vhdx-rs 0.2.0

//! Shared internal constants used across modules.

use bitvec::prelude::*;
use core::marker::PhantomData;

use crate::types::Guid;

// ---------------------------------------------------------------------------
// Size units
// ---------------------------------------------------------------------------
//
// The VHDX spec and common tooling use KB/MB/GB/TB to mean 1024-based units
// (kibibytes, mebibytes, etc.).  We follow the IEC 80000-13 standard instead
// and name our constants KiB, MiB, GiB, TiB to make the 1024-based semantics
// unambiguous.

/// Kibibyte.
pub(crate) const KIB: u16 = 1024;

/// Mebibyte.
pub(crate) const MIB: u32 = 1024 * (KIB as u32);

/// Gibibyte.
pub(crate) const GIB: u32 = 1024 * MIB;

/// Tebibyte.
pub(crate) const TIB: u64 = 1024 * (GIB as u64);

// ---------------------------------------------------------------------------
// Header/region layout offsets
// ---------------------------------------------------------------------------

/// Offset of Header 1 within the header section/file.
pub(crate) const HEADER1_OFFSET: u32 = 64 * (KIB as u32);

/// Offset of Header 2 within the header section/file.
pub(crate) const HEADER2_OFFSET: u32 = 128 * (KIB as u32);

/// Offset of Region Table 1 within the header section/file.
pub(crate) const REGION_TABLE1_OFFSET: u32 = 192 * (KIB as u32);

/// Offset of Region Table 2 within the header section/file.
pub(crate) const REGION_TABLE2_OFFSET: u32 = 256 * (KIB as u32);

/// Log starts at 1 MiB (first MiB-aligned slot after the header section).
pub(crate) const LOG_OFFSET: u32 = MIB;

/// Minimum log length is 1 MiB.
pub(crate) const LOG_LENGTH: u32 = MIB;

/// BAT region starts at 2 MiB (right after the log).
pub(crate) const BAT_REGION_OFFSET: u32 = 2 * MIB;

/// Metadata region default size: 1 MiB.
pub(crate) const METADATA_REGION_SIZE: u32 = MIB;

// ---------------------------------------------------------------------------
// Core structure sizes
// ---------------------------------------------------------------------------

/// Size of a VHDX header structure in bytes.
pub(crate) const HEADER_SIZE: u16 = 4096;

/// Size of the buffered VHDX header section (first 1 MiB).
pub(crate) const HEADER_BUFFER_SIZE: usize = MIB as usize;

/// Size of a VHDX region table in bytes.
pub(crate) const REGION_TABLE_SIZE: u32 = 64 * 1024;

/// Metadata table fixed size: 64 KiB.
pub(crate) const METADATA_TABLE_SIZE: u32 = 64 * 1024;

/// Metadata table header size in bytes.
pub(crate) const TABLE_HEADER_SIZE: u8 = 32;

/// Metadata table entry size in bytes.
pub(crate) const TABLE_ENTRY_SIZE: u8 = 32;

/// Parent locator header size in bytes.
pub(crate) const LOCATOR_HEADER_SIZE: u8 = 20;

/// Parent locator key-value entry size in bytes.
pub(crate) const KV_ENTRY_SIZE: u8 = 12;

// ---------------------------------------------------------------------------
// Region table layout
// ---------------------------------------------------------------------------

/// Size of each region table entry (32 bytes per MS-VHDX).
pub(crate) const REGION_ENTRY_SIZE: u8 = 32;

/// Maximum number of region table entries per MS-VHDX.
pub(crate) const MAX_REGION_ENTRIES: u16 = 2047;

/// Creator field size in the file type identifier (512 bytes).
pub(crate) const CREATOR_SIZE: u16 = 512;

/// Region table header size: 16 bytes (signature + checksum + `entry_count` + reserved).
pub(crate) const RT_HEADER_SIZE: u8 = 16;

// ---------------------------------------------------------------------------
// Log layout
// ---------------------------------------------------------------------------

/// Log entry header size in bytes.
pub(crate) const ENTRY_HEADER_SIZE: u8 = 64;

/// Log descriptor size in bytes.
pub(crate) const DESCRIPTOR_SIZE: u8 = 32;

// ---------------------------------------------------------------------------
// Log signatures
// ---------------------------------------------------------------------------

/// VHDX log/data sector size in bytes.
pub(crate) const SECTOR_SIZE: u16 = 4096;

/// Log entry signature.
pub(crate) const SIGNATURE_LOGE: BitArray<u32, Lsb0> = BitArray {
    data: u32::from_le_bytes(*b"loge"),
    _ord: PhantomData,
};

/// Data descriptor signature.
pub(crate) const SIGNATURE_DESC: BitArray<u32, Lsb0> = BitArray {
    data: u32::from_le_bytes(*b"desc"),
    _ord: PhantomData,
};

/// Zero descriptor signature.
pub(crate) const SIGNATURE_ZERO: BitArray<u32, Lsb0> = BitArray {
    data: u32::from_le_bytes(*b"zero"),
    _ord: PhantomData,
};

/// Data sector signature.
#[cfg(test)]
pub(crate) const SIGNATURE_DATA: BitArray<u32, Lsb0> = BitArray {
    data: u32::from_le_bytes(*b"data"),
    _ord: PhantomData,
};

// ---------------------------------------------------------------------------
// File/structure signatures
// ---------------------------------------------------------------------------

/// VHDX file signature bytes: "vhdxfile" (8 bytes).
pub(crate) const VHDX_SIGNATURE_BYTES: BitArray<u64, Lsb0> = BitArray {
    data: u64::from_le_bytes(*b"vhdxfile"),
    _ord: PhantomData,
};

/// Header structure signature: "head".
pub(crate) const HEADER_SIGNATURE: BitArray<u32, Lsb0> = BitArray {
    data: u32::from_le_bytes(*b"head"),
    _ord: PhantomData,
};

/// Region table signature: "regi".
pub(crate) const REGION_SIGNATURE: BitArray<u32, Lsb0> = BitArray {
    data: u32::from_le_bytes(*b"regi"),
    _ord: PhantomData,
};

/// Metadata table signature: "metadata" (8 bytes).
pub(crate) const METADATA_SIGNATURE: BitArray<u64, Lsb0> = BitArray {
    data: u64::from_le_bytes(*b"metadata"),
    _ord: PhantomData,
};

// ---------------------------------------------------------------------------
// Known region GUIDs
// ---------------------------------------------------------------------------

/// BAT region GUID: 2DC27766-F623-4200-9D64-115E9BFD4A08.
pub(crate) const BAT_REGION_GUID: Guid = Guid::from_bytes([
    0x66, 0x77, 0xC2, 0x2D, 0x23, 0xF6, 0x00, 0x42, 0x9D, 0x64, 0x11, 0x5E, 0x9B, 0xFD, 0x4A, 0x08,
]);

/// Metadata region GUID: 8B7CA206-4790-4B9A-B8FE-575F050F886E.
pub(crate) const METADATA_REGION_GUID: Guid = Guid::from_bytes([
    0x06, 0xA2, 0x7C, 0x8B, 0x90, 0x47, 0x9A, 0x4B, 0xB8, 0xFE, 0x57, 0x5F, 0x05, 0x0F, 0x88, 0x6E,
]);

// ---------------------------------------------------------------------------
// Known metadata item GUIDs
// ---------------------------------------------------------------------------

/// File Parameters metadata item GUID.
pub(crate) const FILE_PARAMETERS_GUID: Guid = Guid::from_bytes([
    0x37, 0x67, 0xA1, 0xCA, 0x36, 0xFA, 0x43, 0x4D, 0xB3, 0xB6, 0x33, 0xF0, 0xAA, 0x44, 0xE7, 0x6B,
]);

/// Virtual Disk Size metadata item GUID.
pub(crate) const VIRTUAL_DISK_SIZE_GUID: Guid = Guid::from_bytes([
    0x24, 0x42, 0xA5, 0x2F, 0x1B, 0xCD, 0x76, 0x48, 0xB2, 0x11, 0x5D, 0xBE, 0xD8, 0x3B, 0xF4, 0xB8,
]);

/// Virtual Disk ID metadata item GUID.
pub(crate) const VIRTUAL_DISK_ID_GUID: Guid = Guid::from_bytes([
    0xAB, 0x12, 0xCA, 0xBE, 0xE6, 0xB2, 0x23, 0x45, 0x93, 0xEF, 0xC3, 0x09, 0xE0, 0x00, 0xC7, 0x46,
]);

/// Logical Sector Size metadata item GUID.
pub(crate) const LOGICAL_SECTOR_SIZE_GUID: Guid = Guid::from_bytes([
    0x1D, 0xBF, 0x41, 0x81, 0x6F, 0xA9, 0x09, 0x47, 0xBA, 0x47, 0xF2, 0x33, 0xA8, 0xFA, 0xAB, 0x5F,
]);

/// Physical Sector Size metadata item GUID.
pub(crate) const PHYSICAL_SECTOR_SIZE_GUID: Guid = Guid::from_bytes([
    0xC7, 0x48, 0xA3, 0xCD, 0x5D, 0x44, 0x71, 0x44, 0x9C, 0xC9, 0xE9, 0x88, 0x52, 0x51, 0xC5, 0x56,
]);

/// Parent Locator metadata item GUID.
pub(crate) const PARENT_LOCATOR_GUID: Guid = Guid::from_bytes([
    0x2D, 0x5F, 0xD3, 0xA8, 0x0B, 0xB3, 0x4D, 0x45, 0xAB, 0xF7, 0xD3, 0xD8, 0x48, 0x34, 0xAB, 0x0C,
]);

/// VHDX Parent Locator Type GUID.
pub(crate) const LOCATOR_TYPE_VHDX_GUID: Guid = Guid::from_bytes([
    0xB7, 0xEF, 0x4A, 0xB0, 0x9E, 0xD1, 0x81, 0x4A, 0xB7, 0x89, 0x25, 0xB8, 0xE9, 0x44, 0x59, 0x13,
]);

/// Known VHDX region GUIDs.
pub(crate) const KNOWN_REGION_GUIDS: &[Guid] = &[BAT_REGION_GUID, METADATA_REGION_GUID];

/// Known VHDX metadata item GUIDs.
pub(crate) const KNOWN_METADATA_GUIDS: &[Guid] = &[
    FILE_PARAMETERS_GUID,
    VIRTUAL_DISK_SIZE_GUID,
    VIRTUAL_DISK_ID_GUID,
    LOGICAL_SECTOR_SIZE_GUID,
    PHYSICAL_SECTOR_SIZE_GUID,
    PARENT_LOCATOR_GUID,
];

// ---------------------------------------------------------------------------
// FileParameters bit layout
// ---------------------------------------------------------------------------

/// `FileParameters.BlockSize` bit range.
pub(crate) const FP_BLOCK_SIZE: std::ops::Range<usize> = 0..32;

/// `FileParameters.BitFields` bit range.
pub(crate) const FP_BITFIELDS: std::ops::Range<usize> = 32..64;

/// `FileParameters.LeaveBlockAllocated` bit index.
pub(crate) const FP_LEAVE_BLOCK_ALLOCATED: usize = 32;

/// `FileParameters.HasParent` bit index.
pub(crate) const FP_HAS_PARENT: usize = 33;

/// First reserved bit in `FileParameters.BitFields`.
pub(crate) const FP_RESERVED_START: usize = 34;

/// End of the `FileParameters` bit view.
pub(crate) const FP_BITS_END: usize = 64;