8268435: (ch) ChannelInputStream could override readAllBytes

Reviewed-by: alanb, lancea

src/java.base/share/classes/java/io/FileInputStream.java

@@ -339,7 +339,7 @@ public byte[] readNBytes(int len) throws IOException {
         int n;
         do {
             n = read(buf, nread, remaining);
-            if (n > 0 ) {
+            if (n > 0) {
                 nread += n;
                 remaining -= n;
             } else if (n == 0) {

src/java.base/share/classes/sun/nio/ch/ChannelInputStream.java

@@ -25,11 +25,18 @@
 
 package sun.nio.ch;
 
-import java.io.*;
-import java.nio.*;
-import java.nio.channels.*;
-import java.nio.channels.spi.*;
+import java.io.InputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.IllegalBlockingModeException;
+import java.nio.channels.ReadableByteChannel;
+import java.nio.channels.SeekableByteChannel;
+import java.nio.channels.SelectableChannel;
+import java.util.Arrays;
 import java.util.Objects;
+import jdk.internal.util.ArraysSupport;
 
 /**
  * This class is defined here rather than in java.nio.channels.Channels
@@ -43,13 +50,13 @@
 public class ChannelInputStream
     extends InputStream
 {
+    private static final int DEFAULT_BUFFER_SIZE = 8192;
 
     public static int read(ReadableByteChannel ch, ByteBuffer bb,
                            boolean block)
         throws IOException
     {
-        if (ch instanceof SelectableChannel) {
-            SelectableChannel sc = (SelectableChannel)ch;
+        if (ch instanceof SelectableChannel sc) {
             synchronized (sc.blockingLock()) {
                 boolean bm = sc.isBlocking();
                 if (!bm)
@@ -107,10 +114,95 @@ protected int read(ByteBuffer bb)
         return ChannelInputStream.read(ch, bb, true);
     }
 
+    @Override
+    public byte[] readAllBytes() throws IOException {
+        if (!(ch instanceof SeekableByteChannel sbc))
+            return super.readAllBytes();
+
+        long length = sbc.size();
+        long position = sbc.position();
+        long size = length - position;
+
+        if (length <= 0 || size <= 0)
+            return super.readAllBytes();
+
+        if (size > (long) Integer.MAX_VALUE) {
+            String msg =
+                String.format("Required array size too large: %d = %d - %d",
+                    size, length, position);
+            throw new OutOfMemoryError(msg);
+        }
+
+        int capacity = (int)size;
+        byte[] buf = new byte[capacity];
+
+        int nread = 0;
+        int n;
+        for (;;) {
+            // read to EOF which may read more or less than initial size, e.g.,
+            // file is truncated while we are reading
+            while ((n = read(buf, nread, capacity - nread)) > 0)
+                nread += n;
+
+            // if last call to read() returned -1, we are done; otherwise,
+            // try to read one more byte and if that fails we're done too
+            if (n < 0 || (n = read()) < 0)
+                break;
+
+            // one more byte was read; need to allocate a larger buffer
+            capacity = Math.max(ArraysSupport.newLength(capacity,
+                                                        1,         // min growth
+                                                        capacity), // pref growth
+                                DEFAULT_BUFFER_SIZE);
+            buf = Arrays.copyOf(buf, capacity);
+            buf[nread++] = (byte)n;
+        }
+        return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
+    }
+
+    @Override
+    public byte[] readNBytes(int len) throws IOException {
+        if (len < 0)
+            throw new IllegalArgumentException("len < 0");
+        if (len == 0)
+            return new byte[0];
+
+        if (!(ch instanceof SeekableByteChannel sbc))
+            return super.readAllBytes();
+
+        long length = sbc.size();
+        long position = sbc.position();
+        long size = length - position;
+
+        if (length <= 0 || size <= 0)
+            return super.readNBytes(len);
+
+        int capacity = (int)Math.min(len, size);
+        byte[] buf = new byte[capacity];
+
+        int remaining = capacity;
+        int nread = 0;
+        int n;
+        do {
+            n = read(buf, nread, remaining);
+            if (n > 0) {
+                nread += n;
+                remaining -= n;
+            } else if (n == 0) {
+                // Block until a byte is read or EOF is detected
+                byte b = (byte)read();
+                if (b == -1 )
+                    break;
+                buf[nread++] = b;
+                remaining--;
+            }
+        } while (n >= 0 && remaining > 0);
+        return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
+    }
+
     public int available() throws IOException {
         // special case where the channel is to a file
-        if (ch instanceof SeekableByteChannel) {
-            SeekableByteChannel sbc = (SeekableByteChannel)ch;
+        if (ch instanceof SeekableByteChannel sbc) {
             long rem = Math.max(0, sbc.size() - sbc.position());
             return (rem > Integer.MAX_VALUE) ? Integer.MAX_VALUE : (int)rem;
         }
@@ -119,8 +211,7 @@ public int available() throws IOException {
 
     public synchronized long skip(long n) throws IOException {
         // special case where the channel is to a file
-        if (ch instanceof SeekableByteChannel) {
-            SeekableByteChannel sbc = (SeekableByteChannel)ch;
+        if (ch instanceof SeekableByteChannel sbc) {
             long pos = sbc.position();
             long newPos;
             if (n > 0) {