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Use CESU-8 lookup table to improve lit_get_unicode_char_size_by_utf8_… #793

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Use CESU-8 lookup table to improve lit_get_unicode_char_size_by_utf8_… #793

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30 changes: 17 additions & 13 deletions jerry-core/lit/lit-strings.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -757,6 +757,15 @@ lit_utf8_string_code_unit_at (const lit_utf8_byte_t *utf8_buf_p, /**< utf-8 stri
return code_unit;
} /* lit_utf8_string_code_unit_at */

/* CESU-8 number of bytes occupied lookup table */
const __attribute__ ((aligned (CESU_8_TABLE_MEM_ALIGNMENT))) lit_utf8_byte_t table[]
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Why do we need the alignment attribute?

{
1, 1, 1, 1, 1, 1, 1, 1,
0, 0, 0, 0,
2, 2,
3, 0
};

/**
* Get CESU-8 encoded size of character
*
Expand All @@ -765,19 +774,14 @@ lit_utf8_string_code_unit_at (const lit_utf8_byte_t *utf8_buf_p, /**< utf-8 stri
lit_utf8_size_t
lit_get_unicode_char_size_by_utf8_first_byte (const lit_utf8_byte_t first_byte) /**< buffer with characters */
{
if ((first_byte & LIT_UTF8_1_BYTE_MASK) == LIT_UTF8_1_BYTE_MARKER)
{
return 1;
}
else if ((first_byte & LIT_UTF8_2_BYTE_MASK) == LIT_UTF8_2_BYTE_MARKER)
{
return 2;
}
else
{
JERRY_ASSERT ((first_byte & LIT_UTF8_3_BYTE_MASK) == LIT_UTF8_3_BYTE_MARKER);
return 3;
}
JERRY_ASSERT (((first_byte >> 4) == 0 ||
(first_byte >> 4) == 1 || (first_byte >> 4) == 2 ||
(first_byte >> 4) == 3 || (first_byte >> 4) == 4 ||
(first_byte >> 4) == 5 || (first_byte >> 4) == 6 ||
(first_byte >> 4) == 7 || (first_byte >> 4) == 12 ||
(first_byte >> 4) == 13 || (first_byte >> 4) == 14));
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I have no objection against big asserts, but in this case wouldn't be better to use (first_byte >> 4) <= 7 ? This is just a note, so if others prefer the current one, it is ok for me.


return table[first_byte >> 4];
} /* lit_get_unicode_char_size_by_utf8_first_byte */

/**
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1 change: 1 addition & 0 deletions jerry-core/lit/lit-strings.h
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Expand Up @@ -157,6 +157,7 @@ lit_string_hash_t lit_utf8_string_calc_hash (const lit_utf8_byte_t *, lit_utf8_s
lit_string_hash_t lit_utf8_string_hash_combine (lit_string_hash_t, const lit_utf8_byte_t *, lit_utf8_size_t);

/* code unit access */
#define CESU_8_TABLE_MEM_ALIGNMENT 16
ecma_char_t lit_utf8_string_code_unit_at (const lit_utf8_byte_t *, lit_utf8_size_t, ecma_length_t);
lit_utf8_size_t lit_get_unicode_char_size_by_utf8_first_byte (lit_utf8_byte_t);

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