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@@ -0,0 +1,233 @@
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+/* gcc -shared -o utf8.so -fpic -O2 -Wall -I.. utf8.c */
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+
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+#include <assert.h>
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+#include <stdlib.h>
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+#include <string.h>
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+
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+#include "lua.h"
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+#include "lauxlib.h"
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+
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+#define MAXUNICODE 0x10FFFF
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+
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+#define iscont(p) ((*(p) & 0xC0) == 0x80)
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+
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+
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+/* from strlib */
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+/* translate a relative string position: negative means back from end */
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+static lua_Integer posrelat (lua_Integer pos, size_t len) {
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+ if (pos >= 0) return pos;
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+ else if (0u - (size_t)pos > len) return 0;
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+ else return (lua_Integer)len + pos + 1;
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+}
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+
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+
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+/*
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+** Decode an UTF-8 sequence, returning NULL if byte sequence is invalid.
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+*/
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+static const char *utf8_decode (const char *o, int *val) {
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+ static unsigned int limits[] = {0xFF, 0x7F, 0x7FF, 0xFFFF};
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+ const unsigned char *s = (const unsigned char *)o;
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+ unsigned int c = s[0];
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+ unsigned int res = 0; /* final result */
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+ if (c < 0x80) /* ascii? */
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+ res = c;
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+ else {
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+ int count = 0; /* to count number of continuation bytes */
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+ while (c & 0x40) { /* still have continuation bytes? */
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+ int cc = s[++count]; /* read next byte */
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+ if ((cc & 0xC0) != 0x80) /* not a continuation byte? */
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+ return NULL; /* invalid byte sequence */
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+ res = (res << 6) | (cc & 0x3F); /* add lower 6 bits from cont. byte */
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+ c <<= 1; /* to test next bit */
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+ }
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+ res |= ((c & 0x7F) << (count * 5)); /* add first byte */
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+ if (count > 3 || res > MAXUNICODE || res <= limits[count])
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+ return NULL; /* invalid byte sequence */
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+ s += count; /* skip continuation bytes read */
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+ }
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+ if (val) *val = res;
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+ return (const char *)s + 1; /* +1 to include first byte */
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+}
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+
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+
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+/*
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+** utf8len(s, [i]) --> number of codepoints in 's' after 'i';
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+** nil if 's' not well formed
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+*/
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+static int utflen (lua_State *L) {
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+ int n = 0;
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+ const char *ends;
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+ size_t len;
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+ const char *s = luaL_checklstring(L, 1, &len);
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+ lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), 1);
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+ luaL_argcheck(L, 1 <= posi && posi <= (lua_Integer)len, 1,
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+ "initial position out of string");
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+ ends = s + len;
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+ s += posi - 1;
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+ while (s < ends && (s = utf8_decode(s, NULL)) != NULL)
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+ n++;
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+ if (s == ends)
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+ lua_pushinteger(L, n);
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+ else
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+ lua_pushnil(L);
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+ return 1;
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+}
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+
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+
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+/*
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+** codepoint(s, [i, [j]]) -> returns codepoints for all characters
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+** between i and j
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+*/
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+static int codepoint (lua_State *L) {
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+ size_t len;
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+ const char *s = luaL_checklstring(L, 1, &len);
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+ lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), len);
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+ lua_Integer pose = posrelat(luaL_optinteger(L, 3, posi), len);
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+ int n;
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+ const char *se;
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+ luaL_argcheck(L, posi >= 1, 2, "out of range");
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+ luaL_argcheck(L, pose <= (lua_Integer)len, 3, "out of range");
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+ if (posi > pose) return 0; /* empty interval; return no values */
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+ n = (int)(pose - posi + 1);
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+ if (posi + n <= pose) /* (lua_Integer -> int) overflow? */
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+ return luaL_error(L, "string slice too long");
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+ luaL_checkstack(L, n, "string slice too long");
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+ n = 0;
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+ se = s + pose;
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+ for (s += posi - 1; s < se;) {
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+ int code;
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+ s = utf8_decode(s, &code);
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+ if (s == NULL)
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+ luaL_error(L, "invalid UTF-8 code");
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+ lua_pushinteger(L, code);
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+ n++;
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+ }
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+ return n;
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+}
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+
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+
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+static void pushutfchar (lua_State *L, int arg) {
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+ int code = luaL_checkint(L, arg);
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+ luaL_argcheck(L, 0 <= code && code <= MAXUNICODE, arg, "value out of range");
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+ lua_pushfstring(L, "%U", code);
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+}
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+
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+
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+/*
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+** utfchar(n1, n2, ...) -> char(n1)..char(n2)...
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+*/
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+static int utfchar (lua_State *L) {
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+ int n = lua_gettop(L); /* number of arguments */
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+ if (n == 1) /* optimize common case of single char */
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+ pushutfchar(L, 1);
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+ else {
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+ int i;
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+ luaL_Buffer b;
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+ luaL_buffinit(L, &b);
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+ for (i = 1; i <= n; i++) {
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+ pushutfchar(L, i);
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+ luaL_addvalue(&b);
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+ }
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+ luaL_pushresult(&b);
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+ }
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+ return 1;
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+}
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+
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+
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+/*
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+** offset(s, n, [i]) -> index where n-th character *after*
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+** position 'i' starts; 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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+ const char *s = luaL_checklstring(L, 1, &len);
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+ int n = luaL_checkint(L, 2);
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+ lua_Integer posi = posrelat(luaL_optinteger(L, 3, 1), len) - 1;
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+ luaL_argcheck(L, 0 <= posi && posi <= (lua_Integer)len, 3,
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+ "position out of range");
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+ if (n == 0) {
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+ /* find beginning of current byte sequence */
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+ while (posi > 0 && iscont(s + posi)) posi--;
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+ }
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+ else if (n < 0) {
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+ while (n < 0 && posi > 0) { /* move back */
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+ do { /* find beginning of previous character */
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+ posi--;
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+ } while (posi > 0 && iscont(s + posi));
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+ n++;
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+ }
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+ }
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+ else {
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+ n--; /* do not move for 1st character */
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+ while (n > 0 && posi < (lua_Integer)len) {
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+ do { /* find beginning of next character */
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+ posi++;
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+ } while (iscont(s + posi)); /* ('\0' is not continuation) */
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+ n--;
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+ }
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+ }
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+ if (n == 0)
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+ lua_pushinteger(L, posi + 1);
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+ else
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+ lua_pushnil(L); /* no such position */
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+ return 1;
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+}
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+
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+
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+static int iter_aux (lua_State *L) {
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+ size_t len;
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+ const char *s = luaL_checklstring(L, 1, &len);
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+ int n = lua_tointeger(L, 2) - 1;
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+ if (n < 0) /* first iteration? */
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+ n = 0; /* start from here */
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+ else if (n < (lua_Integer)len) {
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+ n++; /* skip current byte */
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+ while (iscont(s + n)) n++; /* and its continuations */
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+ }
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+ if (n >= (lua_Integer)len)
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+ return 0; /* no more codepoints */
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+ else {
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+ int code;
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+ const char *next = utf8_decode(s + n, &code);
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+ if (next == NULL || iscont(next))
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+ luaL_error(L, "invalid UTF-8 code");
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+ lua_pushinteger(L, n + 1);
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+ lua_pushinteger(L, code);
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+ return 2;
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+ }
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+}
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+
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+
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+static int iter_codes (lua_State *L) {
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+ luaL_checkstring(L, 1);
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+ lua_pushcfunction(L, iter_aux);
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+ lua_pushvalue(L, 1);
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+ lua_pushinteger(L, 0);
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+ return 3;
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+}
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+
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+
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+/* pattern to match a single UTF-8 character */
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+#define UTF8PATT "[\0-\x7F\xC2-\xF4][\x80-\xBF]*"
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+
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+
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+static struct luaL_Reg funcs[] = {
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+ {"offset", byteoffset},
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+ {"codepoint", codepoint},
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+ {"char", utfchar},
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+ {"len", utflen},
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+ {"codes", iter_codes},
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+ {NULL, NULL}
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+};
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+
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+
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+
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+int luaopen_utf8 (lua_State *L);
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+
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+int luaopen_utf8 (lua_State *L) {
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+ luaL_newlib(L, funcs);
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+ lua_pushliteral(L, UTF8PATT);
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+ lua_setfield(L, -2, "charpatt");
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+ return 1;
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+}
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+
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Roberto Ierusalimschy