Improvements about the block address of empty data files

doc/boot_sectors.txt

@@ -258,7 +258,7 @@ Sources:
 
 The candidates for MBR booting will normally use El Torito rather than MBR
 if the ISO image is presented on CD, DVD, or BD media.
-The eventual MBR comes into effect it the image is on a media that is
+The eventual MBR comes into effect if the image is on a media that is
 interpreted by the BIOS as some kind of hard disk. Usually real hard disks,
 floppy disks, USB sticks, memory cards.
 
@@ -526,46 +526,6 @@ Byte Range | Value      | Meaning
 up to 2048 |          0 | ISO 9660 Block end padding
 ---------- | ---------- | ----------------------------------------------------
 
-Test image produced by
-  genisoimage -o /u/test/mips_boot.iso -mips-boot checksum.c jte
-which reports
-  Found mips boot image checksum.c, using extent 636 (0x27C), #blocks 14336 (0x3800)
-
-xorriso reports as 2048 byte LBA of the boot image dummy file
-  File data lba:  0 ,      159 ,        7 ,    14330 , '/CHECKSUM.C'
-
-First 512 bytes in hex:
-       0 :    0b  e5  a9  41  00  00  00  00  00  00  00  00  00  00  00  00
-      16 :    00  00  00  00  00  00  00  00  00  00  00  00  00  51  00  00
-      32 :    00  01  00  00  00  00  00  20  02  00  00  00  00  00  00  34
-      48 :    00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
-      64 :    00  00  00  00  00  00  00  00  63  68  65  63  6b  73  75  6d
-      80 :    00  00  02  7c  00  00  38  00  00  00  00  00  00  00  00  00
-... 0 ...
-     400 :    00  00  00  00  00  00  00  00  00  00  0a  28  00  00  00  00
-     416 :    00  00  00  00  00  00  00  00  00  00  00  00  00  00  00  00
-     432 :    00  00  0a  28  00  00  00  00  00  00  00  06  00  00  00  00
-... 0 ...
-     496 :    00  00  00  00  00  00  00  00  22  ec  2c  c9  00  00  00  00
-
-The 32 bit two's complement of bytes 0 to 503 is 0x22ec2cc9.
-
-In decimal:
-       0 :    11 229 169  65   0   0   0   0   0   0   0   0   0   0   0   0
-      16 :     0   0   0   0   0   0   0   0   0   0   0   0   0  81   0   0
-      32 :     0   1   0   0   0   0   0  32   2   0   0   0   0   0   0  52
-      48 :     0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0
-      64 :     0   0   0   0   0   0   0   0  99 104 101  99 107 115 117 109
-      80 :     0   0   2 124   0   0  56   0   0   0   0   0   0   0   0   0
-... 0 ...
-     400 :     0   0   0   0   0   0   0   0   0   0  10  40   0   0   0   0
-     416 :     0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0
-     432 :     0   0  10  40   0   0   0   0   0   0   0   6   0   0   0   0
-... 0 ...
-     496 :     0   0   0   0   0   0   0   0  34 236  44 201   0   0   0   0
-
-Cleartext part:
-      64 :                                     c   h   e   c   k   s   u   m
 
 ------------------------------------------------------------------------------
 

libisofs/ecma119.c

@@ -1730,6 +1730,8 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
     target->mipsel_p_vaddr = 0;
     target->mipsel_p_filesz = 0;
 
+    target->empty_file_block = 0;
+
     for (i = 0; i < ISO_MAX_PARTITIONS; i++) {
         target->appended_partitions[i] = NULL;
         if (opts->appended_partitions[i] != NULL) {
@@ -1833,6 +1835,11 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
     /* Volume Descriptor Set Terminator */
     target->curblock++;
 
+    /* All empty files point to the Volume Descriptor Set Terminator
+     * rather than to addresses of non-empty files.
+     */
+    target->empty_file_block = target->curblock - 1;
+
     /*
      * Create the writer for possible padding to ensure that in case of image
      * growing we can safely overwrite the first 64 KiB of image.

libisofs/ecma119.h

@@ -470,6 +470,11 @@ struct ecma119_image
      */
     uint32_t curblock;
 
+    /*
+     * The address to be used for the content pointer of empty data files.
+     */
+    uint32_t empty_file_block;
+
     /*
      * number of dirs in ECMA-119 tree, computed together with dir position,
      * and needed for path table computation in a efficient way

libisofs/eltorito.c

@@ -309,6 +309,7 @@ int create_image(IsoImage *image, const char *image_path,
     int boot_media_type = 0;
     int load_sectors = 0; /* number of sector to load */
     unsigned char partition_type = 0;
+    off_t size;
     IsoNode *imgfile;
     IsoStream *stream;
 
@@ -331,9 +332,16 @@ int create_image(IsoImage *image, const char *image_path,
         return ISO_BOOT_IMAGE_NOT_VALID;
     }
 
+    size = iso_stream_get_size(stream);
+    if (size <= 0) {
+        iso_msg_submit(image->id, ISO_BOOT_IMAGE_NOT_VALID, 0,
+                       "Boot image file is empty");
+        return ISO_BOOT_IMAGE_NOT_VALID;
+    }
+
     switch (type) {
     case ELTORITO_FLOPPY_EMUL:
-        switch (iso_stream_get_size(stream)) {
+        switch (size) {
         case 1200 * 1024:
             boot_media_type = 1; /* 1.2 meg diskette */
             break;

libisofs/filesrc.c

@@ -266,7 +266,12 @@ int filesrc_writer_compute_data_blocks(IsoImageWriter *writer)
         /*
          * final section
          */
-        file->sections[extent].block = t->curblock + extent * (ISO_EXTENT_SIZE / BLOCK_SIZE);
+        if (section_size <= 0) {
+            file->sections[extent].block = t->empty_file_block;
+        } else {
+            file->sections[extent].block =
+                         t->curblock + extent * (ISO_EXTENT_SIZE / BLOCK_SIZE);
+        }
         file->sections[extent].size = (uint32_t)section_size;
 
         t->curblock += DIV_UP(iso_file_src_get_size(file), BLOCK_SIZE);

libisofs/libisofs.h

@@ -1224,7 +1224,6 @@ void iso_write_opts_free(IsoWriteOpts *opts);
  */
 int iso_write_opts_set_will_cancel(IsoWriteOpts *opts, int will_cancel);
 
-
 /**
  * Set the ISO-9960 level to write at.
  *