From: lars.schneider@autodesk.com
To: git@vger.kernel.org
Cc: gitster@pobox.com, tboegi@web.de, j6t@kdbg.org,
sunshine@sunshineco.com, peff@peff.net,
ramsay@ramsayjones.plus.com, Johannes.Schindelin@gmx.de,
Lars Schneider <larsxschneider@gmail.com>
Subject: [PATCH v8 4/7] utf8: add function to detect a missing UTF-16/32 BOM
Date: Sat, 24 Feb 2018 17:27:58 +0100 [thread overview]
Message-ID: <20180224162801.98860-5-lars.schneider@autodesk.com> (raw)
In-Reply-To: <20180224162801.98860-1-lars.schneider@autodesk.com>
From: Lars Schneider <larsxschneider@gmail.com>
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>
---
utf8.c | 13 +++++++++++++
utf8.h | 16 ++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/utf8.c b/utf8.c
index 914881cd1f..5113d26e56 100644
--- a/utf8.c
+++ b/utf8.c
@@ -562,6 +562,19 @@ 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 (
+ !strcmp(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)))
+ ) || (
+ !strcmp(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`.
diff --git a/utf8.h b/utf8.h
index 4711429af9..62f86fba64 100644
--- a/utf8.h
+++ b/utf8.h
@@ -79,4 +79,20 @@ 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].
+ *
+ * [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
--
2.16.1
next prev parent reply other threads:[~2018-02-24 16:30 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-24 16:27 [PATCH v8 0/7] convert: add support for different encodings lars.schneider
2018-02-24 16:27 ` [PATCH v8 1/7] strbuf: remove unnecessary NUL assignment in xstrdup_tolower() lars.schneider
2018-02-24 16:27 ` [PATCH v8 2/7] strbuf: add xstrdup_toupper() lars.schneider
2018-02-24 16:27 ` [PATCH v8 3/7] utf8: add function to detect prohibited UTF-16/32 BOM lars.schneider
2018-02-25 3:41 ` Eric Sunshine
2018-02-25 11:35 ` Lars Schneider
2018-02-27 5:17 ` Eric Sunshine
2018-02-28 21:34 ` Lars Schneider
2018-02-24 16:27 ` lars.schneider [this message]
2018-02-25 3:52 ` [PATCH v8 4/7] utf8: add function to detect a missing " Eric Sunshine
2018-02-25 11:41 ` Lars Schneider
2018-02-24 16:27 ` [PATCH v8 5/7] convert: add 'working-tree-encoding' attribute lars.schneider
2018-02-25 7:15 ` Eric Sunshine
2018-02-27 11:16 ` Lars Schneider
2018-02-28 21:20 ` Eric Sunshine
2018-02-24 16:28 ` [PATCH v8 6/7] convert: add tracing for " lars.schneider
2018-02-24 16:28 ` [PATCH v8 7/7] convert: add round trip check based on 'core.checkRoundtripEncoding' lars.schneider
2018-02-25 19:50 ` Eric Sunshine
2018-03-04 19:08 ` Lars Schneider
2018-03-04 19:58 ` Eric Sunshine
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