mariadb/sql/sql_digest.h

/* Copyright (c) 2008, 2015, Oracle and/or its affiliates. All rights reserved.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; version 2 of the License.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software Foundation,
  51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */

#ifndef SQL_DIGEST_H
#define SQL_DIGEST_H

#include <string.h>
class String;
#include "my_md5.h"

#define MAX_DIGEST_STORAGE_SIZE (1024*1024)

/**
  Structure to store token count/array for a statement
  on which digest is to be calculated.
*/
struct sql_digest_storage
{
  bool m_full;
  uint m_byte_count;
  unsigned char m_md5[MD5_HASH_SIZE];
  /** Character set number. */
  uint m_charset_number;
  /**
    Token array.
    Token array is an array of bytes to store tokens received during parsing.
    Following is the way token array is formed.
    ... &lt;non-id-token&gt; &lt;non-id-token&gt; &lt;id-token&gt; &lt;id_len&gt; &lt;id_text&gt; ...
    For Example:
    SELECT * FROM T1;
    &lt;SELECT_TOKEN&gt; &lt;*&gt; &lt;FROM_TOKEN&gt; &lt;ID_TOKEN&gt; &lt;2&gt; &lt;T1&gt;

    @note Only the first @c m_byte_count bytes are initialized,
      out of @c m_token_array_length.
  */
  unsigned char *m_token_array;
  /* Length of the token array to be considered for DIGEST_TEXT calculation. */
  uint m_token_array_length;

  sql_digest_storage()
  {
    reset(NULL, 0);
  }

  inline void reset(unsigned char *token_array, size_t length)
  {
    m_token_array= token_array;
    m_token_array_length= (uint)length;
    reset();
  }

  inline void reset()
  {
    m_full= false;
    m_byte_count= 0;
    m_charset_number= 0;
    memset(m_md5, 0, MD5_HASH_SIZE);
  }

  inline bool is_empty()
  {
    return (m_byte_count == 0);
  }

  inline void copy(const sql_digest_storage *from)
  {
    /*
      Keep in mind this is a dirty copy of something that may change,
      as the thread producing the digest is executing concurrently,
      without any lock enforced.
    */
    uint byte_count_copy= m_token_array_length < from->m_byte_count ?
                          m_token_array_length : from->m_byte_count;

    if (byte_count_copy > 0)
    {
      m_full= from->m_full;
      m_byte_count= byte_count_copy;
      m_charset_number= from->m_charset_number;
      memcpy(m_token_array, from->m_token_array, m_byte_count);
      memcpy(m_md5, from->m_md5, MD5_HASH_SIZE);
    }
    else
    {
      m_full= false;
      m_byte_count= 0;
      m_charset_number= 0;
    }
  }
};
typedef struct sql_digest_storage sql_digest_storage;

/**
  Compute a digest hash.
  @param digest_storage The digest
  @param [out] md5 The computed digest hash. This parameter is a buffer of size @c MD5_HASH_SIZE.
*/
void compute_digest_md5(const sql_digest_storage *digest_storage, unsigned char *md5);

/**
  Compute a digest text.
  A 'digest text' is a textual representation of a query,
  where:
  - comments are removed,
  - non significant spaces are removed,
  - literal values are replaced with a special '?' marker,
  - lists of values are collapsed using a shorter notation
  @param digest_storage The digest
  @param [out] digest_text
  @param digest_text_length Size of @c digest_text.
  @param [out] truncated true if the text representation was truncated
*/
void compute_digest_text(const sql_digest_storage *digest_storage,
                         String *digest_text);

#endif