perlclib - Internal replacements for standard C library functions


   One thing Perl porters should note is that perl doesn't tend to use
   that much of the C standard library internally; you'll see very little
   use of, for example, the ctype.h functions in there. This is because
   Perl tends to reimplement or abstract standard library functions, so
   that we know exactly how they're going to operate.

   This is a reference card for people who are familiar with the C library
   and who want to do things the Perl way; to tell them which functions
   they ought to use instead of the more normal C functions.

   In the following tables:

      is a type.

      is a pointer.

      is a number.

      is a string.

   "sv", "av", "hv", etc. represent variables of their respective types.

   File Operations
   Instead of the stdio.h functions, you should use the Perl abstraction
   layer. Instead of "FILE*" types, you need to be handling "PerlIO*"
   types.  Don't forget that with the new PerlIO layered I/O abstraction
   "FILE*" types may not even be available. See also the "perlapio"
   documentation for more information about the following functions:

    Instead Of:                 Use:

    stdin                       PerlIO_stdin()
    stdout                      PerlIO_stdout()
    stderr                      PerlIO_stderr()

    fopen(fn, mode)             PerlIO_open(fn, mode)
    freopen(fn, mode, stream)   PerlIO_reopen(fn, mode, perlio) (Dep-
    fflush(stream)              PerlIO_flush(perlio)
    fclose(stream)              PerlIO_close(perlio)

   File Input and Output
    Instead Of:                 Use:

    fprintf(stream, fmt, ...)   PerlIO_printf(perlio, fmt, ...)

    [f]getc(stream)             PerlIO_getc(perlio)
    [f]putc(stream, n)          PerlIO_putc(perlio, n)
    ungetc(n, stream)           PerlIO_ungetc(perlio, n)

   Note that the PerlIO equivalents of "fread" and "fwrite" are slightly
   different from their C library counterparts:

    fread(p, size, n, stream)   PerlIO_read(perlio, buf, numbytes)
    fwrite(p, size, n, stream)  PerlIO_write(perlio, buf, numbytes)

    fputs(s, stream)            PerlIO_puts(perlio, s)

   There is no equivalent to "fgets"; one should use "sv_gets" instead:

    fgets(s, n, stream)         sv_gets(sv, perlio, append)

   File Positioning
    Instead Of:                 Use:

    feof(stream)                PerlIO_eof(perlio)
    fseek(stream, n, whence)    PerlIO_seek(perlio, n, whence)
    rewind(stream)              PerlIO_rewind(perlio)

    fgetpos(stream, p)          PerlIO_getpos(perlio, sv)
    fsetpos(stream, p)          PerlIO_setpos(perlio, sv)

    ferror(stream)              PerlIO_error(perlio)
    clearerr(stream)            PerlIO_clearerr(perlio)

   Memory Management and String Handling
    Instead Of:                    Use:

    t* p = malloc(n)               Newx(p, n, t)
    t* p = calloc(n, s)            Newxz(p, n, t)
    p = realloc(p, n)              Renew(p, n, t)
    memcpy(dst, src, n)            Copy(src, dst, n, t)
    memmove(dst, src, n)           Move(src, dst, n, t)
    memcpy(dst, src, sizeof(t))    StructCopy(src, dst, t)
    memset(dst, 0, n * sizeof(t))  Zero(dst, n, t)
    memzero(dst, 0)                Zero(dst, n, char)
    free(p)                        Safefree(p)

    strdup(p)                      savepv(p)
    strndup(p, n)                  savepvn(p, n) (Hey, strndup doesn't

    strstr(big, little)            instr(big, little)
    strcmp(s1, s2)                 strLE(s1, s2) / strEQ(s1, s2)
                                                 / strGT(s1,s2)
    strncmp(s1, s2, n)             strnNE(s1, s2, n) / strnEQ(s1, s2, n)

    memcmp(p1, p2, n)              memNE(p1, p2, n)
    !memcmp(p1, p2, n)             memEQ(p1, p2, n)

   Notice the different order of arguments to "Copy" and "Move" than used
   in "memcpy" and "memmove".

   Most of the time, though, you'll want to be dealing with SVs internally
   instead of raw "char *" strings:

    strlen(s)                   sv_len(sv)
    strcpy(dt, src)             sv_setpv(sv, s)
    strncpy(dt, src, n)         sv_setpvn(sv, s, n)
    strcat(dt, src)             sv_catpv(sv, s)
    strncat(dt, src)            sv_catpvn(sv, s)
    sprintf(s, fmt, ...)        sv_setpvf(sv, fmt, ...)

   Note also the existence of "sv_catpvf" and "sv_vcatpvfn", combining
   concatenation with formatting.

   Sometimes instead of zeroing the allocated heap by using Newxz() you
   should consider "poisoning" the data.  This means writing a bit pattern
   into it that should be illegal as pointers (and floating point
   numbers), and also hopefully surprising enough as integers, so that any
   code attempting to use the data without forethought will break sooner
   rather than later.  Poisoning can be done using the Poison() macros,
   which have similar arguments to Zero():

    PoisonWith(dst, n, t, b)    scribble memory with byte b
    PoisonNew(dst, n, t)        equal to PoisonWith(dst, n, t, 0xAB)
    PoisonFree(dst, n, t)       equal to PoisonWith(dst, n, t, 0xEF)
    Poison(dst, n, t)           equal to PoisonFree(dst, n, t)

   Character Class Tests
   There are several types of character class tests that Perl implements.
   The only ones described here are those that directly correspond to C
   library functions that operate on 8-bit characters, but there are
   equivalents that operate on wide characters, and UTF-8 encoded strings.
   All are more fully described in "Character classification" in perlapi
   and "Character case changing" in perlapi.

   The C library routines listed in the table below return values based on
   the current locale.  Use the entries in the final column for that
   functionality.  The other two columns always assume a POSIX (or C)
   locale.  The entries in the ASCII column are only meaningful for ASCII
   inputs, returning FALSE for anything else.  Use these only when you
   know that is what you want.  The entries in the Latin1 column assume
   that the non-ASCII 8-bit characters are as Unicode defines, them, the
   same as ISO-8859-1, often called Latin 1.

    Instead Of:  Use for ASCII:   Use for Latin1:      Use for locale:

    isalpha(c)  isALPHA(c)        isALPHA_L1(c)        isALPHA_LC(u )
    isascii(c)  isASCII(c)                             isASCII_LC(c)
    isblank(c)  isBLANK(c)        isBLANK_L1(c)        isBLANK_LC(c)
    iscntrl(c)  isCNTRL(c)        isCNTRL_L1(c)        isCNTRL_LC(c)
    isdigit(c)  isDIGIT(c)        isDIGIT_L1(c)        isDIGIT_LC(c)
    isgraph(c)  isGRAPH(c)        isGRAPH_L1(c)        isGRAPH_LC(c)
    islower(c)  isLOWER(c)        isLOWER_L1(c)        isLOWER_LC(c)
    isprint(c)  isPRINT(c)        isPRINT_L1(c)        isPRINT_LC(c)
    ispunct(c)  isPUNCT(c)        isPUNCT_L1(c)        isPUNCT_LC(c)
    isspace(c)  isSPACE(c)        isSPACE_L1(c)        isSPACE_LC(c)
    isupper(c)  isUPPER(c)        isUPPER_L1(c)        isUPPER_LC(c)
    isxdigit(c) isXDIGIT(c)       isXDIGIT_L1(c)       isXDIGIT_LC(c)

    tolower(c)  toLOWER(c)        toLOWER_L1(c)        toLOWER_LC(c)
    toupper(c)  toUPPER(c)                             toUPPER_LC(c)

   To emphasize that you are operating only on ASCII characters, you can
   append "_A" to each of the macros in the ASCII column: "isALPHA_A",
   "isDIGIT_A", and so on.

   (There is no entry in the Latin1 column for "isascii" even though there
   is an "isASCII_L1", which is identical to "isASCII";  the latter name
   is clearer.  There is no entry in the Latin1 column for "toupper"
   because the result can be non-Latin1.  You have to use "toUPPER_uni",
   as described in "Character case changing" in perlapi.)

   stdlib.h functions
    Instead Of:                 Use:

    atof(s)                     Atof(s)
    atoi(s)                     grok_atoUV(s, &uv, &e)
    atol(s)                     grok_atoUV(s, &uv, &e)
    strtod(s, &p)               Nothing.  Just don't use it.
    strtol(s, &p, n)            grok_atoUV(s, &uv, &e)
    strtoul(s, &p, n)           grok_atoUV(s, &uv, &e)

   Typical use is to do range checks on "uv" before casting:

     int i; UV uv; char* end_ptr;
     if (grok_atoUV(input, &uv, &end_ptr)
         && uv <= INT_MAX)
       i = (int)uv;
       ... /* continue parsing from end_ptr */
     } else {
       ... /* parse error: not a decimal integer in range 0 .. MAX_IV */

   Notice also the "grok_bin", "grok_hex", and "grok_oct" functions in
   numeric.c for converting strings representing numbers in the respective
   bases into "NV"s.  Note that grok_atoUV() doesn't handle negative
   inputs, or leading whitespace (being purposefully strict).

   Note that strtol() and strtoul() may be disguised as Strtol(),
   Strtoul(), Atol(), Atoul().  Avoid those, too.

   In theory "Strtol" and "Strtoul" may not be defined if the machine perl
   is built on doesn't actually have strtol and strtoul. But as those 2
   functions are part of the 1989 ANSI C spec we suspect you'll find them
   everywhere by now.

    int rand()                  double Drand01()
    srand(n)                    { seedDrand01((Rand_seed_t)n);
                                  PL_srand_called = TRUE; }

    exit(n)                     my_exit(n)
    system(s)                   Don't. Look at pp_system or use my_popen.

    getenv(s)                   PerlEnv_getenv(s)
    setenv(s, val)              my_setenv(s, val)

   Miscellaneous functions
   You should not even want to use setjmp.h functions, but if you think
   you do, use the "JMPENV" stack in scope.h instead.

   For "signal"/"sigaction", use "rsignal(signo, handler)".


   perlapi, perlapio, perlguts


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