archive/iso9660: another fix for unaligned reads

Commit 79b23663 added the field `skip` to support unaligned reads, but set the `offset` field to a wrong value. This resulted in miscalculation of `remaining`, causing an assertion failure. The fix is to assign `offset` the correct value, but consider the `skip` value in the assertion. Closes https://github.com/MusicPlayerDaemon/MPD/issues/1067

archive/iso9660: another fix for unaligned reads
e7da5b10 · Max Kellermann · 4be76f3c · e7da5b10 · e7da5b10
Commit e7da5b10 authored Feb 07, 2021 by Max Kellermann
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NEWS NEWS +2 -0

Iso9660ArchivePlugin.cxx src/archive/plugins/Iso9660ArchivePlugin.cxx +2 -2

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--- a/NEWS
+++ b/NEWS
 ver 0.22.5 (not yet released)
 * tags
  - id: translate TPE3 to Conductor, not Performer
+* archive
+  - iso9660: another fix for unaligned reads
 * output
  - httpd: error handling on Windows improved


--- a/src/archive/plugins/Iso9660ArchivePlugin.cxx
+++ b/src/archive/plugins/Iso9660ArchivePlugin.cxx
@@ -221,8 +221,8 @@ public:
 		if (new_offset > size)
 			throw std::runtime_error("Invalid seek offset");

+		offset = new_offset;
 		skip = new_offset % ISO_BLOCKSIZE;
-		offset = new_offset - skip;
 		buffer.Clear();
 	}
 };
@@ -260,7 +260,7 @@ Iso9660InputStream::Read(std::unique_lock<Mutex> &,
 	if (r.empty()) {
 		/* the buffer is empty - read more data from the ISO file */

-		assert(offset % ISO_BLOCKSIZE == 0);
+		assert((offset - skip) % ISO_BLOCKSIZE == 0);

 		const ScopeUnlock unlock(mutex);