Refine integer signedness use for static analyizers (#24)


diff --git a/src/UsefulBuf.c b/src/UsefulBuf.c
index 1d13f10..a96f74e 100644
--- a/src/UsefulBuf.c
+++ b/src/UsefulBuf.c
@@ -41,7 +41,8 @@
 
  when        who          what, where, why
  --------    ----         ---------------------------------------------------
- 01/08/2020 llundblade    Documentation corrections & improved code formatting.
+ 01/28/2020  llundblade   Refine integer signedness to quiet static analysis.
+ 01/08/2020  llundblade   Documentation corrections & improved code formatting.
  11/08/2019  llundblade   Re check pointer math and update comments
  3/6/2019    llundblade   Add UsefulBuf_IsValue()
  09/07/17    llundbla     Fix critical bug in UsefulBuf_Find() -- a read off
@@ -109,7 +110,8 @@
    for(const uint8_t *p = UB.ptr; p < pEnd; p++) {
       if(*p != uValue) {
          /* Byte didn't match */
-         return p - (uint8_t *)UB.ptr;
+         /* Cast from signed  to unsigned . Safe because the loop increments.*/
+         return (size_t)(p - (uint8_t *)UB.ptr);
       }
    }