On Mon, 24 Jul 2023 13:04:56 GMT, Alan Bateman <al...@openjdk.org> wrote:
>> src/java.base/share/native/libjava/io_util.c line 99:
>>
>>> 97: return 0;
>>> 98: } else if (len > BUF_SIZE) {
>>> 99: if (len > MAX_MALLOC_SIZE)
>>
>> Hi Brian if I am reading code correctly then with the current code change
>> FIS.read(byte[] b, int off, int len) will always read (MAX_MALLOC_SIZE
>> 2097152) bytes if len > MAX_MALLOC_SIZE.
>>
>> The java doc of read as below
>>
>> public int read(byte[] b,
>> int off,
>> int len)
>> throws IOException
>> Reads up to len bytes of data from the input stream into an array of bytes.
>> An attempt is made to read as many as len bytes, but a smaller number may be
>> read. The number of bytes actually read is returned as an integer.
>>
>> I think if you are limiting the internal dynamic buffer to 2097152 byte
>> then you have to at least attempt to read as many as len bytes if possible
>> before returning.
>>
>> If I simply the run the following code
>>
>> int size = 501 * 501 * 501 * 3;
>>
>> FileInputStream fis = new
>> FileInputStream("/home/vyom1/test.img"); // Any file with size >=
>> 501*501*501*2
>>
>> System.out.println("size: " + size);
>>
>> byte buf[] = new byte[size];
>>
>> System.out.println("buf ok");
>>
>> int bytesRead = fis.read(buf, 0, size);
>> System.out.println("Bytes read " + bytesRead);
>>
>> It will always print “Bytes read 2097152” which is not as per Java
>> specification of InputStream.read(byte[]b, int off, int len).
>
> A short read is okay but changing long standing behavior could potentially
> break already broken code that calls the method with a large byte array and
> assumes it will read to EOF. So I think it's a forced move to read until
> there is no space remaining or EOF is reached. This is logic for the Java
> level, not the native code of course. If an I/O exception is on the
> second/subsequent reads then it will have to return the bytes that are read,
> not throw with bytes in the buffer.
Addressed in 973e848a84113f8d6eb65702a148138f2edca1ee.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/14981#discussion_r1274219415
