diff --git a/src/file_bld.c b/src/file_bld.c
index 05828230..dd7cb060 100644
--- a/src/file_bld.c
+++ b/src/file_bld.c
@@ -34,7 +34,7 @@
 #include "log.h"
 
 /*@
-  @ requires \valid(file_stat);
+  @ requires valid_register_header_check(file_stat);
   @*/
 static void register_header_check_blend(file_stat_t *file_stat);
 
@@ -68,15 +68,10 @@ struct blend8_block
 } __attribute__ ((gcc_struct, __packed__));
 
 /*@
-  @ requires buffer_size > 0;
-  @ requires (buffer_size&1)==0;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires \valid(file_recovery);
   @ requires file_recovery->data_check==&data_check_blend4le;
-  @ requires file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE;
-  @ requires \separated(buffer, file_recovery);
-  @ ensures \result == DC_CONTINUE || \result == DC_STOP;
-  @ assigns file_recovery->calculated_file_size;
+  @ requires valid_data_check_param(buffer, buffer_size, file_recovery);
+  @ ensures  valid_data_check_result(\result, file_recovery);
+  @ assigns  file_recovery->calculated_file_size;
   @*/
 static data_check_t data_check_blend4le(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
 {
@@ -106,14 +101,9 @@ static data_check_t data_check_blend4le(const unsigned char *buffer, const unsig
 }
 
 /*@
-  @ requires buffer_size > 0;
-  @ requires (buffer_size&1)==0;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires \valid(file_recovery);
   @ requires file_recovery->data_check==&data_check_blend8le;
-  @ requires file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE;
-  @ requires \separated(buffer, file_recovery);
-  @ ensures \result == DC_CONTINUE || \result == DC_STOP;
+  @ requires valid_data_check_param(buffer, buffer_size, file_recovery);
+  @ ensures  valid_data_check_result(\result, file_recovery);
   @ assigns file_recovery->calculated_file_size;
   @*/
 static data_check_t data_check_blend8le(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
@@ -144,14 +134,9 @@ static data_check_t data_check_blend8le(const unsigned char *buffer, const unsig
 }
 
 /*@
-  @ requires buffer_size > 0;
-  @ requires (buffer_size&1)==0;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires \valid(file_recovery);
   @ requires file_recovery->data_check==&data_check_blend4be;
-  @ requires file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE;
-  @ requires \separated(buffer, file_recovery);
-  @ ensures \result == DC_CONTINUE || \result == DC_STOP;
+  @ requires valid_data_check_param(buffer, buffer_size, file_recovery);
+  @ ensures  valid_data_check_result(\result, file_recovery);
   @ assigns file_recovery->calculated_file_size;
   @*/
 static data_check_t data_check_blend4be(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
@@ -183,14 +168,9 @@ static data_check_t data_check_blend4be(const unsigned char *buffer, const unsig
 }
 
 /*@
-  @ requires buffer_size > 0;
-  @ requires (buffer_size&1)==0;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires \valid(file_recovery);
   @ requires file_recovery->data_check==&data_check_blend8be;
-  @ requires file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE;
-  @ requires \separated(buffer, file_recovery);
-  @ ensures \result == DC_CONTINUE || \result == DC_STOP;
+  @ requires valid_data_check_param(buffer, buffer_size, file_recovery);
+  @ ensures  valid_data_check_result(\result, file_recovery);
   @ assigns file_recovery->calculated_file_size;
   @*/
 static data_check_t data_check_blend8be(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
@@ -224,29 +204,11 @@ static data_check_t data_check_blend8be(const unsigned char *buffer, const unsig
 }
 
 /*@
-  @ requires buffer_size > 0;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires valid_file_recovery(file_recovery);
-  @ requires \valid(file_recovery_new);
-  @ requires file_recovery_new->blocksize > 0;
-  @
   @ requires buffer_size >= 8;
   @ requires separation: \separated(&file_hint_blend, buffer+(..), file_recovery, file_recovery_new);
-  @
-  @ ensures \result == 0 || \result == 1;
-  @ ensures (\result == 1) ==> (file_recovery_new->file_stat == \null);
-  @ ensures (\result == 1) ==> (file_recovery_new->handle == \null);
-  @ ensures (\result == 1) ==> \initialized(&file_recovery_new->time);
-  @ ensures (\result == 1) ==> \initialized(&file_recovery_new->calculated_file_size);
+  @ requires valid_header_check_param(buffer, buffer_size, safe_header_only, file_recovery, file_recovery_new);
+  @ ensures  valid_header_check_result(\result, file_recovery_new);
   @ ensures (\result == 1) ==> file_recovery_new->file_size == 0;
-  @ ensures (\result == 1) ==> \initialized(&file_recovery_new->min_filesize);
-  @ ensures (\result == 1) ==> (file_recovery_new->data_check == \null || \valid_function(file_recovery_new->data_check));
-  @ ensures (\result == 1) ==> (file_recovery_new->file_check == \null || \valid_function(file_recovery_new->file_check));
-  @ ensures (\result == 1) ==> (file_recovery_new->file_rename == \null || \valid_function(file_recovery_new->file_rename));
-  @ ensures (\result != 0) ==> file_recovery_new->extension != \null;
-  @ ensures (\result == 1) ==> (valid_read_string(file_recovery_new->extension));
-  @ ensures (\result == 1) ==>  \separated(file_recovery_new, file_recovery_new->extension);
-  @
   @ ensures (\result == 1) ==> (file_recovery_new->time == 0);
   @ ensures (\result == 1) ==> (file_recovery_new->calculated_file_size == 12);
   @ ensures (\result == 1) ==> (file_recovery_new->extension == file_hint_blend.extension);
@@ -257,7 +219,6 @@ static data_check_t data_check_blend8be(const unsigned char *buffer, const unsig
   );
   @ ensures (\result == 1) ==> (file_recovery_new->file_check == &file_check_size);
   @ ensures (\result == 1) ==> (file_recovery_new->file_rename == \null);
-  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
   @ assigns  *file_recovery_new;
   @*/
 static int header_check_blend(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new)