CE Implement line editing

ce/gapbuffer.c

@@ -0,0 +1,126 @@
+#include "gapbuffer.h"
+#include "arena_alloc.h"
+#include <liballoc.h>
+#include <stddef.h>
+#include <string.h>
+
+void gapbuffer_init (struct gapbuffer* gb, size_t capacity) {
+  gb->buffer = arena_malloc (&arena, capacity);
+
+  if (gb->buffer == NULL)
+    return;
+
+  memset (gb->buffer, 0, capacity);
+  gb->size = capacity;
+  gb->gap_start = 0;
+  gb->gap_end = capacity;
+}
+
+void gapbuffer_fini (struct gapbuffer* gb) { memset (gb, 0, sizeof (*gb)); }
+
+void gapbuffer_grow (struct gapbuffer* gb) {
+  size_t old_size = gb->size;
+  size_t new_size = gb->size * 2;
+
+  char* new = arena_realloc (&arena, gb->buffer, old_size, new_size);
+
+  if (new == NULL)
+    return;
+
+  gb->buffer = new;
+
+  size_t post_gap_size = old_size - gb->gap_end;
+  size_t new_gap_end = new_size - post_gap_size;
+
+  memmove (gb->buffer + new_gap_end, gb->buffer + gb->gap_end, post_gap_size);
+
+  gb->gap_end = new_gap_end;
+  gb->size = new_size;
+}
+
+void gapbuffer_move (struct gapbuffer* gb, size_t pos) {
+  if (pos > (gb->size - (gb->gap_end - gb->gap_start)))
+    pos = (gb->size - (gb->gap_end - gb->gap_start));
+
+  while (gb->gap_start > pos) {
+    gb->gap_start--;
+    gb->gap_end--;
+    gb->buffer[gb->gap_end] = gb->buffer[gb->gap_start];
+  }
+
+  while (gb->gap_start < pos) {
+    gb->buffer[gb->gap_start] = gb->buffer[gb->gap_end];
+    gb->gap_start++;
+    gb->gap_end++;
+  }
+}
+
+void gapbuffer_insert (struct gapbuffer* gb, char c) {
+  if (gb->gap_start == gb->gap_end)
+    gapbuffer_grow (gb);
+
+  gb->buffer[gb->gap_start] = c;
+  gb->gap_start++;
+}
+
+void gapbuffer_backspace (struct gapbuffer* gb) {
+  if (gb->gap_start > 0)
+    gb->gap_start--;
+}
+
+char* gapbuffer_get_string (struct gapbuffer* gb) {
+  size_t size = gb->size - (gb->gap_end - gb->gap_start);
+
+  char* str = arena_malloc (&arena, size + 1);
+
+  if (str == NULL)
+    return NULL;
+
+  memcpy (str, gb->buffer, gb->gap_start);
+
+  memcpy (str + gb->gap_start, gb->buffer + gb->gap_end, gb->size - gb->gap_end);
+
+  str[size] = '\0';
+  return str;
+}
+
+size_t gapbuffer_length (struct gapbuffer* gb) { return gb->size - (gb->gap_end - gb->gap_start); }
+
+char* gapbuffer_string_at (struct gapbuffer* gb, size_t pos) {
+  size_t total_size = gapbuffer_length (gb);
+
+  if (pos >= total_size)
+    return "";
+
+  size_t tail_size = total_size - pos;
+
+  char* res = arena_malloc (&arena, tail_size + 1);
+
+  if (res == NULL)
+    return NULL;
+
+  size_t written = 0;
+
+  if (pos < gb->gap_start) {
+    size_t copy = gb->gap_start - pos;
+
+    if (copy > tail_size)
+      copy = tail_size;
+
+    memcpy (res, &gb->buffer[pos], copy);
+    written += copy;
+    pos += copy;
+  }
+
+  if (written < tail_size) {
+    size_t gap_size = gb->gap_end - gb->gap_start;
+    size_t phys_pos = pos + gap_size;
+
+    size_t copy = tail_size - written;
+    memcpy (&res[written], &gb->buffer[phys_pos], copy);
+    written += copy;
+  }
+
+  res[written] = '\0';
+  return res;
+}