From: Lars Schneider <larsxschnei...@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 <larsxschnei...@gmail.com> --- utf8.c | 26 ++++++++++++++++++++++++++ utf8.h | 9 +++++++++ 2 files changed, 35 insertions(+) diff --git a/utf8.c b/utf8.c index 2c27ce0137..e4b99580f0 100644 --- a/utf8.c +++ b/utf8.c @@ -538,6 +538,32 @@ 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 ( + (!strcasecmp(enc, "UTF-16BE") || !strcasecmp(enc, "UTF-16LE") || + !strcasecmp(enc, "UTF16BE") || !strcasecmp(enc, "UTF16LE")) && + (has_bom_prefix(data, len, utf16_be_bom, sizeof(utf16_be_bom)) || + has_bom_prefix(data, len, utf16_le_bom, sizeof(utf16_le_bom))) + ) || ( + (!strcasecmp(enc, "UTF-32BE") || !strcasecmp(enc, "UTF-32LE") || + !strcasecmp(enc, "UTF32BE") || !strcasecmp(enc, "UTF32LE")) && + (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..0db1db4519 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); +/* + * If a data stream is declared as UTF-16BE or UTF-16LE, then a UTF-16 + * BOM must not be used [1]. The same applies for the UTF-32 equivalents. + * The function returns true if this rule is violated. + * + * [1] http://unicode.org/faq/utf_bom.html#bom10 + */ +int has_prohibited_utf_bom(const char *enc, const char *data, size_t len); + #endif -- 2.16.2
