Convert-Scalar/Scalar.pm

=head1 NAME

Convert::Scalar - convert between different representations of perl scalars

=head1 SYNOPSIS

 use Convert::Scalar;

=head1 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.

=over 4

=cut

package Convert::Scalar;

BEGIN {
   $VERSION = '1.1';
   @ISA = qw(Exporter);
   @EXPORT_OK = qw(readonly readonly_on readonly_off weaken unmagic len grow extend);
   %EXPORT_TAGS = (
      taint  => [qw(taint untaint tainted)],
      utf8   => [qw(utf8 utf8_on utf8_off utf8_valid utf8_upgrade utf8_downgrade utf8_encode utf8_decode utf8_length)],
      refcnt => [qw(refcnt refcnt_inc refcnt_dec refcnt_rv refcnt_inc_rv refcnt_dec_rv)],
      ok     => [qw(ok uok rok pok nok niok)],
   );

   require Exporter;
   Exporter::export_ok_tags(keys %EXPORT_TAGS);

   require XSLoader;
   XSLoader::load Convert::Scalar, $VERSION;
}

=item 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.

=item utf8_on scalar

Similar to C<utf8 scalar, 1>, but additionally returns the scalar (the
argument is still modified in-place).

=item utf8_off scalar

Similar to C<utf8 scalar, 0>, but additionally returns the scalar (the
argument is still modified in-place).

=item 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).

=item utf8_upgrade scalar

Convert the string content of the scalar in-place to its UTF8-encoded form
(and also returns it).

=item 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 C<fail_ok> is
not true (the default), croaks.

=item utf8_encode scalar

Convert the string value of the scalar to UTF8-encoded, but then turn off
the C<SvUTF8> flag so that it looks like bytes to perl again. (Might be
removed in future versions).

=item utf8_length scalar

Returns the number of characters in the string, counting wide UTF8
characters as a single character, independent of wether the scalar is
marked as containing bytes or mulitbyte characters.

=item $old = readonly scalar[, $new]

Returns whether the scalar is currently readonly, and sets or clears the
readonly status if a new status is given.

=item readonly_on scalar

Sets the readonly flag on the scalar.

=item readonly_off scalar

Clears the readonly flag on the scalar.

=item unmagic scalar, type

Remove the specified magic from the scalar (DANGEROUS!).

=item weaken scalar

Weaken a reference. (See also L<WeakRef>).

=item taint scalar

Taint the scalar.

=item tainted scalar

returns true when the scalar is tainted, false otherwise.

=item untaint scalar

Remove the tainted flag from the specified scalar.

=item length = len scalar

Returns SvLEN (scalar), that is, the actual number of bytes allocated to
the string value, or C<undef>, is the scalar has no string value.

=item 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).

=item scalar = extend scalar, addlen

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 C<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.

=item refcnt scalar[, newrefcnt]

Returns the current reference count of the given scalar and optionally sets it to
the given reference count.

=item refcnt_inc scalar

Increments the reference count of the given scalar inplace.

=item refcnt_dec scalar

Decrements the reference count of the given scalar inplace. Use C<weaken>
instead if you understand what this function is fore. Better yet: don't
use this module in this case.

=item refcnt_rv scalar[, newrefcnt]

Works like C<refcnt>, but dereferences the given reference first. This is
useful to find the reference count of arrays or hashes, which cnanot be
passed directly. Remember that taking a reference of some object increases
it's reference count, so the reference count used by the C<*_rv>-functions
tend to be one higher.

=item refcnt_inc_rv scalar

Works like C<refcnt_inc>, but dereferences the given reference first.

=item refcnt_dec_rv scalar

Works like C<refcnt_dec>, but dereferences the given reference first.

=item ok scalar

=item uok scalar

=item rok scalar

=item pok scalar

=item nok scalar

=item niok scalar

Calls SvOK, SvUOK, SvROK, SvPOK, SvNOK or SvNIOK on the given scalar,
respectively.

=back

=head2 CANDIDATES FOR FUTURE RELEASES

The following API functions (L<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

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

1

Revision:	1.15
Committed:	Mon Feb 3 03:32:13 2014 UTC (10 years, 3 months ago) by root
Branch:	MAIN
Changes since 1.14:	+2 -4 lines
Log Message:	* empty log message *
#	Content
1	=head1 NAME
2
3	Convert::Scalar - convert between different representations of perl scalars
4
5	=head1 SYNOPSIS
6
7	use Convert::Scalar;
8
9	=head1 DESCRIPTION
10
11	This module exports various internal perl methods that change the internal
12	representation or state of a perl scalar. All of these work in-place, that
13	is, they modify their scalar argument. No functions are exported by default.
14
15	The following export tags exist:
16
17	:utf8 all functions with utf8 in their name
18	:taint all functions with taint in their name
19	:refcnt all functions with refcnt in their name
20	:ok all *ok-functions.
21
22	=over 4
23
24	=cut
25
26	package Convert::Scalar;
27
28	BEGIN {
29	$VERSION = '1.1';
30	@ISA = qw(Exporter);
31	@EXPORT_OK = qw(readonly readonly_on readonly_off weaken unmagic len grow extend);
32	%EXPORT_TAGS = (
33	taint => [qw(taint untaint tainted)],
34	utf8 => [qw(utf8 utf8_on utf8_off utf8_valid utf8_upgrade utf8_downgrade utf8_encode utf8_decode utf8_length)],
35	refcnt => [qw(refcnt refcnt_inc refcnt_dec refcnt_rv refcnt_inc_rv refcnt_dec_rv)],
36	ok => [qw(ok uok rok pok nok niok)],
37	);
38
39	require Exporter;
40	Exporter::export_ok_tags(keys %EXPORT_TAGS);
41
42	require XSLoader;
43	XSLoader::load Convert::Scalar, $VERSION;
44	}
45
46	=item utf8 scalar[, mode]
47
48	Returns true when the given scalar is marked as utf8, false otherwise. If
49	the optional mode argument is given, also forces the interpretation of the
50	string to utf8 (mode true) or plain bytes (mode false). The actual (byte-)
51	content is not changed. The return value always reflects the state before
52	any modification is done.
53
54	This function is useful when you "import" utf8-data into perl, or when
55	some external function (e.g. storing/retrieving from a database) removes
56	the utf8-flag.
57
58	=item utf8_on scalar
59
60	Similar to C<utf8 scalar, 1>, but additionally returns the scalar (the
61	argument is still modified in-place).
62
63	=item utf8_off scalar
64
65	Similar to C<utf8 scalar, 0>, but additionally returns the scalar (the
66	argument is still modified in-place).
67
68	=item utf8_valid scalar [Perl 5.7]
69
70	Returns true if the bytes inside the scalar form a valid utf8 string,
71	false otherwise (the check is independent of the actual encoding perl
72	thinks the string is in).
73
74	=item utf8_upgrade scalar
75
76	Convert the string content of the scalar in-place to its UTF8-encoded form
77	(and also returns it).
78
79	=item utf8_downgrade scalar[, fail_ok=0]
80
81	Attempt to convert the string content of the scalar from UTF8-encoded to
82	ISO-8859-1. This may not be possible if the string contains characters
83	that cannot be represented in a single byte; if this is the case, it
84	leaves the scalar unchanged and either returns false or, if C<fail_ok> is
85	not true (the default), croaks.
86
87	=item utf8_encode scalar
88
89	Convert the string value of the scalar to UTF8-encoded, but then turn off
90	the C<SvUTF8> flag so that it looks like bytes to perl again. (Might be
91	removed in future versions).
92
93	=item utf8_length scalar
94
95	Returns the number of characters in the string, counting wide UTF8
96	characters as a single character, independent of wether the scalar is
97	marked as containing bytes or mulitbyte characters.
98
99	=item $old = readonly scalar[, $new]
100
101	Returns whether the scalar is currently readonly, and sets or clears the
102	readonly status if a new status is given.
103
104	=item readonly_on scalar
105
106	Sets the readonly flag on the scalar.
107
108	=item readonly_off scalar
109
110	Clears the readonly flag on the scalar.
111
112	=item unmagic scalar, type
113
114	Remove the specified magic from the scalar (DANGEROUS!).
115
116	=item weaken scalar
117
118	Weaken a reference. (See also L<WeakRef>).
119
120	=item taint scalar
121
122	Taint the scalar.
123
124	=item tainted scalar
125
126	returns true when the scalar is tainted, false otherwise.
127
128	=item untaint scalar
129
130	Remove the tainted flag from the specified scalar.
131
132	=item length = len scalar
133
134	Returns SvLEN (scalar), that is, the actual number of bytes allocated to
135	the string value, or C<undef>, is the scalar has no string value.
136
137	=item scalar = grow scalar, newlen
138
139	Sets the memory area used for the scalar to the given length, if the
140	current length is less than the new value. This does not affect the
141	contents of the scalar, but is only useful to "pre-allocate" memory space
142	if you know the scalar will grow. The return value is the modified scalar
143	(the scalar is modified in-place).
144
145	=item scalar = extend scalar, addlen
146
147	Reserves enough space in the scalar so that addlen bytes can be appended
148	without reallocating it. The actual contents of the scalar will not be
149	affected. The modified scalar will also be returned.
150
151	This function is meant to make append workloads efficient - if you append
152	a short string to a scalar many times (millions of times), then perl will
153	have to reallocate and copy the scalar basically every time.
154
155	If you instead use C<extend $scalar, length $shortstring>, then
156	Convert::Scalar will use a "size to next power of two, roughly" algorithm,
157	so as the scalar grows, perl will have to resize and copy it less and less
158	often.
159
160	=item refcnt scalar[, newrefcnt]
161
162	Returns the current reference count of the given scalar and optionally sets it to
163	the given reference count.
164
165	=item refcnt_inc scalar
166
167	Increments the reference count of the given scalar inplace.
168
169	=item refcnt_dec scalar
170
171	Decrements the reference count of the given scalar inplace. Use C<weaken>
172	instead if you understand what this function is fore. Better yet: don't
173	use this module in this case.
174
175	=item refcnt_rv scalar[, newrefcnt]
176
177	Works like C<refcnt>, but dereferences the given reference first. This is
178	useful to find the reference count of arrays or hashes, which cnanot be
179	passed directly. Remember that taking a reference of some object increases
180	it's reference count, so the reference count used by the C<*_rv>-functions
181	tend to be one higher.
182
183	=item refcnt_inc_rv scalar
184
185	Works like C<refcnt_inc>, but dereferences the given reference first.
186
187	=item refcnt_dec_rv scalar
188
189	Works like C<refcnt_dec>, but dereferences the given reference first.
190
191	=item ok scalar
192
193	=item uok scalar
194
195	=item rok scalar
196
197	=item pok scalar
198
199	=item nok scalar
200
201	=item niok scalar
202
203	Calls SvOK, SvUOK, SvROK, SvPOK, SvNOK or SvNIOK on the given scalar,
204	respectively.
205
206	=back
207
208	=head2 CANDIDATES FOR FUTURE RELEASES
209
210	The following API functions (L<perlapi>) are considered for future
211	inclusion in this module If you want them, write me.
212
213	sv_upgrade
214	sv_pvn_force
215	sv_pvutf8n_force
216	the sv2xx family
217
218	=head1 AUTHOR
219
220	Marc Lehmann <schmorp@schmorp.de>
221	http://home.schmorp.de/
222
223	=cut
224
225	1
226