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utf8.offset returns also final position of character
'utf8.offset' returns two values: the initial and the final position of the given character.
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lutf8lib.c
20
lutf8lib.c
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@ -181,8 +181,8 @@ static int utfchar (lua_State *L) {
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/*
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** offset(s, n, [i]) -> index where n-th character counting from
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** position 'i' starts; 0 means character at 'i'.
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** offset(s, n, [i]) -> indices where n-th character counting from
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** position 'i' starts and ends; 0 means character at 'i'.
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*/
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static int byteoffset (lua_State *L) {
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size_t len;
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@ -217,11 +217,19 @@ static int byteoffset (lua_State *L) {
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}
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}
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}
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if (n == 0) /* did it find given character? */
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lua_pushinteger(L, posi + 1);
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else /* no such character */
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if (n != 0) { /* did not find given character? */
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luaL_pushfail(L);
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return 1;
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return 1;
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}
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lua_pushinteger(L, posi + 1); /* initial position */
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if ((s[posi] & 0x80) != 0) { /* multi-byte character? */
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do {
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posi++;
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} while (iscontp(s + posi + 1)); /* skip to final byte */
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}
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/* else one-byte character: final position is the initial one */
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lua_pushinteger(L, posi + 1); /* 'posi' now is the final position */
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return 2;
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}
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@ -7958,21 +7958,27 @@ returns @fail plus the position of the first invalid byte.
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@LibEntry{utf8.offset (s, n [, i])|
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Returns the position (in bytes) where the encoding of the
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@id{n}-th character of @id{s}
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(counting from position @id{i}) starts.
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Returns the the position of the @id{n}-th character of @id{s}
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(counting from byte position @id{i}) as two integers:
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The index (in bytes) where its encoding starts and the
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index (in bytes) where it ends.
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If the specified character is right after the end of @id{s},
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the function behaves as if there was a @Char{\0} there.
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If the specified character is neither in the subject
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nor right after its end,
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the function returns @fail.
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A negative @id{n} gets characters before position @id{i}.
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The default for @id{i} is 1 when @id{n} is non-negative
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and @T{#s + 1} otherwise,
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so that @T{utf8.offset(s, -n)} gets the offset of the
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@id{n}-th character from the end of the string.
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If the specified character is neither in the subject
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nor right after its end,
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the function returns @fail.
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As a special case,
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when @id{n} is 0 the function returns the start of the encoding
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of the character that contains the @id{i}-th byte of @id{s}.
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when @id{n} is 0 the function returns the start and end
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of the encoding of the character that contains the
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@id{i}-th byte of @id{s}.
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This function assumes that @id{s} is a valid UTF-8 string.
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@ -52,25 +52,35 @@ local function check (s, t, nonstrict)
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for i = 1, #t do assert(t[i] == t1[i]) end -- 't' is equal to 't1'
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for i = 1, l do -- for all codepoints
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local pi = utf8.offset(s, i) -- position of i-th char
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local pi, pie = utf8.offset(s, i) -- position of i-th char
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local pi1 = utf8.offset(s, 2, pi) -- position of next char
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assert(pi1 == pie + 1)
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assert(string.find(string.sub(s, pi, pi1 - 1), justone))
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assert(utf8.offset(s, -1, pi1) == pi)
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assert(utf8.offset(s, i - l - 1) == pi)
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assert(pi1 - pi == #utf8.char(utf8.codepoint(s, pi, pi, nonstrict)))
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for j = pi, pi1 - 1 do
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assert(utf8.offset(s, 0, j) == pi)
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local off1, off2 = utf8.offset(s, 0, j)
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assert(off1 == pi and off2 == pi1 - 1)
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end
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for j = pi + 1, pi1 - 1 do
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assert(not utf8.len(s, j))
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end
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assert(utf8.len(s, pi, pi, nonstrict) == 1)
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assert(utf8.len(s, pi, pi1 - 1, nonstrict) == 1)
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assert(utf8.len(s, pi, -1, nonstrict) == l - i + 1)
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assert(utf8.len(s, pi1, -1, nonstrict) == l - i)
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assert(utf8.len(s, 1, pi, nonstrict) == i)
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assert(utf8.len(s, pi, pi, nonstrict) == 1)
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assert(utf8.len(s, pi, pi1 - 1, nonstrict) == 1)
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assert(utf8.len(s, pi, -1, nonstrict) == l - i + 1)
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assert(utf8.len(s, pi1, -1, nonstrict) == l - i)
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assert(utf8.len(s, 1, pi, nonstrict) == i)
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end
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local expected = 1 -- expected position of "current" character
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for i = 1, l + 1 do
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local p, e = utf8.offset(s, i)
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assert(p == expected)
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expected = e + 1
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end
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assert(expected - 1 == #s + 1)
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local i = 0
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for p, c in utf8.codes(s, nonstrict) do
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i = i + 1
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@ -94,20 +104,20 @@ end
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do -- error indication in utf8.len
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local function check (s, p)
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local function checklen (s, p)
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local a, b = utf8.len(s)
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assert(not a and b == p)
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end
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check("abc\xE3def", 4)
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check("\xF4\x9F\xBF", 1)
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check("\xF4\x9F\xBF\xBF", 1)
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checklen("abc\xE3def", 4)
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checklen("\xF4\x9F\xBF", 1)
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checklen("\xF4\x9F\xBF\xBF", 1)
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-- spurious continuation bytes
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check("汉字\x80", #("汉字") + 1)
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check("\x80hello", 1)
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check("hel\x80lo", 4)
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check("汉字\xBF", #("汉字") + 1)
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check("\xBFhello", 1)
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check("hel\xBFlo", 4)
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checklen("汉字\x80", #("汉字") + 1)
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checklen("\x80hello", 1)
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checklen("hel\x80lo", 4)
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checklen("汉字\xBF", #("汉字") + 1)
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checklen("\xBFhello", 1)
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checklen("hel\xBFlo", 4)
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end
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-- errors in utf8.codes
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