fix: Skip the padding field when calculating header checksums

CMakeLists.txt

@@ -29,4 +29,6 @@ else()
 endif()
 
 install(TARGETS minitar DESTINATION lib)
-install(FILES minitar.h DESTINATION include)
+install(FILES minitar.h DESTINATION include)
+
+add_subdirectory(examples)

examples/CMakeLists.txt

@@ -0,0 +1,5 @@
+add_executable(list EXCLUDE_FROM_ALL list.c)
+target_link_libraries(list PRIVATE minitar)
+
+add_executable(untar EXCLUDE_FROM_ALL untar.c)
+target_link_libraries(untar PRIVATE minitar)

src/util.c

@@ -203,7 +203,7 @@ uint32_t minitar_checksum_header(const struct tar_header* hdr)
     const uint8_t* ptr = (const uint8_t*)hdr;
 
     // Sum up all bytes in the header, as unsigned bytes...
-    while (ptr < (const uint8_t*)hdr + sizeof *hdr)
+    while (ptr < (const uint8_t*)hdr + (sizeof *hdr - sizeof hdr->padding))
     {
         sum += *ptr;
         ptr++;