llvm-native-core 0.1.15

//! Endian utilities — byte swapping and endian conversion.
//! Phase 1 — LLVM.SUPPORT.1 Court.
//!
//! Provides functions for converting between host byte order and
//! big/little endian, reading/writing multi-byte values from byte
//! buffers, and aligned/unaligned memory access helpers.
//!
//! Clean-room behavioral reconstruction from POSIX htonl/ntohl and
//! standard endian conversion semantics.

use std::mem;

/// Swap bytes in a 16-bit value.
#[inline]
pub fn byte_swap_16(x: u16) -> u16 {
    x.swap_bytes()
}

/// Swap bytes in a 32-bit value.
#[inline]
pub fn byte_swap_32(x: u32) -> u32 {
    x.swap_bytes()
}

/// Swap bytes in a 64-bit value.
#[inline]
pub fn byte_swap_64(x: u64) -> u64 {
    x.swap_bytes()
}

// ============================================================================
// Host to Network byte order (always big-endian)
// ============================================================================

/// Convert 16-bit host to network byte order (big-endian).
#[inline]
pub fn hton_16(x: u16) -> u16 {
    x.to_be()
}

/// Convert 32-bit host to network byte order (big-endian).
#[inline]
pub fn hton_32(x: u32) -> u32 {
    x.to_be()
}

/// Convert 64-bit host to network byte order (big-endian).
#[inline]
pub fn hton_64(x: u64) -> u64 {
    x.to_be()
}

// ============================================================================
// Network to Host byte order (from big-endian)
// ============================================================================

/// Convert 16-bit network to host byte order.
#[inline]
pub fn ntoh_16(x: u16) -> u16 {
    u16::from_be(x)
}

/// Convert 32-bit network to host byte order.
#[inline]
pub fn ntoh_32(x: u32) -> u32 {
    u32::from_be(x)
}

/// Convert 64-bit network to host byte order.
#[inline]
pub fn ntoh_64(x: u64) -> u64 {
    u64::from_be(x)
}

// ============================================================================
// Host to Little-Endian
// ============================================================================

/// Convert 16-bit to little-endian.
#[inline]
pub fn htole_16(x: u16) -> u16 {
    x.to_le()
}

/// Convert 32-bit to little-endian.
#[inline]
pub fn htole_32(x: u32) -> u32 {
    x.to_le()
}

/// Convert 64-bit to little-endian.
#[inline]
pub fn htole_64(x: u64) -> u64 {
    x.to_le()
}

// ============================================================================
// Little-Endian to Host
// ============================================================================

/// Convert 16-bit little-endian to host.
#[inline]
pub fn letoh_16(x: u16) -> u16 {
    u16::from_le(x)
}

/// Convert 32-bit little-endian to host.
#[inline]
pub fn letoh_32(x: u32) -> u32 {
    u32::from_le(x)
}

/// Convert 64-bit little-endian to host.
#[inline]
pub fn letoh_64(x: u64) -> u64 {
    u64::from_le(x)
}

// ============================================================================
// Multi-byte read/write from byte slices (safe, bounds-checked)
// ============================================================================

/// Read a 16-bit value from a byte slice in big-endian order.
///
/// Returns `None` if the slice is too short.
pub fn read_u16_be(bytes: &[u8], offset: usize) -> Option<u16> {
    if offset + 2 <= bytes.len() {
        Some(u16::from_be_bytes([bytes[offset], bytes[offset + 1]]))
    } else {
        None
    }
}

/// Read a 32-bit value from a byte slice in big-endian order.
pub fn read_u32_be(bytes: &[u8], offset: usize) -> Option<u32> {
    if offset + 4 <= bytes.len() {
        Some(u32::from_be_bytes([
            bytes[offset],
            bytes[offset + 1],
            bytes[offset + 2],
            bytes[offset + 3],
        ]))
    } else {
        None
    }
}

/// Read a 64-bit value from a byte slice in big-endian order.
pub fn read_u64_be(bytes: &[u8], offset: usize) -> Option<u64> {
    if offset + 8 <= bytes.len() {
        Some(u64::from_be_bytes([
            bytes[offset],
            bytes[offset + 1],
            bytes[offset + 2],
            bytes[offset + 3],
            bytes[offset + 4],
            bytes[offset + 5],
            bytes[offset + 6],
            bytes[offset + 7],
        ]))
    } else {
        None
    }
}

/// Read a 16-bit value from a byte slice in little-endian order.
pub fn read_u16_le(bytes: &[u8], offset: usize) -> Option<u16> {
    if offset + 2 <= bytes.len() {
        Some(u16::from_le_bytes([bytes[offset], bytes[offset + 1]]))
    } else {
        None
    }
}

/// Read a 32-bit value from a byte slice in little-endian order.
pub fn read_u32_le(bytes: &[u8], offset: usize) -> Option<u32> {
    if offset + 4 <= bytes.len() {
        Some(u32::from_le_bytes([
            bytes[offset],
            bytes[offset + 1],
            bytes[offset + 2],
            bytes[offset + 3],
        ]))
    } else {
        None
    }
}

/// Read a 64-bit value from a byte slice in little-endian order.
pub fn read_u64_le(bytes: &[u8], offset: usize) -> Option<u64> {
    if offset + 8 <= bytes.len() {
        Some(u64::from_le_bytes([
            bytes[offset],
            bytes[offset + 1],
            bytes[offset + 2],
            bytes[offset + 3],
            bytes[offset + 4],
            bytes[offset + 5],
            bytes[offset + 6],
            bytes[offset + 7],
        ]))
    } else {
        None
    }
}

// ============================================================================
// Multi-byte write into byte slices (safe, bounds-checked)
// ============================================================================

/// Write a 16-bit value into a byte slice in big-endian order.
///
/// Returns `false` if the slice is too short.
pub fn write_u16_be(bytes: &mut [u8], offset: usize, value: u16) -> bool {
    if offset + 2 <= bytes.len() {
        let be_bytes = value.to_be_bytes();
        bytes[offset] = be_bytes[0];
        bytes[offset + 1] = be_bytes[1];
        true
    } else {
        false
    }
}

/// Write a 32-bit value into a byte slice in big-endian order.
pub fn write_u32_be(bytes: &mut [u8], offset: usize, value: u32) -> bool {
    if offset + 4 <= bytes.len() {
        let be_bytes = value.to_be_bytes();
        bytes[offset] = be_bytes[0];
        bytes[offset + 1] = be_bytes[1];
        bytes[offset + 2] = be_bytes[2];
        bytes[offset + 3] = be_bytes[3];
        true
    } else {
        false
    }
}

/// Write a 64-bit value into a byte slice in big-endian order.
pub fn write_u64_be(bytes: &mut [u8], offset: usize, value: u64) -> bool {
    if offset + 8 <= bytes.len() {
        let be_bytes = value.to_be_bytes();
        bytes[offset] = be_bytes[0];
        bytes[offset + 1] = be_bytes[1];
        bytes[offset + 2] = be_bytes[2];
        bytes[offset + 3] = be_bytes[3];
        bytes[offset + 4] = be_bytes[4];
        bytes[offset + 5] = be_bytes[5];
        bytes[offset + 6] = be_bytes[6];
        bytes[offset + 7] = be_bytes[7];
        true
    } else {
        false
    }
}

/// Write a 16-bit value into a byte slice in little-endian order.
pub fn write_u16_le(bytes: &mut [u8], offset: usize, value: u16) -> bool {
    if offset + 2 <= bytes.len() {
        let le_bytes = value.to_le_bytes();
        bytes[offset] = le_bytes[0];
        bytes[offset + 1] = le_bytes[1];
        true
    } else {
        false
    }
}

/// Write a 32-bit value into a byte slice in little-endian order.
pub fn write_u32_le(bytes: &mut [u8], offset: usize, value: u32) -> bool {
    if offset + 4 <= bytes.len() {
        let le_bytes = value.to_le_bytes();
        bytes[offset] = le_bytes[0];
        bytes[offset + 1] = le_bytes[1];
        bytes[offset + 2] = le_bytes[2];
        bytes[offset + 3] = le_bytes[3];
        true
    } else {
        false
    }
}

/// Write a 64-bit value into a byte slice in little-endian order.
pub fn write_u64_le(bytes: &mut [u8], offset: usize, value: u64) -> bool {
    if offset + 8 <= bytes.len() {
        let le_bytes = value.to_le_bytes();
        bytes[offset] = le_bytes[0];
        bytes[offset + 1] = le_bytes[1];
        bytes[offset + 2] = le_bytes[2];
        bytes[offset + 3] = le_bytes[3];
        bytes[offset + 4] = le_bytes[4];
        bytes[offset + 5] = le_bytes[5];
        bytes[offset + 6] = le_bytes[6];
        bytes[offset + 7] = le_bytes[7];
        true
    } else {
        false
    }
}

// ============================================================================
// System endianness detection
// ============================================================================

/// Returns true if the host is little-endian (true on x86/x86-64).
#[inline]
pub fn is_little_endian() -> bool {
    cfg!(target_endian = "little")
}

/// Returns true if the host is big-endian.
#[inline]
pub fn is_big_endian() -> bool {
    cfg!(target_endian = "big")
}

/// LLVM's internal endianness: llvm::support::endian
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Endianness {
    Little,
    Big,
}

impl Endianness {
    /// Detect the host endianness.
    pub fn native() -> Self {
        if is_little_endian() {
            Endianness::Little
        } else {
            Endianness::Big
        }
    }

    /// Detect the network byte order (always big-endian).
    pub fn network() -> Self {
        Endianness::Big
    }

    pub fn is_little(&self) -> bool {
        *self == Endianness::Little
    }

    pub fn is_big(&self) -> bool {
        *self == Endianness::Big
    }

    /// Convert a value from this endianness to host byte order.
    pub fn read_u16(&self, bytes: &[u8], offset: usize) -> Option<u16> {
        match self {
            Endianness::Little => read_u16_le(bytes, offset),
            Endianness::Big => read_u16_be(bytes, offset),
        }
    }

    pub fn read_u32(&self, bytes: &[u8], offset: usize) -> Option<u32> {
        match self {
            Endianness::Little => read_u32_le(bytes, offset),
            Endianness::Big => read_u32_be(bytes, offset),
        }
    }

    pub fn read_u64(&self, bytes: &[u8], offset: usize) -> Option<u64> {
        match self {
            Endianness::Little => read_u64_le(bytes, offset),
            Endianness::Big => read_u64_be(bytes, offset),
        }
    }

    /// Write a value in this endianness into a byte slice.
    pub fn write_u16(&self, bytes: &mut [u8], offset: usize, value: u16) -> bool {
        match self {
            Endianness::Little => write_u16_le(bytes, offset, value),
            Endianness::Big => write_u16_be(bytes, offset, value),
        }
    }

    pub fn write_u32(&self, bytes: &mut [u8], offset: usize, value: u32) -> bool {
        match self {
            Endianness::Little => write_u32_le(bytes, offset, value),
            Endianness::Big => write_u32_be(bytes, offset, value),
        }
    }

    pub fn write_u64(&self, bytes: &mut [u8], offset: usize, value: u64) -> bool {
        match self {
            Endianness::Little => write_u64_le(bytes, offset, value),
            Endianness::Big => write_u64_be(bytes, offset, value),
        }
    }
}

// ============================================================================
// Packed endian-aware types (used for parsing binary formats)
// ============================================================================

/// A 16-bit value stored in a specific endianness.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct PackedU16<const IS_LE: bool>(u16);

/// A 32-bit value stored in a specific endianness.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct PackedU32<const IS_LE: bool>(u32);

/// A 64-bit value stored in a specific endianness.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct PackedU64<const IS_LE: bool>(u64);

impl<const IS_LE: bool> PackedU16<IS_LE> {
    /// Create from a native host value.
    pub fn new(value: u16) -> Self {
        if IS_LE {
            Self(value.to_le())
        } else {
            Self(value.to_be())
        }
    }

    /// Get the native host value.
    pub fn get(&self) -> u16 {
        if IS_LE {
            u16::from_le(self.0)
        } else {
            u16::from_be(self.0)
        }
    }

    /// Set from a native host value.
    pub fn set(&mut self, value: u16) {
        *self = Self::new(value);
    }
}

impl<const IS_LE: bool> PackedU32<IS_LE> {
    pub fn new(value: u32) -> Self {
        if IS_LE {
            Self(value.to_le())
        } else {
            Self(value.to_be())
        }
    }

    pub fn get(&self) -> u32 {
        if IS_LE {
            u32::from_le(self.0)
        } else {
            u32::from_be(self.0)
        }
    }

    pub fn set(&mut self, value: u32) {
        *self = Self::new(value);
    }
}

impl<const IS_LE: bool> PackedU64<IS_LE> {
    pub fn new(value: u64) -> Self {
        if IS_LE {
            Self(value.to_le())
        } else {
            Self(value.to_be())
        }
    }

    pub fn get(&self) -> u64 {
        if IS_LE {
            u64::from_le(self.0)
        } else {
            u64::from_be(self.0)
        }
    }

    pub fn set(&mut self, value: u64) {
        *self = Self::new(value);
    }
}

/// Type aliases for common endian formats.
pub type U16Le = PackedU16<true>;
pub type U16Be = PackedU16<false>;
pub type U32Le = PackedU32<true>;
pub type U32Be = PackedU32<false>;
pub type U64Le = PackedU64<true>;
pub type U64Be = PackedU64<false>;

// ============================================================================
// Tests
// ============================================================================

#[cfg(test)]
mod tests {
    use super::*;

    // === Byte swap tests ===

    #[test]
    fn test_byte_swap_16() {
        assert_eq!(byte_swap_16(0x1234), 0x3412);
        assert_eq!(byte_swap_16(0x00FF), 0xFF00);
    }

    #[test]
    fn test_byte_swap_32() {
        assert_eq!(byte_swap_32(0x12345678), 0x78563412);
    }

    #[test]
    fn test_byte_swap_64() {
        assert_eq!(byte_swap_64(0x0123456789ABCDEF), 0xEFCDAB8967452301);
    }

    // === Network byte order tests ===

    #[test]
    fn test_hton_ntoh_roundtrip_16() {
        let original: u16 = 0xABCD;
        assert_eq!(ntoh_16(hton_16(original)), original);
    }

    #[test]
    fn test_hton_ntoh_roundtrip_32() {
        let original: u32 = 0xDEADBEEF;
        assert_eq!(ntoh_32(hton_32(original)), original);
    }

    #[test]
    fn test_hton_ntoh_roundtrip_64() {
        let original: u64 = 0x0123456789ABCDEF;
        assert_eq!(ntoh_64(hton_64(original)), original);
    }

    #[test]
    fn test_hton_be_equivalent_16() {
        assert_eq!(hton_16(0x1234), 0x1234u16.to_be());
    }

    #[test]
    fn test_hton_be_equivalent_32() {
        assert_eq!(hton_32(0x12345678), 0x12345678u32.to_be());
    }

    // === Little-endian roundtrip tests ===

    #[test]
    fn test_htole_letoh_roundtrip_32() {
        let original: u32 = 0xCAFEBABE;
        assert_eq!(letoh_32(htole_32(original)), original);
    }

    #[test]
    fn test_htole_letoh_roundtrip_64() {
        let original: u64 = 0xFEDCBA9876543210;
        assert_eq!(letoh_64(htole_64(original)), original);
    }

    // === Read tests ===

    #[test]
    fn test_read_u16_be() {
        let bytes = [0x12, 0x34, 0x56];
        assert_eq!(read_u16_be(&bytes, 0), Some(0x1234));
        assert_eq!(read_u16_be(&bytes, 1), Some(0x3456));
        assert_eq!(read_u16_be(&bytes, 2), None);
    }

    #[test]
    fn test_read_u32_le() {
        let bytes = [0x78, 0x56, 0x34, 0x12, 0xFF];
        assert_eq!(read_u32_le(&bytes, 0), Some(0x12345678));
        assert_eq!(read_u32_le(&bytes, 1), Some(0xFF123456));
        assert_eq!(read_u32_le(&bytes, 2), None);
    }

    #[test]
    fn test_read_u64_be() {
        let bytes = [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x42, 0x00];
        // Offset 0: 0x0000000000000042 = 66
        assert_eq!(read_u64_be(&bytes, 0), Some(66));
        // Offset 1: 0x0000000000004200 = 66 * 256 = 16896
        assert_eq!(read_u64_be(&bytes, 1), Some(16896));
        assert_eq!(read_u64_be(&bytes, 2), None);
    }

    #[test]
    fn test_read_u16_le() {
        let bytes = [0x34, 0x12];
        assert_eq!(read_u16_le(&bytes, 0), Some(0x1234));
    }

    #[test]
    fn test_read_out_of_bounds() {
        let bytes = [0x01];
        assert_eq!(read_u16_le(&bytes, 0), None);
        assert_eq!(read_u32_le(&bytes, 0), None);
        assert_eq!(read_u64_be(&bytes, 0), None);
    }

    // === Write tests ===

    #[test]
    fn test_write_u16_be() {
        let mut bytes = [0u8; 4];
        assert!(write_u16_be(&mut bytes, 0, 0x1234));
        assert_eq!(bytes[0..2], [0x12, 0x34]);
    }

    #[test]
    fn test_write_u32_le() {
        let mut bytes = [0u8; 6];
        assert!(write_u32_le(&mut bytes, 1, 0xDEADBEEF));
        assert_eq!(bytes[1..5], [0xEF, 0xBE, 0xAD, 0xDE]);
    }

    #[test]
    fn test_write_u64_be() {
        let mut bytes = [0u8; 8];
        assert!(write_u64_be(&mut bytes, 0, 0x0102030405060708));
        assert_eq!(bytes, [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08]);
    }

    #[test]
    fn test_write_oob() {
        let mut bytes = [0u8; 3];
        assert!(!write_u32_le(&mut bytes, 0, 0x12345678));
        assert!(!write_u64_be(&mut bytes, 0, 0));
        assert!(write_u16_le(&mut bytes, 1, 0xABCD)); // 2 bytes at offset 1 fits
    }

    // === Write-read roundtrip ===

    #[test]
    fn test_write_read_roundtrip_be() {
        let mut bytes = [0u8; 100];
        write_u32_be(&mut bytes, 10, 0xCAFEBABE);
        assert_eq!(read_u32_be(&bytes, 10), Some(0xCAFEBABE));
    }

    #[test]
    fn test_write_read_roundtrip_le() {
        let mut bytes = [0u8; 100];
        write_u64_le(&mut bytes, 5, 0xFEDCBA9876543210);
        assert_eq!(read_u64_le(&bytes, 5), Some(0xFEDCBA9876543210));
    }

    // === Endianness detection ===

    #[test]
    fn test_is_little_endian() {
        assert!(is_little_endian()); // x86/x86-64 is always LE
        assert!(!is_big_endian());
    }

    #[test]
    fn test_endianness_native() {
        assert_eq!(Endianness::native(), Endianness::Little);
    }

    #[test]
    fn test_endianness_network() {
        assert_eq!(Endianness::network(), Endianness::Big);
    }

    // === Endianness read/write ===

    #[test]
    fn test_endianness_read_write_le() {
        let mut bytes = [0u8; 10];
        let le = Endianness::Little;
        le.write_u32(&mut bytes, 2, 0x12345678);
        assert_eq!(le.read_u32(&bytes, 2), Some(0x12345678));
        // Reading as big should give different value
        assert_ne!(Endianness::Big.read_u32(&bytes, 2), Some(0x12345678));
    }

    // === Packed types ===

    #[test]
    fn test_packed_u16_le() {
        let packed = U16Le::new(0x1234);
        assert_eq!(packed.get(), 0x1234);
    }

    #[test]
    fn test_packed_u16_be() {
        let packed = U16Be::new(0x1234);
        assert_eq!(packed.get(), 0x1234);
    }

    #[test]
    fn test_packed_u32_le() {
        let packed = U32Le::new(0xDEADBEEF);
        assert_eq!(packed.get(), 0xDEADBEEF);
    }

    #[test]
    fn test_packed_u32_be() {
        let packed = U32Be::new(0xCAFEBABE);
        assert_eq!(packed.get(), 0xCAFEBABE);
    }

    #[test]
    fn test_packed_u64_le() {
        let packed = U64Le::new(0x0123456789ABCDEF);
        assert_eq!(packed.get(), 0x0123456789ABCDEF);
    }

    #[test]
    fn test_packed_u64_be() {
        let packed = U64Be::new(0xFEDCBA9876543210);
        assert_eq!(packed.get(), 0xFEDCBA9876543210);
    }

    #[test]
    fn test_packed_set() {
        let mut packed = U32Le::new(0x100);
        packed.set(0x200);
        assert_eq!(packed.get(), 0x200);
    }

    #[test]
    fn test_packed_le_be_distinct() {
        // Same value packed LE vs BE should produce different raw bytes
        let le = U32Le::new(0x01020304);
        let be = U32Be::new(0x01020304);
        // The internal representations differ (one stores LE, other stores BE bytes)
        assert_ne!(le.0, be.0);
        // But they both roundtrip to the same value
        assert_eq!(le.get(), be.get());
    }

    #[test]
    fn test_identity() {
        // On little-endian, htole should be identity
        assert_eq!(htole_32(0x12345678), 0x12345678u32.to_le());
        // byte_swap twice = identity
        assert_eq!(byte_swap_16(byte_swap_16(0xABCD)), 0xABCD);
        assert_eq!(byte_swap_32(byte_swap_32(0xDEADBEEF)), 0xDEADBEEF);
    }

    #[test]
    fn test_read_empty_slice() {
        let empty: [u8; 0] = [];
        assert_eq!(read_u16_le(&empty, 0), None);
        assert_eq!(read_u32_be(&empty, 0), None);
    }
}