[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)            	Newx(id, p, n, t)
    t* p = calloc(n, s)         	Newxz(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(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)

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.

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)

=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

L<perlapi>, L<perlapio>, L<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
702eb6d0 JH	100	Instead Of: Use:
702eb6d0 JH	101
9f653bb5 SH	102	t* p = malloc(n) Newx(id, p, n, t)
9f653bb5 SH	103	t* p = calloc(n, s) Newxz(id, p, n, t)
702eb6d0 JH	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)
4d567a56	107	memcpy(dst, src, sizeof(t)) StructCopy(src, dst, t)
702eb6d0 JH	108	memset(dst, 0, n * sizeof(t)) Zero(dst, n, t)
	109	memzero(dst, 0) Zero(dst, n, char)
	110	free(p) Safefree(p)
f40a6c71 SC	111
	112	strdup(p) savepv(p)
	113	strndup(p, n) savepvn(p, n) (Hey, strndup doesn't exist!)
	114
	115	strstr(big, little) instr(big, little)
	116	strcmp(s1, s2) strLE(s1, s2) / strEQ(s1, s2) / strGT(s1,s2)
	117	strncmp(s1, s2, n) strnNE(s1, s2, n) / strnEQ(s1, s2, n)
	118
	119	Notice the different order of arguments to C<Copy> and C<Move> than used
	120	in C<memcpy> and C<memmove>.
	121
	122	Most of the time, though, you'll want to be dealing with SVs internally
	123	instead of raw C<char *> strings:
	124
	125	strlen(s) sv_len(sv)
	126	strcpy(dt, src) sv_setpv(sv, s)
	127	strncpy(dt, src, n) sv_setpvn(sv, s, n)
	128	strcat(dt, src) sv_catpv(sv, s)
	129	strncat(dt, src) sv_catpvn(sv, s)
	130	sprintf(s, fmt, ...) sv_setpvf(sv, fmt, ...)
	131
328bf373	132	Note also the existence of C<sv_catpvf> and C<sv_vcatpvfn>, combining
f40a6c71 SC	133	concatenation with formatting.
f40a6c71 SC	134
9f653bb5	135	Sometimes instead of zeroing the allocated heap by using Newxz() you
9965345d JH	136	should consider "poisoning" the data. This means writing a bit
	137	pattern into it that should be illegal as pointers (and floating point
	138	numbers), and also hopefully surprising enough as integers, so that
	139	any code attempting to use the data without forethought will break
	140	sooner rather than later. Poisoning can be done using the Poison()
ea787f3b	141	macros, which have similar arguments to Zero():
9965345d	142
7e337ee0 JH	143	PoisonWith(dst, n, t, b) scribble memory with byte b
	144	PoisonNew(dst, n, t) equal to PoisonWith(dst, n, t, 0xAB)
	145	PoisonFree(dst, n, t) equal to PoisonWith(dst, n, t, 0xEF)
	146	Poison(dst, n, t) equal to PoisonFree(dst, n, t)
9965345d	147
f40a6c71 SC	148	=head2 Character Class Tests
	149
	150	There are two types of character class tests that Perl implements: one
	151	type deals in C<char>s and are thus B<not> Unicode aware (and hence
	152	deprecated unless you B<know> you should use them) and the other type
	153	deal in C<UV>s and know about Unicode properties. In the following
	154	table, C<c> is a C<char>, and C<u> is a Unicode codepoint.
	155
	156	Instead Of: Use: But better use:
	157
	158	isalnum(c) isALNUM(c) isALNUM_uni(u)
	159	isalpha(c) isALPHA(c) isALPHA_uni(u)
	160	iscntrl(c) isCNTRL(c) isCNTRL_uni(u)
	161	isdigit(c) isDIGIT(c) isDIGIT_uni(u)
	162	isgraph(c) isGRAPH(c) isGRAPH_uni(u)
	163	islower(c) isLOWER(c) isLOWER_uni(u)
	164	isprint(c) isPRINT(c) isPRINT_uni(u)
	165	ispunct(c) isPUNCT(c) isPUNCT_uni(u)
	166	isspace(c) isSPACE(c) isSPACE_uni(u)
	167	isupper(c) isUPPER(c) isUPPER_uni(u)
	168	isxdigit(c) isXDIGIT(c) isXDIGIT_uni(u)
	169
	170	tolower(c) toLOWER(c) toLOWER_uni(u)
	171	toupper(c) toUPPER(c) toUPPER_uni(u)
	172
	173	=head2 F<stdlib.h> functions
	174
	175	Instead Of: Use:
	176
	177	atof(s) Atof(s)
	178	atol(s) Atol(s)
4d567a56 VP	179	strtod(s, &p) Nothing. Just don't use it.
	180	strtol(s, &p, n) Strtol(s, &p, n)
	181	strtoul(s, &p, n) Strtoul(s, &p, n)
f40a6c71	182
53305cf1	183	Notice also the C<grok_bin>, C<grok_hex>, and C<grok_oct> functions in
2826e23d	184	F<numeric.c> for converting strings representing numbers in the respective
f40a6c71 SC	185	bases into C<NV>s.
	186
	187	In theory C<Strtol> and C<Strtoul> may not be defined if the machine perl is
	188	built on doesn't actually have strtol and strtoul. But as those 2
	189	functions are part of the 1989 ANSI C spec we suspect you'll find them
	190	everywhere by now.
	191
	192	int rand() double Drand01()
	193	srand(n) { seedDrand01((Rand_seed_t)n);
	194	PL_srand_called = TRUE; }
56d22bd2	195
f40a6c71 SC	196	exit(n) my_exit(n)
	197	system(s) Don't. Look at pp_system or use my_popen
	198
	199	getenv(s) PerlEnv_getenv(s)
	200	setenv(s, val) my_putenv(s, val)
	201
	202	=head2 Miscellaneous functions
	203
	204	You should not even B<want> to use F<setjmp.h> functions, but if you
	205	think you do, use the C<JMPENV> stack in F<scope.h> instead.
	206
	207	For C<signal>/C<sigaction>, use C<rsignal(signo, handler)>.
	208
	209	=head1 SEE ALSO
	210
d974f73b	211	L<perlapi>, L<perlapio>, L<perlguts>
f40a6c71	212