Added check for integer overflow in get_num_images (#1397)

As discussed in pull request 1396, added a check for integer overflow.
Change list:
Defined num_images as unsigned int
Moved the if statement to check for an empty directory to the beginning of the read directory section
Added a check to see if num images would roll back to zero when incrementing.

1 files changed, 12 insertions, 5 deletions

diff --git a/src/bin/jp2/opj_compress.c b/src/bin/jp2/opj_compress.c
index 646f1375..2bbe5c4c 100644
--- a/src/bin/jp2/opj_compress.c
+++ b/src/bin/jp2/opj_compress.c
@@ -44,6 +44,7 @@
 #include <stdlib.h>
 #include <math.h>
 #include <assert.h>
+#include <limits.h>
 
 #ifdef _WIN32
 #include "windirent.h"
@@ -485,6 +486,11 @@ static unsigned int get_num_images(char *imgdirpath)
         if (strcmp(".", content->d_name) == 0 || strcmp("..", content->d_name) == 0) {
             continue;
         }
+        if (num_images == UINT_MAX) {
+            fprintf(stderr, "Too many files in folder %s\n", imgdirpath);
+            num_images = 0;
+            break;
+        }
         num_images++;
     }
     closedir(dir);
@@ -1957,6 +1963,11 @@ int main(int argc, char **argv)
     /* Read directory if necessary */
     if (img_fol.set_imgdir == 1) {
         num_images = get_num_images(img_fol.imgdirpath);
+        if (num_images == 0) {
+            fprintf(stdout, "Folder is empty\n");
+            ret = 0;
+            goto fin;
+        }
         dirptr = (dircnt_t*)malloc(sizeof(dircnt_t));
         if (dirptr) {
             dirptr->filename_buf = (char*)calloc(num_images, OPJ_PATH_LEN * sizeof(
@@ -1974,11 +1985,7 @@ int main(int argc, char **argv)
             ret = 0;
             goto fin;
         }
-        if (num_images == 0) {
-            fprintf(stdout, "Folder is empty\n");
-            ret = 0;
-            goto fin;
-        }
+
     } else {
         num_images = 1;
     }