Simplify FileInputStream.skip to match the RI.

The RI throws IOException on any non-seekable stream, including stdin.
This patch removes harmony's special-case hack for stdin, and the native
cruft that wasn't even necessary if you did want a special hack for
stdin.

Bug: 1542253

4 files changed, 27 insertions, 47 deletions

diff --git a/luni/src/main/java/java/io/FileInputStream.java b/luni/src/main/java/java/io/FileInputStream.java
index 1243262..c236888 100644
--- a/luni/src/main/java/java/io/FileInputStream.java
+++ b/luni/src/main/java/java/io/FileInputStream.java
@@ -312,25 +312,24 @@ public class FileInputStream extends InputStream implements Closeable {
         }
         openCheck();
         synchronized (repositioningLock) {
-            // stdin requires special handling
-            if (fd == FileDescriptor.in) {
-                return (int) fileSystem.ttyRead(buffer, offset, count);
-            }
+            // BEGIN android-changed
+            // If you only support Linux, there's nothing special about stdin.
             return (int) fileSystem.read(fd.descriptor, buffer, offset, count);
+            // END android-changed
         }
     }
 
     /**
      * Skips {@code count} number of bytes in this stream. Subsequent
-     * {@code read()}'s will not return these bytes unless {@code reset()} is
-     * used. This method may perform multiple reads to read {@code count} bytes.
+     * {@code read()}s will not return these bytes unless {@code reset()} is
+     * used. If the underlying stream is unseekable, an IOException is thrown.
      *
      * @param count
      *            the number of bytes to skip.
      * @return the number of bytes actually skipped.
      * @throws IOException
-     *             if {@code count < 0}, this stream is closed or another
-     *             IOException occurs.
+     *             if {@code count < 0}, this stream is closed or unseekable,
+     *             or another IOException occurs.
      */
     @Override
     public long skip(long count) throws IOException {
@@ -344,29 +343,18 @@ public class FileInputStream extends InputStream implements Closeable {
             throw new IOException(Msg.getString("KA013")); //$NON-NLS-1$
         }
 
-        // stdin requires special handling
-        if (fd == FileDescriptor.in) {
-            // Read and discard count bytes in 8k chunks
-            long skipped = 0, numRead;
-            int chunk = count < 8192 ? (int) count : 8192;
-            byte[] buffer = new byte[chunk];
-            for (long i = count / chunk; i >= 0; i--) {
-                numRead = fileSystem.ttyRead(buffer, 0, chunk);
-                skipped += numRead;
-                if (numRead < chunk) {
-                    return skipped;
-                }
-            }
-            return skipped;
-        }
-
+        // BEGIN android-changed
+        // The RI doesn't treat stdin as special. It throws IOException for
+        // all non-seekable streams, so we do too. If you did want to support
+        // non-seekable streams, the best way to do it would be to recognize
+        // when lseek(2) fails with ESPIPE and call super.skip(count).
         synchronized (repositioningLock) {
-            final long currentPosition = fileSystem.seek(fd.descriptor, 0L,
-                    IFileSystem.SEEK_CUR);
-            final long newPosition = fileSystem.seek(fd.descriptor,
-                    currentPosition + count, IFileSystem.SEEK_SET);
-            return newPosition - currentPosition;
+            // Our seek returns the new offset, but we know it will throw an
+            // exception if it couldn't perform exactly the seek we asked for.
+            fileSystem.seek(fd.descriptor, count, IFileSystem.SEEK_CUR);
+            return count;
         }
+        // END android-changed
     }
 
     private synchronized void openCheck() throws IOException {
diff --git a/luni/src/main/java/org/apache/harmony/luni/platform/IFileSystem.java b/luni/src/main/java/org/apache/harmony/luni/platform/IFileSystem.java
index 7613f0e..bee1557 100644
--- a/luni/src/main/java/org/apache/harmony/luni/platform/IFileSystem.java
+++ b/luni/src/main/java/org/apache/harmony/luni/platform/IFileSystem.java
@@ -108,10 +108,9 @@ public interface IFileSystem {
 
     // BEGIN android-deleted
     // public long ttyAvailable() throws IOException;
+    // public long ttyRead(byte[] bytes, int offset, int length) throws IOException;
     // END android-deleted
     
-    public long ttyRead(byte[] bytes, int offset, int length) throws IOException;
-    
     // BEGIN android-added
     public int ioctlAvailable(int fileDescriptor) throws IOException;
     // END android-added
diff --git a/luni/src/main/java/org/apache/harmony/luni/platform/OSFileSystem.java b/luni/src/main/java/org/apache/harmony/luni/platform/OSFileSystem.java
index 0338a52..b7a62e2 100644
--- a/luni/src/main/java/org/apache/harmony/luni/platform/OSFileSystem.java
+++ b/luni/src/main/java/org/apache/harmony/luni/platform/OSFileSystem.java
@@ -182,16 +182,15 @@ class OSFileSystem implements IFileSystem {
     // private native long ttyAvailableImpl();
     // END android-deleted
 
-    // BEGIN android-changed
-    public long ttyRead(byte[] bytes, int offset, int length) throws IOException {
-        if (bytes == null) {
-            throw new NullPointerException();
-        }
-        return ttyReadImpl(bytes, offset, length);
-    }
-
-    private native long ttyReadImpl(byte[] bytes, int offset, int length) throws IOException;
-    // END android-changed
+    // BEGIN android-deleted
+    // public long ttyRead(byte[] bytes, int offset, int length) throws IOException {
+    //    if (bytes == null) {
+    //        throw new NullPointerException();
+    //    }
+    //    return ttyReadImpl(bytes, offset, length);
+    // }
+    // private native long ttyReadImpl(byte[] bytes, int offset, int length) throws IOException;
+    // END android-deleted
 
     // BEGIN android-added
     public native int ioctlAvailable(int fileDescriptor) throws IOException;
diff --git a/luni/src/main/native/org_apache_harmony_luni_platform_OSFileSystem.cpp b/luni/src/main/native/org_apache_harmony_luni_platform_OSFileSystem.cpp
index 14fabbe..3e229d0 100644
--- a/luni/src/main/native/org_apache_harmony_luni_platform_OSFileSystem.cpp
+++ b/luni/src/main/native/org_apache_harmony_luni_platform_OSFileSystem.cpp
@@ -495,11 +495,6 @@ static jint harmony_io_ioctlAvailable(JNIEnv*env, jobject, jint fd) {
     return (jint) avail;
 }
 
-static jlong harmony_io_ttyReadImpl(JNIEnv* env, jobject thiz,
-        jbyteArray byteArray, jint offset, jint nbytes) {
-    return harmony_io_readImpl(env, thiz, STDIN_FILENO, byteArray, offset, nbytes);
-}
-
 /*
  * JNI registration
  */
@@ -518,7 +513,6 @@ static JNINativeMethod gMethods[] = {
     { "transfer",           "(ILjava/io/FileDescriptor;JJ)J",
                                           (void*) harmony_io_transfer },
     { "truncate",           "(IJ)V",      (void*) harmony_io_truncate },
-    { "ttyReadImpl",        "([BII)J",    (void*) harmony_io_ttyReadImpl },
     { "unlockImpl",         "(IJJ)V",     (void*) harmony_io_unlockImpl },
     { "writeDirect",        "(IIII)J",    (void*) harmony_io_writeDirect },
     { "writeImpl",          "(I[BII)J",   (void*) harmony_io_writeImpl },