[p5sagit/p5-mst-13.2.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)
    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 Newz() 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()
macro, which has similar arguments as Zero():

    Poison(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

C<perlapi>, C<perlapio>, C<perlguts>
Commit	Line	Data
f40a6c71	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	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	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	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	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	memset(dst, 0, n * sizeof(t)) Zero(dst, n, t)
	109	memzero(dst, 0) Zero(dst, n, char)
	110	free(p) Safefree(p)
f40a6c71	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	133	concatenation with formatting.
f40a6c71	134
9965345d	135	Sometimes instead of zeroing the allocated heap by using Newz() you
	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()
	141	macro, which has similar arguments as Zero():
	142
	143	Poison(dst, n, t)
	144
f40a6c71	145	=head2 Character Class Tests
	146
	147	There are two types of character class tests that Perl implements: one
	148	type deals in C<char>s and are thus B<not> Unicode aware (and hence
	149	deprecated unless you B<know> you should use them) and the other type
	150	deal in C<UV>s and know about Unicode properties. In the following
	151	table, C<c> is a C<char>, and C<u> is a Unicode codepoint.
	152
	153	Instead Of: Use: But better use:
	154
	155	isalnum(c) isALNUM(c) isALNUM_uni(u)
	156	isalpha(c) isALPHA(c) isALPHA_uni(u)
	157	iscntrl(c) isCNTRL(c) isCNTRL_uni(u)
	158	isdigit(c) isDIGIT(c) isDIGIT_uni(u)
	159	isgraph(c) isGRAPH(c) isGRAPH_uni(u)
	160	islower(c) isLOWER(c) isLOWER_uni(u)
	161	isprint(c) isPRINT(c) isPRINT_uni(u)
	162	ispunct(c) isPUNCT(c) isPUNCT_uni(u)
	163	isspace(c) isSPACE(c) isSPACE_uni(u)
	164	isupper(c) isUPPER(c) isUPPER_uni(u)
	165	isxdigit(c) isXDIGIT(c) isXDIGIT_uni(u)
	166
	167	tolower(c) toLOWER(c) toLOWER_uni(u)
	168	toupper(c) toUPPER(c) toUPPER_uni(u)
	169
	170	=head2 F<stdlib.h> functions
	171
	172	Instead Of: Use:
	173
	174	atof(s) Atof(s)
	175	atol(s) Atol(s)
56d22bd2	176	strtod(s, *p) Nothing. Just don't use it.
f40a6c71	177	strtol(s, p, n) Strtol(s, p, n)
	178	strtoul(s, p, n) Strtoul(s, p, n)
	179
53305cf1	180	Notice also the C<grok_bin>, C<grok_hex>, and C<grok_oct> functions in
2826e23d	181	F<numeric.c> for converting strings representing numbers in the respective
f40a6c71	182	bases into C<NV>s.
	183
	184	In theory C<Strtol> and C<Strtoul> may not be defined if the machine perl is
	185	built on doesn't actually have strtol and strtoul. But as those 2
	186	functions are part of the 1989 ANSI C spec we suspect you'll find them
	187	everywhere by now.
	188
	189	int rand() double Drand01()
	190	srand(n) { seedDrand01((Rand_seed_t)n);
	191	PL_srand_called = TRUE; }
56d22bd2	192
f40a6c71	193	exit(n) my_exit(n)
	194	system(s) Don't. Look at pp_system or use my_popen
	195
	196	getenv(s) PerlEnv_getenv(s)
	197	setenv(s, val) my_putenv(s, val)
	198
	199	=head2 Miscellaneous functions
	200
	201	You should not even B<want> to use F<setjmp.h> functions, but if you
	202	think you do, use the C<JMPENV> stack in F<scope.h> instead.
	203
	204	For C<signal>/C<sigaction>, use C<rsignal(signo, handler)>.
	205
	206	=head1 SEE ALSO
	207
	208	C<perlapi>, C<perlapio>, C<perlguts>
	209