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bstr: add function for UTF-8 parsing (taken from libav) 

Parts taken from libavutil's GET_UTF8 and slightly modified.
This commit is contained in:
wm4 2012-01-13 07:38:40 +01:00
parent 827faa3843
commit 7700e6effc
2 changed files with 45 additions and 0 deletions
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32
bstr.c
View File

@ -201,3 +201,35 @@ int bstr_sscanf(struct bstr str, const char *format, ...)
talloc_free(ptr);
return ret;
}
int bstr_parse_utf8_code_length(unsigned char b)
{
if (b < 128)
return 1;
int bytes = 7 - av_log2(b ^ 255);
return (bytes >= 2 && bytes <= 4) ? bytes : -1;
}
int bstr_decode_utf8(struct bstr s, struct bstr *out_next)
{
if (s.len == 0)
return -1;
unsigned int codepoint = s.start[0];
s.start++; s.len--;
if (codepoint >= 128) {
int bytes = bstr_parse_utf8_code_length(codepoint);
if (bytes < 0 || s.len < bytes - 1)
return -1;
codepoint &= 127 >> bytes;
for (int n = 1; n < bytes; n++) {
int tmp = s.start[0];
if ((tmp & 0xC0) != 0x80)
return -1;
codepoint = (codepoint << 6) | (tmp & ~0xC0);
s.start++; s.len--;
}
}
if (out_next)
*out_next = s;
return codepoint;
}

13
bstr.h
View File

@ -69,6 +69,19 @@ double bstrtod(struct bstr str, struct bstr *rest);
void bstr_lower(struct bstr str);
int bstr_sscanf(struct bstr str, const char *format, ...);
// Decode the UTF-8 code point at the start of the string,, and return the
// character.
// After calling this function, *out_next will point to the next character.
// out_next can be NULL.
// On error, -1 is returned, and *out_next is not modified.
int bstr_decode_utf8(struct bstr str, struct bstr *out_next);
// Return the length of the UTF-8 sequence that starts with the given byte.
// Given a string char *s, the next UTF-8 code point is to be expected at
// s + bstr_parse_utf8_code_length(s[0])
// On error, -1 is returned. On success, it returns a value in the range [1, 4].
int bstr_parse_utf8_code_length(unsigned char b);
static inline struct bstr bstr_cut(struct bstr str, int n)
{
if (n > str.len)