1/*
2** $Id: lmem.c $
3** Interface to Memory Manager
4** See Copyright Notice in lua.h
5*/
6
7#define lmem_c
8#define LUA_CORE
9
10#include "lprefix.h"
11
12
13#include <stddef.h>
14
15#include "lua.h"
16
17#include "ldebug.h"
18#include "ldo.h"
19#include "lgc.h"
20#include "lmem.h"
21#include "lobject.h"
22#include "lstate.h"
23
24
25#if defined(EMERGENCYGCTESTS)
26/*
27** First allocation will fail whenever not building initial state.
28** (This fail will trigger 'tryagain' and a full GC cycle at every
29** allocation.)
30*/
31static void *firsttry (global_State *g, void *block, size_t os, size_t ns) {
32 if (completestate(g) && ns > 0) /* frees never fail */
33 return NULL; /* fail */
34 else /* normal allocation */
35 return (*g->frealloc)(g->ud, block, os, ns);
36}
37#else
38#define firsttry(g,block,os,ns) ((*g->frealloc)(g->ud, block, os, ns))
39#endif
40
41
42
43
44
45/*
46** About the realloc function:
47** void *frealloc (void *ud, void *ptr, size_t osize, size_t nsize);
48** ('osize' is the old size, 'nsize' is the new size)
49**
50** - frealloc(ud, p, x, 0) frees the block 'p' and returns NULL.
51** Particularly, frealloc(ud, NULL, 0, 0) does nothing,
52** which is equivalent to free(NULL) in ISO C.
53**
54** - frealloc(ud, NULL, x, s) creates a new block of size 's'
55** (no matter 'x'). Returns NULL if it cannot create the new block.
56**
57** - otherwise, frealloc(ud, b, x, y) reallocates the block 'b' from
58** size 'x' to size 'y'. Returns NULL if it cannot reallocate the
59** block to the new size.
60*/
61
62
63
64
65/*
66** {==================================================================
67** Functions to allocate/deallocate arrays for the Parser
68** ===================================================================
69*/
70
71/*
72** Minimum size for arrays during parsing, to avoid overhead of
73** reallocating to size 1, then 2, and then 4. All these arrays
74** will be reallocated to exact sizes or erased when parsing ends.
75*/
76#define MINSIZEARRAY 4
77
78
79void *luaM_growaux_ (lua_State *L, void *block, int nelems, int *psize,
80 int size_elems, int limit, const char *what) {
81 void *newblock;
82 int size = *psize;
83 if (nelems + 1 <= size) /* does one extra element still fit? */
84 return block; /* nothing to be done */
85 if (size >= limit / 2) { /* cannot double it? */
86 if (l_unlikely(size >= limit)) /* cannot grow even a little? */
87 luaG_runerror(L, "too many %s (limit is %d)", what, limit);
88 size = limit; /* still have at least one free place */
89 }
90 else {
91 size *= 2;
92 if (size < MINSIZEARRAY)
93 size = MINSIZEARRAY; /* minimum size */
94 }
95 lua_assert(nelems + 1 <= size && size <= limit);
96 /* 'limit' ensures that multiplication will not overflow */
97 newblock = luaM_saferealloc_(L, block, cast_sizet(*psize) * size_elems,
98 cast_sizet(size) * size_elems);
99 *psize = size; /* update only when everything else is OK */
100 return newblock;
101}
102
103
104/*
105** In prototypes, the size of the array is also its number of
106** elements (to save memory). So, if it cannot shrink an array
107** to its number of elements, the only option is to raise an
108** error.
109*/
110void *luaM_shrinkvector_ (lua_State *L, void *block, int *size,
111 int final_n, int size_elem) {
112 void *newblock;
113 size_t oldsize = cast_sizet((*size) * size_elem);
114 size_t newsize = cast_sizet(final_n * size_elem);
115 lua_assert(newsize <= oldsize);
116 newblock = luaM_saferealloc_(L, block, oldsize, newsize);
117 *size = final_n;
118 return newblock;
119}
120
121/* }================================================================== */
122
123
124l_noret luaM_toobig (lua_State *L) {
125 luaG_runerror(L, "memory allocation error: block too big");
126}
127
128
129/*
130** Free memory
131*/
132void luaM_free_ (lua_State *L, void *block, size_t osize) {
133 global_State *g = G(L);
134 lua_assert((osize == 0) == (block == NULL));
135 (*g->frealloc)(g->ud, block, osize, 0);
136 g->GCdebt -= osize;
137}
138
139
140/*
141** In case of allocation fail, this function will do an emergency
142** collection to free some memory and then try the allocation again.
143** The GC should not be called while state is not fully built, as the
144** collector is not yet fully initialized. Also, it should not be called
145** when 'gcstopem' is true, because then the interpreter is in the
146** middle of a collection step.
147*/
148static void *tryagain (lua_State *L, void *block,
149 size_t osize, size_t nsize) {
150 global_State *g = G(L);
151 if (completestate(g) && !g->gcstopem) {
152 luaC_fullgc(L, 1); /* try to free some memory... */
153 return (*g->frealloc)(g->ud, block, osize, nsize); /* try again */
154 }
155 else return NULL; /* cannot free any memory without a full state */
156}
157
158
159/*
160** Generic allocation routine.
161*/
162void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) {
163 void *newblock;
164 global_State *g = G(L);
165 lua_assert((osize == 0) == (block == NULL));
166 newblock = firsttry(g, block, osize, nsize);
167 if (l_unlikely(newblock == NULL && nsize > 0)) {
168 newblock = tryagain(L, block, osize, nsize);
169 if (newblock == NULL) /* still no memory? */
170 return NULL; /* do not update 'GCdebt' */
171 }
172 lua_assert((nsize == 0) == (newblock == NULL));
173 g->GCdebt = (g->GCdebt + nsize) - osize;
174 return newblock;
175}
176
177
178void *luaM_saferealloc_ (lua_State *L, void *block, size_t osize,
179 size_t nsize) {
180 void *newblock = luaM_realloc_(L, block, osize, nsize);
181 if (l_unlikely(newblock == NULL && nsize > 0)) /* allocation failed? */
182 luaM_error(L);
183 return newblock;
184}
185
186
187void *luaM_malloc_ (lua_State *L, size_t size, int tag) {
188 if (size == 0)
189 return NULL; /* that's all */
190 else {
191 global_State *g = G(L);
192 void *newblock = firsttry(g, NULL, tag, size);
193 if (l_unlikely(newblock == NULL)) {
194 newblock = tryagain(L, NULL, tag, size);
195 if (newblock == NULL)
196 luaM_error(L);
197 }
198 g->GCdebt += size;
199 return newblock;
200 }
201}
202