perf: optimize hot-path loops, data structures, and cache locality

1 files changed, 11 insertions, 14 deletions

diff --git a/src/wayland/clipboard.c b/src/wayland/clipboard.c
index 7df1a70..e3eec0f 100644
--- a/src/wayland/clipboard.c
+++ b/src/wayland/clipboard.c
@@ -118,21 +118,18 @@ static int transfer_io(int fd, short events, void *ud)
         if (t->offset == t->len || n == 0 ||
             (n < 0 && errno != EAGAIN && errno != EINTR)) transfer_destroy(t);
     } else {
-        char buf[8192];
-        ssize_t n = read(fd, buf, sizeof(buf));
+        if (t->capacity - t->len < 4096) {
+            size_t capacity = t->capacity ? t->capacity * 2 : 8192;
+            if (capacity > CLIPBOARD_TEXT_MAX) capacity = CLIPBOARD_TEXT_MAX;
+            if (capacity <= t->len) { transfer_destroy(t); return 0; }
+            char *text = realloc(t->text, capacity);
+            if (!text) { transfer_destroy(t); return 0; }
+            t->text = text;
+            t->capacity = capacity;
+        }
+        ssize_t n = read(fd, t->text + t->len, t->capacity - t->len);
         if (n > 0) {
-            size_t need = t->len + (size_t)n;
-            if (need > CLIPBOARD_TEXT_MAX) { transfer_destroy(t); return 0; }
-            if (need > t->capacity) {
-                size_t capacity = t->capacity ? t->capacity * 2 : sizeof(buf);
-                if (capacity > CLIPBOARD_TEXT_MAX) capacity = CLIPBOARD_TEXT_MAX;
-                char *text = realloc(t->text, capacity);
-                if (!text) { transfer_destroy(t); return 0; }
-                t->text = text;
-                t->capacity = capacity;
-            }
-            memcpy(t->text + t->len, buf, (size_t)n);
-            t->len += n;
+            t->len += (size_t)n;
         } else if (n == 0) {
             t->owner->receive(t->text ? t->text : "", t->len, t->uri_list,
                               t->drop_surface, t->owner->ud);