/*-------------------------------------------------------------------------

 *

 * scansup.c

 *    scanner support routines used by the core lexer

 *

 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group

 * Portions Copyright (c) 1994, Regents of the University of California

 *

 *

 * IDENTIFICATION

 *    src/backend/parser/scansup.c

 *

 *-------------------------------------------------------------------------

 */

#include "postgres.h"

#include <ctype.h>

#include "mb/pg_wchar.h"

#include "parser/scansup.h"

/*

 * downcase_truncate_identifier() --- do appropriate downcasing and

 * truncation of an unquoted identifier.  Optionally warn of truncation.

 *

 * Returns a palloc'd string containing the adjusted identifier.

 *

 * Note: in some usages the passed string is not null-terminated.

 *

 * Note: the API of this function is designed to allow for downcasing

 * transformations that increase the string length, but we don't yet

 * support that.  If you want to implement it, you'll need to fix

 * SplitIdentifierString() in utils/adt/varlena.c.

 */

char *

downcase_truncate_identifier(const char *ident, int len, bool warn)

{

  return downcase_identifier(ident, len, warn, true);

}

/*

 * a workhorse for downcase_truncate_identifier

 */

char *

downcase_identifier(const char *ident, int len, bool warn, bool truncate)

{

  char     *result;

  int     i;

  bool    enc_is_single_byte;

  result = palloc(len + 1);

  enc_is_single_byte = pg_database_encoding_max_length() == 1;

  /*

   * SQL99 specifies Unicode-aware case normalization, which we don't yet

   * have the infrastructure for.  Instead we use tolower() to provide a

   * locale-aware translation.  However, there are some locales where this

   * is not right either (eg, Turkish may do strange things with 'i' and

   * 'I').  Our current compromise is to use tolower() for characters with

   * the high bit set, as long as they aren't part of a multi-byte

   * character, and use an ASCII-only downcasing for 7-bit characters.

   */

  for (i = 0; i < len; i++)

  {

    unsigned char ch = (unsigned char) ident[i];

    if (ch >= 'A' && ch <= 'Z')

      ch += 'a' - 'A';

    else if (enc_is_single_byte && IS_HIGHBIT_SET(ch) && isupper(ch))

      ch = tolower(ch);

    result[i] = (char) ch;

  }

  result[i] = '\0';

  if (i >= NAMEDATALEN && truncate)

    truncate_identifier(result, i, warn);

  return result;

}

/*

 * truncate_identifier() --- truncate an identifier to NAMEDATALEN-1 bytes.

 *

 * The given string is modified in-place, if necessary.  A warning is

 * issued if requested.

 *

 * We require the caller to pass in the string length since this saves a

 * strlen() call in some common usages.

 */

void

truncate_identifier(char *ident, int len, bool warn)

{

  if (len >= NAMEDATALEN)

  {

    len = pg_mbcliplen(ident, len, NAMEDATALEN - 1);

    if (warn)

      ereport(NOTICE,

          (errcode(ERRCODE_NAME_TOO_LONG),

           errmsg("identifier \"%s\" will be truncated to \"%.*s\"",

              ident, len, ident)));

    ident[len] = '\0';

  }

}

/*

 * scanner_isspace() --- return true if flex scanner considers char whitespace

 *

 * This should be used instead of the potentially locale-dependent isspace()

 * function when it's important to match the lexer's behavior.

 *

 * In principle we might need similar functions for isalnum etc, but for the

 * moment only isspace seems needed.

 */

bool

scanner_isspace(char ch)

{

  /* This must match scan.l's list of {space} characters */

  if (ch == ' ' ||

    ch == '\t' ||

    ch == '\n' ||

    ch == '\r' ||

    ch == '\v' ||

    ch == '\f')

    return true;

  return false;

}