[perl5.git] / pod / perlclib.pod

=head1 NAME

perlclib - Internal replacements for standard C library functions

=head1 DESCRIPTION

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

=head2 Conventions

In the following tables:

=over 3

=item C<t>

is a type.

=item C<p>

is a pointer.

=item C<n>

is a number.

=item C<s>

is a string.

=back

C<sv>, C<av>, C<hv>, etc. represent variables of their respective types.

=head2 File Operations

Instead of the F<stdio.h> functions, you should use the Perl abstraction
layer. Instead of C<FILE*> types, you need to be handling C<PerlIO*>
types.  Don't forget that with the new PerlIO layered I/O abstraction 
C<FILE*> types may not even be available. See also the C<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) (Deprecated)
    fflush(stream)              PerlIO_flush(perlio)
    fclose(stream)              PerlIO_close(perlio)

=head2 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 C<fread> and C<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 C<fgets>; one should use C<sv_gets> instead:

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

=head2 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)

=head2 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)
    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 C<Copy> and C<Move> than used
in C<memcpy> and C<memmove>.

Most of the time, though, you'll want to be dealing with SVs internally
instead of raw C<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 C<sv_catpvf> and C<sv_vcatpvfn>, combining
concatenation with formatting.

=head2 Character Class Tests

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

=head2 F<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 C<grok_bin>, C<grok_hex>, and C<grok_oct> functions in
F<numeric.c> for converting strings representing numbers in the respective
bases into C<NV>s.

In theory C<Strtol> and C<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)

=head2 Miscellaneous functions

You should not even B<want> to use F<setjmp.h> functions, but if you
think you do, use the C<JMPENV> stack in F<scope.h> instead.

For C<signal>/C<sigaction>, use C<rsignal(signo, handler)>.

=head1 SEE ALSO

C<perlapi>, C<perlapio>, C<perlguts>
Commit	Line	Data
f40a6c71 SC	1	=head1 NAME
	2
	3	perlclib - Internal replacements for standard C library functions
	4
	5	=head1 DESCRIPTION
	6
	7	One thing Perl porters should note is that F<perl> doesn't tend to use that
	8	much of the C standard library internally; you'll see very little use of,
	9	for example, the F<ctype.h> functions in there. This is because Perl
	10	tends to reimplement or abstract standard library functions, so that we
	11	know exactly how they're going to operate.
	12
	13	This is a reference card for people who are familiar with the C library
56d22bd2	14	and who want to do things the Perl way; to tell them which functions
f40a6c71 SC	15	they ought to use instead of the more normal C functions.
	16
	17	=head2 Conventions
	18
	19	In the following tables:
	20
	21	=over 3
	22
	23	=item C<t>
	24
	25	is a type.
	26
	27	=item C<p>
	28
	29	is a pointer.
	30
	31	=item C<n>
	32
	33	is a number.
	34
	35	=item C<s>
	36
	37	is a string.
	38
	39	=back
	40
	41	C<sv>, C<av>, C<hv>, etc. represent variables of their respective types.
	42
	43	=head2 File Operations
	44
	45	Instead of the F<stdio.h> functions, you should use the Perl abstraction
	46	layer. Instead of C<FILE> types, you need to be handling C<PerlIO>
56d22bd2	47	types. Don't forget that with the new PerlIO layered I/O abstraction
f40a6c71 SC	48	C<FILE*> types may not even be available. See also the C<perlapio>
	49	documentation for more information about the following functions:
	50
	51	Instead Of: Use:
56d22bd2	52
f40a6c71 SC	53	stdin PerlIO_stdin()
	54	stdout PerlIO_stdout()
	55	stderr PerlIO_stderr()
	56
	57	fopen(fn, mode) PerlIO_open(fn, mode)
	58	freopen(fn, mode, stream) PerlIO_reopen(fn, mode, perlio) (Deprecated)
	59	fflush(stream) PerlIO_flush(perlio)
	60	fclose(stream) PerlIO_close(perlio)
	61
	62	=head2 File Input and Output
	63
	64	Instead Of: Use:
	65
	66	fprintf(stream, fmt, ...) PerlIO_printf(perlio, fmt, ...)
	67
	68	[f]getc(stream) PerlIO_getc(perlio)
	69	[f]putc(stream, n) PerlIO_putc(perlio, n)
	70	ungetc(n, stream) PerlIO_ungetc(perlio, n)
	71
	72	Note that the PerlIO equivalents of C<fread> and C<fwrite> are slightly
	73	different from their C library counterparts:
	74
	75	fread(p, size, n, stream) PerlIO_read(perlio, buf, numbytes)
	76	fwrite(p, size, n, stream) PerlIO_write(perlio, buf, numbytes)
	77
	78	fputs(s, stream) PerlIO_puts(perlio, s)
	79
	80	There is no equivalent to C<fgets>; one should use C<sv_gets> instead:
	81
	82	fgets(s, n, stream) sv_gets(sv, perlio, append)
	83
	84	=head2 File Positioning
	85
	86	Instead Of: Use:
	87
	88	feof(stream) PerlIO_eof(perlio)
	89	fseek(stream, n, whence) PerlIO_seek(perlio, n, whence)
	90	rewind(stream) PerlIO_rewind(perlio)
	91
	92	fgetpos(stream, p) PerlIO_getpos(perlio, sv)
	93	fsetpos(stream, p) PerlIO_setpos(perlio, sv)
	94
	95	ferror(stream) PerlIO_error(perlio)
	96	clearerr(stream) PerlIO_clearerr(perlio)
	97
	98	=head2 Memory Management and String Handling
	99
	100	Instead Of: Use:
	101
	102	t* p = malloc(n) New(id, p, n, t)
	103	t* p = calloc(n, s) Newz(id, p, n, t)
	104	p = realloc(p, n) Renew(p, n, t)
	105	memcpy(dst, src, n) Copy(src, dst, n, t)
	106	memmove(dst, src, n) Move(src, dst, n, t)
	107	memcpy/(struct foo ) StructCopy(src, dst, t)
	108	free(p) Safefree(p)
	109
	110	strdup(p) savepv(p)
	111	strndup(p, n) savepvn(p, n) (Hey, strndup doesn't exist!)
	112
	113	strstr(big, little) instr(big, little)
	114	strcmp(s1, s2) strLE(s1, s2) / strEQ(s1, s2) / strGT(s1,s2)
	115	strncmp(s1, s2, n) strnNE(s1, s2, n) / strnEQ(s1, s2, n)
	116
117	Notice the different order of arguments to C<Copy> and C<Move> than used
118	in C<memcpy> and C<memmove>.
119
120	Most of the time, though, you'll want to be dealing with SVs internally
121	instead of raw C<char *> strings:
122
123	strlen(s) sv_len(sv)
124	strcpy(dt, src) sv_setpv(sv, s)
125	strncpy(dt, src, n) sv_setpvn(sv, s, n)
126	strcat(dt, src) sv_catpv(sv, s)
127	strncat(dt, src) sv_catpvn(sv, s)
128	sprintf(s, fmt, ...) sv_setpvf(sv, fmt, ...)
129
328bf373	130	Note also the existence of C<sv_catpvf> and C<sv_vcatpvfn>, combining
f40a6c71 SC	131	concatenation with formatting.
	132
	133	=head2 Character Class Tests
	134
	135	There are two types of character class tests that Perl implements: one
	136	type deals in C<char>s and are thus B<not> Unicode aware (and hence
	137	deprecated unless you B<know> you should use them) and the other type
	138	deal in C<UV>s and know about Unicode properties. In the following
	139	table, C<c> is a C<char>, and C<u> is a Unicode codepoint.
	140
	141	Instead Of: Use: But better use:
	142
	143	isalnum(c) isALNUM(c) isALNUM_uni(u)
	144	isalpha(c) isALPHA(c) isALPHA_uni(u)
	145	iscntrl(c) isCNTRL(c) isCNTRL_uni(u)
	146	isdigit(c) isDIGIT(c) isDIGIT_uni(u)
	147	isgraph(c) isGRAPH(c) isGRAPH_uni(u)
	148	islower(c) isLOWER(c) isLOWER_uni(u)
	149	isprint(c) isPRINT(c) isPRINT_uni(u)
	150	ispunct(c) isPUNCT(c) isPUNCT_uni(u)
	151	isspace(c) isSPACE(c) isSPACE_uni(u)
	152	isupper(c) isUPPER(c) isUPPER_uni(u)
	153	isxdigit(c) isXDIGIT(c) isXDIGIT_uni(u)
	154
	155	tolower(c) toLOWER(c) toLOWER_uni(u)
	156	toupper(c) toUPPER(c) toUPPER_uni(u)
	157
	158	=head2 F<stdlib.h> functions
	159
	160	Instead Of: Use:
	161
	162	atof(s) Atof(s)
	163	atol(s) Atol(s)
56d22bd2	164	strtod(s, *p) Nothing. Just don't use it.
f40a6c71 SC	165	strtol(s, p, n) Strtol(s, p, n)
	166	strtoul(s, p, n) Strtoul(s, p, n)
	167
53305cf1	168	Notice also the C<grok_bin>, C<grok_hex>, and C<grok_oct> functions in
2826e23d	169	F<numeric.c> for converting strings representing numbers in the respective
f40a6c71 SC	170	bases into C<NV>s.
	171
	172	In theory C<Strtol> and C<Strtoul> may not be defined if the machine perl is
	173	built on doesn't actually have strtol and strtoul. But as those 2
	174	functions are part of the 1989 ANSI C spec we suspect you'll find them
	175	everywhere by now.
	176
	177	int rand() double Drand01()
	178	srand(n) { seedDrand01((Rand_seed_t)n);
	179	PL_srand_called = TRUE; }
56d22bd2	180
f40a6c71 SC	181	exit(n) my_exit(n)
	182	system(s) Don't. Look at pp_system or use my_popen
	183
	184	getenv(s) PerlEnv_getenv(s)
	185	setenv(s, val) my_putenv(s, val)
	186
	187	=head2 Miscellaneous functions
	188
	189	You should not even B<want> to use F<setjmp.h> functions, but if you
	190	think you do, use the C<JMPENV> stack in F<scope.h> instead.
	191
	192	For C<signal>/C<sigaction>, use C<rsignal(signo, handler)>.
	193
	194	=head1 SEE ALSO
	195
	196	C<perlapi>, C<perlapio>, C<perlguts>
	197