Commit e88153ea authored by Kevin Wolf's avatar Kevin Wolf
Browse files

qcow2 spec: Describe string header extensions 



Be more specific about the string representation in header extensions.

Suggested-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 9c2b28e4

docs/interop/qcow2.txt

+12 −2
Original line number Diff line number Diff line
@@ -170,11 +170,11 @@ be stored. Each extension has a structure like the following: 


    Byte  0 -  3:   Header extension type:

                        0x00000000 - End of the header extension area

                        0xE2792ACA - Backing file format name

                        0xE2792ACA - Backing file format name string

                        0x6803f857 - Feature name table

                        0x23852875 - Bitmaps extension

                        0x0537be77 - Full disk encryption header pointer

                        0x44415441 - External data file name

                        0x44415441 - External data file name string

                        other      - Unknown header extension, can be safely

                                     ignored
@@ -196,6 +196,16 @@ data of compatible features that it doesn't support. Compatible features that 
need space for additional data can use a header extension.





== String header extensions ==



Some header extensions (such as the backing file format name and the external

data file name) are just a single string. In this case, the header extension

length is the string length and the string is not '\0' terminated. (The header

extension padding can make it look like a string is '\0' terminated, but

neither is padding always necessary nor is there a guarantee that zero bytes

are used for padding.)





== Feature name table ==



The feature name table is an optional header extension that contains the name