From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15655 invoked by alias); 26 Mar 2018 10:22:22 -0000 Mailing-List: contact newlib-cvs-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: newlib-cvs-owner@sourceware.org Received: (qmail 15598 invoked by uid 9078); 26 Mar 2018 10:22:21 -0000 Date: Mon, 26 Mar 2018 10:22:00 -0000 Message-ID: <20180326102221.15595.qmail@sourceware.org> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Corinna Vinschen To: newlib-cvs@sourceware.org Subject: [newlib-cygwin] comments to document struct caseconv_entry X-Act-Checkin: newlib-cygwin X-Git-Author: Thomas Wolff X-Git-Refname: refs/heads/master X-Git-Oldrev: b49ce5af1b97c4f2ec7f116c393c5e52917f3712 X-Git-Newrev: fc59da00c85de5307ff74e043ec2d802a3ec4655 X-SW-Source: 2018-q1/txt/msg00066.txt.bz2 https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=fc59da00c85de5307ff74e043ec2d802a3ec4655 commit fc59da00c85de5307ff74e043ec2d802a3ec4655 Author: Thomas Wolff Date: Mon Mar 26 11:46:40 2018 +0200 comments to document struct caseconv_entry explain design of compact (packed) struct caseconv_entry, in case it needs to be modified for future Unicode versions Diff: --- newlib/libc/ctype/towctrans_l.c | 36 +++++++++++++++++++++++++++++++++--- 1 file changed, 33 insertions(+), 3 deletions(-) diff --git a/newlib/libc/ctype/towctrans_l.c b/newlib/libc/ctype/towctrans_l.c index ca7e89f..9759cf7 100644 --- a/newlib/libc/ctype/towctrans_l.c +++ b/newlib/libc/ctype/towctrans_l.c @@ -4,8 +4,36 @@ //#include #include "local.h" -enum {EVENCAP, ODDCAP}; +/* + struct caseconv_entry describes the case conversion behaviour + of a range of Unicode characters. + It was designed to be compact for a minimal table size. + The range is first...first + diff. + Conversion behaviour for a character c in the respective range: + mode == TOLO towlower (c) = c + delta + mode == TOUP towupper (c) = c + delta + mode == TOBOTH (titling case characters) + towlower (c) = c + 1 + towupper (c) = c - 1 + mode == TO1 capital/small letters are alternating + delta == EVENCAP even codes are capital + delta == ODDCAP odd codes are capital + (this correlates with an even/odd first range value + as of Unicode 10.0 but we do not rely on this) + As of Unicode 10.0, the following field lengths are sufficient + first: 17 bits + diff: 8 bits + delta: 17 bits + mode: 2 bits + The reserve of 4 bits (to limit the struct to 6 bytes) + is currently added to the 'first' field; + should a future Unicode version make it necessary to expand the others, + the 'first' field could be reduced as needed, or larger ranges could + be split up (reduce limit max=255 e.g. to max=127 or max=63 in + script mkcaseconv, check increasing table size). + */ enum {TO1, TOLO, TOUP, TOBOTH}; +enum {EVENCAP, ODDCAP}; static struct caseconv_entry { unsigned int first: 21; unsigned short diff: 8; @@ -71,6 +99,7 @@ toulower (wint_t c) default: break; } + return c; } @@ -102,9 +131,10 @@ touupper (wint_t c) default: break; } - default: - break; + default: + break; } + return c; }