scansup.c

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/*-------------------------------------------------------------------------
 *
 * 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;
}