mysql-5.7.36/sql/gen_lex_hash.cc

/*
   Copyright (c) 2000, 2021, 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.

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   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
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   This program is distributed in the hope that it will be useful,
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   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 */

/**
  @file

  @details
@verbatim
The idea of presented algorithm see in
"The Art of Computer Programming" by Donald E. Knuth
Volume 3 "Sorting and searching"
(chapter 6.3 "Digital searching" - name and number of chapter
   is back translation from Russian edition :))

as illustration of data structures, imagine next table:

static SYMBOL symbols[] = {
  { "ADD",              SYM(ADD),0,0},
  { "AND",              SYM(AND),0,0},
  { "DAY",              SYM(DAY_SYM),0,0},
};

for this structure, presented program generate next searching-structure:

+-----------+-+-+-+
|       len |1|2|3|
+-----------+-+-+-+
|first_char |0|0|a|
|last_char  |0|0|d|
|link       |0|0|+|
                 |
                 V
       +----------+-+-+-+--+
       |    1 char|a|b|c|d |
       +----------+-+-+-+--+
       |first_char|d|0|0|0 |
       |last_char |n|0|0|-1|
       |link      |+|0|0|+ |
                   |     |
                   |     V
                   |  symbols[2] ( "DAY" )
                   V
+----------+--+-+-+-+-+-+-+-+-+-+--+
|    2 char|d |e|f|j|h|i|j|k|l|m|n |
+----------+--+-+-+-+-+-+-+-+-+-+--+
|first_char|0 |0|0|0|0|0|0|0|0|0|0 |
|last_char |-1|0|0|0|0|0|0|0|0|0|-1|
|link      |+ |0|0|0|0|0|0|0|0|0|+ |
            |                    |
            V                    V
         symbols[0] ( "ADD" )  symbols[1] ( "AND" )

for optimization, link is the 16-bit index in 'symbols'
or search-array..

So, we can read full search-structure as 32-bit word
@endverbatim

@todo
    use instead to_upper_lex, special array
    (substitute chars) without skip codes..
@todo
    try use reverse order of comparing..

*/

#define NO_YACC_SYMBOLS
#include <my_global.h>
#include "mysql_version.h"
#include "lex.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <set>

#include <welcome_copyright_notice.h> /* ORACLE_WELCOME_COPYRIGHT_NOTICE */


static bool check_duplicates(uint group_mask);


struct hash_lex_struct
{
  int first_char;
  char last_char;
  // union value is undefined if first_char == 0
  union{
    hash_lex_struct *char_tails; // if first_char > 0
    int iresult;                 // if first_char == -1
  };
  int ithis;

  void destroy()
  {
    if (first_char <= 0)
      return;
    for (int i= 0, size= static_cast<uchar>(last_char) - first_char + 1;
         i < size; i++)
      char_tails[i].destroy();
    free(char_tails);
  }
};


class hash_map_info
{
public:
  hash_lex_struct *root_by_len;
  int max_len;

  char *hash_map;
  int size_hash_map;

  hash_map_info()
  : root_by_len(NULL), max_len(0), hash_map(NULL), size_hash_map(0)
  {}

  ~hash_map_info()
  {
    for (int i= 0; i < max_len; i++)
      root_by_len[i].destroy();
    free(root_by_len);
    free(hash_map);
  }

  hash_lex_struct *get_hash_struct_by_len(int len);
  void insert_symbols(int group_mask);
  void add_structs_to_map(hash_lex_struct *st, int len);
  void add_struct_to_map(hash_lex_struct *st);
  void set_links(hash_lex_struct *st, int len);
  bool print_hash_map(const char *name, uint group_mask);
};


hash_lex_struct *hash_map_info::get_hash_struct_by_len(int len)
{
  if (max_len < len)
  {
    root_by_len= (hash_lex_struct *) realloc((char*) root_by_len,
                                             sizeof(hash_lex_struct) * len);
    hash_lex_struct *cur, *end= root_by_len + len;
    for (cur= root_by_len + max_len; cur < end; cur++)
      cur->first_char= 0;
    max_len= len;
  }
  return root_by_len + len - 1;
}

void insert_into_hash(hash_lex_struct *root, const char *name,
		      int len_from_begin, int index)
{
  hash_lex_struct *end, *cur, *tails;

  if (!root->first_char)
  {
    root->first_char= -1;
    root->iresult= index;
    return;
  }

  if (root->first_char == -1)
  {
    int index2= root->iresult;
    const char *name2= symbols[index2].name + len_from_begin;
    root->first_char= (int) (uchar) name2[0];
    root->last_char= (char) root->first_char;
    tails= (hash_lex_struct*)malloc(sizeof(hash_lex_struct));
    root->char_tails= tails;
    tails->first_char= -1;
    tails->iresult= index2;
  }

  size_t real_size= (root->last_char-root->first_char+1);

  if (root->first_char>(*name))
  {
    size_t new_size= root->last_char-(*name)+1;
    if (new_size<real_size) printf("error!!!!\n");
    tails= root->char_tails;
    tails= (hash_lex_struct*)realloc((char*)tails,
				       sizeof(hash_lex_struct)*new_size);
    root->char_tails= tails;
    memmove(tails+(new_size-real_size),tails,real_size*sizeof(hash_lex_struct));
    end= tails + new_size - real_size;
    for (cur= tails; cur<end; cur++)
      cur->first_char= 0;
    root->first_char= (int) (uchar) *name;
  }

  if (root->last_char<(*name))
  {
    size_t new_size= (*name)-root->first_char+1;
    if (new_size<real_size) printf("error!!!!\n");
    tails= root->char_tails;
    tails= (hash_lex_struct*)realloc((char*)tails,
				    sizeof(hash_lex_struct)*new_size);
    root->char_tails= tails;
    end= tails + new_size;
    for (cur= tails+real_size; cur<end; cur++)
      cur->first_char= 0;
    root->last_char= (*name);
  }

  insert_into_hash(root->char_tails+(*name)-root->first_char,
		   name+1,len_from_begin+1,index);
}


void hash_map_info::insert_symbols(int group_mask)
{
  size_t i= 0;
  const SYMBOL *cur;
  for (cur= symbols; i < array_elements(symbols); cur++, i++)
  {
    if (!(cur->group & group_mask))
      continue;
    hash_lex_struct *root= get_hash_struct_by_len(cur->length);
    insert_into_hash(root, cur->name, 0, i);
  }
}


void hash_map_info::add_struct_to_map(hash_lex_struct *st)
{
  st->ithis= size_hash_map/4;
  size_hash_map+= 4;
  hash_map= (char*)realloc(hash_map,size_hash_map);
  hash_map[size_hash_map-4]= (char) (st->first_char == -1 ? 0 :
				     st->first_char);
  hash_map[size_hash_map-3]= (char) (st->first_char == -1 ||
				     st->first_char == 0 ? 0 : st->last_char);
  if (st->first_char == -1)
  {
    hash_map[size_hash_map-2]= ((unsigned int)(int16)st->iresult)&255;
    hash_map[size_hash_map-1]= ((unsigned int)(int16)st->iresult)>>8;
  }
  else if (st->first_char == 0)
  {
    hash_map[size_hash_map-2]= ((unsigned int)(int16)array_elements(symbols))&255;
    hash_map[size_hash_map-1]= ((unsigned int)(int16)array_elements(symbols))>>8;
  }
}


void hash_map_info::add_structs_to_map(hash_lex_struct *st, int len)
{
  hash_lex_struct *cur, *end= st+len;
  for (cur= st; cur<end; cur++)
    add_struct_to_map(cur);
  for (cur= st; cur<end; cur++)
  {
    if (cur->first_char && cur->first_char != -1)
      add_structs_to_map(cur->char_tails,cur->last_char-cur->first_char+1);
  }
}


void hash_map_info::set_links(hash_lex_struct *st, int len)
{
  hash_lex_struct *cur, *end= st+len;
  for (cur= st; cur<end; cur++)
  {
    if (cur->first_char != 0 && cur->first_char != -1)
    {
      int ilink= cur->char_tails->ithis;
      hash_map[cur->ithis*4+2]= ilink%256;
      hash_map[cur->ithis*4+3]= ilink/256;
      set_links(cur->char_tails,cur->last_char-cur->first_char+1);
    }
  }
}


bool hash_map_info::print_hash_map(const char *name, uint group_mask)
{
  if (check_duplicates(group_mask))
    return true;
  insert_symbols(group_mask);
  add_structs_to_map(root_by_len, max_len);
  set_links(root_by_len, max_len);

  printf("static const unsigned char %s_map[%d]= {\n", name, size_hash_map);

  char *cur;
  int i;
  for (i=0, cur= hash_map; i < size_hash_map; i++, cur++)
  {
    switch(i%4){
    case 0: case 1:
      if (!*cur)
	printf("0,   ");
      else
	printf("\'%c\', ",*cur);
      break;
    case 2: printf("%u, ",(uint)(uchar)*cur); break;
    case 3: printf("%u,\n",(uint)(uchar)*cur); break;
    }
  }
  printf("};\n\n");
  printf("const unsigned int %s_max_len=%d;\n", name, max_len);
  return false;
}


bool check_duplicates(uint group_mask)
{
  std::set<const char *> names;

  size_t i= 0;
  const SYMBOL *cur;
  for (cur= symbols; i < array_elements(symbols); cur++, i++)
  {
    if (!(cur->group & group_mask))
      continue;
    if (!names.insert(cur->name).second)
    {
      const char *err_tmpl= "\ngen_lex_hash fatal error : "
        "Unfortunately gen_lex_hash can not generate a hash,\n since "
        "your lex.h has duplicate definition for a symbol \"%s\"\n\n";
      printf (err_tmpl, cur->name);
      fprintf (stderr, err_tmpl, cur->name);
      return true;
    }
  }
  return false;
}


int main(int argc,char **argv)
{


  /* Broken up to indicate that it's not advice to you, gentle reader. */
  printf("/*\n\n  Do " "not " "edit " "this " "file " "directly!\n\n*/\n");

  puts("/*");
  puts(ORACLE_WELCOME_COPYRIGHT_NOTICE("2000"));
  puts("*/");

  /* Broken up to indicate that it's not advice to you, gentle reader. */
  printf("/* Do " "not " "edit " "this " "file!  This is generated by "
         "gen_lex_hash.cc\nthat seeks for a perfect hash function */\n\n");

  /* Print sql_keywords_and_funcs_map[] and sql_keyword_and_funcs_max_len: */
  if (hash_map_info().print_hash_map("sql_keywords_and_funcs", SG_MAIN_PARSER))
    exit(1);

  printf("\n");

  /* Print sql_keywords_map[] and sql_keywords_max_len values: */
  if (hash_map_info().print_hash_map("sql_keywords",
                                     SG_KEYWORDS | SG_HINTABLE_KEYWORDS))
    exit(1);

  printf("\n");

  /* Print hint_keywords_map[] and hint_keywords_max_len values: */
  if (hash_map_info().print_hash_map("hint_keywords", SG_HINTS))
    exit(1);

  exit(0);
}