@ -261,9 +263,10 @@ class FileInputStream extends InputStream /** * Returns an estimate of the number of remaining bytes that can be read (or * skipped over) from this input stream without blocking by the next - * invocation of a method for this input stream. The next invocation might be - * the same thread or another thread. A single read or skip of this - * many bytes will not block, but may read or skip fewer bytes. + * invocation of a method for this input stream. Returns 0 when the file + * position is beyond EOF. The next invocation might be the same thread + * or another thread. A single read or skip of this many bytes will not + * block, but may read or skip fewer bytes. * *
In some cases, a non-blocking read (or skip) may appear to be
* blocked when it is merely slow, for example when reading large
diff --git a/src/share/classes/java/io/InputStream.java b/src/share/classes/java/io/InputStream.java
index cb61314b01db29eada561a1c938e28f25617c758..3c7ff17f60900f71b03529bc5c38ce86aca17650 100644
--- a/src/share/classes/java/io/InputStream.java
+++ b/src/share/classes/java/io/InputStream.java
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1994, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -193,8 +193,10 @@ public abstract class InputStream implements Closeable {
* up skipping over some smaller number of bytes, possibly 0.
* This may result from any of a number of conditions; reaching end of file
* before n bytes have been skipped is only one possibility.
- * The actual number of bytes skipped is returned. If n is
- * negative, no bytes are skipped.
+ * The actual number of bytes skipped is returned. If {@code n} is
+ * negative, the {@code skip} method for class {@code InputStream} always
+ * returns 0, and no bytes are skipped. Subclasses may handle the negative
+ * value differently.
*
*
The skip method of this class creates a
* byte array and then repeatedly reads into it until n bytes
diff --git a/src/share/native/java/io/FileInputStream.c b/src/share/native/java/io/FileInputStream.c
index 37deaf84efb3107c8c7852040a027753b0c75d5c..52e2cdd8e6b30f8d2a34827c039ec133e7d58bd7 100644
--- a/src/share/native/java/io/FileInputStream.c
+++ b/src/share/native/java/io/FileInputStream.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -100,6 +100,8 @@ Java_java_io_FileInputStream_available(JNIEnv *env, jobject this) {
if (IO_Available(fd, &ret)) {
if (ret > INT_MAX) {
ret = (jlong) INT_MAX;
+ } else if (ret < 0) {
+ ret = 0;
}
return jlong_to_jint(ret);
}
diff --git a/test/java/io/FileInputStream/LargeFileAvailable.java b/test/java/io/FileInputStream/LargeFileAvailable.java
index 90eed30d1dc3e1a322fed8acf17f5a541a273c2a..94f6f856c2a822b24dc7695fced22e91b01fa122 100644
--- a/test/java/io/FileInputStream/LargeFileAvailable.java
+++ b/test/java/io/FileInputStream/LargeFileAvailable.java
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2010, 2012, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -23,7 +23,7 @@
/*
* @test
- * @bug 6402006 7030573
+ * @bug 6402006 7030573 8011136
* @summary Test if available returns correct value when reading
* a large file.
*/
@@ -61,9 +61,12 @@ public class LargeFileAvailable {
remaining -= skipBytes(fis, bigSkip, remaining);
remaining -= skipBytes(fis, 10L, remaining);
remaining -= skipBytes(fis, bigSkip, remaining);
- if (fis.available() != (int) remaining) {
- throw new RuntimeException("available() returns "
- + fis.available() + " but expected " + remaining);
+ int expected = (remaining >= Integer.MAX_VALUE)
+ ? Integer.MAX_VALUE
+ : (remaining > 0 ? (int) remaining : 0);
+ if (fis.available() != expected) {
+ throw new RuntimeException("available() returns "
+ + fis.available() + " but expected " + expected);
}
} finally {
file.delete();
@@ -77,19 +80,18 @@ public class LargeFileAvailable {
long skip = is.skip(toSkip);
if (skip != toSkip) {
throw new RuntimeException("skip() returns " + skip
- + " but expected " + toSkip);
+ + " but expected " + toSkip);
}
long remaining = avail - skip;
- int expected = remaining >= Integer.MAX_VALUE
- ? Integer.MAX_VALUE
- : (int) remaining;
+ int expected = (remaining >= Integer.MAX_VALUE)
+ ? Integer.MAX_VALUE
+ : (remaining > 0 ? (int) remaining : 0);
- System.out.println("Skipped " + skip + " bytes "
- + " available() returns " + expected +
- " remaining=" + remaining);
+ System.out.println("Skipped " + skip + " bytes, available() returns "
+ + expected + ", remaining " + remaining);
if (is.available() != expected) {
throw new RuntimeException("available() returns "
- + is.available() + " but expected " + expected);
+ + is.available() + " but expected " + expected);
}
return skip;
}
diff --git a/test/java/io/FileInputStream/NegativeAvailable.java b/test/java/io/FileInputStream/NegativeAvailable.java
index a4dedbcdcf7137ccd56b52950b3dddc16bd6b8ef..a0e0e9992310c31f2ab19e71b47374f28123c0ed 100644
--- a/test/java/io/FileInputStream/NegativeAvailable.java
+++ b/test/java/io/FileInputStream/NegativeAvailable.java
@@ -23,7 +23,7 @@
/*
* @test
- * @bug 8010837
+ * @bug 8010837 8011136
* @summary Test if available returns correct value when skipping beyond
* the end of a file.
* @author Dan Xu
@@ -42,6 +42,7 @@ public class NegativeAvailable {
public static void main(String[] args) throws IOException {
final int SIZE = 10;
final int SKIP = 5;
+ final int NEGATIVE_SKIP = -5;
// Create a temporary file with size of 10 bytes.
Path tmp = Files.createTempFile(null, null);
@@ -56,12 +57,15 @@ public class NegativeAvailable {
try (FileInputStream fis = new FileInputStream(tempFile)) {
if (tempFile.length() != SIZE) {
throw new RuntimeException("unexpected file size = "
- + tempFile.length());
+ + tempFile.length());
}
long space = skipBytes(fis, SKIP, SIZE);
+ space = skipBytes(fis, NEGATIVE_SKIP, space);
space = skipBytes(fis, SKIP, space);
space = skipBytes(fis, SKIP, space);
space = skipBytes(fis, SKIP, space);
+ space = skipBytes(fis, NEGATIVE_SKIP, space);
+ space = skipBytes(fis, NEGATIVE_SKIP, space);
}
Files.deleteIfExists(tmp);
}
@@ -74,17 +78,18 @@ public class NegativeAvailable {
long skip = fis.skip(toSkip);
if (skip != toSkip) {
throw new RuntimeException("skip() returns " + skip
- + " but expected " + toSkip);
+ + " but expected " + toSkip);
}
- long remaining = space - toSkip;
+ long newSpace = space - toSkip;
+ long remaining = newSpace > 0 ? newSpace : 0;
int avail = fis.available();
if (avail != remaining) {
throw new RuntimeException("available() returns " + avail
- + " but expected " + remaining);
+ + " but expected " + remaining);
}
System.out.println("Skipped " + skip + " bytes "
- + " available() returns " + avail);
- return remaining;
+ + " available() returns " + avail);
+ return newSpace;
}
}