The previous coding effectively only verified that the second byte of a
multibyte character was in the expected range; moreover, it wasn't careful
to make sure that the second byte even exists in the buffer before touching
it.  The latter seems unlikely to cause any real problems in the field
(in particular, it could never be a problem with null-terminated input),
but it's still a bug.

Since GB18030 is not a supported backend encoding, the only thing we'd
really be doing with GB18030 text is converting it to UTF8 in LocalToUtf,
which would fail anyway on any invalid character for lack of a match in
its lookup table.  So the only user-visible consequence of this change
should be that you'll get "invalid byte sequence for encoding" rather than
"character has no equivalent" for malformed GB18030 input.  However,
impending changes to the GB18030 conversion code will require these tighter
up-front checks to avoid producing bogus results.

This includes removing tabs after periods in C comments, which was
applied to back branches, so this change should not effect backpatching.

Assert errors were thrown for functions being passed invalid encodings,
while the main code handled it just fine.

Also document that libpq's PQclientEncoding() returns -1 for an encoding
lookup failure.

Per report from Peter Geoghegan

These changes should generally improve correctness/maintainability.
A nice side benefit is that several kilobytes move from initialized
data to text segment, allowing them to be shared across processes and
probably reducing copy-on-write overhead while forking a new backend.
Unfortunately this doesn't seem to help libpq in the same way (at least
not when it's compiled with -fpic on x86_64), but we can hope the linker
at least collects all nominally-const data together even if it's not
actually part of the text segment.

Also, make pg_encname_tbl[] static in encnames.c, since there seems
no very good reason for any other code to use it; per a suggestion
from Wim Lewis, who independently submitted a patch that was mostly
a subset of this one.

Oskari Saarenmaa, with some editorialization by me

This is the first run of the Perl-based pgindent script.  Also update
pgindent instructions.

Quiet compiler warnings noted by Peter Eisentraut.

Also some cosmetic improvements for wchar-to-mblen patch.

Bug spotted by Tom Lane.

This is infrastructure for Alexander Korotkov's work on indexing regular
expression searches.

Alexander Korotkov, with a bit of further hackery on the MULE conversion
by me

This commit improves the comments in pg_wchar.h and creates #define symbols
for some formerly hard-coded values.  No substantive code changes.

Tatsuo Ishii and Tom Lane

commit-fest.

Josh Kupershmidt

Make sure that it considers all the possibilities that the old code did,
instead of trying only one possibility per character position.  To keep the
runtime in bounds, instead tweak the character incrementers to not try
every possible multibyte character code.  Remove unnecessary logic to
restore the old character value on failure.  Additional comment and
formatting cleanup.

This infrastructure doesn't in any way guarantee that the character
we produce will sort before the one we incremented; but it does at least
make it much more likely that we'll end up with something that is a valid
character, which improves our chances.

Kyotaro Horiguchi, with various adjustments by me.

It used to say

ERROR:  invalid byte sequence for encoding "UTF8": 0xdb24

Change this to

ERROR:  invalid byte sequence for encoding "UTF8": 0xdb 0x24

to make it clear that this is a byte sequence and not a code point.

Also fix the adjacent "character has no equivalent" message that has
the same issue.

elsewhere.

Similarly rename the version in mbprint.c, not because this affects anything
but just to keep the two copies in exact sync.  There was some discussion of
having only one copy in src/port/ instead, but this function is so small
and unlikely to change that that seems like overkill.

Slightly editorialized version of a patch by Joseph Adams.  (The bug-fix
aspect of his patch was applied separately, and back-patched.)

provided by Andrew.

encoding conversion of any elog/ereport message being sent to the frontend.
This generalizes a patch that I put in last October, which suppressed
translation of only specific messages known to be associated with recursive
can't-translate-the-message behavior.  As shown in bug #4680, we need a more
general answer in order to have some hope of coping with broken encoding
conversion setups.  This approach seems a good deal less klugy anyway.

Patch in all supported branches.

make maintenance harder.

encoding conversion functions.  These are not can't-happen cases because
it's possible to create a conversion with the wrong conversion function
for the specified encoding pair.  That would lead to an Assert crash in
an Assert-enabled build, or incorrect conversion otherwise, neither of
which is desirable.  This would be a DOS issue if production databases
were customarily built with asserts enabled, but fortunately that's not so.
Per an observation by Heikki.

Back-patch to all supported branches.

recursion when we are unable to convert a localized error message to the
client's encoding.  We've been over this ground before, but as reported by
Ibrar Ahmed, it still didn't work in the case of conversion failures for
the conversion-failure message itself :-(.  Fix by installing a "circuit
breaker" that disables attempts to localize this message once we get into
recursion trouble.

Patch all supported branches, because it is in fact broken in all of them;
though I had to add some missing translations to the older branches in
order to expose the failure in the particular test case I was using.

Add some comments so hopefully the next poor sod doesn't fall into the
same trap.  (Wrong comments are worse than none at all...)

database via builtin functions, as recently discussed on -hackers.

chr() now returns a character in the database encoding. For UTF8 encoded databases
the argument is treated as a Unicode code point. For other multi-byte encodings
the argument must designate a strict ascii character, or an error is raised,
as is also the case if the argument is 0.

ascii() is adjusted so that it remains the inverse of chr().

The two argument form of convert() is gone, and the three argument form now
takes a bytea first argument and returns a bytea. To cover this loss three new
functions are introduced:
. convert_from(bytea, name) returns text - converts the first argument from the
  named encoding to the database encoding
. convert_to(text, name) returns bytea - converts the first argument from the
  database encoding to the named encoding
. length(bytea, name) returns int - gives the length of the first argument in
  characters in the named encoding

"Server-side support of all encodings" around 2007/3/26.
initdb required.

and GB18030. patches from ITAGAKI Takahiro.

along with new conversions among EUC_JIS_2004, SHIFT_JIS_2004 and UTF-8.
catalog version has been bump up.

page about the maximum UTF8 sequence length we support (4 bytes since 8.1,
3 before that).  pg_utf2wchar_with_len never got updated to support 4-byte
characters at all, and in any case had a buffer-overrun risk in that it
could produce multiple pg_wchars from what mblen claims to be just one UTF8
character.  The only reason we don't have a major security hole is that most
callers allocate worst-case output buffers; the sole exception in released
versions appears to be pre-8.2 iwchareq() (ie, ILIKE), which can be crashed
due to zeroing out its return address --- but AFAICS that can't be exploited
for anything more than a crash, due to inability to control what gets written
there.  Per report from James Russell and Michael Fuhr.

Pre-8.1 the risk is much less, but I still think pg_utf2wchar_with_len's
behavior given an incomplete final character risks buffer overrun, so
back-patch that logic change anyway.

This patch also makes sure that UTF8 sequences exceeding the supported
length (whichever it is) are consistently treated as error cases, rather
than being treated like a valid shorter sequence in some places.

"failure".

suggesting review of client_encoding.

characters in all cases.  Formerly we mostly just threw warnings for invalid
input, and failed to detect it at all if no encoding conversion was required.
The tighter check is needed to defend against SQL-injection attacks as per
CVE-2006-2313 (further details will be published after release).  Embedded
zero (null) bytes will be rejected as well.  The checks are applied during
input to the backend (receipt from client or COPY IN), so it no longer seems
necessary to check in textin() and related routines; any string arriving at
those functions will already have been validated.  Conversion failure
reporting (for characters with no equivalent in the destination encoding)
has been cleaned up and made consistent while at it.

Also, fix a few longstanding errors in little-used encoding conversion
routines: win1251_to_iso, win866_to_iso, euc_tw_to_big5, euc_tw_to_mic,
mic_to_euc_tw were all broken to varying extents.

Patches by Tatsuo Ishii and Tom Lane.  Thanks to Akio Ishida and Yasuo Ohgaki
for identifying the security issues.

up a bunch of the support utilities.

In src/backend/utils/mb/Unicode remove nearly duplicate copies of the
UCS_to_XXX perl script and replace with one version to handle all generic
files.  Update the Makefile so that it knows about all the map files.
This produces a slight difference in some of the map files, using a
uniform naming convention and not mapping the null character.

In src/backend/utils/mb/conversion_procs create a master utf8<->win
codepage function like the ISO 8859 versions instead of having a separate
handler for each conversion.

There is an externally visible change in the name of the win1258 to utf8
conversion.  According to the documentation notes, it was named
incorrectly and this changes it to a standard name.

Running the Unicode mapping perl scripts has shown some additional mapping
changes in koi8r and iso8859-7.

  If the second output column value is 'a\nb', the 'b' should appear
  in the second display column, rather than the first column as it
  does now.

Change libpq's PQdsplen() to return more useful values.

> Note: this changes the PQdsplen function, it can now return zero or
> minus one which was not possible before. It doesn't appear anyone is
> actually using the functions other than psql but it is a change. The
> functions are not actually documentated anywhere so it's not like we're
> breaking a defined interface. The new semantics follow the Unicode
> standard.

BACKWARD COMPATIBLE CHANGE.

The only user-visible change I saw in the regression tests is that a
SELECT * on a table where all the columns have been dropped doesn't
return a blank line like before.  This seems like a step forward.

Martijn van Oosterhout