Esx

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Format of Morrowind's ESM Plug-In File

Basic Overall Format:

The ESM/ESP/ESS files are composed entirely of Records with this format.

Record

4 bytes, char[4]. Name.
    -- 4-byte record name string. all CAPS, not null-terminated.
4 bytes, integer. Record size.
    -- Size of the record not including the 16 bytes of header data.
4 bytes, integer. Unknown.
    -- Unknown value, usually 0 (deleted/ignored flag?).
4 bytes, integer. Record flags.
    --   0x00002000 = Blocked
    --   0x00000400 = Persistant
Record size bytes, SubRecords[]. 
    -- All records are composed of a variable number of sub-records. There
    -- is no sub-record count, just use the record Size value to determine
    -- when to stop reading a record.

Sub-Record

The sub-record is the tail of the record and it contains data specific to the record type.

4 bytes, char[4]. Name.
    -- 4-byte sub-record name string, all CAPS, not null-terminated
4 bytes, long. Size of sub-record.
    -- Size of the sub-record not including the 8 bytes of header data.
Size of sub-record bytes, various format. Sub-Record data.
    -- Format depends on the sub-record type.

Record types

Tes3, Main header.

Gmst, Game setting.

GLOB, Global variable.