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/*
* This project is MIT licensed. Please see the
* COPYING file in the source package for more information.
*
* Copyright (C) 2016 Kim Alvefur
*/
#include <lua.h>
#include <lauxlib.h>
#include <sys/param.h>
#include <limits.h>
/* TODO Deduplicate code somehow */
static int strop_and(lua_State *L) {
luaL_Buffer buf;
size_t a, b, i;
const char *str_a = luaL_checklstring(L, 1, &a);
const char *str_b = luaL_checklstring(L, 2, &b);
luaL_buffinit(L, &buf);
if(a == 0 || b == 0) {
lua_settop(L, 1);
return 1;
}
for(i = 0; i < a; i++) {
luaL_addchar(&buf, str_a[i] & str_b[i % b]);
}
luaL_pushresult(&buf);
return 1;
}
static int strop_or(lua_State *L) {
luaL_Buffer buf;
size_t a, b, i;
const char *str_a = luaL_checklstring(L, 1, &a);
const char *str_b = luaL_checklstring(L, 2, &b);
luaL_buffinit(L, &buf);
if(a == 0 || b == 0) {
lua_settop(L, 1);
return 1;
}
for(i = 0; i < a; i++) {
luaL_addchar(&buf, str_a[i] | str_b[i % b]);
}
luaL_pushresult(&buf);
return 1;
}
static int strop_xor(lua_State *L) {
luaL_Buffer buf;
size_t a, b, i;
const char *str_a = luaL_checklstring(L, 1, &a);
const char *str_b = luaL_checklstring(L, 2, &b);
luaL_buffinit(L, &buf);
if(a == 0 || b == 0) {
lua_settop(L, 1);
return 1;
}
for(i = 0; i < a; i++) {
luaL_addchar(&buf, str_a[i] ^ str_b[i % b]);
}
luaL_pushresult(&buf);
return 1;
}
unsigned int clz(unsigned char c) {
#if __GNUC__
return __builtin_clz((unsigned int) c) - ((sizeof(int)-1)*CHAR_BIT);
#else
if(c & 0x80) return 0;
if(c & 0x40) return 1;
if(c & 0x20) return 2;
if(c & 0x10) return 3;
if(c & 0x08) return 4;
if(c & 0x04) return 5;
if(c & 0x02) return 6;
if(c & 0x01) return 7;
return 8;
#endif
}
LUA_API int strop_common_prefix_bits(lua_State *L) {
size_t a, b, i;
const char *str_a = luaL_checklstring(L, 1, &a);
const char *str_b = luaL_checklstring(L, 2, &b);
size_t min_len = MIN(a, b);
for(i=0; i<min_len; i++) {
if(str_a[i] != str_b[i]) {
lua_pushinteger(L, i*8 + (clz(str_a[i] ^ str_b[i])));
return 1;
}
}
lua_pushinteger(L, i*8);
return 1;
}
LUA_API int luaopen_prosody_util_strbitop(lua_State *L) {
luaL_Reg exports[] = {
{ "sand", strop_and },
{ "sor", strop_or },
{ "sxor", strop_xor },
{ "common_prefix_bits", strop_common_prefix_bits },
{ NULL, NULL }
};
lua_newtable(L);
luaL_setfuncs(L, exports, 0);
return 1;
}
LUA_API int luaopen_util_strbitop(lua_State *L) {
return luaopen_prosody_util_strbitop(L);
}
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