perlebcdic.1

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "PERLEBCDIC 1"
.TH PERLEBCDIC 1 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
perlebcdic \- Considerations for running Perl on EBCDIC platforms
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
An exploration of some of the issues facing Perl programmers
on \s-1EBCDIC\s0 based computers.  We do not cover localization, 
internationalization, or multi byte character set issues other
than some discussion of \s-1UTF\-8\s0 and UTF-EBCDIC.
.PP
Portions that are still incomplete are marked with \s-1XXX\s0.
.SH "COMMON CHARACTER CODE SETS"
.IX Header "COMMON CHARACTER CODE SETS"
.Sh "\s-1ASCII\s0"
.IX Subsection "ASCII"
The American Standard Code for Information Interchange is a set of
integers running from 0 to 127 (decimal) that imply character 
interpretation by the display and other system(s) of computers.  
The range 0..127 can be covered by setting the bits in a 7\-bit binary 
digit, hence the set is sometimes referred to as a \*(L"7\-bit \s-1ASCII\s0\*(R".  
\&\s-1ASCII\s0 was described by the American National Standards Institute 
document \s-1ANSI\s0 X3.4\-1986.  It was also described by \s-1ISO\s0 646:1991 
(with localization for currency symbols).  The full \s-1ASCII\s0 set is 
given in the table below as the first 128 elements.  Languages that 
can be written adequately with the characters in \s-1ASCII\s0 include 
English, Hawaiian, Indonesian, Swahili and some Native American 
languages.
.PP
There are many character sets that extend the range of integers
from 0..2**7\-1 up to 2**8\-1, or 8 bit bytes (octets if you prefer).
One common one is the \s-1ISO\s0 8859\-1 character set.
.Sh "\s-1ISO\s0 8859"
.IX Subsection "ISO 8859"
The \s-1ISO\s0 8859\-$n are a collection of character code sets from the 
International Organization for Standardization (\s-1ISO\s0) each of which 
adds characters to the \s-1ASCII\s0 set that are typically found in European 
languages many of which are based on the Roman, or Latin, alphabet.
.Sh "Latin 1 (\s-1ISO\s0 8859\-1)"
.IX Subsection "Latin 1 (ISO 8859-1)"
A particular 8\-bit extension to \s-1ASCII\s0 that includes grave and acute 
accented Latin characters.  Languages that can employ \s-1ISO\s0 8859\-1 
include all the languages covered by \s-1ASCII\s0 as well as Afrikaans, 
Albanian, Basque, Catalan, Danish, Faroese, Finnish, Norwegian, 
Portuguese, Spanish, and Swedish.  Dutch is covered albeit without 
the ij ligature.  French is covered too but without the oe ligature. 
German can use \s-1ISO\s0 8859\-1 but must do so without German-style
quotation marks.  This set is based on Western European extensions 
to \s-1ASCII\s0 and is commonly encountered in world wide web work.
In \s-1IBM\s0 character code set identification terminology \s-1ISO\s0 8859\-1 is
also known as \s-1CCSID\s0 819 (or sometimes 0819 or even 00819).
.Sh "\s-1EBCDIC\s0"
.IX Subsection "EBCDIC"
The Extended Binary Coded Decimal Interchange Code refers to a 
large collection of slightly different single and multi byte 
coded character sets that are different from \s-1ASCII\s0 or \s-1ISO\s0 8859\-1 
and typically run on host computers.  The \s-1EBCDIC\s0 encodings derive 
from 8 bit byte extensions of Hollerith punched card encodings.
The layout on the cards was such that high bits were set for the
upper and lower case alphabet characters [a\-z] and [A\-Z], but there
were gaps within each latin alphabet range.
.PP
Some \s-1IBM\s0 \s-1EBCDIC\s0 character sets may be known by character code set 
identification numbers (\s-1CCSID\s0 numbers) or code page numbers.  Leading
zero digits in \s-1CCSID\s0 numbers within this document are insignificant.
E.g. \s-1CCSID\s0 0037 may be referred to as 37 in places.
.Sh "13 variant characters"
.IX Subsection "13 variant characters"
Among \s-1IBM\s0 \s-1EBCDIC\s0 character code sets there are 13 characters that
are often mapped to different integer values.  Those characters
are known as the 13 \*(L"variant\*(R" characters and are:
.PP
.Vb 1
\&    \e [ ] { } ^ ~ ! # | $ @ \`
.Ve
.Sh "0037"
.IX Subsection "0037"
Character code set \s-1ID\s0 0037 is a mapping of the \s-1ASCII\s0 plus Latin\-1 
characters (i.e. \s-1ISO\s0 8859\-1) to an \s-1EBCDIC\s0 set.  0037 is used 
in North American English locales on the \s-1OS/400\s0 operating system 
that runs on \s-1AS/400\s0 computers.  \s-1CCSID\s0 37 differs from \s-1ISO\s0 8859\-1 
in 237 places, in other words they agree on only 19 code point values.
.Sh "1047"
.IX Subsection "1047"
Character code set \s-1ID\s0 1047 is also a mapping of the \s-1ASCII\s0 plus 
Latin\-1 characters (i.e. \s-1ISO\s0 8859\-1) to an \s-1EBCDIC\s0 set.  1047 is 
used under Unix System Services for \s-1OS/390\s0 or z/OS, and OpenEdition 
for \s-1VM/ESA\s0.  \s-1CCSID\s0 1047 differs from \s-1CCSID\s0 0037 in eight places.
.Sh "POSIX-BC"
.IX Subsection "POSIX-BC"
The \s-1EBCDIC\s0 code page in use on Siemens' \s-1BS2000\s0 system is distinct from
1047 and 0037.  It is identified below as the POSIX-BC set.
.Sh "Unicode code points versus \s-1EBCDIC\s0 code points"
.IX Subsection "Unicode code points versus EBCDIC code points"
In Unicode terminology a \fIcode point\fR is the number assigned to a
character: for example, in \s-1EBCDIC\s0 the character \*(L"A\*(R" is usually assigned
the number 193.  In Unicode the character \*(L"A\*(R" is assigned the number 65.
This causes a problem with the semantics of the pack/unpack \*(L"U\*(R", which
are supposed to pack Unicode code points to characters and back to numbers.
The problem is: which code points to use for code points less than 256?
(for 256 and over there's no problem: Unicode code points are used)
In \s-1EBCDIC\s0, for the low 256 the \s-1EBCDIC\s0 code points are used.  This
means that the equivalences
.PP
.Vb 2
\&        pack("U", ord($character)) eq $character
\&        unpack("U", $character) == ord $character
.Ve
.PP
will hold.  (If Unicode code points were applied consistently over