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,
pclouds@gmail.com, avarab@gmail.com,
Lars Schneider <larsxschneider@gmail.com>
Subject: [PATCH v13 06/10] utf8: add function to detect a missing UTF-16/32 BOM
Date: Sun, 15 Apr 2018 20:16:06 +0200 [thread overview]
Message-ID: <20180415181610.1612-7-lars.schneider@autodesk.com> (raw)
In-Reply-To: <20180415181610.1612-1-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 | 19 +++++++++++++++++++
2 files changed, 32 insertions(+)
diff --git a/utf8.c b/utf8.c
index 83af3a9f6b..25d366d6b3 100644
--- a/utf8.c
+++ b/utf8.c
@@ -586,6 +586,19 @@ 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`.
diff --git a/utf8.h b/utf8.h
index 0db1db4519..cce654a64a 100644
--- a/utf8.h
+++ b/utf8.h
@@ -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
--
2.16.2
next prev parent reply other threads:[~2018-04-15 18:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-15 18:16 [PATCH v13 00/10] convert: add support for different encodings lars.schneider
2018-04-15 18:16 ` [PATCH v13 01/10] strbuf: remove unnecessary NUL assignment in xstrdup_tolower() lars.schneider
2018-04-15 18:16 ` [PATCH v13 02/10] strbuf: add xstrdup_toupper() lars.schneider
2018-04-15 18:16 ` [PATCH v13 03/10] strbuf: add a case insensitive starts_with() lars.schneider
2018-04-15 18:16 ` [PATCH v13 04/10] utf8: teach same_encoding() alternative UTF encoding names lars.schneider
2018-04-15 18:16 ` [PATCH v13 05/10] utf8: add function to detect prohibited UTF-16/32 BOM lars.schneider
2018-04-15 18:16 ` lars.schneider [this message]
2018-04-15 18:16 ` [PATCH v13 07/10] convert: add 'working-tree-encoding' attribute lars.schneider
2018-04-15 18:16 ` [PATCH v13 08/10] convert: check for detectable errors in UTF encodings lars.schneider
2018-04-15 18:16 ` [PATCH v13 09/10] convert: add tracing for 'working-tree-encoding' attribute lars.schneider
2018-04-15 18:16 ` [PATCH v13 10/10] convert: add round trip check based on 'core.checkRoundtripEncoding' lars.schneider
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