From: Nick Ing-Simmons <nik@tiuk.ti.com>
Date: Wed, 13 Dec 2000 23:16:13 +0000 (+0000)
Subject: Beginings of compiled encodings - checked in as a snapshot of thoughts
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=017e2addf6da99b3f648d9518de5a848be394ab8;p=p5sagit%2Fp5-mst-13.2.git

Beginings of compiled encodings - checked in as a snapshot of thoughts
so far and so it does not get lost.

p4raw-id: //depot/perlio@8103
---

diff --git a/ext/Encode/compile b/ext/Encode/compile
new file mode 100755
index 0000000..e2db8ab
--- /dev/null
+++ b/ext/Encode/compile
@@ -0,0 +1,257 @@
+#!../../perl -w
+@INC = '../../lib';
+use strict;
+
+sub encode_U
+{
+ my $uv = shift;
+ if ($uv < 0x80)
+  {
+   return chr($uv)
+  }
+ if ($uv < 0x800)
+  {
+   return chr(($uv >> 6)        | 0xC0).
+          chr(($uv & 0x3F)      | 0x80);
+  }
+ return chr(($uv >> 12)         | 0xE0).
+        chr((($uv >> 6) & 0x3F) | 0x80).
+        chr(($uv & 0x3F)        | 0x80);
+}
+
+sub encode_S
+{
+ my ($ch,$page) = @_;
+ return chr($ch);
+}
+
+sub encode_D
+{
+ my ($ch,$page) = @_;
+ return chr($page).chr($ch);
+}
+
+sub encode_M
+{
+ my ($ch,$page) = @_;
+ return &encode_D if $page;
+ return &encode_S;
+}
+
+my $cname = shift(@ARGV);
+open(C,">$cname") || die "Cannot open $cname:$!";
+print C "#include \"encode.h\"\n";
+
+my %encoding;
+my %strings;
+
+foreach my $enc (@ARGV)
+ {
+  my ($name) = $enc =~ /^.*?([\w-]+)(\.enc)$/;
+  if (open(E,$enc))
+   {
+    compile(\*E,$name,\*C);
+   }
+  else
+   {
+    warn "Cannot open $enc for $name:$!";
+   }
+ }
+
+print C "encode_t encodings[] = {\n";
+foreach my $enc (sort keys %encoding)
+ {
+  print C " {",join(',',"\"$enc\"",@{$encoding{$enc}}),"},\n";
+ }
+print C " {0,0,0,0,0}\n};\n";
+
+close(C);
+
+
+
+sub compile
+{
+ my ($fh,$name,$ch) = @_;
+ my $e2u = {};
+ my $u2e = {};
+
+ my $type;
+ while ($type = <$fh>)
+  {
+   last if $type !~ /^\s*#/;
+  }
+ chomp($type);
+ return if $type eq 'E';
+ my ($def,$sym,$pages) = split(/\s+/,scalar(<$fh>));
+ warn "t=$type s=$sym d=$def p=$pages $name\n";
+ my $rep = '';
+ {
+  my $v = hex($def);
+  no strict 'refs';
+  $rep = &{"encode_$type"}($v & 0xFF, ($v >> 8) & 0xffe);
+ }
+ while ($pages--)
+  {
+   my $line = <$fh>;
+   chomp($line);
+   my $page = hex($line);
+   my $ch = 0;
+   for (my $i = 0; $i < 16; $i++)
+    {
+     my $line = <$fh>;
+     for (my $j = 0; $j < 16; $j++)
+      {
+       no strict 'refs';
+       my $ech = &{"encode_$type"}($ch,$page);
+       my $val = hex(substr($line,0,4,''));
+       if ($val || (!$ch && !$page))
+        {
+         my $uch = encode_U($val);
+         enter($e2u,$ech,$uch,$e2u);
+         enter($u2e,$uch,$ech,$u2e);
+        }
+       else
+        {
+         # No character at this position
+         # enter($e2u,$ech,undef,$e2u);
+        }
+       $ch++;
+      }
+    }
+  }
+ output($ch,$name.'_utf8',$e2u);
+ output($ch,'utf8_'.$name,$u2e);
+ $encoding{$name} = [$e2u->{Cname},$u2e->{Cname},
+                     outstring($ch,$e2u->{Cname}.'_def',$rep),length($rep)];
+}
+
+sub enter
+{
+ my ($a,$s,$d,$t) = @_;
+ $t = $a if @_ < 4;
+ my $b = substr($s,0,1);
+ my $e = $a->{$b};
+ unless ($e)
+  {     # 0  1  2  3         4  5
+   $e = [$b,$b,'',{},length($s),0];
+   $a->{$b} = $e;
+  }
+ if (length($s) > 1)
+  {
+   enter($e->[3],substr($s,1),$d,$t);
+  }
+ else
+  {
+   $e->[2] = $d;
+   $e->[3] = $t;
+   $e->[5] = length($d);
+  }
+}
+
+
+sub outstring
+{
+ my ($fh,$name,$s) = @_;
+ my $sym = $strings{$s};
+ unless ($sym)
+  {
+   if (1)
+    {
+     foreach my $o (keys %strings)
+      {
+       my $i = index($o,$s);
+       if ($i >= 0)
+        {
+         $sym = $strings{$o};
+         $sym .= sprintf("+0x%02x",$i) if ($i);
+         return $sym;
+        }
+      }
+    }
+   $strings{$s} = $sym = $name;
+   printf $fh "static const U8 %s[%d] =\n",$name,length($s);
+   while (length($s))
+    {
+     my $c = substr($s,0,16,'');
+     print  $fh '"',join('',map(sprintf('\x%02x',ord($_)),split(//,$c))),'"';
+     print  $fh "\n" if length($s);
+    }
+   printf $fh ";\n\n";
+  }
+ return $sym;
+}
+
+
+
+sub output
+{
+ my ($fh,$name,$a) = @_;
+ $name =~ s/\W+/_/g;
+ $a->{Cname} = $name;
+ my @keys = grep(ref($a->{$_}),sort keys %$a);
+ print $fh "\nstatic encpage_t $name\[\];\n";
+ # Sub-tables
+ my %str;
+ my $l;
+ my @ent;
+ foreach my $b (@keys)
+  {
+   my ($s,$f,$out,$t,$end) = @{$a->{$b}};
+   if (defined($l) &&
+       ord($b) == ord($a->{$l}[1])+1 &&
+       $a->{$l}[3] == $a->{$b}[3] &&
+       $a->{$l}[4] == $a->{$b}[4] &&
+       $a->{$l}[5] == $a->{$b}[5] )
+    {
+     my $i = ord($b)-ord($a->{$l}[0]);
+     $a->{$l}[1]  = $b;
+     $a->{$l}[2] .= $a->{$b}[2];
+    }
+   else
+    {
+     $l = $b;
+     push(@ent,$b);
+    }
+   unless (exists $t->{Cname})
+    {
+     output($fh,sprintf("%s_%02x",$name,ord($s)),$t);
+    }
+  }
+ if (ord($keys[-1]) < 255)
+  {
+   my $t = chr(ord($keys[-1])+1);
+   $a->{$t} = [$t,chr(255),undef,$a,0,0];
+   push(@ent,$t);
+  }
+ # String tables
+ foreach my $b (@ent)
+  {
+   next unless $a->{$b}[5];
+   my $s = ord($a->{$b}[0]);
+   my $e = ord($a->{$b}[1]);
+   outstring($fh,sprintf("%s__%02x_%02x",$name,$s,$e),$a->{$b}[2]);
+  }
+
+ print $fh "\n";
+ print $fh "static encpage_t $name\[",scalar(@ent),"] = {\n";
+ foreach my $b (@ent)
+  {
+   my ($s,$e,$out,$t,$end,$l) = @{$a->{$b}};
+   my $sc = ord($s);
+   my $ec = ord($e);
+   print  $fh "{";
+   if ($l)
+    {
+     printf $fh outstring($fh,'',$out);
+    }
+   else
+    {
+     print  $fh "0";
+    }
+   print  $fh ",",$t->{Cname};
+   printf $fh ",0x%02x,0x%02x,$end},\n",$sc,$ec;
+  }
+ print $fh "};\n\n";
+}
+
+
diff --git a/ext/Encode/encengine.c b/ext/Encode/encengine.c
new file mode 100644
index 0000000..a73be73
--- /dev/null
+++ b/ext/Encode/encengine.c
@@ -0,0 +1,134 @@
+/*
+Data structures for encoding transformations.
+
+Perl works internally in either a native 'byte' encoding or
+in UTF-8 encoded Unicode.  We have no immediate need for a "wchar_t"
+representation. When we do we can use utf8_to_uv().
+
+Most character encodings are either simple byte mappings or
+variable length multi-byte encodings. UTF-8 can be viewed as a
+rather extreme case of the latter.
+
+So to solve an important part of perl's encode needs we need to solve the
+"multi-byte -> multi-byte" case. The simple byte forms are then just degenerate
+case. (Where one of multi-bytes will usually be UTF-8.)
+
+The other type of encoding is a shift encoding where a prefix sequence
+determines what subsequent bytes mean. Such encodings have state.
+
+We also need to handle case where a character in one encoding has to be
+represented as multiple characters in the other. e.g. letter+diacritic.
+
+The process can be considered as pseudo perl:
+
+my $dst = '';
+while (length($src))
+ {
+  my $size    = $count($src);
+  my $in_seq  = substr($src,0,$size,'');
+  my $out_seq = $s2d_hash{$in_seq};
+  if (defined $out_seq)
+   {
+    $dst .= $out_seq;
+   }
+  else
+   {
+    # an error condition
+   }
+ }
+return $dst;
+
+That has the following components:
+ &src_count - a "rule" for how many bytes make up the next character in the
+              source.
+ %s2d_hash  - a mapping from input sequences to output sequences
+
+The problem with that scheme is that it does not allow the output
+character repertoire to affect the characters considered from the
+input.
+
+So we use a "trie" representation which can also be considered
+a state machine:
+
+my $dst   = '';
+my $seq   = \@s2d_seq;
+my $next  = \@s2d_next;
+while (length($src))
+ {
+  my $byte    = $substr($src,0,1,'');
+  my $out_seq = $seq->[$byte];
+  if (defined $out_seq)
+   {
+    $dst .= $out_seq;
+   }
+  else
+   {
+    # an error condition
+   }
+  ($next,$seq) = @$next->[$byte] if $next;
+ }
+return $dst;
+
+There is now a pair of data structures to represent everything.
+It is valid for output sequence at a particular point to
+be defined but zero length, that just means "don't know yet".
+For the single byte case there is no 'next' so new tables will be the same as
+the original tables. For a multi-byte case a prefix byte will flip to the tables
+for  the next page (adding nothing to the output), then the tables for the page
+will provide the actual output and set tables back to original base page.
+
+This scheme can also handle shift encodings.
+
+A slight enhancement to the scheme also allows for look-ahead - if
+we add a flag to re-add the removed byte to the source we could handle
+  a" -> ä
+  ab -> a (and take b back please)
+
+*/
+
+#include <EXTERN.h>
+#include <perl.h>
+#define U8 U8
+#include "encode.h"
+
+STRLEN
+translate(encpage_t *enc, const U8 *src, STRLEN slen, U8 *dst, STRLEN dlen)
+{
+ const U8 *send = src+slen;
+ U8 *dend = dst+dlen;
+ U8 *dptr = dst;
+ while (src < send)
+  {
+   encpage_t *e = enc;
+   U8 byte = *src++;
+   while (byte > e->max)
+    e++;
+   if (byte >= e->min)
+    {
+     STRLEN n = e->dlen;
+     if (n)
+      {
+       const U8 *out = e->seq+n*(byte - e->min);
+       STRLEN n = *out++;
+       if (dptr+n <= dend)
+        {
+         if (dst)
+          Copy(out,dptr,n,U8);
+         dptr += n;
+        }
+       else
+        {
+         /* No room */
+        }
+      }
+     enc = e->next;
+    }
+   else
+    {
+     /* Cannot represent */
+    }
+  }
+ return dptr-dst;
+}
+
+
diff --git a/ext/Encode/encode.h b/ext/Encode/encode.h
new file mode 100644
index 0000000..10f8386
--- /dev/null
+++ b/ext/Encode/encode.h
@@ -0,0 +1,26 @@
+#ifndef U8
+typedef unsigned char U8;
+#endif
+
+typedef struct encpage_s encpage_t;
+
+struct encpage_s
+{
+ const U8   *seq;
+ encpage_t  *next;
+ U8         min;
+ U8         max;
+ U8         dlen;
+ U8         slen;
+};
+
+typedef struct encode_s encode_t;
+struct encode_s
+{
+ const char *name;
+ encpage_t  *t_utf8;
+ encpage_t  *f_utf8;
+ const U8   *rep;
+ int        replen;
+};
+