PERLCLIB(1) Perl Programmers Reference Guide PERLCLIB(1)

PERLCLIB(1) Perl Programmers Reference Guide PERLCLIB(1) #

PERLCLIB(1) Perl Programmers Reference Guide PERLCLIB(1)

NNAAMMEE #

 perlclib - Internal replacements for standard C library functions

DDEESSCCRRIIPPTTIIOONN #

 One thing Perl porters should note is that _p_e_r_l doesn't tend to use that
 much of the C standard library internally; you'll see very little use of,
 for example, the _c_t_y_p_e_._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.

CCoonnvveennttiioonnss In the following tables:

 "t"
    is a type.

 "p"
    is a pointer.

 "n"
    is a number.

 "s"
    is a string.

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

FFiillee OOppeerraattiioonnss Instead of the _s_t_d_i_o_._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-
                                recated)
  fflush(stream)              PerlIO_flush(perlio)
  fclose(stream)              PerlIO_close(perlio)

FFiillee IInnppuutt aanndd OOuuttppuutt 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)

FFiillee PPoossiittiioonniinngg 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)

MMeemmoorryy MMaannaaggeemmeenntt aanndd SSttrriinngg HHaannddlliinngg 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
                                                exist!)

  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 NNeewwxxzz(()) 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 PPooiissoonn(()) macros, which have
 similar arguments to ZZeerroo(()):

  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)

CChhaarraacctteerr CCllaassss TTeessttss 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 kknnooww
 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:

  isalnum(c)  isALPHANUMERIC(c) isALPHANUMERIC_L1(c) isALPHANUMERIC_LC(c)
  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)
  toupper(c)  toUPPER(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_uvchr", as
 described in "Character case changing" in perlapi.)

_s_t_d_l_i_b_._h ffuunnccttiioonnss Instead Of: Use:

  atof(s)                     Atof(s)
  atoi(s)                     grok_atoUV(s, &uv, &e)
  atol(s)                     grok_atoUV(s, &uv, &e)
  strtod(s, &p)               Strtod(s, &p)
  strtol(s, &p, n)            Strtol(s, &p, b)
  strtoul(s, &p, n)           Strtoul(s, &p, b)

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

   int i; UV uv;
   char* end_ptr = input_end;
   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
 _n_u_m_e_r_i_c_._c for converting strings representing numbers in the respective
 bases into "NV"s.  Note that ggrrookk__aattooUUVV(()) doesn't handle negative inputs,
 or leading whitespace (being purposefully strict).

 Note that ssttrrttooll(()) and ssttrrttoouull(()) may be disguised as SSttrrttooll(()), SSttrrttoouull(()),
 AAttooll(()), AAttoouull(()).  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)

MMiisscceellllaanneeoouuss ffuunnccttiioonnss You should not even wwaanntt to use _s_e_t_j_m_p_._h functions, but if you think you do, use the “JMPENV” stack in _s_c_o_p_e_._h instead.

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

SSEEEE AALLSSOO #

 perlapi, perlapio, perlguts

perl v5.36.3 2023-02-15 PERLCLIB(1)