/* Copyright (c) 2008, 2023, Oracle and/or its affiliates.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.

  This program is also distributed with certain software (including
  but not limited to OpenSSL) that is licensed under separate terms,
  as designated in a particular file or component or in included license
  documentation.  The authors of MySQL hereby grant you an additional
  permission to link the program and your derivative works with the
  separately licensed software that they have included with MySQL.

  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, version 2.0, 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, Suite 500, Boston, MA 02110-1335 USA */

#ifndef SQL_DIGEST_H
#define SQL_DIGEST_H

#include <string.h>
#include "sql_string.h"
#include "my_md5.h"

#define MAX_DIGEST_STORAGE_SIZE (1024*1024)

ulong get_max_digest_length();

/**
  Structure to store token count/array for a statement
  on which digest is to be calculated.
*/
struct sql_digest_storage
{
  bool m_full;
  size_t 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. */
  size_t 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= 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.
    */
    size_t 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