[clang] [NFC] [Serializer] Pack information in serializer (PR #69287)

[Vassil Vassilev via cfe-commits]

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@@ -2407,6 +2407,53 @@ class ASTReader
   bool isProcessingUpdateRecords() { return ProcessingUpdateRecords; }
 };
 
+/// A simple helper class to unpack an integer to bits and consuming
+/// the bits in order.
+class BitsUnpacker {
+  constexpr static uint32_t BitsIndexUpbound = 32;
+
+public:
+  BitsUnpacker(uint32_t V) { updateValue(V); }
+  BitsUnpacker(const BitsUnpacker &) = delete;
+  BitsUnpacker(BitsUnpacker &&) = delete;
+  BitsUnpacker operator=(const BitsUnpacker &) = delete;
+  BitsUnpacker operator=(BitsUnpacker &&) = delete;
+  ~BitsUnpacker() {
+#ifndef NDEBUG
+    while (isValid())
+      assert(!getNextBit() && "There are bits failed to read!");
+#endif
+  }
+
+  void updateValue(uint32_t V) {
+    Value = V;
+    CurrentBitsIndex = 0;
+  }
+
+  bool getNextBit() {
+    assert(isValid());
+    return Value & (1 << CurrentBitsIndex++);
+  }
+
+  uint32_t getNextBits(uint32_t Width) {
+    assert(isValid());
+    assert(Width < BitsIndexUpbound);
+    uint32_t Ret = (Value >> CurrentBitsIndex) & ((1 << Width) - 1);
+    CurrentBitsIndex += Width;
+    return Ret;
+  }
+
+  bool isValidToGetNextNBits(uint32_t Width) const {
----------------
vgvassilev wrote:

```suggestion
  bool canGetNextNBits(uint32_t Width) const {
```

https://github.com/llvm/llvm-project/pull/69287