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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 v3 3/7] utf8: add function to detect prohibited UTF-16/32 BOM
Date: Sat,  6 Jan 2018 01:48:04 +0100	[thread overview]
Message-ID: <20180106004808.77513-4-lars.schneider@autodesk.com> (raw)
In-Reply-To: <20180106004808.77513-1-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
-- 
2.15.1


  parent reply	other threads:[~2018-01-06  0:48 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-06  0:48 [PATCH v3 0/7] convert: add support for different encodings lars.schneider
2018-01-06  0:48 ` [PATCH v3 1/7] strbuf: remove unnecessary NUL assignment in xstrdup_tolower() lars.schneider
2018-01-06  0:48 ` [PATCH v3 2/7] strbuf: add xstrdup_toupper() lars.schneider
2018-01-06  0:48 ` lars.schneider [this message]
2018-01-06  0:48 ` [PATCH v3 4/7] utf8: add function to detect a missing UTF-16/32 BOM lars.schneider
2018-01-06  0:48 ` [PATCH v3 5/7] convert_to_git(): safe_crlf/checksafe becomes int conv_flags lars.schneider
2018-01-08 21:28   ` Junio C Hamano
2018-01-08 22:47     ` Lars Schneider
2018-01-08 23:17       ` Junio C Hamano
2018-01-09  6:20       ` Torsten Bögershausen
2018-01-06  0:48 ` [PATCH v3 6/7] convert: add support for 'checkout-encoding' attribute lars.schneider
2018-01-06  0:48 ` [PATCH v3 7/7] convert: add tracing for checkout-encoding lars.schneider
2018-01-07  9:38 ` [PATCH v3 0/7] convert: add support for different encodings Torsten Bögershausen
2018-01-08 14:38   ` Lars Schneider
2018-01-08 18:08     ` Torsten Bögershausen

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