perlclib



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




NAME

       perlclib - Internal replacements for standard C library functions


DESCRIPTION

       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.

       Conventions

       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.

       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" docu-
       mentation 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) (Deprecated)
           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)                    New(id, p, n, t)
           t* p = calloc(n, s)                 Newz(id, 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/*(struct foo *)              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)

       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 Newz() you
       should consider "poisoning" the data.  This means writing a bit pattern
       into it that should be illegal as pointers (and floating point num-
       bers), 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() macro,
       which has similar arguments as Zero():

           Poison(dst, n, t)

       Character Class Tests

       There are two types of character class tests that Perl implements: one
       type deals in "char"s and are thus not Unicode aware (and hence depre-
       cated unless you know you should use them) and the other type deal in
       "UV"s and know about Unicode properties. In the following table, "c" is
       a "char", and "u" is a Unicode codepoint.

           Instead Of:                 Use:            But better use:

           isalnum(c)                  isALNUM(c)      isALNUM_uni(u)
           isalpha(c)                  isALPHA(c)      isALPHA_uni(u)
           iscntrl(c)                  isCNTRL(c)      isCNTRL_uni(u)
           isdigit(c)                  isDIGIT(c)      isDIGIT_uni(u)
           isgraph(c)                  isGRAPH(c)      isGRAPH_uni(u)
           islower(c)                  isLOWER(c)      isLOWER_uni(u)
           isprint(c)                  isPRINT(c)      isPRINT_uni(u)
           ispunct(c)                  isPUNCT(c)      isPUNCT_uni(u)
           isspace(c)                  isSPACE(c)      isSPACE_uni(u)
           isupper(c)                  isUPPER(c)      isUPPER_uni(u)
           isxdigit(c)                 isXDIGIT(c)     isXDIGIT_uni(u)

           tolower(c)                  toLOWER(c)      toLOWER_uni(u)
           toupper(c)                  toUPPER(c)      toUPPER_uni(u)

       stdlib.h functions

           Instead Of:                 Use:

           atof(s)                     Atof(s)
           atol(s)                     Atol(s)
           strtod(s, *p)               Nothing.  Just don’t use it.
           strtol(s, *p, n)            Strtol(s, *p, n)
           strtoul(s, *p, n)           Strtoul(s, *p, n)

       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.

       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_putenv(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)".


SEE ALSO

       "perlapi", "perlapio", "perlguts"



perl v5.8.6                       2004-11-05                       PERLCLIB(1)

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