Re: C data reflection in LuaJIT
- From: Peter Colberg <peter@xxxxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Fri, 3 Oct 2014 12:53:05 -0400
On Fri, Oct 03, 2014 at 02:06:34PM +0200, Mike Pall wrote:
> Sorry, no. That would mean I'd have to maintain it as part of the
> core and update it for any changes to the internals.
I understand that this was a too big request to make.
Could you take a quick look at the attached patch and test? It adds
three minimal functions ffi.elemtypeof(), ffi.fieldtypeof(), and
ffi.fieldsof().
ffi.fieldsof() returns an iterator to retrieve the field names of a
composite type, which may then be passed to ffi.offsetof() and
ffi.fieldtypeof().
Please let me know if these minimal functions would be acceptable
maintainance-wise; then I will complete the contribution with
documentation.
Thanks,
Peter
diff --git a/src/lib_ffi.c b/src/lib_ffi.c
index 989fddd..7e61dc4 100644
--- a/src/lib_ffi.c
+++ b/src/lib_ffi.c
@@ -559,6 +559,100 @@ LJLIB_CF(ffi_typeof) LJLIB_REC(.)
return 1;
}
+LJLIB_CF(ffi_elemtypeof)
+{
+ CTState *cts = ctype_cts(L);
+ CTypeID id = ffi_checkctype(L, cts, L->base+1);
+ CType *ct = ctype_raw(cts, id);
+ if (ctype_isref(ct->info))
+ ct = ctype_rawchild(cts, ct);
+ if (ctype_ispointer(ct->info)) {
+ GCcdata *cd = lj_cdata_new(cts, CTID_CTYPEID, 4);
+ *(CTypeID *)cdataptr(cd) = ctype_cid(ct->info);
+ setcdataV(L, L->top-1, cd);
+ lj_gc_check(L);
+ return 1;
+ }
+ return 0;
+}
+
+LJLIB_CF(ffi_fieldtypeof)
+{
+ CTState *cts = ctype_cts(L);
+ CTypeID id = ffi_checkctype(L, cts, NULL);
+ GCstr *name = lj_lib_checkstr(L, 2);
+ CType *ct = lj_ctype_rawref(cts, id);
+ CTSize ofs;
+ if ((ctype_isstruct(ct->info) || ctype_isenum(ct->info)) &&
+ ct->size != CTSIZE_INVALID) {
+ CType *fct = lj_ctype_getfield(cts, ct, name, &ofs);
+ if (fct) {
+ GCcdata *cd = lj_cdata_new(cts, CTID_CTYPEID, 4);
+ *(CTypeID *)cdataptr(cd) = ctype_cid(fct->info);
+ setcdataV(L, L->top-1, cd);
+ lj_gc_check(L);
+ return 1;
+ }
+ }
+ return 0;
+}
+
+CType *ffi_fieldsof_next(CTState *cts, CType *ct, int *i)
+{
+ while (ct->sib) {
+ ct = ctype_get(cts, ct->sib);
+ if (gcref(ct->name) != NULL) {
+ if (*i == 0) return ct;
+ (*i)--;
+ }
+ if (ctype_isxattrib(ct->info, CTA_SUBTYPE)) {
+ CType *cct = ctype_child(cts, ct);
+ while (ctype_isattrib(cct->info)) {
+ cct = ctype_child(cts, cct);
+ }
+ cct = ffi_fieldsof_next(cts, cct, i);
+ if (cct != NULL) return cct;
+ }
+ }
+ return NULL;
+}
+
+static int ffi_fieldsof_iter(lua_State *L)
+{
+ CTState *cts = ctype_cts(L);
+ GCcdata *cd = cdataV(lj_lib_upvalue(L, 1));
+ CTypeID id = *(CTypeID *)cdataptr(cd);
+ CType *ct = lj_ctype_rawref(cts, id);
+ int i, n = numV(lj_lib_upvalue(L, 2)); /* FIXME why is intV() always 0? */
+ i = n;
+ ct = ffi_fieldsof_next(cts, ct, &i);
+ if (ct != NULL) {
+ setstrV(L, L->top++, strref(ct->name));
+ setintV(lj_lib_upvalue(L, 2), n+1);
+ lj_gc_check(L);
+ return 1;
+ }
+ return 0;
+}
+
+LJLIB_CF(ffi_fieldsof)
+{
+ CTState *cts = ctype_cts(L);
+ CTypeID id = ffi_checkctype(L, cts, NULL);
+ CType *ct = lj_ctype_rawref(cts, id);
+ if ((ctype_isstruct(ct->info) || ctype_isenum(ct->info)) &&
+ ct->size != CTSIZE_INVALID) {
+ GCcdata *cd = lj_cdata_new(cts, CTID_CTYPEID, 4);
+ *(CTypeID *)cdataptr(cd) = id;
+ setcdataV(L, L->top-1, cd);
+ setintV(L->top++, 0);
+ lua_pushcclosure(L, ffi_fieldsof_iter, 2);
+ lj_gc_check(L);
+ return 1;
+ }
+ return 0;
+}
+
LJLIB_CF(ffi_istype) LJLIB_REC(.)
{
CTState *cts = ctype_cts(L);
local ffi = require("ffi")
assert(ffi.elemtypeof("double") == nil)
assert(ffi.istype("double", ffi.elemtypeof("double[5]")))
assert(ffi.istype("double", ffi.elemtypeof("double[?]")))
assert(ffi.istype("float", ffi.elemtypeof("float (&)[3]")))
assert(ffi.istype("double[3]", ffi.elemtypeof("double[5][3]")))
assert(ffi.istype("double[3][2]", ffi.elemtypeof("double[5][3][2]")))
assert(ffi.istype("double", ffi.elemtypeof("double *")))
ffi.cdef[[struct foo { double x, y, z; }]]
local s = ffi.typeof("struct { double x; int y; float z; }")
assert(ffi.istype("double", ffi.fieldtypeof(s, "x")))
assert(ffi.istype("int", ffi.fieldtypeof(s, "y")))
assert(ffi.istype("float", ffi.fieldtypeof(s, "z")))
local iter = ffi.fieldsof(s)
assert(iter() == "x")
assert(iter() == "y")
assert(iter() == "z")
assert(iter() == nil)
local iter = ffi.fieldsof("struct { struct { struct { int a; }; int b; };
struct { int c; } d;}")
assert(iter() == "a")
assert(iter() == "b")
assert(iter() == "d")
assert(iter() == nil)
local e = ffi.typeof("enum { A, B }")
assert(ffi.istype("int", ffi.fieldtypeof(e, "A")))
assert(ffi.istype("int", ffi.fieldtypeof(e, "B")))
local iter = ffi.fieldsof(e)
assert(iter() == "A")
assert(iter() == "B")
assert(iter() == nil)
local u = ffi.typeof("union { int X; float Y; }")
assert(ffi.istype("int", ffi.fieldtypeof(u, "X")))
assert(ffi.istype("float", ffi.fieldtypeof(u, "Y")))
local iter = ffi.fieldsof(u)
assert(iter() == "X")
assert(iter() == "Y")
assert(iter() == nil)
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