write structs and unions for tape

.gitignore

@@ -12,3 +12,6 @@ cachegrind.out.*
 # sometimes i make these files when benchmarking, don't want to accidentally commit them
 benchmark_result.txt
 valgrind.txt
+
+# thanks rust
+rustc-ice*.txt

simdnbt/src/borrow/mod.rs

@@ -3,6 +3,7 @@
 mod compound;
 mod list;
 mod tag_alloc;
+mod tape;
 
 use std::{io::Cursor, ops::Deref};
 

simdnbt/src/borrow/tape.rs

@@ -0,0 +1,95 @@
+pub struct Tape {
+    pub elements: Vec<TapeElement>,
+}
+
+#[repr(C)]
+pub union TapeElement {
+    kind: (TapeTagKind, TapeTagValue),
+
+    long: i64,
+    double: f64,
+}
+
+#[repr(C, packed)]
+#[derive(Copy, Clone)]
+pub union TapeTagValue {
+    byte: i8,
+    short: i16,
+    int: i32,
+    long: (), // value is in next tape element
+    float: f32,
+    double: (),                    // value is in next tape element
+    byte_array: u56,               // pointer to the original data
+    string: u56,                   // pointer to the original data
+    compound: (u24, UnalignedU32), // length estimate + tape index to the end of the compound
+    int_array: u56,                // pointer to the original data
+    long_array: u56,               // pointer to the original data
+
+    // lists
+    empty_list: (),
+    byte_list: u56,                     // pointer to the original data
+    short_list: u56,                    // pointer to the original data
+    int_list: u56,                      // pointer to the original data
+    long_list: u56,                     // pointer to the original data
+    float_list: u56,                    // pointer to the original data
+    double_list: u56,                   // pointer to the original data
+    byte_array_list: u56, // pointer to a fat pointer we keep elsewhere that points to the original data
+    string_list: u56,     // pointer to a fat pointer
+    list_list: (u24, UnalignedU32), // length estimate + tape index to the end of the list
+    compound_list: (u24, UnalignedU32), // length estimate + tape index to the end of the list
+    int_array_list: u56,  // pointer to a fat pointer
+    long_array_list: u56, // pointer to a fat pointer
+}
+
+#[derive(Debug, Copy, Clone)]
+#[repr(packed)]
+pub struct u56 {
+    a: u8,
+    b: u16,
+    c: u32,
+}
+#[derive(Debug, Copy, Clone)]
+#[repr(packed)]
+pub struct u48 {
+    a: u16,
+    b: u32,
+}
+#[derive(Debug, Copy, Clone)]
+#[repr(packed)]
+pub struct u24 {
+    a: u8,
+    b: u16,
+}
+#[derive(Debug, Copy, Clone)]
+#[repr(packed)]
+pub struct UnalignedU32(pub u32);
+
+#[derive(Clone, Copy)]
+#[repr(u8)]
+enum TapeTagKind {
+    Byte,
+    Short,
+    Int,
+    Long,
+    Float,
+    Double,
+    ByteArray,
+    String,
+    Compound,
+    IntArray,
+    LongArray,
+
+    EmptyList,
+    ByteList,
+    ShortList,
+    IntList,
+    LongList,
+    FloatList,
+    DoubleList,
+    ByteArrayList,
+    StringList,
+    ListList,
+    CompoundList,
+    IntArrayList,
+    LongArrayList,
+}