Convert::Scalar - convert between different representations of perl scalars
use Convert::Scalar;
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.
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
Marc Lehmann <[email protected]>
http://home.schmorp.de/