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Diffstat (limited to 'src/util/parse_utf8_char.h')
| -rw-r--r-- | src/util/parse_utf8_char.h | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/src/util/parse_utf8_char.h b/src/util/parse_utf8_char.h new file mode 100644 index 0000000..b00a1c2 --- /dev/null +++ b/src/util/parse_utf8_char.h @@ -0,0 +1,122 @@ +/*++ +/* NAME +/* parse_utf8_char 3h +/* SUMMARY +/* parse one UTF-8 multibyte character +/* SYNOPSIS +/* #include <parse_utf8_char.h> +/* +/* char *parse_utf8_char(str, end) +/* const char *str; +/* const char *end; +/* DESCRIPTION +/* parse_utf8_char() determines if the byte sequence starting +/* at \fBstr\fR begins with a complete UTF-8 character as +/* defined in RFC 3629. That is, a proper encoding of code +/* points U+0000..U+10FFFF, excluding over-long encodings and +/* excluding U+D800..U+DFFF surrogates. +/* +/* When the byte sequence starting at \fBstr\fR begins with a +/* complete UTF-8 character, this function returns a pointer +/* to the last byte in that character. Otherwise, it returns +/* a null pointer. +/* +/* The \fBend\fR argument is either null (the byte sequence +/* starting at \fBstr\fR must be null terminated), or \fBend +/* - str\fR specifies the length of the byte sequence. +/* BUGS +/* Code points in the range U+FDD0..U+FDEF and ending in FFFE +/* or FFFF are non-characters in UNICODE. This function does +/* not reject these. +/* LICENSE +/* .ad +/* .fi +/* The Secure Mailer license must be distributed with this software. +/* AUTHOR(S) +/* Wietse Venema +/* IBM T.J. Watson Research +/* P.O. Box 704 +/* Yorktown Heights, NY 10598, USA +/* +/* Wietse Venema +/* porcupine.org +/* Amawalk, NY 10501, USA +/*--*/ + + /* + * System library. + */ +#include <sys_defs.h> + +#ifdef NO_INLINE +#define inline /* */ +#endif + +/* parse_utf8_char - parse and validate one UTF8 multibyte sequence */ + +static inline char *parse_utf8_char(const char *str, const char *end) +{ + const unsigned char *cp = (const unsigned char *) str; + const unsigned char *ep = (const unsigned char *) end; + unsigned char c0, ch; + + /* + * Optimized for correct input, time, space, and for CPUs that have a + * decent number of registers. Other implementation considerations: + * + * - In the UTF-8 encoding, a non-leading byte is never null. Therefore, + * this function will correctly reject a partial UTF-8 character at the + * end of a null-terminated string. + * + * - If the "end" argument is a null constant, and if this function is + * inlined, then an optimizing compiler should propagate the constant + * through the "ep" variable, and eliminate any code branches that + * require ep != 0. + */ + /* Single-byte encodings. */ + if (EXPECTED((c0 = *cp) <= 0x7f) /* we know that c0 >= 0x0 */ ) { + return ((char *) cp); + } + /* Two-byte encodings. */ + else if (EXPECTED(c0 <= 0xdf) /* we know that c0 >= 0x80 */ ) { + /* Exclude over-long encodings. */ + if (UNEXPECTED(c0 < 0xc2) + || UNEXPECTED(ep && cp + 1 >= ep) + /* Require UTF-8 tail byte. */ + || UNEXPECTED(((ch = *++cp) & 0xc0) != 0x80)) + return (0); + return ((char *) cp); + } + /* Three-byte encodings. */ + else if (EXPECTED(c0 <= 0xef) /* we know that c0 >= 0xe0 */ ) { + if (UNEXPECTED(ep && cp + 2 >= ep) + /* Exclude over-long encodings. */ + || UNEXPECTED((ch = *++cp) < (c0 == 0xe0 ? 0xa0 : 0x80)) + /* Exclude U+D800..U+DFFF. */ + || UNEXPECTED(ch > (c0 == 0xed ? 0x9f : 0xbf)) + /* Require UTF-8 tail byte. */ + || UNEXPECTED(((ch = *++cp) & 0xc0) != 0x80)) + return (0); + return ((char *) cp); + } + /* Four-byte encodings. */ + else if (EXPECTED(c0 <= 0xf4) /* we know that c0 >= 0xf0 */ ) { + if (UNEXPECTED(ep && cp + 3 >= ep) + /* Exclude over-long encodings. */ + || UNEXPECTED((ch = *++cp) < (c0 == 0xf0 ? 0x90 : 0x80)) + /* Exclude code points above U+10FFFF. */ + || UNEXPECTED(ch > (c0 == 0xf4 ? 0x8f : 0xbf)) + /* Require UTF-8 tail byte. */ + || UNEXPECTED(((ch = *++cp) & 0xc0) != 0x80) + /* Require UTF-8 tail byte. */ + || UNEXPECTED(((ch = *++cp) & 0xc0) != 0x80)) + return (0); + return ((char *) cp); + } + /* Invalid: c0 >= 0xf5 */ + else { + return (0); + } +} + +#undef inline |