Bug#773058: review fixes.

Adjust signature of tbuf_ltrim, add comments,
replace a check with an assert.

core/tbuf.c

@@ -124,17 +124,16 @@ tbuf_peek(struct tbuf *b, size_t count)
 	return NULL;
 }
 
-void *
+/** Remove first count bytes from the beginning. */
+
+void
 tbuf_ltrim(struct tbuf *b, size_t count)
 {
-	void *p = NULL;
-
 	tbuf_assert(b);
-	if (count <= b->len) {
-		p = memmove(b->data, b->data + count, b->len - count);
-		b->len -= count;
-	}
-	return p;
+	assert(count <= b->len);
+
+	memmove(b->data, b->data + count, b->len - count);
+	b->len -= count;
 }
 
 size_t

include/tbuf.h

@@ -63,7 +63,16 @@ struct tbuf *tbuf_split(struct tbuf *e, size_t at);
 size_t tbuf_reserve(struct tbuf *b, size_t count);
 void tbuf_reset(struct tbuf *b);
 void *tbuf_peek(struct tbuf *b, size_t count);
-void *tbuf_ltrim(struct tbuf *b, size_t count);
+
+/**
+ * Remove count bytes from the beginning, and adjust all sizes
+ * accordingly.
+ *
+ * @param    count   the number of bytes to forget about.
+ *
+ * @pre      0 <= count <= tbuf->len
+ */
+void tbuf_ltrim(struct tbuf *b, size_t count);
 
 void tbuf_append_field(struct tbuf *b, void *f);
 void tbuf_vprintf(struct tbuf *b, const char *format, va_list ap)