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✏️ Editing: my_compare.h

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, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1335  USA */

#ifndef _my_compare_h
#define _my_compare_h

#include "myisampack.h"
#ifdef	__cplusplus
extern "C" {
#endif

#include "m_ctype.h"                            /* CHARSET_INFO */

/*
  There is a hard limit for the maximum number of keys as there are only
  8 bits in the index file header for the number of keys in a table.
  This means that 0..255 keys can exist for a table. The idea of
  HA_MAX_POSSIBLE_KEY is to ensure that one can use myisamchk & tools on
  a MyISAM table for which one has more keys than MyISAM is normally
  compiled for. If you don't have this, you will get a core dump when
  running myisamchk compiled for 128 keys on a table with 255 keys.
*/

#define HA_MAX_POSSIBLE_KEY         255         /* For myisamchk */
/*
  The following defines can be increased if necessary.
  But beware the dependency of MI_MAX_POSSIBLE_KEY_BUFF and HA_MAX_KEY_LENGTH.
*/

#define HA_MAX_KEY_LENGTH           1000        /* Max length in bytes */
#define HA_MAX_KEY_SEG              32          /* Max segments for key */

#define HA_MAX_POSSIBLE_KEY_BUFF    (HA_MAX_KEY_LENGTH + 24+ 6+6)
#define HA_MAX_KEY_BUFF  (HA_MAX_KEY_LENGTH+HA_MAX_KEY_SEG*6+8+8)

typedef struct st_HA_KEYSEG		/* Key-portion */
{
  CHARSET_INFO *charset;
  uint32 start;				/* Start of key in record */
  uint32 null_pos;			/* position to NULL indicator */
  uint16 bit_pos;                       /* Position to bit part */
  uint16 flag;
  uint16 length;			/* Keylength */
  uint16 language;
  uint8  type;				/* Type of key (for sort) */
  uint8  null_bit;			/* bitmask to test for NULL */
  uint8  bit_start;
  uint8  bit_length;                    /* Length of bit part */
} HA_KEYSEG;

#define get_key_length(length,key) \
{ if (*(const uchar*) (key) != 255) \
    length= (uint) *(const uchar*) ((key)++); \
  else \
  { length= mi_uint2korr((key)+1); (key)+=3; } \
}

#define get_key_length_rdonly(length,key) \
{ if (*(const uchar*) (key) != 255) \
    length= ((uint) *(const uchar*) ((key))); \
  else \
  { length= mi_uint2korr((key)+1); } \
}

#define get_key_pack_length(length,length_pack,key) \
{ if (*(const uchar*) (key) != 255) \
  { length= (uint) *(const uchar*) ((key)++); length_pack= 1; }\
  else \
  { length=mi_uint2korr((key)+1); (key)+= 3; length_pack= 3; } \
}

#define store_key_length_inc(key,length) \
{ if ((length) < 255) \
  { *(key)++= (uchar)(length); } \
  else \
  { *(key)=255; mi_int2store((key)+1,(length)); (key)+=3; } \
}

#define size_to_store_key_length(length) ((length) < 255 ? 1 : 3)

static inline uchar get_rec_bits(const uchar *ptr, uchar ofs, uint len)
{
  uint16 val= ptr[0];
  if (ofs + len > 8)
    val|= (uint16)(((uint) ptr[1]) << 8);
  return (uchar) ((val >> ofs) & ((1 << len) - 1));
}

static inline void set_rec_bits(uint16 bits, uchar *ptr, uchar ofs, uint len)
{
  ptr[0]= (uchar) ((ptr[0] & ~(((1 << len) - 1) << ofs)) | (bits << ofs));
  if (ofs + len > 8)
    ptr[1]= (uchar) ((ptr[1] & ~((1 << (len - 8 + ofs)) - 1)) |
                     bits >> (8 - ofs));
}

#define clr_rec_bits(bit_ptr, bit_ofs, bit_len) \
  set_rec_bits(0, bit_ptr, bit_ofs, bit_len)

/*
  Compare two VARCHAR values.
  @param charset_info  - The character set and collation
  @param a             - The pointer to the first string
  @param a_length      - The length of the first string
  @param b             - The pointer to the second string
  @param b_length      - The length of the second string
  @param b_is_prefix   - Whether "b" is a prefix of "a",
                         e.g. in a prefix key (partial length key).
  @returns             - The result of comparison

- If "b_is_prefix" is FALSE, then the two strings are compared
    taking into account the PAD SPACE/NO PAD attribute of the collation.

- If "b_is_prefix" is TRUE, then trailing spaces are compared in NO PAD style.
    This is done e.g. when we compare a column value to its prefix key value
    (the value of "a" to the value of "key_a"):
      CREATE TABLE t1 (a VARCHAR(10), KEY(key_a(5));
*/
static inline int ha_compare_char_varying(CHARSET_INFO *charset_info,
                                          const uchar *a, size_t a_length,
                                          const uchar *b, size_t b_length,
                                          my_bool b_is_prefix)
{
  if (!b_is_prefix)
    return charset_info->coll->strnncollsp(charset_info, a, a_length,
                                                         b, b_length);
  return charset_info->coll->strnncoll(charset_info,
                                       a, a_length,
                                       b, b_length, TRUE/*prefix*/);
}

/*
  Compare two CHAR values of the same declared character length,
  e.g. CHAR(5) to CHAR(5).

@param charset_info  - The character set and collation
  @param a             - The pointer to the first string
  @param a_length      - The length of the first string
  @param b             - The pointer to the second string
  @param b_length      - The length of the second string
  @param nchars        - The declared length (in characters)
  @param b_is_prefix   - Whether "b" is a prefix of "a",
                         e.g. in a prefix key (partial length key).
  @returns             - The result of comparison

- If "b_is_prefix" is FALSE, then the two strings are compared
    taking into account the PAD SPACE/NO PAD attribute of the collation.
    Additionally, this function assumes that the underlying storage could
    optionally apply trailing space compression, so values can come into this
    comparison function in different states:
    - all trailing spaces removed
    - some trailing spaced removed
    - no trailing spaces removed (exactly "nchars" characters on the two sides)
    This function virtually reconstructs trailing spaces up to the defined
    length specified in "nchars".
    If either of the sides have more than "nchar" characters,
    then only leftmost "nchar" characters are compared.

- If "b_is_prefix" is TRUE, then trailing spaces are compared in NO PAD style.
    This is done e.g. when we compare a column value to its prefix key value
    (the value of "a" to the value of "key_a"):
      CREATE TABLE t1 (a CHAR(10), KEY(key_a(5));
*/
static inline int ha_compare_char_fixed(CHARSET_INFO *charset_info,
                                        const uchar *a, size_t a_length,
                                        const uchar *b, size_t b_length,
                                        size_t nchars,
                                        my_bool b_is_prefix)
{
  if (!b_is_prefix)
    return charset_info->coll->strnncollsp_nchars(charset_info,
                                                  a, a_length,
                                                  b, b_length,
                                                  nchars,
         MY_STRNNCOLLSP_NCHARS_EMULATE_TRIMMED_TRAILING_SPACES);
  return charset_info->coll->strnncoll(charset_info,
                                       a, a_length,
                                       b, b_length, TRUE/*prefix*/);
}

/*
  A function to compare words of a text.
  This is a common operation in full-text search:
    SELECT MATCH (title) AGAINST ('word') FROM t1;
*/
static inline int ha_compare_word(CHARSET_INFO *charset_info,
                                  const uchar *a, size_t a_length,
                                  const uchar *b, size_t b_length)
{
  return charset_info->coll->strnncollsp(charset_info,
                                         a, a_length,
                                         b, b_length);
}

/*
  A function to compare a word of a text to a word prefix.
  This is a common operation in full-text search:
    SELECT MATCH (title) AGAINST ('wor*' IN BOOLEAN MODE) FROM t1;
*/
static inline int ha_compare_word_prefix(CHARSET_INFO *charset_info,
                                        const uchar *a, size_t a_length,
                                        const uchar *b, size_t b_length)
{
  return charset_info->coll->strnncoll(charset_info,
                                       a, a_length,
                                       b, b_length,
                                       TRUE/*b_is_prefix*/);
}

/*
  Compare words (full match or prefix match), e.g. for full-text search.
*/
static inline int ha_compare_word_or_prefix(CHARSET_INFO *charset_info,
                                            const uchar *a, size_t a_length,
                                            const uchar *b, size_t b_length,
                                            my_bool b_is_prefix)
{
  if (!b_is_prefix)
    return ha_compare_word(charset_info, a, a_length, b, b_length);
  return ha_compare_word_prefix(charset_info, a, a_length, b, b_length);
}

extern int ha_key_cmp(HA_KEYSEG *keyseg, const uchar *a,
		      const uchar *b, uint key_length, uint nextflag,
		      uint *diff_pos);
extern HA_KEYSEG *ha_find_null(HA_KEYSEG *keyseg, const uchar *a);

/*
  Inside an in-memory data record, memory pointers to pieces of the
  record (like BLOBs) are stored in their native byte order and in
  this amount of bytes.
*/
#define portable_sizeof_char_ptr 8
#ifdef	__cplusplus
}
#endif

/**
  Return values for pushed index condition or rowid filter check functions.

0=CHECK_NEG  - The filter is not satisfied. The engine should discard this
                 index tuple and continue the scan.
  1=CHECK_POS  - The filter is satisfied. Current index tuple should be
                 returned to the SQL layer.
  2=CHECK_OUT_OF_RANGE - the index tuple is outside of the range that we're
                 scanning. (Example: if we're scanning "t.key BETWEEN 10 AND
                 20" and got a "t.key=21" tuple) Tthe engine should stop
                 scanning and return HA_ERR_END_OF_FILE right away).
  3=CHECK_ABORTED_BY_USER - the engine must stop scanning and should return
                            HA_ERR_ABORTED_BY_USER right away
 -1=CHECK_ERROR - Reserved for internal errors in engines. Should not be
                  returned by ICP or rowid filter check functions.
*/

typedef enum check_result {
  CHECK_ERROR=-1,
  CHECK_NEG=0,
  CHECK_POS=1,
  CHECK_OUT_OF_RANGE=2,
  CHECK_ABORTED_BY_USER=3
} check_result_t;

typedef check_result_t (*index_cond_func_t)(void *param);
typedef check_result_t (*rowid_filter_func_t)(void *param);

#endif /* _my_compare_h */

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