fix: wrong data from Blob/Clob when mark/reset is used (#971)

BlobInputStream#reset() did not invalidate read buffer, thus it resulted in reading wrong data.

CHANGELOG.md

@@ -7,6 +7,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
### Fixed
- Avoid failure for `insert ... on conflict...update` for `reWriteBatchedInserts=true` case [PR 1130](https://github.com/pgjdbc/pgjdbc/pull/1130)
- fix: allowEncodingChanges should allow set client_encoding=... [PR 1125](https://github.com/pgjdbc/pgjdbc/pull/1125)
- Wrong data from Blob/Clob when mark/reset is used [PR 971](https://github.com/pgjdbc/pgjdbc/pull/971)

## [42.2.1] (2018-01-25)
### Known issues

pgjdbc/src/main/java/org/postgresql/largeobject/BlobInputStream.java

@@ -41,7 +41,7 @@
  /**
   * The mark position
   */
  private int mpos = 0;
  private long mpos = 0;

  /**
   * The limit
@@ -156,12 +156,7 @@ public void close() throws IOException {
   * @see java.io.InputStream#reset()
   */
  public synchronized void mark(int readlimit) {
    try {
      mpos = lo.tell();
    } catch (SQLException se) {
      // Can't throw this because mark API doesn't allow it.
      // throw new IOException(se.toString());
    }
    mpos = apos;
  }

  /**
@@ -174,7 +169,13 @@ public synchronized void mark(int readlimit) {
  public synchronized void reset() throws IOException {
    checkClosed();
    try {
      lo.seek(mpos);
      if (mpos <= Integer.MAX_VALUE) {
        lo.seek((int)mpos);
      } else {
        lo.seek64(mpos, LargeObject.SEEK_SET);
      }
      buffer = null;
      apos = mpos;
    } catch (SQLException se) {
      throw new IOException(se.toString());
    }

pgjdbc/src/test/java/org/postgresql/test/jdbc2/BlobTest.java

@@ -155,6 +155,31 @@ public void testUploadBlob_NATIVE() throws Exception {
    assertTrue(compareBlobs());
  }

  @Test
  public void testMarkResetStream() throws Exception {
    assertTrue(uploadFile("/test-file.xml", NATIVE_STREAM) > 0);

    Statement stmt = con.createStatement();
    ResultSet rs = stmt.executeQuery("SELECT lo FROM testblob");
    assertTrue(rs.next());

    LargeObjectManager lom = ((org.postgresql.PGConnection) con).getLargeObjectAPI();

    long oid = rs.getLong(1);
    LargeObject blob = lom.open(oid);
    InputStream bis = blob.getInputStream();

    assertEquals('<', bis.read());
    bis.mark(4);
    assertEquals('?', bis.read());
    assertEquals('x', bis.read());
    assertEquals('m', bis.read());
    assertEquals('l', bis.read());
    bis.reset();
    assertEquals('?', bis.read());
  }


  @Test
  public void testGetBytesOffset() throws Exception {
    assertTrue(uploadFile("/test-file.xml", NATIVE_STREAM) > 0);