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FFI: Add pointer arithmetic.

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This commit is contained in:
Mike Pall
2010-12-23 17:54:54 +01:00
parent ba20871f0f
commit 79ab1a4baa
3 changed files with 118 additions and 6 deletions
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110
src/lib_ffi.c
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@@ -74,6 +74,41 @@ static void *ffi_checkptr(lua_State *L, int narg, CTypeID id)
return p;
}
typedef struct FFIArith {
uint8_t *p[2];
CType *ct[2];
} FFIArith;
/* Check arguments for arithmetic metamethods. */
static void ffi_checkarith(lua_State *L, FFIArith *fa)
{
CTState *cts = ctype_cts(L);
TValue *o = L->base;
MSize i;
if (o+1 >= L->top)
lj_err_argt(L, 1, LUA_TCDATA);
for (i = 0; i < 2; i++, o++) {
if (tviscdata(o)) {
GCcdata *cd = cdataV(o);
CTypeID id = (CTypeID)cd->typeid;
CType *ct = ctype_get(cts, id);
uint8_t *p = (uint8_t *)cdataptr(cd);
if (ctype_isref(ct->info)) {
lua_assert(ct->size == CTSIZE_PTR);
p = *(uint8_t **)p;
id = ctype_cid(ct->info);
}
fa->ct[i] = ctype_raw(cts, id);
fa->p[i] = p;
} else if (tvisnum(o)) {
fa->ct[i] = ctype_get(cts, CTID_DOUBLE);
fa->p[i] = (uint8_t *)&o->n;
} else {
lj_err_optype(L, o, LJ_ERR_OPARITH);
}
}
}
/* -- C type metamethods -------------------------------------------------- */
#define LJLIB_MODULE_ffi_meta
@@ -118,6 +153,81 @@ LJLIB_CF(ffi_meta___call) LJLIB_REC(cdata_call)
return 0; /* unreachable */
}
/* Pointer arithmetic. */
static int ffi_arith_ptr(lua_State *L, FFIArith *fa, int sub)
{
CTState *cts = ctype_cts(L);
CType *ctp = fa->ct[0];
uint8_t *pp = fa->p[0];
ptrdiff_t idx;
CTSize sz;
CTypeID id;
GCcdata *cd;
if (ctype_isptr(ctp->info) || ctype_isrefarray(ctp->info)) {
if (sub &&
(ctype_isptr(fa->ct[1]->info) || ctype_isrefarray(fa->ct[1]->info))) {
/* Pointer difference. */
intptr_t diff;
if (!lj_cconv_compatptr(cts, ctp, fa->ct[1], CCF_IGNQUAL))
lj_err_caller(L, LJ_ERR_FFI_INVTYPE);
sz = lj_ctype_size(cts, ctype_cid(ctp->info)); /* Element size. */
if (sz == 0 || sz == CTSIZE_INVALID)
lj_err_caller(L, LJ_ERR_FFI_INVSIZE);
if (ctype_isptr(ctp->info))
pp = (uint8_t *)cdata_getptr(pp, ctp->size);
if (ctype_isptr(fa->ct[1]->info))
fa->p[1] = (uint8_t *)cdata_getptr(fa->p[1], fa->ct[1]->size);
diff = ((intptr_t)pp - (intptr_t)fa->p[1]) / (int32_t)sz;
/* All valid pointer differences on x64 are in (-2^47, +2^47),
** which fits into a double without loss of precision.
*/
setnumV(L->top-1, (lua_Number)diff);
return 1;
}
lj_cconv_ct_ct(cts, ctype_get(cts, CTID_INT_PSZ), fa->ct[1],
(uint8_t *)&idx, fa->p[1], 0);
if (sub) idx = -idx;
} else if (!sub &&
(ctype_isptr(fa->ct[1]->info) || ctype_isrefarray(fa->ct[1]->info))) {
/* Swap pointer and index. */
ctp = fa->ct[1]; pp = fa->p[1];
lj_cconv_ct_ct(cts, ctype_get(cts, CTID_INT_PSZ), fa->ct[0],
(uint8_t *)&idx, fa->p[0], 0);
} else {
return 0;
}
sz = lj_ctype_size(cts, ctype_cid(ctp->info)); /* Element size. */
if (sz == CTSIZE_INVALID)
lj_err_caller(L, LJ_ERR_FFI_INVSIZE);
if (ctype_isptr(ctp->info))
pp = (uint8_t *)cdata_getptr(pp, ctp->size);
pp += idx*(int32_t)sz; /* Compute pointer + index. */
id = lj_ctype_intern(cts, CTINFO(CT_PTR, CTALIGN_PTR|ctype_cid(ctp->info)),
CTSIZE_PTR);
cd = lj_cdata_new(cts, id, CTSIZE_PTR);
*(uint8_t **)cdataptr(cd) = pp;
setcdataV(L, L->top-1, cd);
return 1;
}
LJLIB_CF(ffi_meta___add)
{
FFIArith fa;
ffi_checkarith(L, &fa);
if (!ffi_arith_ptr(L, &fa, 0))
lj_err_caller(L, LJ_ERR_FFI_INVTYPE);
return 1;
}
LJLIB_CF(ffi_meta___sub)
{
FFIArith fa;
ffi_checkarith(L, &fa);
if (!ffi_arith_ptr(L, &fa, 1))
lj_err_caller(L, LJ_ERR_FFI_INVTYPE);
return 1;
}
LJLIB_CF(ffi_meta___tostring)
{
GCcdata *cd = ffi_checkcdata(L, 1);