EFI_ACPI_5_0_MPST_MEMORY_POWER_STATE_CHARACTERISTICS_STRUCTURE_FLAG_MEMORY_CONTENT_PRESERVED

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
extern (C)
enum EFI_ACPI_5_0_MPST_MEMORY_POWER_STATE_CHARACTERISTICS_STRUCTURE_FLAG_MEMORY_CONTENT_PRESERVED = 0x01;

Meta