Widened the lseek capacity determination to SEEK_SET with wanted size

xorriso/disk_ops.c

@@ -1,7 +1,7 @@
 
 /* xorriso - creates, loads, manipulates and burns ISO 9660 filesystem images.
 
-   Copyright 2007-2019 Thomas Schmitt, <scdbackup@gmx.net>
+   Copyright 2007-2022 Thomas Schmitt, <scdbackup@gmx.net>
 
    Provided under GPL version 2 or later.
 
@@ -2172,3 +2172,108 @@ ex:;
    Xorriso_wait_child_end(xorriso, forked_pid, &status, 0);
  return(ret);
 }
+
+
+/* flag: bit0= *capacity is a desired value.
+               Try SEEK_SET with *capacity
+         bit1= open for writing
+   return:  0= no random access , -1= cannot open path
+            1= *capacity is valid
+*/
+int Xorriso_lseek_capacity(struct XorrisO *xorriso, char *path,
+                           off_t *capacity, int flag)
+{
+ int fd;
+ off_t seek_result;
+
+ if(flag & 2)
+   fd= open(path, O_WRONLY);
+ else
+   fd= open(path, O_RDONLY);
+ if(fd < 0) {
+   sprintf(xorriso->info_text,
+           "Cannot open for determination of random-access capacity: ");
+           Text_shellsafe(path, xorriso->info_text, 1);
+   Xorriso_msgs_submit(xorriso, 0, xorriso->info_text, errno, "FAILURE", 0);
+   return(-1);
+ }
+ if(flag & 1) {
+   seek_result= lseek(fd, *capacity, SEEK_SET);
+ } else {
+   seek_result= lseek(fd, 0, SEEK_END);
+ }
+ close(fd);
+ if(seek_result < 0)
+   return(0);
+ *capacity= seek_result;
+ return(1);
+}
+
+
+/* flag: bit0= *capacity is a desired value.
+               If SEEK_END fails, try SEEK_SET with *capacity
+         bit1= open for writing
+   return: 0= no random access , -1= path does not exist , -2= wrong type
+          -3= cannot open path
+           1= *capacity is valid
+*/
+int Xorriso_determine_capacity(struct XorrisO *xorriso, char *path,
+                               off_t *capacity, char **reason, int flag)
+{
+ int ret;
+ off_t src_size, src_seek_size= -1;
+ struct stat stbuf;
+
+ if(reason != NULL)
+   *reason= "offers no random access";
+ if(lstat(path, &stbuf) == -1) {
+   *capacity= 0;
+   if(reason != NULL)
+     *reason= "does not exist";
+   return(-1);
+ }
+ if(S_ISREG(stbuf.st_mode)) {
+   src_size= stbuf.st_size;
+ } else if(!(S_ISDIR(stbuf.st_mode) || S_ISLNK(stbuf.st_mode) ||
+             S_ISFIFO(stbuf.st_mode) || S_ISSOCK(stbuf.st_mode))) {
+   ret= Xorriso_lseek_capacity(xorriso, path, &src_size, flag & 2);
+   if(ret <= 0 || src_size <= 0) {
+     if(ret == -1 || !(flag & 1)) {
+       *capacity= 0;
+       if(ret == -1) {
+         if(reason != NULL)
+           *reason= "cannot be opened";
+         return(-3);
+       }
+       return(ret > 0);
+     }
+     if(ret > 0)
+       src_seek_size= 0;
+     src_size= *capacity;
+     ret= Xorriso_lseek_capacity(xorriso, path, &src_size, flag & 3);
+     if(ret <= 0 || src_size < src_seek_size) {
+       if(src_seek_size == 0) {
+         src_size= src_seek_size;
+       } else {
+         *capacity= 0;
+         if(ret == -1) {
+           if(reason != NULL)
+             *reason= "cannot be opened";
+           return(-3);
+         }
+         return(0);
+       }
+     }
+   }
+ } else {
+   *capacity= 0;
+   if(reason != NULL)
+     *reason= "is of wrong type";
+   return(-2);
+ }
+ *capacity= src_size;
+ if(reason != NULL)
+   *reason= "";
+ return(1);
+}
+