perlclib - Internal replacements for standard C library
functions
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 [Toc] [Back]
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 [Toc] [Back]
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" 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)
File Input and Output [Toc] [Back]
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 [Toc] [Back]
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 [Toc] [Back]
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 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)
Character Class Tests [Toc] [Back]
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 deprecated 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 [Toc] [Back]
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)".
"perlapi", "perlapio", "perlguts"
perl v5.8.5 2002-11-06 4 [ Back ] |
