update comment

Author: neoremind

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/CharsetMapping.java

@@ -9,7 +9,7 @@
 
 /**
  * <pre>
- *   mysql> SHOW CHARACTER SET;
+ * mysql&gt; SHOW CHARACTER SET;
  * +----------+-----------------------------+---------------------+--------+
  * | Charset  | Description                 | Default collation   | Maxlen |
  * +----------+-----------------------------+---------------------+--------+

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/TableReader.java

@@ -79,7 +79,8 @@ public void open() {
 
   /**
    * Get number of pages. If page size is 16KiB, then the value will be <code>file size / 16384</code>.
-   * @return
+   *
+   * @return number of pages
    */
   public long getNumOfPages() {
     checkNotNull(storageService, "storageService should not null, please make sure TableReader is opened");

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/column/ColumnFactory.java

@@ -217,9 +217,9 @@ public Class<?> typeClass() {
 
   /**
    * https://dev.mysql.com/doc/refman/5.7/en/innodb-row-format.html
-   * <p/>
+   * <p>
    * a CHAR(255) column can exceed 768 bytes if the maximum byte length of the character set is greater than 3, as it is with utf8mb4.
-   * <p/>
+   * <p>
    * 在单字节字符集下，如果存储的是非 NULL 值时，会占满指定的空间。比如 CHAR(10)，存储除 NULL 之外的其它值时，一定会占 10 bytes 空间，不足用 \x20 填充。
    * 在多字节字符集下（测试用的是 utf8mb4），如果存储的是非 NULL 值时
    * 至少占用与指定值相等的字节空间，比如 CHAR(10)，至少会占用 10 bytes 空间，如果存储的内容超过了 10 bytes （对于 ubf8mb4 编码来说，CHAR(10) 最多能存储 40 bytes 内容），那么只占用实际占用的字节数。
@@ -314,7 +314,7 @@ public Class<?> typeClass() {
    * As of MySQL 5.6.4 the TIME, TIMESTAMP, and DATETIME types can have a fractional seconds part.
    * Storage for these types is big endian (for memcmp() compatibility purposes), with the nonfractional
    * part followed by the fractional part. (Storage and encoding for the YEAR and DATE types remains unchanged.)
-   * <p/>
+   * <p>
    * https://dev.mysql.com/doc/internals/en/date-and-time-data-type-representation.html
    * <pre>
    * 1 bit  sign           (1= non-negative, 0= negative)

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/page/PageType.java

@@ -11,7 +11,7 @@
 
 /**
  * PageType
- * <p/>
+ * <p>
  * Please refer to i_ss.cc or fil0fil.h
  *
  * @author xu.zx

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/page/fsphdr/FspHeader.java

@@ -21,14 +21,14 @@ public class FspHeader {
 
   /**
    * Highest page number in file (size)
-   * <p/>
+   * <p>
    * 当前表空间总的PAGE个数，扩展文件时需要更新该值fsp_try_extend_data_file_with_pages
    */
   private long size;
 
   /**
    * Highest page number initialized (free limit)
-   * <p/>
+   * <p>
    * 当前尚未初始化的最小Page No。从该Page往后的都尚未加入到表空间的FREE LIST上。
    */
   private long freeLimit;

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/page/index/FsegHeader.java

@@ -12,7 +12,7 @@
  * the index root page’s FSEG header contains pointers to the file segments
  * used by this index.
  * All other index pages’ FSEG headers are unused and zero-filled.
- * <p/>
+ * <p>
  * 20 bytes header
  *
  * @author xu.zx

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/page/index/Index.java

@@ -85,22 +85,22 @@ public boolean isRootPage() {
    * Get used bytes in a page. For example, given a page like below, the used bytes is
    * <code>1000 + 376 + 8 - 240 = 1144</code>
    * <pre>
-   *      0 +----------------------+ <- page offset 0
+   *      0 +----------------------+  <= page offset 0
    *        |      FilHeader       |
    *     38 +----------------------+
    *    138 |        row 1         |
    *    400 |        row 2         |
-   *    660 | row 3 (mark deleted) |  <- Deleted record will be counted as free space
+   *    660 | row 3 (mark deleted) |  <= Deleted record will be counted as free space
    *    800 |        row 4         |
-   *    920 |        row 5         |  <- Heap top position. The byte offset of the "end" of the currently used space
+   *    920 |        row 5         |  <= Heap top position. The byte offset of the "end" of the currently used space
    *   1000 +----------------------+
    *        |                      |
-   *        |                      |  <- Free space
+   *        |                      |  <= Free space
    *  16000 +----------------------+
    *        |   Directory slots    |
    *  16376 +----------------------+
    *        |      FilTrailer      |
-   *  16384 +----------------------+ <- page offset SIZE_OF_PAGE, usually 16KiB
+   *  16384 +----------------------+ <= page offset SIZE_OF_PAGE, usually 16KiB
    * </pre>
    *
    * @return used bytes

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/page/index/IndexHeader.java

@@ -9,7 +9,7 @@
 
 /**
  * IndexHeader
- * <p/>
+ * <p>
  * 36 bytes header
  *
  * @author xu.zx

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/page/index/OverflowPagePointer.java

@@ -9,23 +9,26 @@
 
 /**
  * https://mysqlserverteam.com/externally-stored-fields-in-innodb/
- * <p/>
+ * <p>
  * https://www.itread01.com/content/1546184536.html
- * <p/>
+ * <p>
  * When a BLOB field is stored externally, a BLOB reference is stored in the clustered index record.
  * The BLOB reference will be stored after the BLOB prefix, if any. This BLOB reference is 20 bytes, and it contains
  * the following information:
- * >>>>當一個BLOB field被儲存在external pages時，會在index pages中儲存該BLOB field的BLOB reference(指示該BLOB的size,external page位置等元資料資訊)。
+ * 當一個BLOB field被儲存在external pages時，會在index pages中儲存該BLOB field的BLOB reference(指示該BLOB的size,external page位置等元資料資訊)。
  * 如果表的row format為COMPACT或者REDUNDANT，那麼BLOB reference儲存在BLOB prefix之後。BLOB reference 佔用20 bytes空間，包含如下資訊：
  * <ul>
- * <li>The space identifier (4 bytes)    >>>>表空間資訊(下圖中的Space ID部分)</li>
- * <li>The page number where the first page of the BLOB is stored (4 bytes)    >>>>儲存BLOB field的起始 page號(下圖中的Page Number部分)</li>
- * <li>The offset of the BLOB header within that page (4 bytes)    >>>>起始page中 BLOB header 的位移量(下圖中的Offset)</li>
- * <li>The total size of the BLOB data (8 bytes)    >>>>該BLOB 的 total size(除了上面三個以外的剩餘部分)</li>
+ * <li>The space identifier (4 bytes)    表空間資訊(下圖中的Space ID部分)</li>
+ * <li>The page number where the first page of the BLOB is stored (4 bytes)
+ * 儲存BLOB field的起始 page號(下圖中的Page Number部分)</li>
+ * <li>The offset of the BLOB header within that page (4 bytes)
+ * 起始page中 BLOB header 的位移量(下圖中的Offset)</li>
+ * <li>The total size of the BLOB data (8 bytes)
+ * 該BLOB 的 total size(除了上面三個以外的剩餘部分)</li>
  * </ul>
  * Even though 8 bytes are available to store the total size of the BLOB data, only the last 4 bytes are actually
  * used. This means that within InnoDB, the maximum size of a single BLOB field is currently 4GB.
- * >>>>儘管上面我們提到有8 bytes的空間可以用來儲存BLOB size資訊，但是實際上僅有 4 bytes空間可以真正用來儲存BLOB size 資訊。
+ * 儘管上面我們提到有8 bytes的空間可以用來儲存BLOB size資訊，但是實際上僅有 4 bytes空間可以真正用來儲存BLOB size 資訊。
  * 這就意味著，innodb中可以儲存的最大 BLOB field size 是4 GB(4 bytes=32 bit ,2^32=4GB)
  *
  * @author xu.zx

innodb-java-reader/src/main/java/com/alibaba/innodb/java/reader/page/index/RecordHeader.java

@@ -45,7 +45,7 @@ public class RecordHeader {
   /**
    * Next Record Offset: A relative offset from the current record to the origin of the next record
    * within the page in ascending order by key.
-   * <p/>
+   * <p>
    * 直接定位到下一个record的数据部分，而不是header
    */
   private int nextRecOffset;