refactor: subdividing IOException.

src/io/io_base.h

@@ -17,6 +17,30 @@ public:
     constexpr std::string category() const { return "exception.io"; }
 };
 
+class OutOfBoundException : public IOException {
+public:
+    explicit OutOfBoundException(size_t op, size_t buffer_size)
+    : IOException("An attempt was made to move the read pointer outside the "
+                  "buffer bounds.") {
+        add_context_v_hex("op", op);
+        add_context_v_hex("buffer_size", buffer_size);
+    }
+
+    constexpr std::string category() const { return "exception.io.outofbound"; }
+};
+
+class CorruptedVarIntException : public IOException {
+public:
+    explicit CorruptedVarIntException(std::string_view msg, size_t position)
+    : IOException("{}", msg) {
+        add_context_v_hex("position", position);
+    }
+
+    constexpr std::string category() const {
+        return "exception.io.corruptedvarint";
+    }
+};
+
 class UnableToOpenException : public UnixException {
 public:
     explicit UnableToOpenException(const fs::path& path) {

src/io/streamed_io.h

@@ -17,7 +17,7 @@ public:
     template <TriviallyCopyable T>
     constexpr T get() {
         if (m_position + sizeof(T) > m_buffer.size()) {
-            throw IOException("Read attempt is out of buffer bounds.");
+            throw OutOfBoundException(sizeof(T), m_buffer.size());
         }
         T value;
 
@@ -41,10 +41,16 @@ public:
 
         while (true) {
             if (m_position >= m_buffer.size()) {
-                throw IOException("Incomplete VarInt at end of buffer.");
+                throw CorruptedVarIntException(
+                    "Incomplete VarInt at end of buffer.",
+                    m_position
+                );
             }
             if (shift >= max_shift) {
-                throw IOException("VarInt is too long for the requested type.");
+                throw CorruptedVarIntException(
+                    "VarInt is too long for the requested type.",
+                    m_position
+                );
             }
 
             auto byte  = static_cast<std::byte>(m_buffer[m_position++]);
@@ -87,7 +93,7 @@ public:
 
     constexpr void seek(size_t pos) {
         if (pos > m_buffer.size()) {
-            throw IOException("Seek position is out of buffer bounds.");
+            throw OutOfBoundException(pos, m_buffer.size());
         }
         m_position = pos;
     }
@@ -98,7 +104,7 @@ public:
 
     constexpr size_t position() const { return m_position; }
 
-    std::string const& data() const { return m_buffer; }
+    std::string& underlying() { return m_buffer; }
 
 private:
     std::string m_buffer;