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Add :pack and :pack-all keywords to allow for struct packing.

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Syntax may need some work but covers both fully packed structs
as well as packing of individual members.
This commit is contained in:
Calvin Rose 2022-06-10 18:53:22 -05:00
parent 33bb08d53b
commit 181f0341f5
1 changed files with 54 additions and 25 deletions
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79
src/core/ffi.c
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@ -84,11 +84,17 @@ struct JanetFFIType {
JanetFFIPrimType prim;
};
typedef struct {
JanetFFIType type;
size_t offset;
} JanetFFIStructMember;
struct JanetFFIStruct {
uint32_t size;
uint32_t align;
uint32_t field_count;
JanetFFIType fields[];
uint32_t is_aligned;
JanetFFIStructMember fields[];
};
/* Specifies how the registers are classified. This is used
@ -153,7 +159,7 @@ int struct_mark(void *p, size_t s) {
(void) s;
JanetFFIStruct *st = p;
for (uint32_t i = 0; i < st->field_count; i++) {
JanetFFIType t = st->fields[i];
JanetFFIType t = st->fields[i].type;
if (t.prim == JANET_FFI_TYPE_STRUCT) {
janet_mark(janet_wrap_abstract(t.st));
}
@ -243,18 +249,50 @@ static JanetFFIPrimType decode_ffi_prim(const uint8_t *name) {
static JanetFFIType decode_ffi_type(Janet x);
static JanetFFIStruct *build_struct_type(int32_t argc, const Janet *argv) {
/* Use :pack to indicate a single packed struct member and :pack-all
* to pack the remaining members */
int32_t member_count = argc;
int all_packed = 0;
for (int32_t i = 0; i < argc; i++) {
if (janet_keyeq(argv[i], "pack")) {
member_count--;
} else if (janet_keyeq(argv[i], "pack-all")) {
member_count--;
all_packed = 1;
}
}
JanetFFIStruct *st = janet_abstract(&janet_struct_type,
sizeof(JanetFFIStruct) + argc * sizeof(JanetFFIType));
st->field_count = argc;
sizeof(JanetFFIStruct) + argc * sizeof(JanetFFIStructMember));
st->field_count = member_count;
st->size = 0;
st->align = 1;
for (int32_t i = 0; i < argc; i++) {
st->fields[i] = decode_ffi_type(argv[i]);
size_t el_align = type_align(st->fields[i]);
size_t el_size = type_size(st->fields[i]);
if (el_align > st->align) st->align = el_align;
st->size = el_size + (((st->size + el_align - 1) / el_align) * el_align);
if (argc == 0) {
janet_panic("invalid empty struct");
}
uint32_t is_aligned = 1;
int32_t i = 0;
for (int32_t j = 0; j < argc; j++) {
int pack_one = 0;
if (janet_keyeq(argv[j], "pack") || janet_keyeq(argv[j], "pack-all")) {
pack_one = 1;
j++;
}
st->fields[i].type = decode_ffi_type(argv[j]);
size_t el_size = type_size(st->fields[i].type);
size_t el_align = type_align(st->fields[i].type);
if (all_packed || pack_one) {
if (st->size % el_align != 0) is_aligned = 0;
st->fields[i].offset = st->size;
st->size += el_size;
} else {
if (el_align > st->align) st->align = el_align;
st->fields[i].offset = (((st->size + el_align - 1) / el_align) * el_align);
st->size = el_size + st->fields[i].offset;
}
i++;
}
st->is_aligned = is_aligned;
return st;
}
@ -311,19 +349,14 @@ static void janet_ffi_write_one(void *to, const Janet *argv, int32_t n, JanetFFI
break;
case JANET_FFI_TYPE_STRUCT: {
JanetView els = janet_getindexed(argv, n);
uint32_t cursor = 0;
JanetFFIStruct *st = type.st;
if ((uint32_t) els.len != st->field_count) {
janet_panicf("wrong number of fields in struct, expected %d, got %d",
(int32_t) st->field_count, els.len);
}
for (int32_t i = 0; i < els.len; i++) {
JanetFFIType tp = st->fields[i];
size_t align = type_align(tp);
size_t size = type_size(tp);
cursor = ((cursor + align - 1) / align) * align;
janet_ffi_write_one(to + cursor, els.items, i, tp, recur - 1);
cursor += size;
JanetFFIType tp = st->fields[i].type;
janet_ffi_write_one(to + st->fields[i].offset, els.items, i, tp, recur - 1);
}
}
break;
@ -378,14 +411,9 @@ static Janet janet_ffi_read_one(const uint8_t *from, JanetFFIType type, int recu
case JANET_FFI_TYPE_STRUCT: {
JanetFFIStruct *st = type.st;
Janet *tup = janet_tuple_begin(st->field_count);
size_t cursor = 0;
for (uint32_t i = 0; i < st->field_count; i++) {
JanetFFIType tp = st->fields[i];
size_t align = type_align(tp);
size_t size = type_size(tp);
cursor = ((cursor + align - 1) / align) * align;
tup[i] = janet_ffi_read_one(from + cursor, tp, recur - 1);
cursor += size;
JanetFFIType tp = st->fields[i].type;
tup[i] = janet_ffi_read_one(from + st->fields[i].offset, tp, recur - 1);
}
return janet_wrap_tuple(janet_tuple_end(tup));
}
@ -452,9 +480,10 @@ static JanetFFIWordSpec sysv64_classify(JanetFFIType type) {
case JANET_FFI_TYPE_STRUCT: {
JanetFFIStruct *st = type.st;
if (st->size > 16) return JANET_SYSV64_MEMORY;
if (!st->is_aligned) return JANET_SYSV64_MEMORY;
JanetFFIWordSpec clazz = JANET_SYSV64_NO_CLASS;
for (uint32_t i = 0; i < st->field_count; i++) {
JanetFFIWordSpec next_class = sysv64_classify(st->fields[i]);
JanetFFIWordSpec next_class = sysv64_classify(st->fields[i].type);
if (next_class != clazz) {
if (clazz == JANET_SYSV64_NO_CLASS) {
clazz = next_class;