Refactor the file size and tell operations

This was done in order to avoid C++ compiler warnings about comparing types with
different signedness.

4 files changed, 54 insertions, 18 deletions

diff --git a/src/backup.c b/src/backup.c
index 4c9dfbd..0b558b6 100644
--- a/src/backup.c
+++ b/src/backup.c
@@ -43,16 +43,18 @@ static int
 check_files(const options_backup_t *const opts,
             const resources_backup_t *const res)
 {
-    const long in_size = file_size(res->in_file);
+    bool in_size_ok = false;
+    const size_t in_size = file_size(res->in_file, &in_size_ok);
 
-    if (in_size < 0) {
+    if (!in_size_ok) {
         print_error("cannot get size of input file: %s", strerror(errno));
         return 1;
     }
 
-    const long ref_size = file_size(res->ref_file);
+    bool ref_size_ok = false;
+    const size_t ref_size = file_size(res->ref_file, &ref_size_ok);
 
-    if (ref_size < 0) {
+    if (!ref_size_ok) {
         print_error("cannot get size of reference file: %s", strerror(errno));
         return 1;
     }
diff --git a/src/file.c b/src/file.c
index 57a847a..d605ceb 100644
--- a/src/file.c
+++ b/src/file.c
@@ -31,22 +31,39 @@
 #include <errno.h>
 #include <string.h>
 
-long
-file_size(FILE *const file)
+size_t
+file_size(FILE *const file, bool *const return_is_ok)
 {
     fpos_t p;
 
     if ((fgetpos(file, &p) != 0) || (fseek(file, 0L, SEEK_END) != 0)) {
-        return -1;
+        *return_is_ok = false;
+        return 0;
     }
 
     const long size = ftell(file);
 
     if (fsetpos(file, &p) != 0) {
-        return -1;
+        *return_is_ok = false;
+        return 0;
     }
 
-    return size;
+    *return_is_ok = true;
+    return (size_t)size;
+}
+
+size_t
+file_tell(FILE *const file, bool *const return_is_ok)
+{
+    const long pos = ftell(file);
+
+    if (pos < 0) {
+        *return_is_ok = false;
+        return 0;
+    } else {
+        *return_is_ok = true;
+        return (size_t)pos;
+    }
 }
 
 size_t
diff --git a/src/file.h b/src/file.h
index 886098b..3e4a6ee 100644
--- a/src/file.h
+++ b/src/file.h
@@ -27,10 +27,12 @@
 #ifndef FILE_H
 #define FILE_H
 
+#include <stdbool.h>
 #include <stdint.h>
 #include <stdio.h>
 
-long file_size(FILE *const file);
+size_t file_size(FILE *const file, bool *const return_is_ok);
+size_t file_tell(FILE *const file, bool *const return_is_ok);
 size_t file_read_sectors(FILE *const file, char *const buffer,
                          uint32_t buffer_size, uint32_t sector_size);
 
diff --git a/src/restore.c b/src/restore.c
index df58ab8..e73e42e 100644
--- a/src/restore.c
+++ b/src/restore.c
@@ -39,9 +39,10 @@
 static bool
 is_input_file_valid(const resources_restore_t *const res, uint32_t sector_size)
 {
-    const long in_size = file_size(res->in_file);
+    bool in_size_ok = false;
+    const size_t in_size = file_size(res->in_file, &in_size_ok);
 
-    if (in_size < 0) {
+    if (!in_size_ok) {
         print_error("cannot get size of input file: %s", strerror(errno));
         return false;
     } else if (in_size == 0) {
@@ -55,9 +56,10 @@ is_input_file_valid(const resources_restore_t *const res, uint32_t sector_size)
         return false;
     }
 
-    const long out_size = file_size(res->out_file);
+    bool out_size_ok = false;
+    const size_t out_size = file_size(res->out_file, &out_size_ok);
 
-    if (out_size < 0) {
+    if (!out_size_ok) {
         print_error("cannot get size of output file: %s", strerror(errno));
         return 1;
     }
@@ -94,7 +96,13 @@ is_input_file_valid(const resources_restore_t *const res, uint32_t sector_size)
         prev_out_offset = out_offset;
     }
 
-    if (ftell(res->in_file) != in_size) {
+    bool pos_ok = false;
+    const size_t pos = file_tell(res->in_file, &pos_ok);
+
+    if (!pos_ok) {
+        print_error("cannot get position in the input file");
+        return false;
+    } else if (pos != in_size) {
         /* The input file must be read completely */
         print_error("input file is not valid");
         return false;
@@ -116,9 +124,10 @@ restore(const options_restore_t *const opts,
         return 1;
     }
 
-    const long in_size = file_size(res->in_file);
+    bool in_size_ok = false;
+    const size_t in_size = file_size(res->in_file, &in_size_ok);
 
-    if (in_size < 0) {
+    if (!in_size_ok) {
         print_error("cannot get size of input file: %s", strerror(errno));
         return 1;
     }
@@ -158,7 +167,13 @@ restore(const options_restore_t *const opts,
     }
 
     /* The input file must be read completely */
-    if (ftell(res->in_file) != in_size) {
+    bool pos_ok = false;
+    const size_t pos = file_tell(res->in_file, &pos_ok);
+
+    if (!pos_ok) {
+        print_error("cannot get position in the input file");
+        return 1;
+    } else if (pos != in_size) {
         print_error("input file is not valid");
         return 1;
     }