new library: utf8

1 files changed, 233 insertions, 0 deletions

diff --git a/lutf8lib.c b/lutf8lib.c
new file mode 100644
index 00000000..dfd52832
--- /dev/null
+++ b/lutf8lib.c
@@ -0,0 +1,233 @@
+/* gcc -shared -o utf8.so -fpic -O2 -Wall -I.. utf8.c */
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "lua.h"
+#include "lauxlib.h"
+
+#define MAXUNICODE      0x10FFFF
+
+#define iscont(p)       ((*(p) & 0xC0) == 0x80)
+
+
+/* from strlib */
+/* translate a relative string position: negative means back from end */
+static lua_Integer posrelat (lua_Integer pos, size_t len) {
+  if (pos >= 0) return pos;
+  else if (0u - (size_t)pos > len) return 0;
+  else return (lua_Integer)len + pos + 1;
+}
+
+
+/*
+** Decode an UTF-8 sequence, returning NULL if byte sequence is invalid.
+*/
+static const char *utf8_decode (const char *o, int *val) {
+  static unsigned int limits[] = {0xFF, 0x7F, 0x7FF, 0xFFFF};
+  const unsigned char *s = (const unsigned char *)o;
+  unsigned int c = s[0];
+  unsigned int res = 0;  /* final result */
+  if (c < 0x80)  /* ascii? */
+    res = c;
+  else {
+    int count = 0;  /* to count number of continuation bytes */
+    while (c & 0x40) {  /* still have continuation bytes? */
+      int cc = s[++count];  /* read next byte */
+      if ((cc & 0xC0) != 0x80)  /* not a continuation byte? */
+        return NULL;  /* invalid byte sequence */
+      res = (res << 6) | (cc & 0x3F);  /* add lower 6 bits from cont. byte */
+      c <<= 1;  /* to test next bit */
+    }
+    res |= ((c & 0x7F) << (count * 5));  /* add first byte */
+    if (count > 3 || res > MAXUNICODE || res <= limits[count])
+      return NULL;  /* invalid byte sequence */
+    s += count;  /* skip continuation bytes read */
+  }
+  if (val) *val = res;
+  return (const char *)s + 1;  /* +1 to include first byte */
+}
+
+
+/*
+** utf8len(s, [i])   --> number of codepoints in 's' after 'i';
+** nil if 's' not well formed
+*/
+static int utflen (lua_State *L) {
+  int n = 0;
+  const char *ends;
+  size_t len;
+  const char *s = luaL_checklstring(L, 1, &len);
+  lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), 1);
+  luaL_argcheck(L, 1 <= posi && posi <= (lua_Integer)len, 1,
+                   "initial position out of string");
+  ends = s + len;
+  s += posi - 1;
+  while (s < ends && (s = utf8_decode(s, NULL)) != NULL)
+    n++;
+  if (s == ends)
+    lua_pushinteger(L, n);
+  else
+    lua_pushnil(L);
+  return 1;
+}
+
+
+/*
+** codepoint(s, [i, [j]])  -> returns codepoints for all characters
+** between i and j
+*/
+static int codepoint (lua_State *L) {
+  size_t len;
+  const char *s = luaL_checklstring(L, 1, &len);
+  lua_Integer posi = posrelat(luaL_optinteger(L, 2, 1), len);
+  lua_Integer pose = posrelat(luaL_optinteger(L, 3, posi), len);
+  int n;
+  const char *se;
+  luaL_argcheck(L, posi >= 1, 2, "out of range");
+  luaL_argcheck(L, pose <= (lua_Integer)len, 3, "out of range");
+  if (posi > pose) return 0;  /* empty interval; return no values */
+  n = (int)(pose -  posi + 1);
+  if (posi + n <= pose)  /* (lua_Integer -> int) overflow? */
+    return luaL_error(L, "string slice too long");
+  luaL_checkstack(L, n, "string slice too long");
+  n = 0;
+  se = s + pose;
+  for (s += posi - 1; s < se;) {
+    int code;
+    s = utf8_decode(s, &code);
+    if (s == NULL)
+      luaL_error(L, "invalid UTF-8 code");
+    lua_pushinteger(L, code);
+    n++;
+  }
+  return n;
+}
+
+
+static void pushutfchar (lua_State *L, int arg) {
+  int code = luaL_checkint(L, arg);
+  luaL_argcheck(L, 0 <= code && code <= MAXUNICODE, arg, "value out of range");
+  lua_pushfstring(L, "%U", code);
+}
+
+
+/*
+** utfchar(n1, n2, ...)  -> char(n1)..char(n2)...
+*/
+static int utfchar (lua_State *L) {
+  int n = lua_gettop(L);  /* number of arguments */
+  if (n == 1)  /* optimize common case of single char */
+    pushutfchar(L, 1);
+  else {
+    int i;
+    luaL_Buffer b;
+    luaL_buffinit(L, &b);
+    for (i = 1; i <= n; i++) {
+      pushutfchar(L, i);
+      luaL_addvalue(&b);
+    }
+    luaL_pushresult(&b);
+  }
+  return 1;
+}
+
+
+/*
+** offset(s, n, [i])  -> index where n-th character *after*
+**   position 'i' starts; 0 means character at 'i'.
+*/
+static int byteoffset (lua_State *L) {
+  size_t len;
+  const char *s = luaL_checklstring(L, 1, &len);
+  int n  = luaL_checkint(L, 2);
+  lua_Integer posi = posrelat(luaL_optinteger(L, 3, 1), len) - 1;
+  luaL_argcheck(L, 0 <= posi && posi <= (lua_Integer)len, 3,
+                   "position out of range");
+  if (n == 0) {
+    /* find beginning of current byte sequence */
+    while (posi > 0 && iscont(s + posi)) posi--;
+  }
+  else if (n < 0) {
+    while (n < 0 && posi > 0) {  /* move back */
+      do {  /* find beginning of previous character */
+        posi--;
+      } while (posi > 0 && iscont(s + posi));
+      n++;
+    }
+  }
+  else {
+    n--;  /* do not move for 1st character */
+    while (n > 0 && posi < (lua_Integer)len) {
+      do {  /* find beginning of next character */
+        posi++;
+      } while (iscont(s + posi));  /* ('\0' is not continuation) */
+      n--;
+    }
+  }
+  if (n == 0)
+    lua_pushinteger(L, posi + 1);
+  else
+    lua_pushnil(L);  /* no such position */
+  return 1;  
+}
+
+
+static int iter_aux (lua_State *L) {
+  size_t len;
+  const char *s = luaL_checklstring(L, 1, &len);
+  int n = lua_tointeger(L, 2) - 1;
+  if (n < 0)  /* first iteration? */
+    n = 0;  /* start from here */
+  else if (n < (lua_Integer)len) {
+    n++;  /* skip current byte */
+    while (iscont(s + n)) n++;  /* and its continuations */
+  }
+  if (n >= (lua_Integer)len)
+    return 0;  /* no more codepoints */
+  else {
+    int code;
+    const char *next = utf8_decode(s + n, &code);
+    if (next == NULL || iscont(next))
+      luaL_error(L, "invalid UTF-8 code");
+    lua_pushinteger(L, n + 1);
+    lua_pushinteger(L, code);
+    return 2;
+  }
+}
+
+
+static int iter_codes (lua_State *L) {
+  luaL_checkstring(L, 1);
+  lua_pushcfunction(L, iter_aux);
+  lua_pushvalue(L, 1);
+  lua_pushinteger(L, 0);
+  return 3;
+}
+
+
+/* pattern to match a single UTF-8 character */
+#define UTF8PATT        "[\0-\x7F\xC2-\xF4][\x80-\xBF]*"
+
+
+static struct luaL_Reg funcs[] = {
+  {"offset", byteoffset},
+  {"codepoint", codepoint},
+  {"char", utfchar},
+  {"len", utflen},
+  {"codes", iter_codes},
+  {NULL, NULL}
+};
+
+
+
+int luaopen_utf8 (lua_State *L);
+
+int luaopen_utf8 (lua_State *L) {
+  luaL_newlib(L, funcs);
+  lua_pushliteral(L, UTF8PATT);
+  lua_setfield(L, -2, "charpatt");
+  return 1;
+}
+