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continue working on nbt_proctag focussing on array processing.

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Quinn
2025-08-22 13:02:12 +02:00
parent 9996e84ef5
commit f1ea7dcef8
1 changed files with 44 additions and 16 deletions
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60
src/dat/nbt.c
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@@ -98,34 +98,62 @@ const u8 *nbt_nexttag(const u8 *restrict buf) {
return tag;
}
MALLOC static void *nbt_procarr(const u8 *restrict buf, i32 nmem, uint size) {
u8 *ptr = malloc(nmem * size);
if (!ptr) NULL;
memcpy(ptr, buf, nmem * size);
/* Only include this code for little-endian systems. Since only they require this logic.
* Producing optimised code for other platforms. */
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
if (size == 1) return ptr;
ssize_t i = 0;
while (i < nmem) {
switch (size) {
case 2:
*(u16 *)(ptr + i) = be16toh(*(u16 *)(ptr + i));
i += 2;
break;
case 4:
*(u32 *)(ptr + i) = be32toh(*(u32 *)(ptr + i));
i += 4;
break;
case 8:
*(u64 *)(ptr + i) = be64toh(*(u64 *)(ptr + i));
i += 8;
break;
default: __builtin_unreachable(); // this should be impossible
}
}
#endif
return ptr;
}
// TODO: not actually doing anything
/* readies the output data for export, returns the new buffer position, or `NULL` upon an error (may be out of bounds) */
static const u8 *nbt_proctag(const u8 *restrict buf, u16 slen) {
static const u8 *nbt_proctag(const u8 *restrict buf, u8 *restrict out, u16 slen) {
const u8 *ptr = buf + 3 + slen;
u8 dat[8];
size_t arrlen = 0;
switch (*buf) {
// integral types
case NBT_I8: *dat = *ptr; return ptr + 1;
case NBT_I16: *(u16 *)dat = be16toh(*(u16 *)ptr); return ptr + 2;
case NBT_I8: *out = *ptr; return ptr + 1;
case NBT_I16: *(u16 *)out = be16toh(*(u16 *)ptr); return ptr + 2;
case NBT_I32: // fall through
case NBT_F32: *(u32 *)dat = be16toh(*(u32 *)ptr); return ptr + 4;
case NBT_F32: *(u32 *)out = be16toh(*(u32 *)ptr); return ptr + 4;
case NBT_I64: // fall through
case NBT_F64: *(u64 *)dat = be16toh(*(u64 *)ptr); return ptr + 8;
case NBT_F64: *(u64 *)out = be16toh(*(u64 *)ptr); return ptr + 8;
// arrays, handled differently
case NBT_LIST:
case NBT_ARR_I8:
case NBT_STR:
case NBT_ARR_I32:
case NBT_ARR_I64:
// TODO: arrlen = nbt_arrbsize(ptr);
break;
case NBT_STR: *(void **)out = nbt_procarr(ptr += 2, be16toh(*(u16 *)buf), 1); break;
case NBT_ARR_I8: *(void **)out = nbt_procarr(ptr += 4, be32toh(*(u32 *)buf), 1); break;
case NBT_ARR_I32: *(void **)out = nbt_procarr(ptr += 4, be32toh(*(u32 *)buf), 4); break;
case NBT_ARR_I64: *(void **)out = nbt_procarr(ptr += 8, be32toh(*(u64 *)buf), 8); break;
default: return NULL;
case NBT_LIST: // TODO: handle simple lists
default:
return NULL;
}
if (!arrlen) return NULL;
return ptr; // TODO: return end of array
}