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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 v7 3/7] utf8: add function to detect prohibited UTF-16/32 BOM
Date: Thu, 15 Feb 2018 16:27:07 +0100	[thread overview]
Message-ID: <20180215152711.158-4-lars.schneider@autodesk.com> (raw)
In-Reply-To: <20180215152711.158-1-lars.schneider@autodesk.com>

From: Lars Schneider <larsxschneider@gmail.com>

Whenever a data stream is declared to be UTF-16BE, UTF-16LE, UTF-32BE
or UTF-32LE a BOM must not be used [1]. The function returns true if
this is the case.

This function is used in a subsequent commit.

[1] http://unicode.org/faq/utf_bom.html#bom10

Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
---
 utf8.c | 24 ++++++++++++++++++++++++
 utf8.h |  9 +++++++++
 2 files changed, 33 insertions(+)

diff --git a/utf8.c b/utf8.c
index 2c27ce0137..914881cd1f 100644
--- a/utf8.c
+++ b/utf8.c
@@ -538,6 +538,30 @@ char *reencode_string_len(const char *in, int insz,
 }
 #endif
 
+static int has_bom_prefix(const char *data, size_t len,
+			  const char *bom, size_t bom_len)
+{
+	return (len >= bom_len) && !memcmp(data, bom, bom_len);
+}
+
+static const char utf16_be_bom[] = {0xFE, 0xFF};
+static const char utf16_le_bom[] = {0xFF, 0xFE};
+static const char utf32_be_bom[] = {0x00, 0x00, 0xFE, 0xFF};
+static const char utf32_le_bom[] = {0xFF, 0xFE, 0x00, 0x00};
+
+int has_prohibited_utf_bom(const char *enc, const char *data, size_t len)
+{
+	return (
+	  (!strcmp(enc, "UTF-16BE") || !strcmp(enc, "UTF-16LE")) &&
+	  (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-32BE") || !strcmp(enc, "UTF-32LE")) &&
+	  (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 6bbcf31a83..4711429af9 100644
--- a/utf8.h
+++ b/utf8.h
@@ -70,4 +70,13 @@ typedef enum {
 void strbuf_utf8_align(struct strbuf *buf, align_type position, unsigned int width,
 		       const char *s);
 
+/*
+ * Whenever a data stream is declared to be UTF-16BE, UTF-16LE, UTF-32BE
+ * or UTF-32LE a BOM must not be used [1]. The function returns true if
+ * this is the case.
+ *
+ * [1] http://unicode.org/faq/utf_bom.html#bom10
+ */
+int has_prohibited_utf_bom(const char *enc, const char *data, size_t len);
+
 #endif
-- 
2.16.1


  parent reply	other threads:[~2018-02-15 18:16 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-15 15:27 [PATCH v7 0/7] convert: add support for different encodings lars.schneider
2018-02-15 15:27 ` [PATCH v7 1/7] strbuf: remove unnecessary NUL assignment in xstrdup_tolower() lars.schneider
2018-02-16 12:55   ` Ævar Arnfjörð Bjarmason
2018-02-16 18:45     ` Jeff King
2018-02-16 19:30       ` Junio C Hamano
2018-02-15 15:27 ` [PATCH v7 2/7] strbuf: add xstrdup_toupper() lars.schneider
2018-02-15 15:27 ` lars.schneider [this message]
2018-02-15 15:27 ` [PATCH v7 4/7] utf8: add function to detect a missing UTF-16/32 BOM lars.schneider
2018-02-15 15:27 ` [PATCH v7 5/7] convert: add 'working-tree-encoding' attribute lars.schneider
2018-02-15 15:27 ` [PATCH v7 6/7] convert: add tracing for " lars.schneider
2018-02-15 15:27 ` [PATCH v7 7/7] convert: add round trip check based on 'core.checkRoundtripEncoding' lars.schneider
2018-02-15 20:03 ` [PATCH v7 0/7] convert: add support for different encodings Junio C Hamano
2018-02-15 22:09   ` Jeff King
2018-02-16 18:55     ` Junio C Hamano
2018-02-16 19:25       ` Jeff King
2018-02-16 19:27         ` Jeff King
2018-02-16 19:41           ` Junio C Hamano
2018-02-21 18:06       ` Lars Schneider
2018-02-16 14:42   ` Lars Schneider
2018-02-16 16:58     ` Torsten Bögershausen
2018-02-22 20:00       ` Lars Schneider
2018-02-22 20:12         ` Jeff King
2018-02-23 16:35         ` Junio C Hamano
2018-02-23 20:11           ` Junio C Hamano
2018-02-24 15:18             ` Lars Schneider
2018-02-26  1:44               ` Jeff King
2018-02-26 17:35                 ` Torsten Bögershausen
2018-02-26 20:46                   ` Jeff King
2018-02-27 21:05                     ` Torsten Bögershausen
2018-02-27 21:25                       ` Jeff King
2018-02-27 21:55                         ` Junio C Hamano
2018-02-27 21:58                           ` Jeff King
2018-02-27 22:10                             ` Junio C Hamano
2018-02-27 22:20                               ` Jeff King
2018-02-28  8:20                         ` Torsten Bögershausen
2018-02-28 13:21                           ` Jeff King
2018-02-28 17:42                             ` Junio C Hamano
2018-03-01  7:49                               ` Jeff King
2018-03-04 10:16                             ` Torsten Bögershausen
2018-02-28 20:46                         ` Lars Schneider
2018-02-16 19:04     ` Junio C Hamano

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