utf8.offset returns also final position of character
'utf8.offset' returns two values: the initial and the final position
of the given character.
diff --git a/lutf8lib.c b/lutf8lib.c
index 3a5b9bc..7b74793 100644
--- a/lutf8lib.c
+++ b/lutf8lib.c
@@ -181,8 +181,8 @@
/*
-** 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 @@
}
}
}
- 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;
}
diff --git a/manual/manual.of b/manual/manual.of
index f830b01..359bd16 100644
--- a/manual/manual.of
+++ b/manual/manual.of
@@ -7958,21 +7958,27 @@
@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.
diff --git a/testes/utf8.lua b/testes/utf8.lua
index efadbd5..dc0f2f0 100644
--- a/testes/utf8.lua
+++ b/testes/utf8.lua
@@ -52,25 +52,35 @@
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 @@
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
