NAME¶
perlclib - Internal replacements for standard C library functions
DESCRIPTION¶
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¶
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¶
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)
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¶
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¶
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 "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
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)
Character Class Tests¶
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¶
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)".
SEE ALSO¶
perlapi, perlapio, perlguts