vim-patch:8.0.0551: the typeahead buffer is reallocated too often (#8598)

Problem:    The typeahead buffer is reallocated too often.
Solution:   Re-use the existing buffer if possible.
https://github.com/vim/vim/commit/d34f9b1155a6b470e1dc766ff98192f440e7eba7

1 files changed, 9 insertions, 3 deletions

diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index 1c0464b575..a77c467fe5 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -835,7 +835,7 @@ static void init_typebuf(void)
     typebuf.tb_noremap = noremapbuf_init;
     typebuf.tb_buflen = TYPELEN_INIT;
     typebuf.tb_len = 0;
-    typebuf.tb_off = 0;
+    typebuf.tb_off = MAXMAPLEN + 4;
     typebuf.tb_change_cnt = 1;
   }
 }
@@ -879,9 +879,15 @@ int ins_typebuf(char_u *str, int noremap, int offset, int nottyped, bool silent)
     // Easy case: there is room in front of typebuf.tb_buf[typebuf.tb_off]
     typebuf.tb_off -= addlen;
     memmove(typebuf.tb_buf + typebuf.tb_off, str, (size_t)addlen);
+  } else if (typebuf.tb_len == 0
+             && typebuf.tb_buflen >= addlen + 3 * (MAXMAPLEN + 4)) {
+    // Buffer is empty and string fits in the existing buffer.
+    // Leave some space before and after, if possible.
+    typebuf.tb_off = (typebuf.tb_buflen - addlen - 3 * (MAXMAPLEN + 4)) / 2;
+    memmove(typebuf.tb_buf + typebuf.tb_off, str, (size_t)addlen);
   } else {
     // Need to allocate a new buffer.
-    // In typebuf.tb_buf there must always be room for 3 * MAXMAPLEN + 4
+    // In typebuf.tb_buf there must always be room for 3 * (MAXMAPLEN + 4)
     // characters.  We add some extra room to avoid having to allocate too
     // often.
     newoff = MAXMAPLEN + 4;
@@ -1145,7 +1151,7 @@ void alloc_typebuf(void)
   typebuf.tb_buf = xmalloc(TYPELEN_INIT);
   typebuf.tb_noremap = xmalloc(TYPELEN_INIT);
   typebuf.tb_buflen = TYPELEN_INIT;
-  typebuf.tb_off = 0;
+  typebuf.tb_off = MAXMAPLEN + 4;     // can insert without realloc
   typebuf.tb_len = 0;
   typebuf.tb_maplen = 0;
   typebuf.tb_silent = 0;