bufq: remove Curl_bufq_skip_and_shift (unused)

Closes #11915

lib/bufq.c

@@ -144,21 +144,6 @@ static size_t chunk_skip(struct buf_chunk *chunk, size_t amount)
   return n;
 }
 
-static void chunk_shift(struct buf_chunk *chunk)
-{
-  if(chunk->r_offset) {
-    if(!chunk_is_empty(chunk)) {
-      size_t n = chunk->w_offset - chunk->r_offset;
-      memmove(chunk->x.data, chunk->x.data + chunk->r_offset, n);
-      chunk->w_offset -= chunk->r_offset;
-      chunk->r_offset = 0;
-    }
-    else {
-      chunk->r_offset = chunk->w_offset = 0;
-    }
-  }
-}
-
 static void chunk_list_free(struct buf_chunk **anchor)
 {
   struct buf_chunk *chunk;
@@ -504,13 +489,6 @@ void Curl_bufq_skip(struct bufq *q, size_t amount)
   }
 }
 
-void Curl_bufq_skip_and_shift(struct bufq *q, size_t amount)
-{
-  Curl_bufq_skip(q, amount);
-  if(q->tail)
-    chunk_shift(q->tail);
-}
-
 ssize_t Curl_bufq_pass(struct bufq *q, Curl_bufq_writer *writer,
                        void *writer_ctx, CURLcode *err)
 {

lib/bufq.h

@@ -209,12 +209,6 @@ bool Curl_bufq_peek_at(struct bufq *q, size_t offset,
  */
 void Curl_bufq_skip(struct bufq *q, size_t amount);
 
-/**
- * Same as `skip` but shift tail data to the start afterwards,
- * so that further writes will find room in tail.
- */
-void Curl_bufq_skip_and_shift(struct bufq *q, size_t amount);
-
 typedef ssize_t Curl_bufq_writer(void *writer_ctx,
                                  const unsigned char *buf, size_t len,
                                  CURLcode *err);