plucky (3) Convert::Scalar.3pm.gz
NAME
Convert::Scalar - convert between different representations of perl scalars
SYNOPSIS
use Convert::Scalar;
DESCRIPTION
This module exports various internal perl methods that change the internal representation or state of a
perl scalar. All of these work in-place, that is, they modify their scalar argument. No functions are
exported by default.
The following export tags exist:
:utf8 all functions with utf8 in their name
:taint all functions with taint in their name
:refcnt all functions with refcnt in their name
:ok all *ok-functions.
utf8 scalar[, mode]
Returns true when the given scalar is marked as utf8, false otherwise. If the optional mode argument
is given, also forces the interpretation of the string to utf8 (mode true) or plain bytes (mode
false). The actual (byte-) content is not changed. The return value always reflects the state before
any modification is done.
This function is useful when you "import" utf8-data into perl, or when some external function (e.g.
storing/retrieving from a database) removes the utf8-flag.
utf8_on scalar
Similar to "utf8 scalar, 1", but additionally returns the scalar (the argument is still modified in-
place).
utf8_off scalar
Similar to "utf8 scalar, 0", but additionally returns the scalar (the argument is still modified in-
place).
utf8_valid scalar [Perl 5.7]
Returns true if the bytes inside the scalar form a valid utf8 string, false otherwise (the check is
independent of the actual encoding perl thinks the string is in).
utf8_upgrade scalar
Convert the string content of the scalar in-place to its UTF8-encoded form (and also returns it).
utf8_downgrade scalar[, fail_ok=0]
Attempt to convert the string content of the scalar from UTF8-encoded to ISO-8859-1. This may not be
possible if the string contains characters that cannot be represented in a single byte; if this is
the case, it leaves the scalar unchanged and either returns false or, if "fail_ok" is not true (the
default), croaks.
utf8_encode scalar
Convert the string value of the scalar to UTF8-encoded, but then turn off the "SvUTF8" flag so that
it looks like bytes to perl again. (Might be removed in future versions).
utf8_length scalar
Returns the number of characters in the string, counting wide UTF8 characters as a single character,
independent of whether the scalar is marked as containing bytes or mulitbyte characters.
$old = readonly scalar[, $new]
Returns whether the scalar is currently readonly, and sets or clears the readonly status if a new
status is given.
readonly_on scalar
Sets the readonly flag on the scalar.
readonly_off scalar
Clears the readonly flag on the scalar.
unmagic scalar, type
Remove the specified magic from the scalar (DANGEROUS!).
weaken scalar
Weaken a reference. (See also WeakRef).
taint scalar
Taint the scalar.
tainted scalar
returns true when the scalar is tainted, false otherwise.
untaint scalar
Remove the tainted flag from the specified scalar.
length = len scalar
Returns SvLEN (scalar), that is, the actual number of bytes allocated to the string value, or
"undef", is the scalar has no string value.
scalar = grow scalar, newlen
Sets the memory area used for the scalar to the given length, if the current length is less than the
new value. This does not affect the contents of the scalar, but is only useful to "pre-allocate"
memory space if you know the scalar will grow. The return value is the modified scalar (the scalar is
modified in-place).
scalar = extend scalar, addlen=64
Reserves enough space in the scalar so that addlen bytes can be appended without reallocating it. The
actual contents of the scalar will not be affected. The modified scalar will also be returned.
This function is meant to make append workloads efficient - if you append a short string to a scalar
many times (millions of times), then perl will have to reallocate and copy the scalar basically every
time.
If you instead use "extend $scalar, length $shortstring", then Convert::Scalar will use a "size to
next power of two, roughly" algorithm, so as the scalar grows, perl will have to resize and copy it
less and less often.
nread = extend_read fh, scalar, addlen=64
Calls "extend scalar, addlen" to ensure some space is available, then do the equivalent of "sysread"
to the end, to try to fill the extra space. Returns how many bytes have been read, 0 on EOF or undef>
on error, just like "sysread".
This function is useful to implement many protocols where you read some data, see if it is enough to
decode, and if not, read some more, where the naive or easy way of doing this would result in bad
performance.
nread = read_all fh, scalar, length
Tries to read "length" bytes into "scalar". Unlike "read" or "sysread", it will try to read more
bytes if not all bytes could be read in one go (this is often called "xread" in C).
Returns the total nunmber of bytes read (normally "length", unless an error or EOF occurred), 0 on
EOF and "undef" on errors.
nwritten = write_all fh, scalar
Like "readall", but for writes - the equivalent of the "xwrite" function often seen in C.
refcnt scalar[, newrefcnt]
Returns the current reference count of the given scalar and optionally sets it to the given reference
count.
refcnt_inc scalar
Increments the reference count of the given scalar inplace.
refcnt_dec scalar
Decrements the reference count of the given scalar inplace. Use "weaken" instead if you understand
what this function is fore. Better yet: don't use this module in this case.
refcnt_rv scalar[, newrefcnt]
Works like "refcnt", but dereferences the given reference first. This is useful to find the reference
count of arrays or hashes, which cannot be passed directly. Remember that taking a reference of some
object increases it's reference count, so the reference count used by the *_rv-functions tend to be
one higher.
refcnt_inc_rv scalar
Works like "refcnt_inc", but dereferences the given reference first.
refcnt_dec_rv scalar
Works like "refcnt_dec", but dereferences the given reference first.
ok scalar
uok scalar
rok scalar
pok scalar
nok scalar
niok scalar
Calls SvOK, SvUOK, SvROK, SvPOK, SvNOK or SvNIOK on the given scalar, respectively.
CANDIDATES FOR FUTURE RELEASES
The following API functions (perlapi) are considered for future inclusion in this module If you want
them, write me.
sv_upgrade
sv_pvn_force
sv_pvutf8n_force
the sv2xx family
AUTHOR
Marc Lehmann <schmorp@schmorp.de> http://home.schmorp.de/