Remove build system test code, add generalized NBT model

This adds support for using the CXX and CXXFLAGS environment varibles, they work as you would expect.

build.sh

@@ -1,13 +1,40 @@
+#!/bin/bash
+
+if [ -z "$CXX" ]; then
+    CXX="c++"
+fi
+if [ -z "$CXXFLAGS" ]; then
+    CXXFLAGS="-std=c++20 -Wall"
+fi
+CXX_WITH_FLAGS="$CXX $CXXFLAGS"
+
+# `.cpp` files in src/lib will be automatically picked up and compiled into dynamic libraries.
 echo "Building libs..."
 mkdir -pv bin/lib
 for lib in $(find ./src/lib -name "*.cpp"); do
-    echo "Compiling $lib"
-    c++ -shared -o $(sed -e 's/^.\/src/.\/bin/;s/cpp$/so/' <<< $lib) $lib;
+    COMPILE_COMMAND="$CXX_WITH_FLAGS -shared -o $(sed -e 's/^.\/src/.\/bin/;s/cpp$/so/' <<< $lib) $lib"
+    echo $COMPILE_COMMAND
+    $COMPILE_COMMAND
 done
 
-echo "Building tools..."
-mkdir -pv bin/tools
+
 # Commands for every program need to be given individually because we can't
 # just add all shared libraries to all programs.
 # Or can we? Idk, cba to find out.
-c++ src/tools/dumpnbt.cpp -Lbin/lib -lnbt -o bin/tools/dumpnbt
+
+# How to build a tool: Tell the compiler where to find shared libraries and
+#       which libraries to use.
+# Example: shared libraries are in bin/lib => -Lbin/lib
+#       one of the libraries in that directory is libnbt.so
+#        => use with -lnbt (omit prefix lib and suffix .so)
+# How to run a tool: specify the library path to use for the dynamic linker
+#       when running a program
+# Example: LD_LIBRARY_PATH=bin/lib bin/tools/dumpnbt
+echo "Building tools..."
+mkdir -pv bin/tools
+# add compile commands to this variable
+COMPILE_COMMANDS="
+set -v
+$CXX_WITH_FLAGS src/tools/dumpnbt.cpp -Lbin/lib -lnbt -o bin/tools/dumpnbt
+"
+sh <<< $COMPILE_COMMANDS

src/lib/libnbt.cpp

@@ -1,3 +1,22 @@
-int blob() {
-    return 1;
+#include <bit>
+
+// This is just an example for how to find out if the system is big endian or little endian. Do not use this.
+int endianness_example() {
+    if constexpr (std::endian::native == std::endian::big)
+    {
+        // Big-endian system
+        return 0;
+    }
+    else if constexpr (std::endian::native == std::endian::little)
+    {
+        // Little-endian system
+        return 1;
+    }
+    else
+    {
+        // Something else
+        return 2;
+        // How did we even end up here?
+    }
 }
+

src/lib/libnbt.h

@@ -1 +1,20 @@
-int blob();
+// information taken from https://wiki.vg/NBT
+// This is an attempt at creating a uniform model for all NBT tags to allow for a uniform interface based on subclassing a single NBT tag super class.
+
+// NBT tags have a type (signed or unsigned?), optionally a name, optionally content type, optionally a size (signed), and content
+// Whether the type id byte is signed or not is unknown at this point. All other numbers are signed unless specified otherwise.
+// All tag types:
+// generic representation:  Tag(Byte:tag_type, String:name, byte[]:content, Byte:content_type, int32:size)
+// end:                     Tag( 0, "",          None,           0, 0) => used to determine the end of a compound tag, only the type gets stored
+// byte:                    Tag( 1, String:name, byte:content,   1, 1) => a single signed byte, size and content type not stored
+// int16:                   Tag( 2, String:name, int16:content,  2, 2) => big endian signed 16 bit integer, size and content type not stored
+// int32:                   Tag( 3, String:name, int32:content,  3, 4) => big endian signed 32 bit integer, size and content type not stored
+// int64:                   Tag( 4, String:name, int64:content,  4, 8) => big endian signed 64 bit integer, size and content type not stored
+// float32:                 Tag( 5, String:name, float32:content,5, 4) => big endian 32 bit floating point number, size and content type not stored
+// float64:                 Tag( 6, String:name, float64:content,6, 8) => big endian 64 bit floating point number, size and content type not stored
+// byte[]:                  Tag( 7, String:name, byte[]:content, 1, int32:size) => content stored prefixed with size, content type not stored
+// String:                  Tag( 8, String:name, byte[]:content, 8, uint16:size) => Java style modified UTF-8 string, size is unique bc it's 16 bit and unsigned, content stored prefixed with size, content type not stored
+// Tag[] (list):            Tag( 9, String:name, Tag[]:content,  byte:content_type, int32:size) => list of nameless tags of the same type prefixed by (in order) content type and size, no closer specification as to what namelessness entails
+// Tag[] (compound):        Tag(10, String:name, Tag[]:content,  None, int32:size) => list of tags, last tag is always an end tag, size and content type not stored
+// int32[]:                 Tag(11, String:name, int32[]:content,3, int32:size) => list of 32 bit signed integers prefixed with its size, content type not stored, endianness unknown at this point
+// int64[]:                 Tag(12, String:name, int64[]:content,4, int32:size) => list of 64 bit signed integers prefixed with its size, content type not stored, endianness unknown at this point

src/tools/dumpnbt.cpp

@@ -1,5 +1,5 @@
 #include "../lib/libnbt.h"
 
 int main(int argc, char* argv[]) {
-    return blob();
+    return 0;
 }