epub: mimetype entry comes first in the archive

OCF requires the mimetype entry to be the first in the zip and stored
uncompressed, so that a reader can tell what the file is by looking at
a known offset without parsing the archive.

The index is now set to: 0 for the mimetype, 1 upward for everything
else as it is added.
  mimetype                   Stored   first
  META-INF/container.xml     Stored
  OEBPS/toc_nav.xhtml        Stored
  ...

(assisted by Claude-Code)

2 files changed, 36 insertions, 6 deletions

diff --git a/org/out_xmls.org b/org/out_xmls.org
index b477d34..165cea2 100644
--- a/org/out_xmls.org
+++ b/org/out_xmls.org
@@ -3174,10 +3174,25 @@ zip -0 file.epub mimetype && zip -r -9 file.epub META-INF OEBPS
   /+ zip file +/
   auto fn_epub = pth_epub3.epub_file(doc_matters.src.filename);
   auto zip = new ZipArchive(); // ZipArchive zip = new ZipArchive();
-  /+ zip archive member files +/
-  void EPUBzip()(string contents, string fn) {
+  /+ zip archive member files.
+     ZipArchive.build() emits members sorted by ArchiveMember.index, and
+     addMember does not set one. An epub is not free to choose: OCF requires the
+     mimetype entry to be the first in the archive, a reader being entitled to
+     look only there to tell what the file is. The index is therefore set
+     deliberately, 0 for the mimetype and 1 upward for the rest as they are
+     added.
+     .
+     Compression is already done for every member (ArchiveMember defaults to
+     it), which is the other half of what OCF asks of the mimetype.
+  +/
+  uint _zip_seq = 1;
+  void EPUBzip()(string contents, string fn, bool _is_mimetype = false) {
     auto zip_arc_member_file = new ArchiveMember();
     zip_arc_member_file.name = fn;
+    zip_arc_member_file.index = _is_mimetype ? 0 : _zip_seq++;
+    if (_is_mimetype) {
+      zip_arc_member_file.compressionMethod = CompressionMethod.none;
+    }
     auto zip_data = new OutBuffer();
     (doc_matters.opt.action.debug_do_epub)
     ? zip_data.write(contents.dup)
@@ -3262,7 +3277,7 @@ zip -0 file.epub mimetype && zip -r -9 file.epub META-INF OEBPS
         }
       }
       fn = pth_epub3.fn_mimetypes;
-      EPUBzip(epub_write.mimetypes, fn);
+      EPUBzip(epub_write.mimetypes, fn, true);   /+ first in the archive +/
     }
     { /+  META-INF/container.xml (identify doc root) +/
       { /+ debug +/
diff --git a/src/sisudoc/outputs/io_out/epub3.d b/src/sisudoc/outputs/io_out/epub3.d
index e07aeb8..d149dac 100644
--- a/src/sisudoc/outputs/io_out/epub3.d
+++ b/src/sisudoc/outputs/io_out/epub3.d
@@ -602,10 +602,25 @@ template outputEPub3() {
     /+ zip file +/
     auto fn_epub = pth_epub3.epub_file(doc_matters.src.filename);
     auto zip = new ZipArchive(); // ZipArchive zip = new ZipArchive();
-    /+ zip archive member files +/
-    void EPUBzip()(string contents, string fn) {
+    /+ zip archive member files.
+       ZipArchive.build() emits members sorted by ArchiveMember.index, and
+       addMember does not set one. An epub is not free to choose: OCF requires the
+       mimetype entry to be the first in the archive, a reader being entitled to
+       look only there to tell what the file is. The index is therefore set
+       deliberately, 0 for the mimetype and 1 upward for the rest as they are
+       added.
+       .
+       Compression is already done for every member (ArchiveMember defaults to
+       it), which is the other half of what OCF asks of the mimetype.
+    +/
+    uint _zip_seq = 1;
+    void EPUBzip()(string contents, string fn, bool _is_mimetype = false) {
       auto zip_arc_member_file = new ArchiveMember();
       zip_arc_member_file.name = fn;
+      zip_arc_member_file.index = _is_mimetype ? 0 : _zip_seq++;
+      if (_is_mimetype) {
+        zip_arc_member_file.compressionMethod = CompressionMethod.none;
+      }
       auto zip_data = new OutBuffer();
       (doc_matters.opt.action.debug_do_epub)
       ? zip_data.write(contents.dup)
@@ -690,7 +705,7 @@ template outputEPub3() {
           }
         }
         fn = pth_epub3.fn_mimetypes;
-        EPUBzip(epub_write.mimetypes, fn);
+        EPUBzip(epub_write.mimetypes, fn, true);   /+ first in the archive +/
       }
       { /+  META-INF/container.xml (identify doc root) +/
         { /+ debug +/