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Preshift the state by 8, to avoid a shift within the decoder.

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Rewrite the size_u to avoid a branch.
This commit is contained in:
Patrick Pelissier committed 2018-05-03 22:11:43 +02:00
1 parent fafce60f9e
commit 122cf63a3f
1 file changed
+12 -12
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m-string.h
+12 -12
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@@ -941,10 +941,10 @@ string_parse_str(string_t v, const char str[], const char **endptr)
/* UTF8 Handling */
typedef enum {
STRINGI_UTF8_STARTING = 0,
STRINGI_UTF8_DECODING_1 = 1,
STRINGI_UTF8_DECODING_2 = 2,
STRINGI_UTF8_DOCODING_3 = 3,
STRINGI_UTF8_ERROR = 4
STRINGI_UTF8_DECODING_1 = 8,
STRINGI_UTF8_DECODING_2 = 16,
STRINGI_UTF8_DOCODING_3 = 24,
STRINGI_UTF8_ERROR = 32
} stringi_utf8_state_e;
typedef unsigned int string_unicode_t;
@@ -969,11 +969,11 @@ typedef unsigned int string_unicode_t;
*/
/* The use of a string allows the compiler/linker to factorize it. */
#define STRINGI_UTF8_STATE_TAB \
"\000\004\001\002\003\004\004\004" \
"\004\000\004\004\004\004\004\004" \
"\004\001\004\004\004\004\004\004" \
"\004\002\004\004\004\004\004\004" \
"\004\004\004\004\004\004\004\004"
"\000\040\010\020\030\040\040\040" \
"\040\000\040\040\040\040\040\040" \
"\040\010\040\040\040\040\040\040" \
"\040\020\040\040\040\040\040\040" \
"\040\040\040\040\040\040\040\040"
/* Main generic UTF8 decoder
It shall be (nearly) branchless on any CPU.
@@ -989,7 +989,7 @@ static inline void stringi_utf8_decode(char c, stringi_utf8_state_e *state,
const string_unicode_t mask2 = (0xFFU >> type);
*unicode = ((*unicode << 6) & mask1) | (c & mask2);
*state = M_ASSIGN_CAST(stringi_utf8_state_e,
STRINGI_UTF8_STATE_TAB[*state * 8 + type]);
STRINGI_UTF8_STATE_TAB[*state + type]);
}
/* Check if the given array of characters is a valid UTF8 stream */
@@ -1018,8 +1018,8 @@ static inline size_t stringi_utf8_length(const char str[])
string_unicode_t u = 0;
while (*str) {
stringi_utf8_decode(*str, &s, &u);
if (s == STRINGI_UTF8_ERROR) return -1;
if (s == STRINGI_UTF8_STARTING) size++;
if (M_UNLIKELY (s == STRINGI_UTF8_ERROR)) return -1;
size += (s == STRINGI_UTF8_STARTING);
str++;
}
return size;