utf8.offset returns also final position of character

'utf8.offset' returns two values: the initial and the final position
of the given character.
This commit is contained in:
Roberto Ierusalimschy 2024-05-27 11:29:39 -03:00
parent cbdf4969ec
commit 814213b65f
3 changed files with 55 additions and 31 deletions

View File

@ -181,8 +181,8 @@ static int utfchar (lua_State *L) {
/*
** offset(s, n, [i]) -> index where n-th character counting from
** position 'i' starts; 0 means character at 'i'.
** offset(s, n, [i]) -> indices where n-th character counting from
** position 'i' starts and ends; 0 means character at 'i'.
*/
static int byteoffset (lua_State *L) {
size_t len;
@ -217,11 +217,19 @@ static int byteoffset (lua_State *L) {
}
}
}
if (n == 0) /* did it find given character? */
lua_pushinteger(L, posi + 1);
else /* no such character */
if (n != 0) { /* did not find given character? */
luaL_pushfail(L);
return 1;
return 1;
}
lua_pushinteger(L, posi + 1); /* initial position */
if ((s[posi] & 0x80) != 0) { /* multi-byte character? */
do {
posi++;
} while (iscontp(s + posi + 1)); /* skip to final byte */
}
/* else one-byte character: final position is the initial one */
lua_pushinteger(L, posi + 1); /* 'posi' now is the final position */
return 2;
}

View File

@ -7958,21 +7958,27 @@ returns @fail plus the position of the first invalid byte.
@LibEntry{utf8.offset (s, n [, i])|
Returns the position (in bytes) where the encoding of the
@id{n}-th character of @id{s}
(counting from position @id{i}) starts.
Returns the the position of the @id{n}-th character of @id{s}
(counting from byte position @id{i}) as two integers:
The index (in bytes) where its encoding starts and the
index (in bytes) where it ends.
If the specified character is right after the end of @id{s},
the function behaves as if there was a @Char{\0} there.
If the specified character is neither in the subject
nor right after its end,
the function returns @fail.
A negative @id{n} gets characters before position @id{i}.
The default for @id{i} is 1 when @id{n} is non-negative
and @T{#s + 1} otherwise,
so that @T{utf8.offset(s, -n)} gets the offset of the
@id{n}-th character from the end of the string.
If the specified character is neither in the subject
nor right after its end,
the function returns @fail.
As a special case,
when @id{n} is 0 the function returns the start of the encoding
of the character that contains the @id{i}-th byte of @id{s}.
when @id{n} is 0 the function returns the start and end
of the encoding of the character that contains the
@id{i}-th byte of @id{s}.
This function assumes that @id{s} is a valid UTF-8 string.

View File

@ -52,25 +52,35 @@ local function check (s, t, nonstrict)
for i = 1, #t do assert(t[i] == t1[i]) end -- 't' is equal to 't1'
for i = 1, l do -- for all codepoints
local pi = utf8.offset(s, i) -- position of i-th char
local pi, pie = utf8.offset(s, i) -- position of i-th char
local pi1 = utf8.offset(s, 2, pi) -- position of next char
assert(pi1 == pie + 1)
assert(string.find(string.sub(s, pi, pi1 - 1), justone))
assert(utf8.offset(s, -1, pi1) == pi)
assert(utf8.offset(s, i - l - 1) == pi)
assert(pi1 - pi == #utf8.char(utf8.codepoint(s, pi, pi, nonstrict)))
for j = pi, pi1 - 1 do
assert(utf8.offset(s, 0, j) == pi)
local off1, off2 = utf8.offset(s, 0, j)
assert(off1 == pi and off2 == pi1 - 1)
end
for j = pi + 1, pi1 - 1 do
assert(not utf8.len(s, j))
end
assert(utf8.len(s, pi, pi, nonstrict) == 1)
assert(utf8.len(s, pi, pi1 - 1, nonstrict) == 1)
assert(utf8.len(s, pi, -1, nonstrict) == l - i + 1)
assert(utf8.len(s, pi1, -1, nonstrict) == l - i)
assert(utf8.len(s, 1, pi, nonstrict) == i)
assert(utf8.len(s, pi, pi, nonstrict) == 1)
assert(utf8.len(s, pi, pi1 - 1, nonstrict) == 1)
assert(utf8.len(s, pi, -1, nonstrict) == l - i + 1)
assert(utf8.len(s, pi1, -1, nonstrict) == l - i)
assert(utf8.len(s, 1, pi, nonstrict) == i)
end
local expected = 1 -- expected position of "current" character
for i = 1, l + 1 do
local p, e = utf8.offset(s, i)
assert(p == expected)
expected = e + 1
end
assert(expected - 1 == #s + 1)
local i = 0
for p, c in utf8.codes(s, nonstrict) do
i = i + 1
@ -94,20 +104,20 @@ end
do -- error indication in utf8.len
local function check (s, p)
local function checklen (s, p)
local a, b = utf8.len(s)
assert(not a and b == p)
end
check("abc\xE3def", 4)
check("\xF4\x9F\xBF", 1)
check("\xF4\x9F\xBF\xBF", 1)
checklen("abc\xE3def", 4)
checklen("\xF4\x9F\xBF", 1)
checklen("\xF4\x9F\xBF\xBF", 1)
-- spurious continuation bytes
check("汉字\x80", #("汉字") + 1)
check("\x80hello", 1)
check("hel\x80lo", 4)
check("汉字\xBF", #("汉字") + 1)
check("\xBFhello", 1)
check("hel\xBFlo", 4)
checklen("汉字\x80", #("汉字") + 1)
checklen("\x80hello", 1)
checklen("hel\x80lo", 4)
checklen("汉字\xBF", #("汉字") + 1)
checklen("\xBFhello", 1)
checklen("hel\xBFlo", 4)
end
-- errors in utf8.codes