From: Bagas Sanjaya Date: Fri, 25 Mar 2022 08:59:09 GMT Subject: Re: [PATCH v4 26/27] t/lib-unicode-nfc-nfd: helper prereqs for testing unicode nfc/nfd Message-ID: <9c584888-2dd2-139a-cf41-b2974386d1f8@gmail.com> In-Reply-To: On 24/03/22 23.51, Jeff Hostetler via GitGitGadget wrote: > From: Jeff Hostetler > > Create a set of prereqs to help understand how file names > are handled by the filesystem when they contain NFC and NFD > Unicode characters. > > Signed-off-by: Jeff Hostetler > --- > t/lib-unicode-nfc-nfd.sh | 167 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 167 insertions(+) > create mode 100755 t/lib-unicode-nfc-nfd.sh > > diff --git a/t/lib-unicode-nfc-nfd.sh b/t/lib-unicode-nfc-nfd.sh > new file mode 100755 > index 00000000000..cf9c26d1e22 > --- /dev/null > +++ b/t/lib-unicode-nfc-nfd.sh > @@ -0,0 +1,167 @@ > +# Help detect how Unicode NFC and NFD are handled on the filesystem. > + > +# A simple character that has a NFD form. > +# > +# NFC: U+00e9 LATIN SMALL LETTER E WITH ACUTE > +# UTF8(NFC): \xc3 \xa9 > +# > +# NFD: U+0065 LATIN SMALL LETTER E > +# U+0301 COMBINING ACUTE ACCENT > +# UTF8(NFD): \x65 + \xcc \x81 > +# > +utf8_nfc=$(printf "\xc3\xa9") > +utf8_nfd=$(printf "\x65\xcc\x81") > + The first nfc-nfd test subject (É) is simple case, right? > +# Is the OS or the filesystem "Unicode composition sensitive"? > +# > +# That is, does the OS or the filesystem allow files to exist with > +# both the NFC and NFD spellings? Or, does the OS/FS lie to us and > +# tell us that the NFC and NFD forms are equivalent. > +# > +# This is or may be independent of what type of filesystem we have, > +# since it might be handled by the OS at a layer above the FS. > +# Testing shows on MacOS using APFS, HFS+, and FAT32 reports a > +# collision, for example. > +# > +# This does not tell us how the Unicode pathname will be spelled > +# on disk, but rather only that the two spelling "collide". We > +# will examine the actual on disk spelling in a later prereq. > +# > +test_lazy_prereq UNICODE_COMPOSITION_SENSITIVE ' > + mkdir trial_${utf8_nfc} && > + mkdir trial_${utf8_nfd} > +' > + > +# Is the spelling of an NFC pathname preserved on disk? > +# > +# On MacOS with HFS+ and FAT32, NFC paths are converted into NFD > +# and on APFS, NFC paths are preserved. As we have established > +# above, this is independent of "composition sensitivity". > +# > +# 0000000 63 5f c3 a9 > +# > +# (/usr/bin/od output contains different amount of whitespace > +# on different platforms, so we need the wildcards here.) > +# > +test_lazy_prereq UNICODE_NFC_PRESERVED ' > + mkdir c_${utf8_nfc} && > + ls | od -t x1 | grep "63 *5f *c3 *a9" > +' > + > +# Is the spelling of an NFD pathname preserved on disk? > +# > +# 0000000 64 5f 65 cc 81 > +# > +test_lazy_prereq UNICODE_NFD_PRESERVED ' > + mkdir d_${utf8_nfd} && > + ls | od -t x1 | grep "64 *5f *65 *cc *81" > +' > + mkdir c_${utf8_nfc} && > + mkdir d_${utf8_nfd} && > + > +# The following _DOUBLE_ forms are more for my curiosity, > +# but there may be quirks lurking when there are multiple > +# combining characters in non-canonical order. > + > +# Unicode also allows multiple combining characters > +# that can be decomposed in pieces. > +# > +# NFC: U+1f67 GREEK SMALL LETTER OMEGA WITH DASIA AND PERISPOMENI > +# UTF8(NFC): \xe1 \xbd \xa7 > +# > +# NFD1: U+1f61 GREEK SMALL LETTER OMEGA WITH DASIA > +# U+0342 COMBINING GREEK PERISPOMENI > +# UTF8(NFD1): \xe1 \xbd \xa1 + \xcd \x82 > +# > +# But U+1f61 decomposes into > +# NFD2: U+03c9 GREEK SMALL LETTER OMEGA > +# U+0314 COMBINING REVERSED COMMA ABOVE > +# UTF8(NFD2): \xcf \x89 + \xcc \x94 > +# > +# Yielding: \xcf \x89 + \xcc \x94 + \xcd \x82 > +# > +# Note that I've used the canonical ordering of the > +# combinining characters. It is also possible to > +# swap them. My testing shows that that non-standard > +# ordering also causes a collision in mkdir. However, > +# the resulting names don't draw correctly on the > +# terminal (implying that the on-disk format also has > +# them out of order). > +# > +greek_nfc=$(printf "\xe1\xbd\xa7") > +greek_nfd1=$(printf "\xe1\xbd\xa1\xcd\x82") > +greek_nfd2=$(printf "\xcf\x89\xcc\x94\xcd\x82") > + The second test subject (greek) is more complex, right? > +# See if a double decomposition also collides. > +# > +test_lazy_prereq UNICODE_DOUBLE_COMPOSITION_SENSITIVE ' > + mkdir trial_${greek_nfc} && > + mkdir trial_${greek_nfd2} > +' > + > +# See if the NFC spelling appears on the disk. > +# > +test_lazy_prereq UNICODE_DOUBLE_NFC_PRESERVED ' > + mkdir c_${greek_nfc} && > + ls | od -t x1 | grep "63 *5f *e1 *bd *a7" > +' > + > +# See if the NFD spelling appears on the disk. > +# > +test_lazy_prereq UNICODE_DOUBLE_NFD_PRESERVED ' > + mkdir d_${greek_nfd2} && > + ls | od -t x1 | grep "64 *5f *cf *89 *cc *94 *cd *82" > +' > + > +# The following is for debugging. I found it useful when > +# trying to understand the various (OS, FS) quirks WRT > +# Unicode and how composition/decomposition is handled. > +# For example, when trying to understand how (macOS, APFS) > +# and (macOS, HFS) and (macOS, FAT32) compare. > +# > +# It is rather noisy, so it is disabled by default. > +# > +if test "$unicode_debug" = "true" > +then > + if test_have_prereq UNICODE_COMPOSITION_SENSITIVE > + then > + echo NFC and NFD are distinct on this OS/filesystem. > + else > + echo NFC and NFD are aliases on this OS/filesystem. > + fi > + > + if test_have_prereq UNICODE_NFC_PRESERVED > + then > + echo NFC maintains original spelling. > + else > + echo NFC is modified. > + fi > + > + if test_have_prereq UNICODE_NFD_PRESERVED > + then > + echo NFD maintains original spelling. > + else > + echo NFD is modified. > + fi > + > + if test_have_prereq UNICODE_DOUBLE_COMPOSITION_SENSITIVE > + then > + echo DOUBLE NFC and NFD are distinct on this OS/filesystem. > + else > + echo DOUBLE NFC and NFD are aliases on this OS/filesystem. > + fi > + > + if test_have_prereq UNICODE_DOUBLE_NFC_PRESERVED > + then > + echo Double NFC maintains original spelling. > + else > + echo Double NFC is modified. > + fi > + > + if test_have_prereq UNICODE_DOUBLE_NFD_PRESERVED > + then > + echo Double NFD maintains original spelling. > + else > + echo Double NFD is modified. > + fi > +fi In general, this test is written from Mac OS perspective, but since we have Git users also from Linux, Windows, and other OSes, I'd like to see from these other perspective. -- An old man doll... just what I always wanted! - Clara