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66 lines
3.0 KiB
C
66 lines
3.0 KiB
C
// Copyright (c) 2025 Quinn
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// Licensed under the MIT Licence. See LICENSE for details
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#pragma once
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#include <assert.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include "../util/atrb.h"
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#include "../util/compat/endian.h"
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#include "../util/types.h"
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/* NBT (named binary tag) is a tree data structure. Tags have a numeric type ID, name and a payload.
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* NBT files are a compressed `compound` tag. GZip is the compression used in most cases,
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* in some (rare) cases it's stored uncompressed.
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* A tag is an individual part of the data tree.
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* The first byte is the ID, followed by a `u16`, for the length of the name.
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* Then the name as `UTF-8`. (end tag does not contain name) */
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/* specifies the NBT tag IDs.
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* NOTE: every type is stored as BE (big-endian) in the file. */
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enum nbt_tagid {
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NBT_END = 0x00, // signifies the end of a compound tag
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NBT_I8 = 0x01, // next byte is for an 8 bit signed integer.
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NBT_I16 = 0x02, // next 2 bytes are for a 16 bit signed integer
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NBT_I32 = 0x03, // next 4 bytes are for a 32 bit signed integer
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NBT_I64 = 0x04, // next 8 bytes are for a 64 bit signed integer
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NBT_F32 = 0x05, // next 4 bytes are for a single-precision floating-point
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NBT_F64 = 0x06, // next 8 bytes are for a double-precision floating-point
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NBT_ARR_I8 = 0x07, // starts with a i32, denoting size, followed by the i8 data
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NBT_STR = 0x08, // starts with a u16, denoting size, followed by the UTF-8 data
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NBT_LIST = 0x09, // starts with an ID, followed by a 32 bit signed integer denoting the size
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NBT_COMPOUND = 0x0A, // compound tag, contains tags and is delimited by `NBT_END`
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NBT_ARR_I32 = 0x0B, // starts with a i32, denoting size, followed by the i32 data
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NBT_ARR_I64 = 0x0C, // starts with a i32, denoting size, followed by the u32 data
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};
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struct nbt_path {
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const char **restrict pat; // specifies the NBT path components as separate elements
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i16 len; // specifies the length of the NBT elements
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};
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/* gets the tag size of primitive types, returns `>0` on success, `<0` on failure */
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CONST int nbt_primsize(u8 tag);
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/* checks whether the tag is a primitive data tag. (not recommended for filtering tags, use a `switch`)
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* returns a boolean value. */
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CONST int nbt_isprim(u8 tag);
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/* returns the name length of a specific tag. `buf` is the pointer to start of the tag */
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atrb_pure atrb_nonnull(1) static inline u16 nbt_namelen(const u8 *restrict buf) {
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assert(*buf != NBT_END);
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return be16toh(*(u16 *)(buf + 1));
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}
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/* returns the (expected) pointer of the tag following this one.
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* `NULL` is returned if anything went wrong. */
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atrb_pure atrb_nonnull(1) const u8 *nbt_nexttag(const u8 *restrict buf, u16 naml);
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/* gets the byte size of an NBT tag's data (excluding id and name), returns `0` upon error. */
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atrb_pure size_t nbt_tagdatlen(const u8 *buf);
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/* processes the uncompressed `NBT` data in `buf`, with a size of `len`. */
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atrb_nonnull(1, 3) int nbt_proc(struct nbt_path const *restrict paths, uint npaths, const u8 *restrict buf, size_t len);
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