Perfect

- Make original buffer use a disk backed mapping to save memory.
- rearrange api function headers for search etc.
- fix bugs with iterators.
- support uint64_t for all byte and line offsets to allow for much larger files to be opened.
- and more minor bug fixes.

include/vase/buffer/append.h

@@ -8,16 +8,16 @@ struct AppendBuffer : Buffer {
   using TChunk = char[APPEND_CHUNK_SIZE];
   std::vector<TChunk *> buf;
   TChunk *t_current;
-  uint32_t current_offset{0};
-  uint32_t t_offset{0};
+  uint64_t current_offset{0};
+  uint64_t t_offset{0};
 
   AppendBuffer();
 
   ~AppendBuffer();
 
-  uint32_t key(char c);
-  uint32_t append(const char *text, uint32_t length);
+  uint64_t append(char c);
+  uint64_t append(const char *text, uint64_t length);
 
-  const char *read(uint32_t pos, uint32_t *out_len);
-  inline uint32_t length();
+  const char *read(uint64_t pos, uint64_t *out_len);
+  inline uint64_t length();
 };