/*!
Length Disassembler
===================

Supports `x86` and `x86_64` up to `SSE4.2`.

Valid opcodes will be length disassembled correctly. Invalid opcodes may be rejected on a best-effort basis.

## Examples

Gets the length of the first opcode in a byte slice:

```
let result = lde::X64.ld(b"\x40\x55\x48\x83\xEC\xFC\x00\x80");
assert_eq!(result, 2);
```

Iterates over the opcodes contained in a byte slice, returning the opcode and its virtual address:

```
let code = b"\x40\x55\x48\x83\xEC*\x00\x80";
# let mut result_opcodes = vec![&code[0..2], &code[2..6]].into_iter();
# let mut result_vas = vec![0x1000, 0x1002].into_iter();

for (opcode, va) in lde::X64.iter(code, 0x1000) {
	println!("{:x}: {}", va, opcode);
# 	assert_eq!(result_opcodes.next(), Some(opcode.into()));
# 	assert_eq!(result_vas.next(), Some(va));
}

// 1000: 4055
// 1002: 4883EC2A
```

Find the opcode boundary after a minimum of 5 bytes:

```
// 1000: 56         push esi
// 1001: 33f6       xor esi,esi
// 1003: 57         push edi
// 1004: bfa0104000 mov edi,0x4010a0
// 1009: 85d2       test edx,edx
// 100b: 7410       je loc_0000001d
// 100d: 8bf2       mov esi,edx
// 100f: 8bfa       mov edi,edx

const INPUT_CODE: &[u8] = b"\x56\x33\xF6\x57\xBF\xA0\x10\x40\x00\x85\xD2\x74\x10\x8B\xF2\x8B\xFA";

// We'd like to overwrite the first 5 bytes with a jmp hook
// Find how many opcodes need to be copied for our hook to work

let mut count = 0;
for (opcode, _) in lde::X86.iter(INPUT_CODE, 0x1000) {
	count += opcode.len();
	if count >= 5 {
		break;
	}
}

// The answer is the first 4 opcodes, or 9 bytes

assert_eq!(count, 9);
```

Custom `Display` and `Debug` formatting including pretty printing support with the alternate flag:

```
let iter = lde::X64.iter(b"\x40\x55\x48\x83\xEC*\x00\x80", 0);

assert_eq!(format!("{:?}", iter), "[4055] [4883EC2A] 0080");
assert_eq!(format!("{:#?}", iter), "[40 55] [48 83 EC 2A] 00 80");
assert_eq!(format!("{:}", iter), "4055\n4883EC2A\n");
assert_eq!(format!("{:#}", iter), "40 55\n48 83 EC 2A\n");
```
*/

#![no_std]
use core::{cmp, ops};

#[cfg(test)]
#[macro_use]
extern crate std;

mod lde;

mod opcode;
pub use self::opcode::OpCode;

mod builder;
pub use self::builder::OcBuilder;

mod iter;
pub use self::iter::Iter;

mod iter_mut;
pub use self::iter_mut::IterMut;

//----------------------------------------------------------------

/// Defines a type which can be safely constructed from a byte array of the same size.
///
/// Used to allow reading/writing immediates and displacements.
pub unsafe trait Int: Copy + 'static {}
unsafe impl Int for u8 {}
unsafe impl Int for u16 {}
unsafe impl Int for u32 {}
unsafe impl Int for u64 {}
unsafe impl Int for i8 {}
unsafe impl Int for i16 {}
unsafe impl Int for i32 {}
unsafe impl Int for i64 {}

/// Virtual address type.
pub trait Va: Copy + Ord + ops::Add<Output = Self> + ops::AddAssign {}
impl Va for u32 {}
impl Va for u64 {}

/// Instruction set architecture.
///
/// Defines the entry points for the length disassembler.
pub trait Isa: Sized {
	/// Virtual address type.
	type Va: Va;
	/// Returns the length of the first opcode in the given byte slice.
	///
	/// When length disassembling fails, eg. the byte slice does not contain a complete and valid instruction, the return value is `0`.
	fn ld(bytes: &[u8]) -> u32;
	/// Returns the first opcode in the byte slice if successful.
	fn peek(bytes: &[u8]) -> Option<&OpCode> {
		// The ld function guarantees that the returned length does not exceed the input byte length
		// Convince the optimizer that this indeed the case with a cmp::min
		let len = cmp::min(Self::ld(bytes) as usize, bytes.len());
		if len > 0 { Some((&bytes[..len]).into()) }
		else { None }
	}
	/// Returns the first opcode mutably in the byte slice if successful.
	fn peek_mut(bytes: &mut [u8]) -> Option<&mut OpCode> {
		// The ld function guarantees that the returned length does not exceed the input byte length
		// Convince the optimizer that this indeed the case with a cmp::min
		let len = cmp::min(Self::ld(bytes) as usize, bytes.len());
		if len > 0 { Some((&mut bytes[..len]).into()) }
		else { None }
	}
	/// Returns an iterator over the opcodes contained in the byte slice.
	///
	/// Given a virtual address to keep track of the instruction pointer.
	fn iter<'a>(bytes: &'a [u8], va: Self::Va) -> Iter<'a, Self> {
		Iter { bytes, va }
	}
	/// Returns an iterator over the opcodes contained in the byte slice.
	///
	/// Given a virtual address to keep track of the instruction pointer.
	fn iter_mut<'a>(bytes: &'a mut [u8], va: Self::Va) -> IterMut<'a, Self> {
		IterMut { bytes, va }
	}
	#[doc(hidden)]
	fn as_va(len: usize) -> Self::Va;
}

//----------------------------------------------------------------

/// Length disassembler for the `x86` instruction set architecture.
pub struct X86;
impl Isa for X86 {
	type Va = u32;
	fn ld(bytes: &[u8]) -> u32 {
		lde::x86::lde_int(bytes)
	}
	#[doc(hidden)]
	fn as_va(len: usize) -> u32 {
		len as u32
	}
}
impl X86 {
	/// Returns the length of the first opcode in the given byte slice.
	///
	/// When length disassembling fails, eg. the byte slice does not contain a complete and valid instruction, the return value is `0`.
	pub fn ld(self, bytes: &[u8]) -> u32 {
		<X86 as Isa>::ld(bytes)
	}
	/// Returns the first opcode in the byte slice if successful.
	pub fn peek(self, bytes: &[u8]) -> Option<&OpCode> {
		<X86 as Isa>::peek(bytes)
	}
	/// Returns the first opcode mutably in the byte slice if successful.
	pub fn peek_mut(self, bytes: &mut [u8]) -> Option<&mut OpCode> {
		<X86 as Isa>::peek_mut(bytes)
	}
	/// Returns an iterator over the opcodes contained in the byte slice.
	///
	/// Given a virtual address to keep track of the instruction pointer.
	pub fn iter<'a>(self, bytes: &'a [u8], va: u32) -> Iter<'a, X86> {
		<X86 as Isa>::iter(bytes, va)
	}
	/// Returns an iterator over the opcodes contained in the byte slice.
	///
	/// Given a virtual address to keep track of the instruction pointer.
	pub fn iter_mut<'a>(self, bytes: &'a mut [u8], va: u32) -> IterMut<'a, X86> {
		<X86 as Isa>::iter_mut(bytes, va)
	}
}

/// Length disassembler for the `x86_64` instruction set architecture.
pub struct X64;
impl Isa for X64 {
	type Va = u64;
	fn ld(bytes: &[u8]) -> u32 {
		lde::x64::lde_int(bytes)
	}
	#[doc(hidden)]
	fn as_va(len: usize) -> u64 {
		len as u64
	}
}
impl X64 {
	/// Returns the length of the first opcode in the given byte slice.
	///
	/// When length disassembling fails, eg. the byte slice does not contain a complete and valid instruction, the return value is `0`.
	///
	/// # Examples
	///
	/// ```
	/// let code = b"\x40\x55\x48\x83\xEC*\x00\x80";
	/// assert_eq!(lde::X64.ld(code), 2);
	/// ```
	///
	/// ```
	/// let invalid = b"";
	/// assert_eq!(lde::X64.ld(invalid), 0);
	/// ```
	pub fn ld(self, bytes: &[u8]) -> u32 {
		<X64 as Isa>::ld(bytes)
	}
	/// Returns the first opcode in the byte slice if successful.
	///
	/// # Examples
	///
	/// ```
	/// let code = b"\x40\x55\x48\x83\xEC*\x00\x80";
	/// assert_eq!(lde::X64.peek(code), Some(b"\x40\x55".into()));
	/// ```
	pub fn peek(self, bytes: &[u8]) -> Option<&OpCode> {
		<X64 as Isa>::peek(bytes)
	}
	/// Returns the first opcode mutably in the byte slice if successful.
	pub fn peek_mut(self, bytes: &mut [u8]) -> Option<&mut OpCode> {
		<X64 as Isa>::peek_mut(bytes)
	}
	/// Returns an iterator over the opcodes contained in the byte slice.
	///
	/// Given a virtual address to keep track of the instruction pointer.
	///
	/// # Examples
	///
	/// ```
	/// let code = b"\x40\x55\x48\x83\xEC*\x00\x80";
	/// # let mut result_opcodes = vec![&code[0..2], &code[2..6]].into_iter();
	/// # let mut result_vas = vec![0x1000, 0x1002].into_iter();
	///
	/// for (opcode, va) in lde::X64.iter(code, 0x1000) {
	/// 	println!("{:x}: {}", va, opcode);
	/// # 	assert_eq!(result_opcodes.next(), Some(opcode.into()));
	/// # 	assert_eq!(result_vas.next(), Some(va));
	/// }
	/// ```
	///
	/// Prints the following result
	///
	/// ```text
	/// 1000: 4055
	/// 1002: 4883EC2A
	/// ```
	pub fn iter<'a>(self, bytes: &'a [u8], va: u64) -> Iter<'a, X64> {
		<X64 as Isa>::iter(bytes, va)
	}
	/// Returns an iterator over the opcodes contained in the byte slice.
	///
	/// Given a virtual address to keep track of the instruction pointer.
	///
	/// # Examples
	///
	/// ```
	/// let mut code = *b"\x40\x55\x48\x83\xEC*\x00\x80";
	///
	/// for (opcode, va) in lde::X64.iter_mut(&mut code, 0x1000) {
	/// 	opcode.write(0, 0xff_u8);
	/// }
	///
	/// assert_eq!(&code, b"\xff\x55\xff\x83\xEC*\x00\x80");
	/// ```
	pub fn iter_mut<'a>(self, bytes: &'a mut [u8], va: u64) -> IterMut<'a, X64> {
		<X64 as Isa>::iter_mut(bytes, va)
	}
}