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Improve commentary in src/character.h

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* src/character.h (BYTES_BY_CHAR_HEAD, MULTIBYTE_LENGTH)
(MULTIBYTE_LENGTH_NO_CHECK, STRING_CHAR_AND_LENGTH): Remove stale
info from commentary and improve it.
This commit is contained in:
Eli Zaretskii 2016-08-18 17:23:22 +03:00
parent 5ccd59339d
commit 37d4723f73
1 changed files with 8 additions and 12 deletions
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20
src/character.h
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@ -237,7 +237,8 @@ enum
#define CHAR_HEAD_P(byte) (((byte) & 0xC0) != 0x80) #define CHAR_HEAD_P(byte) (((byte) & 0xC0) != 0x80)
/* How many bytes a character that starts with BYTE occupies in a /* How many bytes a character that starts with BYTE occupies in a
multibyte form. */ multibyte form. Unlike MULTIBYTE_LENGTH below, this macro does not
validate the multibyte form, but looks only at its first byte. */
#define BYTES_BY_CHAR_HEAD(byte) \ #define BYTES_BY_CHAR_HEAD(byte) \
(!((byte) & 0x80) ? 1 \ (!((byte) & 0x80) ? 1 \
: !((byte) & 0x20) ? 2 \ : !((byte) & 0x20) ? 2 \
@ -247,7 +248,9 @@ enum
/* The byte length of multibyte form at unibyte string P ending at /* The byte length of multibyte form at unibyte string P ending at
PEND. If STR doesn't point to a valid multibyte form, return 0. */ PEND. If the string doesn't point to a valid multibyte form,
return 0. Unlike BYTES_BY_CHAR_HEAD, this macro validates the
multibyte form. */
#define MULTIBYTE_LENGTH(p, pend) \ #define MULTIBYTE_LENGTH(p, pend) \
(p >= pend ? 0 \ (p >= pend ? 0 \
@ -263,7 +266,8 @@ enum
: 0) : 0)
/* Like MULTIBYTE_LENGTH, but don't check the ending address. */ /* Like MULTIBYTE_LENGTH, but don't check the ending address. The
multibyte form is still validated, unlike BYTES_BY_CHAR_HEAD. */
#define MULTIBYTE_LENGTH_NO_CHECK(p) \ #define MULTIBYTE_LENGTH_NO_CHECK(p) \
(!((p)[0] & 0x80) ? 1 \ (!((p)[0] & 0x80) ? 1 \
@ -324,15 +328,7 @@ enum
/* Like STRING_CHAR, but set ACTUAL_LEN to the length of multibyte /* Like STRING_CHAR, but set ACTUAL_LEN to the length of multibyte
form. form. */
Note: This macro returns the actual length of the character's
multibyte sequence as it is stored in a buffer or string. The
character it returns might have a different codepoint that has a
different multibyte sequence of a different length, due to possible
unification of CJK characters inside string_char. Therefore do NOT
assume that the length returned by this macro is identical to the
length of the multibyte sequence of the character it returns. */
#define STRING_CHAR_AND_LENGTH(p, actual_len) \ #define STRING_CHAR_AND_LENGTH(p, actual_len) \
(!((p)[0] & 0x80) \ (!((p)[0] & 0x80) \