> -----Original Message----- > From: git-owner@xxxxxxxxxxxxxxx <git-owner@xxxxxxxxxxxxxxx> On Behalf Of > tboegi@xxxxxx > Sent: Wednesday, January 30, 2019 10:02 AM > To: git@xxxxxxxxxxxxxxx; adrigibal@xxxxxxxxx > Cc: Torsten Bögershausen <tboegi@xxxxxx> > Subject: [PATCH v3 1/1] Support working-tree-encoding "UTF-16LE-BOM" > > From: Torsten Bögershausen <tboegi@xxxxxx> > > Users who want UTF-16 files in the working tree set the .gitattributes > like this: > test.txt working-tree-encoding=UTF-16 > > The unicode standard itself defines 3 allowed ways how to encode UTF-16. > The following 3 versions convert all back to 'g' 'i' 't' in UTF-8: > > a) UTF-16, without BOM, big endian: > $ printf "\000g\000i\000t" | iconv -f UTF-16 -t UTF-8 | od -c > 0000000 g i t > > b) UTF-16, with BOM, little endian: > $ printf "\377\376g\000i\000t\000" | iconv -f UTF-16 -t UTF-8 | od -c > 0000000 g i t > > c) UTF-16, with BOM, big endian: > $ printf "\376\377\000g\000i\000t" | iconv -f UTF-16 -t UTF-8 | od -c > 0000000 g i t > > Git uses libiconv to convert from UTF-8 in the index into ITF-16 in the > working tree. > After a checkout, the resulting file has a BOM and is encoded in "UTF-16", > in the version (c) above. > This is what iconv generates, more details follow below. > > iconv (and libiconv) can generate UTF-16, UTF-16LE or UTF-16BE: > > d) UTF-16 > $ printf 'git' | iconv -f UTF-8 -t UTF-16 | od -c > 0000000 376 377 \0 g \0 i \0 t > > e) UTF-16LE > $ printf 'git' | iconv -f UTF-8 -t UTF-16LE | od -c > 0000000 g \0 i \0 t \0 > > f) UTF-16BE > $ printf 'git' | iconv -f UTF-8 -t UTF-16BE | od -c > 0000000 \0 g \0 i \0 t > > There is no way to generate version (b) from above in a Git working tree, > but that is what some applications need. > (All fully unicode aware applications should be able to read all 3 > variants, > but in practise we are not there yet). > > When producing UTF-16 as an output, iconv generates the big endian version > with a BOM. (big endian is probably chosen for historical reasons). > > iconv can produce UTF-16 files with little endianess by using "UTF-16LE" > as encoding, and that file does not have a BOM. > > Not all users (especially under Windows) are happy with this. > Some tools are not fully unicode aware and can only handle version (b). > > Today there is no way to produce version (b) with iconv (or libiconv). > Looking into the history of iconv, it seems as if version (c) will > be used in all future iconv versions (for compatibility reasons). Reading the RFC 2781 section 3.3: Text in the "UTF-16BE" charset MUST be serialized with the octets which make up a single 16-bit UTF-16 value in big-endian order. Systems labelling UTF-16BE text MUST NOT prepend a BOM to the text. Text in the "UTF-16LE" charset MUST be serialized with the octets which make up a single 16-bit UTF-16 value in little-endian order. Systems labelling UTF-16LE text MUST NOT prepend a BOM to the text. I opened a bug with libiconv... https://savannah.gnu.org/bugs/index.php?55609 > > Solve this dilemma and introduce a Git-specific "UTF-16LE-BOM". > libiconv can not handle the encoding, so Git pick it up, handles the BOM > and uses libiconv to convert the rest of the stream. > (UTF-16BE-BOM is added for consistency) > > Rported-by: Adrián Gimeno Balaguer <adrigibal@xxxxxxxxx> > Signed-off-by: Torsten Bögershausen <tboegi@xxxxxx> > --- > > Changes since v2: > Update the commit message (s/possible/allowed/) > Update the documentation, as suggested by Junio: > ...wonder if the following, > instead of the above hunk, would work better.. > Yes, it does. > > Documentation/gitattributes.txt | 4 ++- > compat/precompose_utf8.c | 2 +- > t/t0028-working-tree-encoding.sh | 12 ++++++++- > utf8.c | 42 ++++++++++++++++++++++++-------- > utf8.h | 2 +- > 5 files changed, 48 insertions(+), 14 deletions(-) > > diff --git a/Documentation/gitattributes.txt > b/Documentation/gitattributes.txt > index b8392fc330..a2310fb920 100644 > --- a/Documentation/gitattributes.txt > +++ b/Documentation/gitattributes.txt > @@ -344,7 +344,9 @@ automatic line ending conversion based on your > platform. > > Use the following attributes if your '*.ps1' files are UTF-16 little > endian encoded without BOM and you want Git to use Windows line endings > -in the working directory. Please note, it is highly recommended to > +in the working directory (use `UTF-16-LE-BOM` instead of `UTF-16LE` if > +you want UTF-16 little endian with BOM). > +Please note, it is highly recommended to > explicitly define the line endings with `eol` if the `working-tree- > encoding` > attribute is used to avoid ambiguity. > > diff --git a/compat/precompose_utf8.c b/compat/precompose_utf8.c > index de61c15d34..136250fbf6 100644 > --- a/compat/precompose_utf8.c > +++ b/compat/precompose_utf8.c > @@ -79,7 +79,7 @@ void precompose_argv(int argc, const char **argv) > size_t namelen; > oldarg = argv[i]; > if (has_non_ascii(oldarg, (size_t)-1, &namelen)) { > - newarg = reencode_string_iconv(oldarg, namelen, > ic_precompose, NULL); > + newarg = reencode_string_iconv(oldarg, namelen, > ic_precompose, 0, NULL); > if (newarg) > argv[i] = newarg; > } > diff --git a/t/t0028-working-tree-encoding.sh b/t/t0028-working-tree- > encoding.sh > index 7e87b5a200..e58ecbfc44 100755 > --- a/t/t0028-working-tree-encoding.sh > +++ b/t/t0028-working-tree-encoding.sh > @@ -11,9 +11,12 @@ test_expect_success 'setup test files' ' > > text="hallo there!\ncan you read me?" && > echo "*.utf16 text working-tree-encoding=utf-16" >.gitattributes && > + echo "*.utf16lebom text working-tree-encoding=UTF-16LE-BOM" > >>.gitattributes && > printf "$text" >test.utf8.raw && > printf "$text" | iconv -f UTF-8 -t UTF-16 >test.utf16.raw && > printf "$text" | iconv -f UTF-8 -t UTF-32 >test.utf32.raw && > + printf "\377\376" >test.utf16lebom.raw && > + printf "$text" | iconv -f UTF-8 -t UTF-32LE >>test.utf16lebom.raw && > > # Line ending tests > printf "one\ntwo\nthree\n" >lf.utf8.raw && > @@ -32,7 +35,8 @@ test_expect_success 'setup test files' ' > # Add only UTF-16 file, we will add the UTF-32 file later > cp test.utf16.raw test.utf16 && > cp test.utf32.raw test.utf32 && > - git add .gitattributes test.utf16 && > + cp test.utf16lebom.raw test.utf16lebom && > + git add .gitattributes test.utf16 test.utf16lebom && > git commit -m initial > ' > > @@ -51,6 +55,12 @@ test_expect_success 're-encode to UTF-16 on checkout' ' > test_cmp_bin test.utf16.raw test.utf16 > ' > > +test_expect_success 're-encode to UTF-16-LE-BOM on checkout' ' > + rm test.utf16lebom && > + git checkout test.utf16lebom && > + test_cmp_bin test.utf16lebom.raw test.utf16lebom > +' > + > test_expect_success 'check $GIT_DIR/info/attributes support' ' > test_when_finished "rm -f test.utf32.git" && > test_when_finished "git reset --hard HEAD" && > diff --git a/utf8.c b/utf8.c > index eb78587504..83824dc2f4 100644 > --- a/utf8.c > +++ b/utf8.c > @@ -4,6 +4,11 @@ > > /* This code is originally from http://www.cl.cam.ac.uk/~mgk25/ucs/ */ > > +static const char utf16_be_bom[] = {'\xFE', '\xFF'}; > +static const char utf16_le_bom[] = {'\xFF', '\xFE'}; > +static const char utf32_be_bom[] = {'\0', '\0', '\xFE', '\xFF'}; > +static const char utf32_le_bom[] = {'\xFF', '\xFE', '\0', '\0'}; > + > struct interval { > ucs_char_t first; > ucs_char_t last; > @@ -470,16 +475,17 @@ int utf8_fprintf(FILE *stream, const char *format, > ...) > #else > typedef char * iconv_ibp; > #endif > -char *reencode_string_iconv(const char *in, size_t insz, iconv_t conv, > size_t *outsz_p) > +char *reencode_string_iconv(const char *in, size_t insz, iconv_t conv, > + size_t bom_len, size_t *outsz_p) > { > size_t outsz, outalloc; > char *out, *outpos; > iconv_ibp cp; > > outsz = insz; > - outalloc = st_add(outsz, 1); /* for terminating NUL */ > + outalloc = st_add(outsz, 1 + bom_len); /* for terminating NUL */ > out = xmalloc(outalloc); > - outpos = out; > + outpos = out + bom_len; > cp = (iconv_ibp)in; > > while (1) { > @@ -540,10 +546,30 @@ char *reencode_string_len(const char *in, size_t > insz, > { > iconv_t conv; > char *out; > + const char *bom_str = NULL; > + size_t bom_len = 0; > > if (!in_encoding) > return NULL; > > + /* UTF-16LE-BOM is the same as UTF-16 for reading */ > + if (same_utf_encoding("UTF-16LE-BOM", in_encoding)) > + in_encoding = "UTF-16"; > + > + /* > + * For writing, UTF-16 iconv typically creates "UTF-16BE-BOM" > + * Some users under Windows want the little endian version > + */ > + if (same_utf_encoding("UTF-16LE-BOM", out_encoding)) { > + bom_str = utf16_le_bom; > + bom_len = sizeof(utf16_le_bom); > + out_encoding = "UTF-16LE"; > + } else if (same_utf_encoding("UTF-16BE-BOM", out_encoding)) { > + bom_str = utf16_be_bom; > + bom_len = sizeof(utf16_be_bom); > + out_encoding = "UTF-16BE"; > + } > + > conv = iconv_open(out_encoding, in_encoding); > if (conv == (iconv_t) -1) { > in_encoding = fallback_encoding(in_encoding); > @@ -553,9 +579,10 @@ char *reencode_string_len(const char *in, size_t > insz, > if (conv == (iconv_t) -1) > return NULL; > } > - > - out = reencode_string_iconv(in, insz, conv, outsz); > + out = reencode_string_iconv(in, insz, conv, bom_len, outsz); > iconv_close(conv); > + if (out && bom_str && bom_len) > + memcpy(out, bom_str, bom_len); > return out; > } > #endif > @@ -566,11 +593,6 @@ static int has_bom_prefix(const char *data, size_t > len, > return data && bom && (len >= bom_len) && !memcmp(data, bom, > bom_len); > } > > -static const char utf16_be_bom[] = {'\xFE', '\xFF'}; > -static const char utf16_le_bom[] = {'\xFF', '\xFE'}; > -static const char utf32_be_bom[] = {'\0', '\0', '\xFE', '\xFF'}; > -static const char utf32_le_bom[] = {'\xFF', '\xFE', '\0', '\0'}; > - > int has_prohibited_utf_bom(const char *enc, const char *data, size_t len) > { > return ( > diff --git a/utf8.h b/utf8.h > index edea55e093..84efbfcb1f 100644 > --- a/utf8.h > +++ b/utf8.h > @@ -27,7 +27,7 @@ void strbuf_utf8_replace(struct strbuf *sb, int pos, int > width, > > #ifndef NO_ICONV > char *reencode_string_iconv(const char *in, size_t insz, > - iconv_t conv, size_t *outsz); > + iconv_t conv, size_t bom_len, size_t *outsz); > char *reencode_string_len(const char *in, size_t insz, > const char *out_encoding, > const char *in_encoding, > -- > 2.20.1.2.gb21ebb671 >
