path: root/src/lj_cdata.c

/*
** C data management.
** Copyright (C) 2005-2011 Mike Pall. See Copyright Notice in luajit.h
*/

#include "lj_obj.h"

#if LJ_HASFFI

#include "lj_gc.h"
#include "lj_err.h"
#include "lj_str.h"
#include "lj_ctype.h"
#include "lj_cconv.h"
#include "lj_cdata.h"

/* -- C data allocation --------------------------------------------------- */

/* Allocate a new C data object holding a reference to another object. */
GCcdata *lj_cdata_newref(CTState *cts, const void *p, CTypeID id)
{
  CTypeID refid = lj_ctype_intern(cts, CTINFO_REF(id), CTSIZE_PTR);
  GCcdata *cd = lj_cdata_new(cts, refid, CTSIZE_PTR);
  *(const void **)cdataptr(cd) = p;
  return cd;
}

/* Allocate variable-sized or specially aligned C data object. */
GCcdata *lj_cdata_newv(CTState *cts, CTypeID id, CTSize sz, CTSize align)
{
  global_State *g;
  MSize extra = sizeof(GCcdataVar) + sizeof(GCcdata) +
		(align > CT_MEMALIGN ? (1u<<align) - (1u<<CT_MEMALIGN) : 0);
  char *p = lj_mem_newt(cts->L, extra + sz, char);
  uintptr_t adata = (uintptr_t)p + sizeof(GCcdataVar) + sizeof(GCcdata);
  uintptr_t almask = (1u << align) - 1u;
  GCcdata *cd = (GCcdata *)(((adata + almask) & ~almask) - sizeof(GCcdata));
  lua_assert((char *)cd - p < 65536);
  cdatav(cd)->offset = (uint16_t)((char *)cd - p);
  cdatav(cd)->extra = extra;
  cdatav(cd)->len = sz;
  g = cts->g;
  setgcrefr(cd->nextgc, g->gc.root);
  setgcref(g->gc.root, obj2gco(cd));
  newwhite(g, obj2gco(cd));
  cd->marked |= 0x80;
  cd->gct = ~LJ_TCDATA;
  cd->typeid = id;
  return cd;
}

/* Free a C data object. */
void LJ_FASTCALL lj_cdata_free(global_State *g, GCcdata *cd)
{
  if (LJ_LIKELY(!cdataisv(cd))) {
    CType *ct = ctype_raw(ctype_ctsG(g), cd->typeid);
    CTSize sz = ctype_hassize(ct->info) ? ct->size : CTSIZE_PTR;
    lua_assert(ctype_hassize(ct->info) || ctype_isfunc(ct->info));
    lj_mem_free(g, cd, sizeof(GCcdata) + sz);
  } else {
    lj_mem_free(g, memcdatav(cd), sizecdatav(cd));
  }
}

/* -- C data indexing ----------------------------------------------------- */

/* Index C data by a TValue. Return CType and pointer. */
CType *lj_cdata_index(CTState *cts, GCcdata *cd, cTValue *key, uint8_t **pp,
		      CTInfo *qual)
{
  uint8_t *p = (uint8_t *)cdataptr(cd);
  CType *ct = ctype_get(cts, cd->typeid);

  /* Resolve reference for cdata object. */
  if (ctype_isref(ct->info)) {
    lua_assert(ct->size == CTSIZE_PTR);
    p = *(uint8_t **)p;
    ct = ctype_child(cts, ct);
  }

collect_attrib:
  /* Skip attributes and collect qualifiers. */
  while (ctype_isattrib(ct->info)) {
    if (ctype_attrib(ct->info) == CTA_QUAL) *qual |= ct->size;
    ct = ctype_child(cts, ct);
  }
  lua_assert(!ctype_isref(ct->info));  /* Interning rejects refs to refs. */

  if (tvisnum(key)) {  /* Numeric key. */
    ptrdiff_t idx = LJ_64 ? (ptrdiff_t)numV(key) :
			    (ptrdiff_t)lj_num2int(numV(key));
    if (ctype_ispointer(ct->info)) {
      CTSize sz = lj_ctype_size(cts, ctype_cid(ct->info));  /* Element size. */
      if (sz != CTSIZE_INVALID) {
	if (ctype_isptr(ct->info))
	  p = (uint8_t *)cdata_getptr(p, ct->size);
	else if ((ct->info & (CTF_VECTOR|CTF_COMPLEX)))
	  *qual |= CTF_CONST;  /* Valarray elements are constant. */
	*pp = p + idx*(int32_t)sz;
	return ct;
      }
    }
  } else if (tvisstr(key)) {  /* String key. */
    GCstr *name = strV(key);
    if (ctype_isptr(ct->info)) {  /* Automatically perform '->'. */
      if (ctype_isstruct(ctype_rawchild(cts, ct)->info)) {
	p = (uint8_t *)cdata_getptr(p, ct->size);
	ct = ctype_child(cts, ct);
	goto collect_attrib;
      }
    } if (ctype_isstruct(ct->info)) {
      CTSize ofs;
      CType *fct = lj_ctype_getfield(cts, ct, name, &ofs);
      if (fct) {
	*pp = p + ofs;
	return fct;
      }
    } else if (ctype_iscomplex(ct->info)) {
      if (name->len == 2) {
	*qual |= CTF_CONST;  /* Complex fields are constant. */
	if (strdata(name)[0] == 'r' && strdata(name)[1] == 'e') {
	  *pp = p;
	  return ct;
	} else if (strdata(name)[0] == 'i' && strdata(name)[1] == 'm') {
	  *pp = p + (ct->size >> 1);
	  return ct;
	}
      }
    }
    {
      GCstr *s = lj_ctype_repr(cts->L, ctype_typeid(cts, ct), NULL);
      lj_err_callerv(cts->L, LJ_ERR_FFI_BADMEMBER, strdata(s), strdata(name));
    }
  }
  {
    GCstr *s = lj_ctype_repr(cts->L, ctype_typeid(cts, ct), NULL);
    lj_err_callerv(cts->L, LJ_ERR_FFI_BADIDX, strdata(s));
  }
  return NULL;  /* unreachable */
}

/* -- C data getters ------------------------------------------------------ */

/* Get constant value and convert to TValue. */
static void cdata_getconst(CTState *cts, TValue *o, CType *ct)
{
  CType *ctt = ctype_child(cts, ct);
  lua_assert(ctype_isinteger(ctt->info) && ctt->size <= 4);
  /* Constants are already zero-extended/sign-extended to 32 bits. */
  if (!(ctt->info & CTF_UNSIGNED))
    setintV(o, (int32_t)ct->size);
  else
    setnumV(o, (lua_Number)(uint32_t)ct->size);
}

/* Get C data value and convert to TValue. */
int lj_cdata_get(CTState *cts, CType *s, TValue *o, uint8_t *sp)
{
  CTypeID sid;

  if (ctype_isconstval(s->info)) {
    cdata_getconst(cts, o, s);
    return 0;  /* No GC step needed. */
  } else if (ctype_isbitfield(s->info)) {
    return lj_cconv_tv_bf(cts, s, o, sp);
  }

  /* Get child type of pointer/array/field. */
  lua_assert(ctype_ispointer(s->info) || ctype_isfield(s->info));
  sid = ctype_cid(s->info);
  s = ctype_get(cts, sid);

  /* Resolve reference for field. */
  if (ctype_isref(s->info)) {
    lua_assert(s->size == CTSIZE_PTR);
    sp = *(uint8_t **)sp;
    sid = ctype_cid(s->info);
    s = ctype_get(cts, sid);
  }

  /* Skip attributes and enums. */
  while (ctype_isattrib(s->info) || ctype_isenum(s->info))
    s = ctype_child(cts, s);

  return lj_cconv_tv_ct(cts, s, sid, o, sp);
}

/* -- C data setters ------------------------------------------------------ */

/* Convert TValue and set C data value. */
void lj_cdata_set(CTState *cts, CType *d, uint8_t *dp, TValue *o, CTInfo qual)
{
  if (ctype_isconstval(d->info)) {
    goto err_const;
  } else if (ctype_isbitfield(d->info)) {
    if (((d->info|qual) & CTF_CONST)) goto err_const;
    lj_cconv_bf_tv(cts, d, dp, o);
    return;
  }

  /* Get child type of pointer/array/field. */
  lua_assert(ctype_ispointer(d->info) || ctype_isfield(d->info));
  d = ctype_child(cts, d);

  /* Resolve reference for field. */
  if (ctype_isref(d->info)) {
    lua_assert(d->size == CTSIZE_PTR);
    dp = *(uint8_t **)dp;
    d = ctype_child(cts, d);
  }

  /* Skip attributes and collect qualifiers. */
  for (;;) {
    if (ctype_isattrib(d->info)) {
      if (ctype_attrib(d->info) == CTA_QUAL) qual |= d->size;
    } else {
      break;
    }
    d = ctype_child(cts, d);
  }

  lua_assert(ctype_hassize(d->info) && !ctype_isvoid(d->info));

  if (((d->info|qual) & CTF_CONST)) {
  err_const:
    lj_err_caller(cts->L, LJ_ERR_FFI_WRCONST);
  }

  lj_cconv_ct_tv(cts, d, dp, o, 0);
}

/* -- 64 bit integer arithmetic helpers ----------------------------------- */

/* 64 bit integer x^k. */
uint64_t lj_cdata_powi64(uint64_t x, uint64_t k, int isunsigned)
{
  uint64_t y = 0;
  if (k == 0)
    return 1;
  if (!isunsigned) {
    if ((int64_t)k < 0) {
      if (x == 0)
	return U64x(7fffffff,ffffffff);
      else if (x == 1)
	return 1;
      else if ((int64_t)x == -1)
	return (k & 1) ? -1 : 1;
      else
	return 0;
    }
  }
  for (; (k & 1) == 0; k >>= 1) x *= x;
  y = x;
  if ((k >>= 1) != 0) {
    for (;;) {
      x *= x;
      if (k == 1) break;
      if (k & 1) y *= x;
      k >>= 1;
    }
    y *= x;
  }
  return y;
}

#endif