update README to include (some) planned features

I was very mistaken, and I feel like an idiot.

docs/README.md

@@ -6,9 +6,7 @@ A from-scratch rewrite of [mcaselector](https://github.com/Querz/mcaselector) in
 
 [![licence](https://img.shields.io/github/license/thepigeongenerator/mcaselector-lite.svg)](https://github.com/thepigeongenerator/mcaselector-lite/blob/main/LICENSE)
 [![issues](https://img.shields.io/github/issues/thepigeongenerator/mcaselector-lite.svg)](https://github.com/thepigeongenerator/mcaselector-lite/issues/)
-
 [![CI](https://github.com/thepigeongenerator/mcaselector-lite/actions/workflows/ci.yaml/badge.svg)](https://github.com/thepigeongenerator/mcaselector-lite/actions/workflows/ci.yaml)
-[![release](https://github.com/thepigeongenerator/mcaselector-lite/actions/workflows/release.yaml/badge.svg)](https://github.com/thepigeongenerator/mcaselector-lite/actions/workflows/release.yaml)
 
 ## what does it do
 MCA selector lite is a tool used to edit [region files](https://minecraft.wiki/w/Region_file_format) of your [Minecraft java](https://minecraft.wiki/w/Java_Edition) worlds.
@@ -20,3 +18,7 @@ MCA selector is a tool written in Java. Where it depends upon JRE21 and JavaFX.
 The goal of this project is to create a version of the original MCA selector, but written in C, leveraging the improved performance due to native execution and more low-level control.
 I have picked C as the language for the core portions of the application, where I prefer fine-grained control with little abstractions.
 This version is not intended to serve to entirely replace MCA selector, just to offer an alternative. Both tools will have their strengths and weaknesses.
+
+# planned features
+- [ ] CLI-only version
+- [ ] filtering chunks based on time spent in them

src/dat/nbt.c

@@ -7,10 +7,76 @@
 #include "../util/compat/endian.h"
 #include "../util/types.h"
 
+int nbt_primsize(u8 tag) {
+	switch (tag) {
+	case NBT_I8:  return 1;
+	case NBT_I16: return 2;
+	case NBT_I32: // fall through
+	case NBT_F32: return 4;
+	case NBT_I64: // fall through
+	case NBT_F64: return 8;
+	default:      return -1;
+	}
+}
+
+const u8 *nbt_nextcompound(const u8 *restrict cdat) {
+	return NULL;
+}
+
+const u8 *nbt_nextlist(const u8 *restrict ldat) {
+	const u8 *ptr = ldat + 5;
+	i32 len = be32toh(*(u32 *)(ldat + 1));
+
+	switch (*ldat) {
+	case NBT_I8:
+	case NBT_I16:
+	case NBT_I32:
+	case NBT_I64:
+	case NBT_F32:
+	case NBT_F64:
+		return ptr + nbt_primsize(*ldat) * len;
+
+	// loop for each compound, whilst `ptr` isn't `NULL`
+	case NBT_COMPOUND: {
+		for (u32 i = 0; i < (u32)len && ptr; i++) {
+			ptr = nbt_nextcompound(ptr);
+		}
+		return ptr;
+	}
+
+	// TODO: implement list/array/string handling
+	case NBT_STR:
+	case NBT_ARR_I8:
+	case NBT_ARR_I32:
+	case NBT_ARR_I64:
+	case NBT_LIST:
+	default:
+		return NULL;
+	}
+}
+
 const u8 *nbt_nexttag(const u8 *restrict buf, u16 naml) {
-	size_t len = nbt_tagdatlen(buf);
+	const u8 *ptr = buf + naml + 3;
-	if (!len) return NULL; // TODO: compound tags should be handled here
+	size_t mems = 0;
-	return buf + naml + len + 3;
+
+	switch (*buf) {
+	case NBT_I8:
+	case NBT_I16:
+	case NBT_I32:
+	case NBT_F32:
+	case NBT_I64:
+	case NBT_F64:
+		return ptr + nbt_primsize(*buf);
+
+	case NBT_ARR_I64: mems += sizeof(i64) - sizeof(i32); __attribute__((fallthrough));
+	case NBT_ARR_I32: mems += sizeof(i32) - sizeof(i8); __attribute__((fallthrough));
+	case NBT_ARR_I8:  return ptr + ++mems * (i32)be32toh(*(u32 *)(ptr)) + 4;
+
+	case NBT_STR:  return ptr + be16toh(*(u16 *)(ptr)) + 2;
+	case NBT_LIST: return nbt_nextlist(ptr);
+
+	default: return NULL;
+	}
 }
 
 // TODO: not actually doing anything
@@ -95,56 +161,3 @@ int nbt_proc(struct nbt_path const *restrict pats, uint npats, const u8 *restric
 	// TODO: finish function
 	return !dpt;
 }
-
-int nbt_primsize(u8 tag) {
-	switch (tag) {
-	case NBT_I8:  return 1;
-	case NBT_I16: return 2;
-	case NBT_I32: // fall through
-	case NBT_F32: return 4;
-	case NBT_I64: // fall through
-	case NBT_F64: return 8;
-	default:      return -1;
-	}
-}
-
-size_t nbt_tagdatlen(const u8 *restrict buf) {
-	size_t mems = 0;
-
-	switch (*buf) {
-	case NBT_I8:
-	case NBT_I16:
-	case NBT_I32:
-	case NBT_F32:
-	case NBT_I64:
-	case NBT_F64:
-		mems = nbt_primsize(*buf);
-		return -(mems >= 0) & mems;
-
-	case NBT_ARR_I64: mems += sizeof(i64) - sizeof(i32); __attribute__((fallthrough));
-	case NBT_ARR_I32: mems += sizeof(i32) - sizeof(i8); __attribute__((fallthrough));
-	case NBT_ARR_I8:  return +mems * (i32)be32toh(*(u32 *)(buf)) + 4;
-
-	case NBT_STR: return be16toh(*(u16 *)buf) + 2;
-
-	case NBT_LIST:
-		mems = nbt_primsize(*buf);
-		if (mems > 0) return mems * (i32)be32toh(*(u32 *)(buf + 1)) + 5;
-		return 0;
-	default: return 0;
-	}
-}
-
-int nbt_isprim(u8 tag) {
-	switch (tag) {
-	case NBT_I8:
-	case NBT_I16:
-	case NBT_I32:
-	case NBT_F32:
-	case NBT_I64:
-	case NBT_F64:
-		return 1;
-	default:
-		return 0;
-	}
-}

src/dat/nbt.h

@@ -41,6 +41,20 @@ struct nbt_path {
 	i16 len;                   // specifies the length of the NBT elements
 };
 
+/* searches for the end of a compound tag without processing data, the final pointer is returned.
+ * `NULL` is returned upon failure, the otherwise returned pointer is not guaranteed to be valid.
+ * `cdat` is assumed to be the start of the **compound tag's data**. */
+PURE NONNULL((1)) const u8 *nbt_nextcompound(const u8 *restrict cdat);
+
+/* searches for the end of a list tag without processing data, the final pointer is returned.
+ * `NULL` is returned upon failure, the otherwise returned pointer is not guaranteed to be valid.
+ * `ldat` is assumed to be the start of the **list tag's data.** */
+PURE NONNULL((1)) const u8 *nbt_nextlist(const u8 *restrict ldat);
+
+/* 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. */
+PURE NONNULL((1)) const u8 *nbt_nexttag(const u8 *restrict buf, u16 naml);
+
 /* returns the name length of a specific tag. `buf` is the pointer to start of the tag */
 atrb_pure atrb_nonnull(1) static inline u16 nbt_namelen(const u8 *restrict buf) {
 	assert(*buf != NBT_END);
@@ -51,13 +65,6 @@ atrb_pure atrb_nonnull(1) static inline u16 nbt_namelen(const u8 *restrict buf)
  * `NULL` is returned if anything went wrong. */
 atrb_pure atrb_nonnull(1) const u8 *nbt_nexttag(const u8 *restrict buf, u16 naml);
 
-/* checks whether the tag is a primitive data tag. (not recommended for filtering tags, use a `switch`)
- * returns a boolean value. */
-atrb_const int nbt_isprim(u8 tag);
-
-/* gets the byte size of an NBT tag's data (excluding id and name), returns `0` upon error. */
-atrb_pure size_t nbt_tagdatlen(const u8 *buf);
-
 /* gets the tag size of primitive types, returns `>0` on success, `<0` on failure */
 atrb_const int nbt_primsize(u8 tag);