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author | Lars Schneider <larsxschneider@gmail.com> | 2018-03-15 23:57:42 +0100 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2018-03-16 10:41:31 -0700 |
commit | f45c985d22623cda1fedcc39efffd317586ef7d9 (patch) | |
tree | 219881d9e2ab0809c34469baf394a992fc91ca45 | |
parent | 7599ca50526a2f76f80f2b80d27cbf0e30009a0c (diff) | |
download | git-f45c985d22623cda1fedcc39efffd317586ef7d9.tar.gz |
utf8: add function to detect a missing UTF-16/32 BOM
If the endianness is not defined in the encoding name, then let's
be strict and require a BOM to avoid any encoding confusion. The
is_missing_required_utf_bom() function returns true if a required BOM
is missing.
The Unicode standard instructs to assume big-endian if there in no BOM
for UTF-16/32 [1][2]. However, the W3C/WHATWG encoding standard used
in HTML5 recommends to assume little-endian to "deal with deployed
content" [3]. Strictly requiring a BOM seems to be the safest option
for content in Git.
This function is used in a subsequent commit.
[1] http://unicode.org/faq/utf_bom.html#gen6
[2] http://www.unicode.org/versions/Unicode10.0.0/ch03.pdf
Section 3.10, D98, page 132
[3] https://encoding.spec.whatwg.org/#utf-16le
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r-- | utf8.c | 13 | ||||
-rw-r--r-- | utf8.h | 19 |
2 files changed, 32 insertions, 0 deletions
@@ -582,6 +582,19 @@ int has_prohibited_utf_bom(const char *enc, const char *data, size_t len) ); } +int is_missing_required_utf_bom(const char *enc, const char *data, size_t len) +{ + return ( + (same_utf_encoding(enc, "UTF-16")) && + !(has_bom_prefix(data, len, utf16_be_bom, sizeof(utf16_be_bom)) || + has_bom_prefix(data, len, utf16_le_bom, sizeof(utf16_le_bom))) + ) || ( + (same_utf_encoding(enc, "UTF-32")) && + !(has_bom_prefix(data, len, utf32_be_bom, sizeof(utf32_be_bom)) || + has_bom_prefix(data, len, utf32_le_bom, sizeof(utf32_le_bom))) + ); +} + /* * Returns first character length in bytes for multi-byte `text` according to * `encoding`. @@ -79,4 +79,23 @@ void strbuf_utf8_align(struct strbuf *buf, align_type position, unsigned int wid */ int has_prohibited_utf_bom(const char *enc, const char *data, size_t len); +/* + * If the endianness is not defined in the encoding name, then we + * require a BOM. The function returns true if a required BOM is missing. + * + * The Unicode standard instructs to assume big-endian if there in no + * BOM for UTF-16/32 [1][2]. However, the W3C/WHATWG encoding standard + * used in HTML5 recommends to assume little-endian to "deal with + * deployed content" [3]. + * + * Therefore, strictly requiring a BOM seems to be the safest option for + * content in Git. + * + * [1] http://unicode.org/faq/utf_bom.html#gen6 + * [2] http://www.unicode.org/versions/Unicode10.0.0/ch03.pdf + * Section 3.10, D98, page 132 + * [3] https://encoding.spec.whatwg.org/#utf-16le + */ +int is_missing_required_utf_bom(const char *enc, const char *data, size_t len); + #endif |