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swap order of nbt_proctag and nbt_nexttag

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Quinn
2025-08-26 11:24:36 +02:00
parent 4e230ae856
commit 2f68574aea
2 changed files with 88 additions and 85 deletions
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166
src/dat/nbt.c
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@@ -4,6 +4,7 @@
#include <assert.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include "../util/compat/endian.h"
@@ -11,6 +12,89 @@
#define MAX_DEPTH 512
/* Processes the incoming array data in `buf`. Which contains `nmem` items of `size`.
* The data shall be converted to little-endian on little-endian systems
* Outputs the allocated data to `out`, returns where the next pointer would be. */
static const u8 *procarr(const u8 *restrict buf, i32 nmem, uint size, struct nbt_array *restrict *restrict out) {
size_t len = nmem * size;
*out = malloc(sizeof(struct nbt_array) + len);
if (!*out) return buf + len;
memcpy((*out)->dat, buf, len);
(*out)->len = nmem;
buf += len;
/* 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 buf;
size_t i = 0;
while (i < len) {
switch (size) {
case 2: *(u16 *)((*out)->dat + i) = be16toh(*(u16 *)((*out)->dat + i)); break;
case 4: *(u32 *)((*out)->dat + i) = be32toh(*(u32 *)((*out)->dat + i)); break;
case 8: *(u64 *)((*out)->dat + i) = be64toh(*(u64 *)((*out)->dat + i)); break;
default: __builtin_unreachable(); // this should be impossible
}
i += size;
}
#endif
return buf;
}
/* calls `procarr` for the simple types available. */
static const u8 *proclist(const u8 *restrict buf, struct nbt_array *restrict *restrict out) {
uint size;
*out = NULL;
switch (*buf) {
case NBT_I8: size = 1; break;
case NBT_I16: size = 2; break;
case NBT_I32: // fall through
case NBT_F32: size = 4; break;
case NBT_I64: // fall though
case NBT_F64: size = 8; break;
default: return NULL;
}
buf++;
i32 len = (i32)be32toh(*(u32 *)buf);
buf += 4;
return procarr(buf, len, size, out);
}
const u8 *nbt_proctag(const u8 *restrict buf, u16 slen, void *restrict out) {
const u8 *ptr, *tmp;
ptr = buf + 3 + slen;
i32 nmem;
uint size;
switch (*buf) {
case NBT_I8: *(u8 *)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 *)out = be16toh(*(u32 *)ptr); return ptr + 4;
case NBT_I64: // fall through
case NBT_F64: *(u64 *)out = be16toh(*(u64 *)ptr); return ptr + 8;
case NBT_STR: nmem = be16toh(*(u16 *)ptr), size = 1, ptr += 2; break;
case NBT_ARR_I8: nmem = be32toh(*(u32 *)ptr), size = 1, ptr += 4; break;
case NBT_ARR_I32: nmem = be32toh(*(u32 *)ptr), size = 4, ptr += 4; break;
case NBT_ARR_I64: nmem = be32toh(*(u32 *)ptr), size = 8, ptr += 4; break;
case NBT_LIST:
return proclist(ptr, (struct nbt_array **)out);
return tmp;
default: return NULL;
}
return procarr(ptr, nmem, size, (struct nbt_array **)out);
}
/* handles incrementing to the next tag in the case of `NBT_LIST`. This function shan't return `NULL`.
* `ptr` is assumed to be the start of the `NBT_LIST` data, e.i. The list's ID, followed by the list's length.
* If `ID` is `NBT_I8`, `NBT_I16`, `NBT_I32`, `NBT_I64`, `NBT_F32`, or `NBT_F64`, the entire list length is computed and returned.
@@ -97,85 +181,3 @@ const u8 *nbt_nexttag(const u8 *restrict buf) {
} while (dpt > 0);
return tag;
}
/* Processes the incoming array data in `buf`. Which contains `nmem` items of `size`.
* The data shall be converted to little-endian on little-endian systems
* Outputs the allocated data to `out`, returns where the next pointer would be. */
static const u8 *procarr(const u8 *restrict buf, i32 nmem, uint size, struct nbt_array *restrict *restrict out) {
size_t len = nmem * size;
*out = malloc(sizeof(struct nbt_array) + len);
if (!*out) return buf + len;
memcpy((*out)->dat, buf, len);
(*out)->len = nmem;
buf += len;
/* 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 buf;
size_t i = 0;
while (i < len) {
switch (size) {
case 2: *(u16 *)((*out)->dat + i) = be16toh(*(u16 *)((*out)->dat + i)); break;
case 4: *(u32 *)((*out)->dat + i) = be32toh(*(u32 *)((*out)->dat + i)); break;
case 8: *(u64 *)((*out)->dat + i) = be64toh(*(u64 *)((*out)->dat + i)); break;
default: __builtin_unreachable(); // this should be impossible
}
i += size;
}
#endif
return buf;
}
/* calls `procarr` for the simple types available. */
static const u8 *proclist(const u8 *restrict buf, struct nbt_array *restrict *restrict out) {
uint size;
*out = NULL;
switch (*buf) {
case NBT_I8: size = 1; break;
case NBT_I16: size = 2; break;
case NBT_I32: // fall through
case NBT_F32: size = 4; break;
case NBT_I64: // fall though
case NBT_F64: size = 8; break;
default: return NULL;
}
buf++;
i32 len = (i32)be32toh(*(u32 *)buf);
buf += 4;
return procarr(buf, len, size, out);
}
const u8 *nbt_proctag(const u8 *restrict buf, u16 slen, void *restrict out) {
const u8 *ptr, *tmp;
ptr = buf + 3 + slen;
i32 nmem;
uint size;
switch (*buf) {
case NBT_I8: *(u8 *)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 *)out = be16toh(*(u32 *)ptr); return ptr + 4;
case NBT_I64: // fall through
case NBT_F64: *(u64 *)out = be16toh(*(u64 *)ptr); return ptr + 8;
case NBT_STR: nmem = be16toh(*(u16 *)ptr), size = 1, ptr += 2; break;
case NBT_ARR_I8: nmem = be32toh(*(u32 *)ptr), size = 1, ptr += 4; break;
case NBT_ARR_I32: nmem = be32toh(*(u32 *)ptr), size = 4, ptr += 4; break;
case NBT_ARR_I64: nmem = be32toh(*(u32 *)ptr), size = 8, ptr += 4; break;
case NBT_LIST:
return proclist(ptr, (struct nbt_array **)out);
return tmp;
default: return NULL;
}
return procarr(ptr, nmem, size, (struct nbt_array **)out);
}

7
src/dat/nbt.h
View File

@@ -41,9 +41,6 @@ struct nbt_array {
u8 dat[];
};
/* searches for the end of a named tag without processing data, the final pointer is returned.
* `NULL` is returned upon failure, the otherwise returned pointer is not guaranteed to be valid. */
const u8 *nbt_nexttag(const u8 *restrict buf) NONNULL((1)) PURE;
/* Acquires the data contained by the named tag.
* - `buf` points to the start of the tag.
@@ -53,3 +50,7 @@ const u8 *nbt_nexttag(const u8 *restrict buf) NONNULL((1)) PURE;
* to have the available byte width for one of these types. In the case of `NBT_ARR*` and `NBT_LIST`
* it must point to a `struct nbt_array*`. Where in the case of `NBT_LIST`, it must be one of the previous static-width types. */
const u8 *nbt_proctag(const u8 *restrict buf, u16 slen, void *restrict out) NONNULL((1, 3));
/* searches for the end of a named tag without processing data, the final pointer is returned.
* `NULL` is returned upon failure, the otherwise returned pointer is not guaranteed to be valid. */
const u8 *nbt_nexttag(const u8 *restrict buf) NONNULL((1)) PURE;