luau/VM/src/lutf8lib.cpp

295 lines
8.9 KiB
C++
Raw Normal View History

// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
// This code is based on Lua 5.x implementation licensed under MIT License; see lua_LICENSE.txt for details
#include "lualib.h"
#include "lcommon.h"
#define MAXUNICODE 0x10FFFF
#define iscont(p) ((*(p)&0xC0) == 0x80)
/* from strlib */
/* translate a relative string position: negative means back from end */
static int u_posrelat(int pos, size_t len)
{
if (pos >= 0)
return pos;
else if (0u - (size_t)pos > len)
return 0;
else
return (int)len + pos + 1;
}
/*
** Decode one UTF-8 sequence, returning NULL if byte sequence is invalid.
*/
static const char* utf8_decode(const char* o, int* val)
{
static const 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 [, j]]) --> number of characters that start in the
** range [i,j], or nil + current position if 's' is not well formed in
** that interval
*/
static int utflen(lua_State* L)
{
int n = 0;
size_t len;
const char* s = luaL_checklstring(L, 1, &len);
int posi = u_posrelat(luaL_optinteger(L, 2, 1), len);
int posj = u_posrelat(luaL_optinteger(L, 3, -1), len);
luaL_argcheck(L, 1 <= posi && --posi <= (int)len, 2, "initial position out of string");
luaL_argcheck(L, --posj < (int)len, 3, "final position out of string");
while (posi <= posj)
{
const char* s1 = utf8_decode(s + posi, NULL);
if (s1 == NULL)
{ /* conversion error? */
lua_pushnil(L); /* return nil ... */
lua_pushinteger(L, posi + 1); /* ... and current position */
return 2;
}
posi = (int)(s1 - s);
n++;
}
lua_pushinteger(L, n);
return 1;
}
/*
** codepoint(s, [i, [j]]) -> returns codepoints for all characters
** that start in the range [i,j]
*/
static int codepoint(lua_State* L)
{
size_t len;
const char* s = luaL_checklstring(L, 1, &len);
int posi = u_posrelat(luaL_optinteger(L, 2, 1), len);
int pose = u_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 <= (int)len, 3, "out of range");
if (posi > pose)
return 0; /* empty interval; return no values */
if (pose - posi >= INT_MAX) /* (int -> int) overflow? */
luaL_error(L, "string slice too long");
n = (int)(pose - posi) + 1;
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;
}
// from Lua 5.3 lobject.h
#define UTF8BUFFSZ 8
// from Lua 5.3 lobject.c, copied verbatim + static
static int luaO_utf8esc(char* buff, unsigned long x)
{
int n = 1; /* number of bytes put in buffer (backwards) */
LUAU_ASSERT(x <= 0x10FFFF);
if (x < 0x80) /* ascii? */
buff[UTF8BUFFSZ - 1] = cast_to(char, x);
else
{ /* need continuation bytes */
unsigned int mfb = 0x3f; /* maximum that fits in first byte */
do
{ /* add continuation bytes */
buff[UTF8BUFFSZ - (n++)] = cast_to(char, 0x80 | (x & 0x3f));
x >>= 6; /* remove added bits */
mfb >>= 1; /* now there is one less bit available in first byte */
} while (x > mfb); /* still needs continuation byte? */
buff[UTF8BUFFSZ - n] = cast_to(char, (~mfb << 1) | x); /* add first byte */
}
return n;
}
// lighter replacement for pushutfchar; doesn't push any string onto the stack
static int buffutfchar(lua_State* L, int arg, char* buff, const char** charstr)
{
int code = luaL_checkinteger(L, arg);
luaL_argcheck(L, 0 <= code && code <= MAXUNICODE, arg, "value out of range");
int l = luaO_utf8esc(buff, cast_to(long, code));
*charstr = buff + UTF8BUFFSZ - l;
return l;
}
/*
** utfchar(n1, n2, ...) -> char(n1)..char(n2)...
**
** This version avoids the need to make more invasive upgrades elsewhere (like
** implementing the %U escape in lua_pushfstring) and avoids pushing string
** objects for each codepoint in the multi-argument case. -Jovanni
*/
static int utfchar(lua_State* L)
{
char buff[UTF8BUFFSZ];
const char* charstr;
int n = lua_gettop(L); /* number of arguments */
if (n == 1)
{ /* optimize common case of single char */
int l = buffutfchar(L, 1, buff, &charstr);
lua_pushlstring(L, charstr, l);
}
else
{
luaL_Buffer b;
luaL_buffinit(L, &b);
for (int i = 1; i <= n; i++)
{
int l = buffutfchar(L, i, buff, &charstr);
luaL_addlstring(&b, charstr, l);
}
luaL_pushresult(&b);
}
return 1;
}
/*
** offset(s, n, [i]) -> index where n-th character counting from
** 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_checkinteger(L, 2);
int posi = (n >= 0) ? 1 : (int)len + 1;
posi = u_posrelat(luaL_optinteger(L, 3, posi), len);
luaL_argcheck(L, 1 <= posi && --posi <= (int)len, 3, "position out of range");
if (n == 0)
{
/* find beginning of current byte sequence */
while (posi > 0 && iscont(s + posi))
posi--;
}
else
{
if (iscont(s + posi))
luaL_error(L, "initial position is a continuation byte");
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 < (int)len)
{
do
{ /* find beginning of next character */
posi++;
} while (iscont(s + posi)); /* (cannot pass final '\0') */
n--;
}
}
}
if (n == 0) /* did it find given character? */
lua_pushinteger(L, posi + 1);
else /* no such character */
lua_pushnil(L);
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 < (int)len)
{
n++; /* skip current byte */
while (iscont(s + n))
n++; /* and its continuations */
}
if (n >= (int)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 const luaL_Reg funcs[] = {
{"offset", byteoffset},
{"codepoint", codepoint},
{"char", utfchar},
{"len", utflen},
{"codes", iter_codes},
{NULL, NULL},
};
LUALIB_API int luaopen_utf8(lua_State* L)
{
luaL_register(L, LUA_UTF8LIBNAME, funcs);
lua_pushlstring(L, UTF8PATT, sizeof(UTF8PATT) / sizeof(char) - 1);
lua_setfield(L, -2, "charpattern");
return 1;
}