lua/src/crc32.c

   1 /***
   2  32-bit Cyclic Redundancy Check
   3  @module liba.crc32
   4 */
   5
   6 #include "crc32.h"
   7 #include "a/crc.h"
   8
   9 struct crc32
  10 {
  11     a_u32 table[0x100];
  12     a_u32 (*eval)(a_u32 const table[0x100], void const *pdata, a_size nbyte, a_u32 value);
  13 };
  14
  15 /***
  16  constructor for 32-bit Cyclic Redundancy Check
  17  @tparam integer poly polynomial that is CRC's divisor
  18  @tparam boolean reversed whether or not to reverse
  19  @treturn a.crc32 32-bit Cyclic Redundancy Check userdata
  20  @function new
  21 */
  22 int liba_crc32_new(lua_State *L)
  23 {
  24     a_u32 poly = 0;
  25     int reversed = 0;
  26     struct crc32 *ctx;
  27     int top = lua_gettop(L);
  28     if (top > 1)
  29     {
  30         luaL_checktype(L, 2, LUA_TBOOLEAN);
  31         reversed = lua_toboolean(L, 2);
  32     }
  33     poly = lua_u32_get(L, 1);
  34     ctx = lua_newclass(L, struct crc32);
  35     lua_registry_get(L, liba_crc32_new);
  36     lua_setmetatable(L, -2);
  37     if (reversed)
  38     {
  39         a_crc32l_init(ctx->table, poly);
  40         ctx->eval = a_crc32l;
  41     }
  42     else
  43     {
  44         a_crc32m_init(ctx->table, poly);
  45         ctx->eval = a_crc32m;
  46     }
  47     return 1;
  48 }
  49
  50 /***
  51  generate for 32-bit Cyclic Redundancy Check
  52  @tparam a.crc32 ctx 32-bit Cyclic Redundancy Check userdata
  53  @tparam integer poly polynomial that is CRC's divisor
  54  @tparam boolean reversed whether or not to reverse
  55  @treturn a.crc32 32-bit Cyclic Redundancy Check userdata
  56  @function gen
  57 */
  58 int liba_crc32_gen(lua_State *L)
  59 {
  60     a_u32 poly = 0;
  61     int reversed = 0;
  62     struct crc32 *ctx;
  63     int top = lua_gettop(L);
  64     if (top > 2)
  65     {
  66         luaL_checktype(L, 3, LUA_TBOOLEAN);
  67         reversed = lua_toboolean(L, 3);
  68     }
  69     poly = lua_u32_get(L, 2);
  70     ctx = (struct crc32 *)lua_touserdata(L, 1);
  71     if (reversed)
  72     {
  73         a_crc32l_init(ctx->table, poly);
  74         ctx->eval = a_crc32l;
  75     }
  76     else
  77     {
  78         a_crc32m_init(ctx->table, poly);
  79         ctx->eval = a_crc32m;
  80     }
  81     lua_pushvalue(L, 1);
  82     return 1;
  83 }
  84
  85 /***
  86  calculate for 32-bit Cyclic Redundancy Check
  87  @tparam a.crc32 ctx 32-bit Cyclic Redundancy Check userdata
  88  @tparam string block block to be processed
  89  @tparam integer value initial value
  90  @treturn integer output value
  91  @function eval
  92 */
  93 int liba_crc32_eval(lua_State *L)
  94 {
  95     struct crc32 *const ctx = (struct crc32 *)lua_touserdata(L, 1);
  96     if (ctx)
  97     {
  98         size_t n = 0;
  99         a_u32 value = 0;
 100         char const *const p = luaL_checklstring(L, 2, &n);
 101         if (lua_gettop(L) > 2) { value = lua_u32_get(L, 3); }
 102         lua_u32_new(L, ctx->eval(ctx->table, p, n, value));
 103         return 1;
 104     }
 105     return 0;
 106 }
 107
 108 /***
 109  pack a block and its 32-bit Cyclic Redundancy Check value
 110  @tparam a.crc32 ctx 32-bit Cyclic Redundancy Check userdata
 111  @tparam string block block to be processed
 112  @tparam integer value initial value
 113  @treturn string packed block
 114  @function pack
 115 */
 116 int liba_crc32_pack(lua_State *L)
 117 {
 118     struct crc32 *const ctx = (struct crc32 *)lua_touserdata(L, 1);
 119     if (ctx)
 120     {
 121         union
 122         {
 123             char const *s;
 124             a_byte *p;
 125         } u;
 126         size_t n = 0;
 127         a_u32 value = 0;
 128         char const *p = luaL_checklstring(L, 2, &n);
 129         if (lua_gettop(L) > 2) { value = lua_u32_get(L, 3); }
 130         value = ctx->eval(ctx->table, p, n, value);
 131         u.s = lua_pushfstring(L, "%s    ", p) + n;
 132         ctx->eval == a_crc32m
 133             ? a_u32_setb(u.p, value)
 134             : a_u32_setl(u.p, value);
 135         return 1;
 136     }
 137     return 0;
 138 }
 139
 140 static int liba_crc32_set(lua_State *L)
 141 {
 142     switch (a_hash_bkdr(lua_tostring(L, 2), 0))
 143     {
 144     case 0xE8859EEB: /* __name */
 145     case 0xE70C48C6: /* __call */
 146     case 0xA65758B2: /* __index */
 147     case 0xAEB551C6: /* __newindex */
 148         break;
 149     default:
 150         lua_getmetatable(L, 1);
 151         lua_replace(L, 1);
 152         lua_rawset(L, 1);
 153     }
 154     return 0;
 155 }
 156
 157 static int liba_crc32_get(lua_State *L)
 158 {
 159     struct crc32 const *const ctx = (struct crc32 const *)lua_touserdata(L, 1);
 160     switch (a_hash_bkdr(lua_tostring(L, 2), 0))
 161     {
 162     case 0x014FE58A: /* table */
 163         lua_array_u32_new(L, ctx->table, 0x100);
 164         break;
 165     case 0xA65758B2: /* __index */
 166         lua_registry_get(L, liba_crc32_new);
 167         lua_pushstring(L, "table");
 168         lua_array_u32_new(L, ctx->table, 0x100);
 169         lua_rawset(L, -3);
 170         break;
 171     default:
 172         lua_getmetatable(L, 1);
 173         lua_replace(L, 1);
 174         lua_rawget(L, 1);
 175     }
 176     return 1;
 177 }
 178
 179 static int liba_crc32_(lua_State *L)
 180 {
 181     lua_pushcfunction(L, liba_crc32_new);
 182     lua_replace(L, 1);
 183     lua_call(L, lua_gettop(L) - 1, 1);
 184     return 1;
 185 }
 186
 187 int luaopen_liba_crc32(lua_State *L)
 188 {
 189     static lua_fun const funcs[] = {
 190         {"new", liba_crc32_new},
 191         {"gen", liba_crc32_gen},
 192         {"eval", liba_crc32_eval},
 193         {"pack", liba_crc32_pack},
 194     };
 195     static lua_fun const metas[] = {
 196         {"__newindex", liba_crc32_set},
 197         {"__index", liba_crc32_get},
 198         {"__call", liba_crc32_eval},
 199     };
 200
 201     lua_createtable(L, 0, A_LEN(funcs));
 202     lua_fun_reg(L, -1, funcs, A_LEN(funcs));
 203     lua_createtable(L, 0, 1);
 204     lua_fun_set(L, -1, "__call", liba_crc32_);
 205     lua_setmetatable(L, -2);
 206
 207     lua_createtable(L, 0, A_LEN(metas) + A_LEN(funcs) + 1);
 208     lua_fun_reg(L, -1, metas, A_LEN(metas));
 209     lua_fun_reg(L, -1, funcs, A_LEN(funcs));
 210     lua_str_set(L, -1, "__name", "a.crc32");
 211     lua_registry_set(L, liba_crc32_new);
 212
 213     return 1;
 214 }