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src/java.base/share/classes/java/io/InputStream.java
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@@ -61,11 +61,12 @@
* {@code close()} method. Subsequent calls to {@code close()} have no
* effect.
*
* <p> While the stream is open, the {@code available()}, {@code read()},
* {@code read(byte[])}, {@code read(byte[], int, int)},
- * {@code readAllBytes()}, {@code readNBytes()}, {@code skip()}, and
+ * {@code readAllBytes()}, {@code readNBytes(byte[], int, int)},
+ * {@code readNBytes(int)}, {@code skip(long)}, and
* {@code transferTo()} methods all behave as if end of stream has been
* reached. After the stream has been closed, these methods all throw
* {@code IOException}.
*
* <p> The {@code markSupported()} method returns {@code false}. The
@@ -121,10 +122,19 @@
ensureOpen();
return 0;
}
@Override
+ public byte[] readNBytes(int len) throws IOException {
+ if (len < 0) {
+ throw new IllegalArgumentException("len < 0");
+ }
+ ensureOpen();
+ return new byte[0];
+ }
+
+ @Override
public long skip(long n) throws IOException {
ensureOpen();
return 0L;
}
@@ -231,12 +241,12 @@
* <code>IOException</code>, the exception is caught and treated as if it
* were end of file; the bytes read up to that point are stored into
* <code>b</code> and the number of bytes read before the exception
* occurred is returned. The default implementation of this method blocks
* until the requested amount of input data <code>len</code> has been read,
- * end of file is detected, or an exception is thrown. Subclasses are encouraged
- * to provide a more efficient implementation of this method.
+ * end of file is detected, or an exception is thrown. Subclasses are
+ * encouraged to provide a more efficient implementation of this method.
*
* @param b the buffer into which the data is read.
* @param off the start offset in array <code>b</code>
* at which the data is written.
* @param len the maximum number of bytes to read.
@@ -306,30 +316,89 @@
* so after some, but not all, bytes have been read. Consequently the input
* stream may not be at end of stream and may be in an inconsistent state.
* It is strongly recommended that the stream be promptly closed if an I/O
* error occurs.
*
+ * @implSpec
+ * This method invokes {@link #readNBytes(int)} with a length of
+ * {@link Integer#MAX_VALUE}.
+ *
* @return a byte array containing the bytes read from this input stream
* @throws IOException if an I/O error occurs
* @throws OutOfMemoryError if an array of the required size cannot be
- * allocated. For example, if an array larger than {@code 2GB} would
- * be required to store the bytes.
+ * allocated.
*
* @since 9
*/
public byte[] readAllBytes() throws IOException {
+ return readNBytes(Integer.MAX_VALUE);
+ }
+
+ /**
+ * Reads up to a specified number of bytes from the input stream. This
+ * method blocks until the requested number of bytes have been read, end
+ * of stream is detected, or an exception is thrown. This method does not
+ * close the input stream.
+ *
+ * <p> The length of the returned array equals the number of bytes read
+ * from the stream. If {@code len} is zero, then no bytes are read and
+ * an empty byte array is returned. Otherwise, up to {@code len} bytes
+ * are read from the stream. Fewer than {@code len} bytes may be read if
+ * end of stream is encountered.
+ *
+ * <p> When this stream reaches end of stream, further invocations of this
+ * method will return an empty byte array.
+ *
+ * <p> Note that this method is intended for simple cases where it is
+ * convenient to read the specified number of bytes into a byte array. The
+ * total amount of memory allocated by this method is proportional to the
+ * number of bytes read from the stream which is bounded by {@code len}.
+ * Therefore, the method may be safely called with very large values of
+ * {@code len} provided sufficient memory is available.
+ *
+ * <p> The behavior for the case where the input stream is <i>asynchronously
+ * closed</i>, or the thread interrupted during the read, is highly input
+ * stream specific, and therefore not specified.
+ *
+ * <p> If an I/O error occurs reading from the input stream, then it may do
+ * so after some, but not all, bytes have been read. Consequently the input
+ * stream may not be at end of stream and may be in an inconsistent state.
+ * It is strongly recommended that the stream be promptly closed if an I/O
+ * error occurs.
+ *
+ * @implNote
+ * The number of bytes allocated to read data from this stream and return
+ * the result is bounded by {@code 2*(long)len}, inclusive.
+ *
+ * @param len the maximum number of bytes to read
+ * @return a byte array containing the bytes read from this input stream
+ * @throws IllegalArgumentException if {@code length} is negative
+ * @throws IOException if an I/O error occurs
+ * @throws OutOfMemoryError if an array of the required size cannot be
+ * allocated.
+ *
+ * @since 11
+ */
+ public byte[] readNBytes(int len) throws IOException {
+ if (len < 0) {
+ throw new IllegalArgumentException("len < 0");
+ }
+
List<byte[]> bufs = null;
byte[] result = null;
int total = 0;
+ int remaining = len;
int n;
do {
- byte[] buf = new byte[DEFAULT_BUFFER_SIZE];
+ byte[] buf = new byte[Math.min(remaining, DEFAULT_BUFFER_SIZE)];
int nread = 0;
// read to EOF which may read more or less than buffer size
- while ((n = read(buf, nread, buf.length - nread)) > 0) {
+ while ((n = read(buf, nread,
+ Math.min(buf.length - nread, remaining))) > 0) {
nread += n;
+ remaining -= n;
}
if (nread > 0) {
if (MAX_BUFFER_SIZE - total < nread) {
throw new OutOfMemoryError("Required array size too large");
@@ -343,11 +412,13 @@
bufs.add(result);
}
bufs.add(buf);
}
}
- } while (n >= 0); // if the last call to read returned -1, then break
+ // if the last call to read returned -1 or the number of bytes
+ // requested have been read then break
+ } while (n >= 0 && remaining > 0);
if (bufs == null) {
if (result == null) {
return new byte[0];
}
@@ -355,16 +426,16 @@
result : Arrays.copyOf(result, total);
}
result = new byte[total];
int offset = 0;
- int remaining = total;
+ remaining = total;
for (byte[] b : bufs) {
- int len = Math.min(b.length, remaining);
- System.arraycopy(b, 0, result, offset, len);
- offset += len;
- remaining -= len;
+ int count = Math.min(b.length, remaining);
+ System.arraycopy(b, 0, result, offset, count);
+ offset += count;
+ remaining -= count;
}
return result;
}
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