Add marks and regex addressing systems

- Hook up parser to buffer edits.
- Other minor fixes.

include/internal/marks/marks.h

@@ -3,5 +3,55 @@
 #include "pch.h"
 
 namespace bed::internal::marks {
-struct MarksEngine {};
+struct MarksEngine {
+  uint64_t marks[1 << UINT8_WIDTH]{UINT64_MAX};
+
+  MarksEngine() {
+    for (auto &m : marks)
+      m = UINT64_MAX;
+  }
+
+  uint64_t get(uint8_t m) {
+    return marks[m];
+  }
+
+  void set(uint8_t m, uint64_t line) {
+    marks[m] = line;
+  }
+
+  void insert(uint64_t start, uint64_t count) {
+    for (uint16_t i = 0; i <= UINT8_MAX; ++i) {
+      if (marks[i] == UINT64_MAX)
+        continue;
+      if (marks[i] >= start)
+        marks[i] += count;
+    }
+  }
+
+  void erase(uint64_t start, uint64_t count) {
+    for (uint16_t i = 0; i <= UINT8_MAX; ++i) {
+      if (marks[i] == UINT64_MAX)
+        continue;
+      if (marks[i] >= start) {
+        if (marks[i] < start + count)
+          marks[i] = UINT64_MAX;
+        else
+          marks[i] -= count;
+      }
+    }
+  }
+
+  void collapse(uint64_t start, uint64_t count) {
+    for (uint16_t i = 0; i <= UINT8_MAX; ++i) {
+      if (marks[i] == UINT64_MAX)
+        continue;
+      if (marks[i] >= start) {
+        if (marks[i] < start + count)
+          marks[i] = start;
+        else
+          marks[i] -= count;
+      }
+    }
+  }
+};
 } // namespace bed::internal::marks