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author | kyren <kerriganw@gmail.com> | 2017-05-21 19:50:59 -0400 |
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committer | kyren <kerriganw@gmail.com> | 2017-05-21 19:50:59 -0400 |
commit | 065c69894a08dc52e7a1baba9154681d6c0fa834 (patch) | |
tree | 76bcf03a8aa291f465dfb5f216389a21baaa5d1a /lua/lstring.c | |
download | mlua-065c69894a08dc52e7a1baba9154681d6c0fa834.zip |
Initial import
Diffstat (limited to 'lua/lstring.c')
-rw-r--r-- | lua/lstring.c | 248 |
1 files changed, 248 insertions, 0 deletions
diff --git a/lua/lstring.c b/lua/lstring.c new file mode 100644 index 0000000..9351766 --- /dev/null +++ b/lua/lstring.c @@ -0,0 +1,248 @@ +/* +** $Id: lstring.c,v 2.56 2015/11/23 11:32:51 roberto Exp $ +** String table (keeps all strings handled by Lua) +** See Copyright Notice in lua.h +*/ + +#define lstring_c +#define LUA_CORE + +#include "lprefix.h" + + +#include <string.h> + +#include "lua.h" + +#include "ldebug.h" +#include "ldo.h" +#include "lmem.h" +#include "lobject.h" +#include "lstate.h" +#include "lstring.h" + + +#define MEMERRMSG "not enough memory" + + +/* +** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to +** compute its hash +*/ +#if !defined(LUAI_HASHLIMIT) +#define LUAI_HASHLIMIT 5 +#endif + + +/* +** equality for long strings +*/ +int luaS_eqlngstr (TString *a, TString *b) { + size_t len = a->u.lnglen; + lua_assert(a->tt == LUA_TLNGSTR && b->tt == LUA_TLNGSTR); + return (a == b) || /* same instance or... */ + ((len == b->u.lnglen) && /* equal length and ... */ + (memcmp(getstr(a), getstr(b), len) == 0)); /* equal contents */ +} + + +unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) { + unsigned int h = seed ^ cast(unsigned int, l); + size_t step = (l >> LUAI_HASHLIMIT) + 1; + for (; l >= step; l -= step) + h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1])); + return h; +} + + +unsigned int luaS_hashlongstr (TString *ts) { + lua_assert(ts->tt == LUA_TLNGSTR); + if (ts->extra == 0) { /* no hash? */ + ts->hash = luaS_hash(getstr(ts), ts->u.lnglen, ts->hash); + ts->extra = 1; /* now it has its hash */ + } + return ts->hash; +} + + +/* +** resizes the string table +*/ +void luaS_resize (lua_State *L, int newsize) { + int i; + stringtable *tb = &G(L)->strt; + if (newsize > tb->size) { /* grow table if needed */ + luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *); + for (i = tb->size; i < newsize; i++) + tb->hash[i] = NULL; + } + for (i = 0; i < tb->size; i++) { /* rehash */ + TString *p = tb->hash[i]; + tb->hash[i] = NULL; + while (p) { /* for each node in the list */ + TString *hnext = p->u.hnext; /* save next */ + unsigned int h = lmod(p->hash, newsize); /* new position */ + p->u.hnext = tb->hash[h]; /* chain it */ + tb->hash[h] = p; + p = hnext; + } + } + if (newsize < tb->size) { /* shrink table if needed */ + /* vanishing slice should be empty */ + lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL); + luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *); + } + tb->size = newsize; +} + + +/* +** Clear API string cache. (Entries cannot be empty, so fill them with +** a non-collectable string.) +*/ +void luaS_clearcache (global_State *g) { + int i, j; + for (i = 0; i < STRCACHE_N; i++) + for (j = 0; j < STRCACHE_M; j++) { + if (iswhite(g->strcache[i][j])) /* will entry be collected? */ + g->strcache[i][j] = g->memerrmsg; /* replace it with something fixed */ + } +} + + +/* +** Initialize the string table and the string cache +*/ +void luaS_init (lua_State *L) { + global_State *g = G(L); + int i, j; + luaS_resize(L, MINSTRTABSIZE); /* initial size of string table */ + /* pre-create memory-error message */ + g->memerrmsg = luaS_newliteral(L, MEMERRMSG); + luaC_fix(L, obj2gco(g->memerrmsg)); /* it should never be collected */ + for (i = 0; i < STRCACHE_N; i++) /* fill cache with valid strings */ + for (j = 0; j < STRCACHE_M; j++) + g->strcache[i][j] = g->memerrmsg; +} + + + +/* +** creates a new string object +*/ +static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) { + TString *ts; + GCObject *o; + size_t totalsize; /* total size of TString object */ + totalsize = sizelstring(l); + o = luaC_newobj(L, tag, totalsize); + ts = gco2ts(o); + ts->hash = h; + ts->extra = 0; + getstr(ts)[l] = '\0'; /* ending 0 */ + return ts; +} + + +TString *luaS_createlngstrobj (lua_State *L, size_t l) { + TString *ts = createstrobj(L, l, LUA_TLNGSTR, G(L)->seed); + ts->u.lnglen = l; + return ts; +} + + +void luaS_remove (lua_State *L, TString *ts) { + stringtable *tb = &G(L)->strt; + TString **p = &tb->hash[lmod(ts->hash, tb->size)]; + while (*p != ts) /* find previous element */ + p = &(*p)->u.hnext; + *p = (*p)->u.hnext; /* remove element from its list */ + tb->nuse--; +} + + +/* +** checks whether short string exists and reuses it or creates a new one +*/ +static TString *internshrstr (lua_State *L, const char *str, size_t l) { + TString *ts; + global_State *g = G(L); + unsigned int h = luaS_hash(str, l, g->seed); + TString **list = &g->strt.hash[lmod(h, g->strt.size)]; + lua_assert(str != NULL); /* otherwise 'memcmp'/'memcpy' are undefined */ + for (ts = *list; ts != NULL; ts = ts->u.hnext) { + if (l == ts->shrlen && + (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) { + /* found! */ + if (isdead(g, ts)) /* dead (but not collected yet)? */ + changewhite(ts); /* resurrect it */ + return ts; + } + } + if (g->strt.nuse >= g->strt.size && g->strt.size <= MAX_INT/2) { + luaS_resize(L, g->strt.size * 2); + list = &g->strt.hash[lmod(h, g->strt.size)]; /* recompute with new size */ + } + ts = createstrobj(L, l, LUA_TSHRSTR, h); + memcpy(getstr(ts), str, l * sizeof(char)); + ts->shrlen = cast_byte(l); + ts->u.hnext = *list; + *list = ts; + g->strt.nuse++; + return ts; +} + + +/* +** new string (with explicit length) +*/ +TString *luaS_newlstr (lua_State *L, const char *str, size_t l) { + if (l <= LUAI_MAXSHORTLEN) /* short string? */ + return internshrstr(L, str, l); + else { + TString *ts; + if (l >= (MAX_SIZE - sizeof(TString))/sizeof(char)) + luaM_toobig(L); + ts = luaS_createlngstrobj(L, l); + memcpy(getstr(ts), str, l * sizeof(char)); + return ts; + } +} + + +/* +** Create or reuse a zero-terminated string, first checking in the +** cache (using the string address as a key). The cache can contain +** only zero-terminated strings, so it is safe to use 'strcmp' to +** check hits. +*/ +TString *luaS_new (lua_State *L, const char *str) { + unsigned int i = point2uint(str) % STRCACHE_N; /* hash */ + int j; + TString **p = G(L)->strcache[i]; + for (j = 0; j < STRCACHE_M; j++) { + if (strcmp(str, getstr(p[j])) == 0) /* hit? */ + return p[j]; /* that is it */ + } + /* normal route */ + for (j = STRCACHE_M - 1; j > 0; j--) + p[j] = p[j - 1]; /* move out last element */ + /* new element is first in the list */ + p[0] = luaS_newlstr(L, str, strlen(str)); + return p[0]; +} + + +Udata *luaS_newudata (lua_State *L, size_t s) { + Udata *u; + GCObject *o; + if (s > MAX_SIZE - sizeof(Udata)) + luaM_toobig(L); + o = luaC_newobj(L, LUA_TUSERDATA, sizeludata(s)); + u = gco2u(o); + u->len = s; + u->metatable = NULL; + setuservalue(L, u, luaO_nilobject); + return u; +} + |