string.c

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/*-------------------------------------------------------------------------
 *
 * string.c
 *      string handling helpers
 *
 *
 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/common/string.c
 *
 *-------------------------------------------------------------------------
 */
 
 
#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif
 
#include "common/string.h"
#include "lib/stringinfo.h"
 
 
/*
 * Returns whether the string `str' has the postfix `end'.
 */
bool
pg_str_endswith(const char *str, const char *end)
{
    size_t      slen = strlen(str);
    size_t      elen = strlen(end);
 
    /* can't be a postfix if longer */
    if (elen > slen)
        return false;
 
    /* compare the end of the strings */
    str += slen - elen;
    return strcmp(str, end) == 0;
}
 
 
/*
 * strtoint --- just like strtol, but returns int not long
 */
int
strtoint(const char *pg_restrict str, char **pg_restrict endptr, int base)
{
    long        val;
 
    val = strtol(str, endptr, base);
    if (val != (int) val)
        errno = ERANGE;
    return (int) val;
}
 
 
/*
 * pg_clean_ascii -- Replace any non-ASCII chars with a "\xXX" string
 *
 * Makes a newly allocated copy of the string passed in, which must be
 * '\0'-terminated. In the backend, additional alloc_flags may be provided and
 * will be passed as-is to palloc_extended(); in the frontend, alloc_flags is
 * ignored and the copy is malloc'd.
 *
 * This function exists specifically to deal with filtering out
 * non-ASCII characters in a few places where the client can provide an almost
 * arbitrary string (and it isn't checked to ensure it's a valid username or
 * database name or similar) and we don't want to have control characters or other
 * things ending up in the log file where server admins might end up with a
 * messed up terminal when looking at them.
 *
 * In general, this function should NOT be used- instead, consider how to handle
 * the string without needing to filter out the non-ASCII characters.
 *
 * Ultimately, we'd like to improve the situation to not require replacing all
 * non-ASCII but perform more intelligent filtering which would allow UTF or
 * similar, but it's unclear exactly what we should allow, so stick to ASCII only
 * for now.
 */
char *
pg_clean_ascii(const char *str, int alloc_flags)
{
    size_t      dstlen;
    char       *dst;
    const char *p;
    size_t      i = 0;
 
    /* Worst case, each byte can become four bytes, plus a null terminator. */
    dstlen = strlen(str) * 4 + 1;
 
#ifdef FRONTEND
    dst = malloc(dstlen);
#else
    dst = palloc_extended(dstlen, alloc_flags);
#endif
 
    if (!dst)
        return NULL;
 
    for (p = str; *p != '\0'; p++)
    {
 
        /* Only allow clean ASCII chars in the string */
        if (*p < 32 || *p > 126)
        {
            Assert(i < (dstlen - 3));
            snprintf(&dst[i], dstlen - i, "\\x%02x", (unsigned char) *p);
            i += 4;
        }
        else
        {
            Assert(i < dstlen);
            dst[i] = *p;
            i++;
        }
    }
 
    Assert(i < dstlen);
    dst[i] = '\0';
    return dst;
}
 
 
/*
 * pg_is_ascii -- Check if string is made only of ASCII characters
 */
bool
pg_is_ascii(const char *str)
{
    while (*str)
    {
        if (IS_HIGHBIT_SET(*str))
            return false;
        str++;
    }
    return true;
}
 
 
/*
 * pg_strip_crlf -- Remove any trailing newline and carriage return
 *
 * Removes any trailing newline and carriage return characters (\r on
 * Windows) in the input string, zero-terminating it.
 *
 * The passed in string must be zero-terminated.  This function returns
 * the new length of the string.
 */
int
pg_strip_crlf(char *str)
{
    int         len = strlen(str);
 
    while (len > 0 && (str[len - 1] == '\n' ||
                       str[len - 1] == '\r'))
        str[--len] = '\0';
 
    return len;
}