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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.
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.
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)
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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)
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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)
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There is no equivalent to fgets; one should use sv_gets instead:
fgets(s, n, stream) sv_gets(sv, perlio, append)
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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)
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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)
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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, ...)
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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():
There are two types of character class tests that Perl implements: one type deals in chars
and are thus not Unicode aware (and hence deprecated unless you know you should
use them) and the other type deal in UVs 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)
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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)
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Notice also the grok_bin, grok_hex, and grok_oct
functions in numeric.c for converting strings representing numbers in the respective
bases into NVs.
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)
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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
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