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authoriximeow <me@iximeow.net>2020-12-06 22:16:43 -0800
committeriximeow <me@iximeow.net>2020-12-06 22:19:55 -0800
commit589e11b0e1ff53f4d3e8edff2e77c72df38036f8 (patch)
tree7811ae1ba1e61718bca23d658db3b1f12a3995f8 /src
initial commit
Diffstat (limited to 'src')
-rw-r--r--src/lib.rs804
1 files changed, 804 insertions, 0 deletions
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..6c0f79c
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,804 @@
+#[cfg(feature="use-serde")]
+#[macro_use] extern crate serde_derive;
+#[cfg(feature="use-serde")]
+extern crate serde;
+
+extern crate yaxpeax_arch;
+
+extern crate core;
+
+use core::fmt;
+
+use yaxpeax_arch::AddressDiff;
+use yaxpeax_arch::Arch;
+use yaxpeax_arch::Decoder;
+use yaxpeax_arch::LengthedInstruction;
+
+#[cfg(feature="use-serde")]
+#[derive(Debug, Serialize, Deserialize)]
+pub struct SM83;
+
+#[cfg(not(feature="use-serde"))]
+#[derive(Debug)]
+pub struct SM83;
+
+impl Arch for SM83 {
+ type Address = u16;
+ type Instruction = Instruction;
+ type DecodeError = DecodeError;
+ type Decoder = InstDecoder;
+ type Operand = Operand;
+}
+
+#[derive(Debug, Copy, Clone)]
+pub struct Instruction {
+ opcode: Opcode,
+ operands: [Operand; 2],
+ length: u8,
+}
+
+impl Instruction {
+ pub fn opcode(&self) -> Opcode {
+ self.opcode
+ }
+
+ pub fn operands(&self) -> &[Operand; 2] {
+ &self.operands
+ }
+
+ pub fn length(&self) -> u8 {
+ self.length
+ }
+}
+
+impl Default for Instruction {
+ fn default() -> Instruction {
+ Instruction {
+ opcode: Opcode::NOP,
+ operands: [Operand::Nothing, Operand::Nothing],
+ length: 1,
+ }
+ }
+}
+
+impl fmt::Display for Instruction {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ write!(f, "{}", self.opcode())?;
+ let ops = self.operands();
+ if ops[0] != Operand::Nothing {
+ write!(f, " {}", ops[0])?;
+ }
+ if ops[1] != Operand::Nothing {
+ write!(f, ", {}", ops[1])?;
+ }
+ Ok(())
+ }
+}
+
+impl LengthedInstruction for Instruction {
+ type Unit = AddressDiff<<SM83 as Arch>::Address>;
+ fn min_size() -> Self::Unit {
+ AddressDiff::from_const(1)
+ }
+ fn len(&self) -> Self::Unit {
+ AddressDiff::from_const(self.length as u16)
+ }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum DecodeError {
+ ExhaustedInput,
+ InvalidOpcode,
+ Incomplete,
+}
+
+impl yaxpeax_arch::DecodeError for DecodeError {
+ fn data_exhausted(&self) -> bool { self == &DecodeError::ExhaustedInput }
+ fn bad_opcode(&self) -> bool { self == &DecodeError::InvalidOpcode }
+ fn bad_operand(&self) -> bool { false }
+}
+
+impl fmt::Display for DecodeError {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ match self {
+ DecodeError::ExhaustedInput => { write!(f, "exhausted input") }
+ DecodeError::InvalidOpcode => { write!(f, "invalid opcode") }
+ DecodeError::Incomplete => { write!(f, "incomplete") }
+ }
+ }
+}
+
+impl yaxpeax_arch::Instruction for Instruction {
+ // only decode well-formed instructions (for now???)
+ fn well_defined(&self) -> bool { true }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub enum Operand {
+ A,
+ B,
+ C,
+ D,
+ E,
+ H,
+ L,
+ AF,
+ BC,
+ DE,
+ HL,
+ SP,
+ DerefHL,
+ DerefBC,
+ DerefDE,
+ DerefDecHL,
+ DerefIncHL,
+ DerefHighC,
+ DerefHighD8(u8),
+ SPWithOffset(i8),
+ Bit(u8),
+ D8(u8),
+ I8(i8),
+ R8(i8),
+ A16(u16),
+ D16(u16),
+
+ CondC,
+ CondNC,
+ CondZ,
+ CondNZ,
+
+ Nothing,
+}
+
+impl fmt::Display for Operand {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ match self {
+ Operand::A => write!(f, "a"),
+ Operand::B => write!(f, "b"),
+ Operand::C => write!(f, "c"),
+ Operand::D => write!(f, "d"),
+ Operand::E => write!(f, "e"),
+ Operand::H => write!(f, "h"),
+ Operand::L => write!(f, "l"),
+ Operand::AF => write!(f, "af"),
+ Operand::BC => write!(f, "bc"),
+ Operand::DE => write!(f, "de"),
+ Operand::HL => write!(f, "hl"),
+ Operand::SP => write!(f, "sp"),
+ Operand::DerefHL => write!(f, "[hl]"),
+ Operand::DerefBC => write!(f, "[bc]"),
+ Operand::DerefDE => write!(f, "[de]"),
+ Operand::DerefDecHL => write!(f, "[hl-]"),
+ Operand::DerefIncHL => write!(f, "[hl+]"),
+ Operand::DerefHighC => write!(f, "[0xff00 + c]"),
+ Operand::DerefHighD8(imm) => write!(f, "[$ff00 + ${:02x}]", imm),
+ Operand::SPWithOffset(imm) => {
+ if *imm == -128 {
+ write!(f, "[sp - $80]")
+ } else if *imm >= 0 {
+ write!(f, "[sp + ${:02x}]", imm)
+ } else {
+ write!(f, "[sp - ${:02x}]", -imm)
+ }
+ }
+ Operand::Bit(imm) => write!(f, "{}", imm),
+ Operand::D8(imm) => write!(f, "${:02x}", imm),
+ Operand::D16(imm) => write!(f, "${:04x}", imm),
+ Operand::I8(imm) => {
+ if *imm == -128 {
+ write!(f, "-0x80")
+ } else if *imm >= 0 {
+ write!(f, "${:02x}", imm)
+ } else {
+ write!(f, "-${:02x}", -imm)
+ }
+ }
+ Operand::R8(imm) => {
+ if *imm == -128 {
+ write!(f, "$-0x80")
+ } else if *imm >= 0 {
+ write!(f, "$+${:02x}", imm)
+ } else {
+ write!(f, "$-${:02x}", -imm)
+ }
+ }
+ Operand::A16(addr) => write!(f, "[${:4x}]", addr),
+
+ Operand::CondC => write!(f, "C"),
+ Operand::CondNC => write!(f, "nC"),
+ Operand::CondZ => write!(f, "Z"),
+ Operand::CondNZ => write!(f, "nZ"),
+
+ Operand::Nothing => write!(f, "nothing (BUG: should not be shown)"),
+ }
+ }
+}
+
+#[derive(Debug, Copy, Clone)]
+enum OperandSpec {
+ A,
+ B,
+ C,
+ D,
+ E,
+ H,
+ L,
+ AF,
+ BC,
+ DE,
+ HL,
+ SP,
+ DerefHL,
+ DerefBC,
+ DerefDE,
+ DerefDecHL,
+ DerefIncHL,
+ DerefHighC,
+ DerefHighD8,
+ SPWithOffset,
+ D8,
+ R8,
+ I8,
+ A16,
+ D16,
+
+ CondC,
+ CondNC,
+ CondZ,
+ CondNZ,
+
+ Bit(u8),
+ Imm(u8),
+
+ Nothing,
+}
+
+#[derive(Debug, Copy, Clone)]
+pub enum Opcode {
+ NOP,
+
+ LD,
+
+ DEC,
+ INC,
+
+ ADC,
+ ADD,
+ SBC,
+ SUB,
+
+ AND,
+ XOR,
+ OR,
+ CP,
+
+ POP,
+ PUSH,
+
+ JP,
+ JR,
+ CALL,
+ RET,
+ RETI,
+ HALT,
+ RST,
+ STOP,
+
+ RLCA,
+ RRCA,
+ RLA,
+ RRA,
+
+ DAA,
+ CPL,
+ SCF,
+ CCF,
+
+ DI,
+ EI,
+
+ LDH,
+
+ RLC,
+ RRC,
+ RL,
+ RR,
+ SLA,
+ SRA,
+ SWAP,
+ SRL,
+ BIT,
+ RES,
+ SET,
+}
+
+impl fmt::Display for Opcode {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ match self {
+ Opcode::NOP => write!(f, "nop"),
+
+ Opcode::LD => write!(f, "ld"),
+
+ Opcode::DEC => write!(f, "dec"),
+ Opcode::INC => write!(f, "inc"),
+
+ Opcode::ADC => write!(f, "adc"),
+ Opcode::ADD => write!(f, "add"),
+ Opcode::SBC => write!(f, "sbc"),
+ Opcode::SUB => write!(f, "sub"),
+
+ Opcode::AND => write!(f, "and"),
+ Opcode::XOR => write!(f, "xor"),
+ Opcode::OR => write!(f, "or"),
+ Opcode::CP => write!(f, "cp"),
+
+ Opcode::POP => write!(f, "pop"),
+ Opcode::PUSH => write!(f, "push"),
+
+ Opcode::JP => write!(f, "jp"),
+ Opcode::JR => write!(f, "jr"),
+ Opcode::CALL => write!(f, "call"),
+ Opcode::RET => write!(f, "ret"),
+ Opcode::RETI => write!(f, "reti"),
+ Opcode::HALT => write!(f, "halt"),
+ Opcode::RST => write!(f, "rst"),
+ Opcode::STOP => write!(f, "stop"),
+
+ Opcode::RLCA => write!(f, "rlca"),
+ Opcode::RRCA => write!(f, "rrca"),
+ Opcode::RLA => write!(f, "rla"),
+ Opcode::RRA => write!(f, "rra"),
+
+ Opcode::DAA => write!(f, "daa"),
+ Opcode::CPL => write!(f, "cpl"),
+ Opcode::SCF => write!(f, "scf"),
+ Opcode::CCF => write!(f, "ccf"),
+
+ Opcode::DI => write!(f, "di"),
+ Opcode::EI => write!(f, "ei"),
+
+ Opcode::LDH => write!(f, "ldh"),
+
+ Opcode::RLC => write!(f, "rlc"),
+ Opcode::RRC => write!(f, "rrc"),
+ Opcode::RL => write!(f, "rl"),
+ Opcode::RR => write!(f, "rr"),
+ Opcode::SLA => write!(f, "sla"),
+ Opcode::SRA => write!(f, "sra"),
+ Opcode::SWAP => write!(f, "swap"),
+ Opcode::SRL => write!(f, "srl"),
+ Opcode::BIT => write!(f, "bit"),
+ Opcode::RES => write!(f, "res"),
+ Opcode::SET => write!(f, "set"),
+ }
+ }
+}
+
+#[derive(Debug)]
+pub struct InstDecoder { }
+
+impl Default for InstDecoder {
+ fn default() -> Self {
+ InstDecoder { }
+ }
+}
+
+// main operand map is used for ld, arithmetic, and $CB-prefixed instructions
+const OPMAP: [OperandSpec; 8] = [
+ OperandSpec::B,
+ OperandSpec::C,
+ OperandSpec::D,
+ OperandSpec::E,
+ OperandSpec::H,
+ OperandSpec::L,
+ OperandSpec::DerefHL,
+ OperandSpec::A,
+];
+
+const UPPER_INSTRUCTIONS: [(Option<Opcode>, [OperandSpec; 2]); 64] = [
+ // 0xc0
+ (Some(Opcode::RET), [OperandSpec::CondNZ, OperandSpec::Nothing]),
+ (Some(Opcode::POP), [OperandSpec::BC, OperandSpec::Nothing]),
+ (Some(Opcode::JP), [OperandSpec::CondNZ, OperandSpec::D16]),
+ (Some(Opcode::JP), [OperandSpec::D16, OperandSpec::Nothing]),
+ (Some(Opcode::CALL), [OperandSpec::CondNZ, OperandSpec::D16]),
+ (Some(Opcode::PUSH), [OperandSpec::BC, OperandSpec::Nothing]),
+ (Some(Opcode::ADD), [OperandSpec::D8, OperandSpec::Nothing]),
+ (Some(Opcode::RST), [OperandSpec::Imm(0x00), OperandSpec::Nothing]),
+ // 0xc8
+ (Some(Opcode::RET), [OperandSpec::CondZ, OperandSpec::Nothing]),
+ (Some(Opcode::RET), [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::JP), [OperandSpec::CondNC, OperandSpec::D16]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::CALL), [OperandSpec::CondZ, OperandSpec::D16]),
+ (Some(Opcode::CALL), [OperandSpec::D16, OperandSpec::Nothing]),
+ (Some(Opcode::ADC), [OperandSpec::D8, OperandSpec::Nothing]),
+ (Some(Opcode::RST), [OperandSpec::Imm(0x08), OperandSpec::Nothing]),
+ // 0xd0
+ (Some(Opcode::RET), [OperandSpec::CondNC, OperandSpec::Nothing]),
+ (Some(Opcode::POP), [OperandSpec::DE, OperandSpec::Nothing]),
+ (Some(Opcode::JP), [OperandSpec::CondNC, OperandSpec::D16]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::CALL), [OperandSpec::CondNC, OperandSpec::D16]),
+ (Some(Opcode::PUSH), [OperandSpec::DE, OperandSpec::Nothing]),
+ (Some(Opcode::SUB), [OperandSpec::D8, OperandSpec::Nothing]),
+ (Some(Opcode::RST), [OperandSpec::Imm(0x10), OperandSpec::Nothing]),
+ // 0xd8
+ (Some(Opcode::RET), [OperandSpec::CondC, OperandSpec::Nothing]),
+ (Some(Opcode::RETI), [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::JP), [OperandSpec::CondC, OperandSpec::D16]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::CALL), [OperandSpec::CondC, OperandSpec::D16]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::SBC), [OperandSpec::D8, OperandSpec::Nothing]),
+ (Some(Opcode::RST), [OperandSpec::Imm(0x18), OperandSpec::Nothing]),
+ // 0xe0
+ (Some(Opcode::LDH), [OperandSpec::DerefHighD8, OperandSpec::A]),
+ (Some(Opcode::POP), [OperandSpec::HL, OperandSpec::Nothing]),
+ (Some(Opcode::LDH), [OperandSpec::DerefHighC, OperandSpec::A]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::PUSH), [OperandSpec::HL, OperandSpec::Nothing]),
+ (Some(Opcode::AND), [OperandSpec::D8, OperandSpec::Nothing]),
+ (Some(Opcode::RST), [OperandSpec::Imm(0x20), OperandSpec::Nothing]),
+ // 0xe8
+ (Some(Opcode::ADD), [OperandSpec::SP, OperandSpec::I8]),
+ (Some(Opcode::JP), [OperandSpec::HL, OperandSpec::Nothing]),
+ (Some(Opcode::LD), [OperandSpec::A16, OperandSpec::A]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::XOR), [OperandSpec::D8, OperandSpec::Nothing]),
+ (Some(Opcode::RST), [OperandSpec::Imm(0x28), OperandSpec::Nothing]),
+ // 0xf0
+ (Some(Opcode::LDH), [OperandSpec::A, OperandSpec::DerefHighD8]),
+ (Some(Opcode::POP), [OperandSpec::AF, OperandSpec::Nothing]),
+ (Some(Opcode::LDH), [OperandSpec::A, OperandSpec::DerefHighC]),
+ (Some(Opcode::DI), [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::PUSH), [OperandSpec::AF, OperandSpec::Nothing]),
+ (Some(Opcode::OR), [OperandSpec::D8, OperandSpec::Nothing]),
+ (Some(Opcode::RST), [OperandSpec::Imm(0x30), OperandSpec::Nothing]),
+ // 0xf8
+ (Some(Opcode::LD), [OperandSpec::HL, OperandSpec::SPWithOffset]),
+ (Some(Opcode::LD), [OperandSpec::SP, OperandSpec::HL]),
+ (Some(Opcode::LD), [OperandSpec::A, OperandSpec::A16]),
+ (Some(Opcode::EI), [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (None, [OperandSpec::Nothing, OperandSpec::Nothing]),
+ (Some(Opcode::CP), [OperandSpec::D8, OperandSpec::Nothing]),
+ (Some(Opcode::RST), [OperandSpec::Imm(0x38), OperandSpec::Nothing]),
+];
+
+impl Decoder<Instruction> for InstDecoder {
+ type Error = DecodeError;
+
+ fn decode_into<T: IntoIterator<Item=u8>>(&self, inst: &mut Instruction, bytes: T) -> Result<(), Self::Error> {
+ let mut iter = bytes.into_iter();
+
+ let opc: u8 = iter.next().ok_or(DecodeError::ExhaustedInput)?;
+ inst.length = 1;
+
+ let high = ((opc >> 3) & 0b111) as usize;
+ let low = (opc & 0b111) as usize;
+
+ // early part of the table is more varied, more special cases
+ if opc < 0x40 {
+ let (opcode, operands) = match low {
+ 0 => {
+ // special case on high
+ match high {
+ 0 => { (Opcode::NOP, [OperandSpec::Nothing, OperandSpec::Nothing]) },
+ 1 => { (Opcode::LD, [OperandSpec::A16, OperandSpec::SP]) },
+ 2 => { (Opcode::STOP, [OperandSpec::Nothing, OperandSpec::Nothing]) },
+ 3 => { (Opcode::JR, [OperandSpec::R8, OperandSpec::Nothing]) },
+ 4 => { (Opcode::JR, [OperandSpec::CondNZ, OperandSpec::R8]) },
+ 5 => { (Opcode::JR, [OperandSpec::CondZ, OperandSpec::R8]) },
+ 6 => { (Opcode::JR, [OperandSpec::CondNC, OperandSpec::R8]) },
+ 7 => { (Opcode::JR, [OperandSpec::CondC, OperandSpec::R8]) },
+ _ => { unreachable!("impossible bit pattern"); }
+ }
+ }
+ 1 => {
+ // also special case, but fewer
+ if high & 1 == 0 {
+ let opcode = Opcode::LD;
+ let ops = [[
+ OperandSpec::BC,
+ OperandSpec::DE,
+ OperandSpec::HL,
+ OperandSpec::SP,
+ ][high as usize >> 1], OperandSpec::D16];
+ (opcode, ops)
+ } else {
+ let opcode = Opcode::ADD;
+ let ops = [OperandSpec::HL, [
+ OperandSpec::BC,
+ OperandSpec::DE,
+ OperandSpec::HL,
+ OperandSpec::SP,
+ ][high as usize >> 1]];
+ (opcode, ops)
+ }
+ }
+ 2 => {
+ let op = Opcode::LD;
+ if high & 1 == 0 {
+ let op0 = [
+ OperandSpec::DerefBC,
+ OperandSpec::DerefDE,
+ OperandSpec::DerefIncHL,
+ OperandSpec::DerefDecHL,
+ ][high as usize >> 1];
+ (op, [op0, OperandSpec::A])
+ } else {
+ let op1 = [
+ OperandSpec::DerefBC,
+ OperandSpec::DerefDE,
+ OperandSpec::DerefIncHL,
+ OperandSpec::DerefDecHL,
+ ][high as usize >> 1];
+ (op, [OperandSpec::A, op1])
+ }
+ }
+ 3 => {
+ if high & 1 == 0 {
+ let op0 = [
+ OperandSpec::BC,
+ OperandSpec::DE,
+ OperandSpec::HL,
+ OperandSpec::SP,
+ ][high as usize >> 1];
+ (Opcode::INC, [op0, OperandSpec::Nothing])
+ } else {
+ let op0 = [
+ OperandSpec::BC,
+ OperandSpec::DE,
+ OperandSpec::HL,
+ OperandSpec::SP,
+ ][high as usize >> 1];
+ (Opcode::DEC, [op0, OperandSpec::Nothing])
+ }
+ }
+ 4 => {
+ let op = Opcode::INC;
+ let op0 = [
+ OperandSpec::B,
+ OperandSpec::C,
+ OperandSpec::D,
+ OperandSpec::E,
+ OperandSpec::H,
+ OperandSpec::L,
+ OperandSpec::DerefHL,
+ OperandSpec::A,
+ ][high as usize];
+ (op, [op0, OperandSpec::Nothing])
+ }
+ 5 => {
+ let op = Opcode::DEC;
+ let op0 = [
+ OperandSpec::B,
+ OperandSpec::C,
+ OperandSpec::D,
+ OperandSpec::E,
+ OperandSpec::H,
+ OperandSpec::L,
+ OperandSpec::DerefHL,
+ OperandSpec::A,
+ ][high as usize];
+ (op, [op0, OperandSpec::Nothing])
+ }
+ 6 => {
+ let op = Opcode::LD;
+ let op0 = [
+ OperandSpec::B,
+ OperandSpec::C,
+ OperandSpec::D,
+ OperandSpec::E,
+ OperandSpec::H,
+ OperandSpec::L,
+ OperandSpec::DerefHL,
+ OperandSpec::A,
+ ][high as usize];
+ (op, [op0, OperandSpec::D8])
+ }
+ 7 => {
+ // special cases here too
+ let op = [
+ Opcode::RLCA,
+ Opcode::RRCA,
+ Opcode::RLA,
+ Opcode::RRA,
+ Opcode::DAA,
+ Opcode::CPL,
+ Opcode::SCF,
+ Opcode::CCF,
+ ][high as usize];
+ (op, [OperandSpec::Nothing, OperandSpec::Nothing])
+ }
+ _ => {
+ unreachable!("impossible bit pattern");
+ }
+ };
+ inst.opcode = opcode;
+ interpret_operands(iter, inst, operands)?;
+ return Ok(());
+ } else if opc < 0x80 {
+ if opc == 0x76 {
+ inst.opcode = Opcode::HALT;
+ inst.operands = [Operand::Nothing, Operand::Nothing];
+ return Ok(());
+ } else {
+ inst.opcode = Opcode::LD;
+ interpret_operands(iter, inst, [OPMAP[high], OPMAP[low]])?;
+ return Ok(());
+ }
+ } else if opc < 0xc0 {
+ const OPCODES: [Opcode; 8] = [
+ Opcode::ADD,
+ Opcode::ADC,
+ Opcode::SUB,
+ Opcode::SBC,
+ Opcode::AND,
+ Opcode::XOR,
+ Opcode::OR,
+ Opcode::CP,
+ ];
+ inst.opcode = OPCODES[high];
+ let operands = [OPMAP[low], OperandSpec::Nothing];
+ interpret_operands(iter, inst, operands)?;
+ return Ok(());
+ } else {
+ if opc == 0xcb {
+ // sm83 special CB-prefixed instructions
+ let opc: u8 = iter.next().ok_or(DecodeError::ExhaustedInput)?;
+ inst.length += 1;
+ if opc < 0x40 {
+ let high = (opc >> 3) & 0b111;
+ let low = opc & 0b111;
+ const LOW_OP: [OperandSpec; 8] = [
+ OperandSpec::B,
+ OperandSpec::C,
+ OperandSpec::D,
+ OperandSpec::E,
+ OperandSpec::H,
+ OperandSpec::L,
+ OperandSpec::DerefHL,
+ OperandSpec::A,
+ ];
+ let operands = [LOW_OP[low as usize], OperandSpec::Nothing];
+ const OPCODES: [Opcode; 8] = [
+ Opcode::RLC,
+ Opcode::RRC,
+ Opcode::RL,
+ Opcode::RR,
+ Opcode::SLA,
+ Opcode::SRA,
+ Opcode::SWAP,
+ Opcode::SRL,
+ ];
+ inst.opcode = OPCODES[high as usize];
+ interpret_operands(iter, inst, operands)?;
+ return Ok(());
+ } else {
+ let bit = (opc >> 3) & 0b111;
+ let low = opc & 0b111;
+ const LOW_OP: [OperandSpec; 8] = [
+ OperandSpec::B,
+ OperandSpec::C,
+ OperandSpec::D,
+ OperandSpec::E,
+ OperandSpec::H,
+ OperandSpec::L,
+ OperandSpec::DerefHL,
+ OperandSpec::A,
+ ];
+ let operands = [OperandSpec::Bit(bit), LOW_OP[low as usize]];
+ const OPCODES: [Opcode; 3] = [
+ Opcode::BIT,
+ Opcode::RES,
+ Opcode::SET,
+ ];
+ inst.opcode = OPCODES[(opc >> 6) as usize - 1];
+ interpret_operands(iter, inst, operands)?;
+ return Ok(());
+ }
+ } else {
+ // there is no special thing we can do here. do a table lookup.
+ let (maybe_opcode, operands) = UPPER_INSTRUCTIONS[opc as usize - 0xc0];
+ if let Some(opcode) = maybe_opcode {
+ inst.opcode = opcode;
+ interpret_operands(iter, inst, operands)?;
+ return Ok(());
+ } else {
+ return Err(DecodeError::InvalidOpcode);
+ }
+ }
+ }
+ }
+}
+
+fn interpret_operands<I: Iterator<Item=u8>>(mut iter: I, inst: &mut Instruction, operands: [OperandSpec; 2]) -> Result<(), DecodeError> {
+ inst.operands[0] = interpret_operand(&mut iter, inst, operands[0])?;
+ inst.operands[1] = interpret_operand(&mut iter, inst, operands[1])?;
+ Ok(())
+}
+
+fn interpret_operand<I: Iterator<Item=u8>>(iter: &mut I, inst: &mut Instruction, operand: OperandSpec) -> Result<Operand, DecodeError> {
+ let operand = match operand {
+ OperandSpec::A => Operand::A,
+ OperandSpec::B => Operand::B,
+ OperandSpec::C => Operand::C,
+ OperandSpec::D => Operand::D,
+ OperandSpec::E => Operand::E,
+ OperandSpec::H => Operand::H,
+ OperandSpec::L => Operand::L,
+ OperandSpec::AF => Operand::AF,
+ OperandSpec::BC => Operand::BC,
+ OperandSpec::DE => Operand::DE,
+ OperandSpec::HL => Operand::HL,
+ OperandSpec::SP => Operand::SP,
+ OperandSpec::DerefHL => Operand::DerefHL,
+ OperandSpec::DerefBC => Operand::DerefBC,
+ OperandSpec::DerefDE => Operand::DerefDE,
+ OperandSpec::DerefDecHL => Operand::DerefDecHL,
+ OperandSpec::DerefIncHL => Operand::DerefIncHL,
+ OperandSpec::D8 => {
+ let imm = iter.next().ok_or(DecodeError::ExhaustedInput)?;
+ inst.length += 1;
+ Operand::D8(imm)
+ }
+ OperandSpec::DerefHighC => {
+ Operand::DerefHighC
+ }
+ OperandSpec::DerefHighD8 => {
+ let imm = iter.next().ok_or(DecodeError::ExhaustedInput)?;
+ inst.length += 1;
+ Operand::DerefHighD8(imm)
+ }
+ OperandSpec::R8 => {
+ let imm = iter.next().ok_or(DecodeError::ExhaustedInput)?;
+ inst.length += 1;
+ Operand::R8(imm as i8)
+ }
+ OperandSpec::I8 => {
+ let imm = iter.next().ok_or(DecodeError::ExhaustedInput)?;
+ inst.length += 1;
+ Operand::I8(imm as i8)
+ }
+ OperandSpec::A16 => {
+ let imm =
+ (iter.next().ok_or(DecodeError::ExhaustedInput)? as u16) |
+ ((iter.next().ok_or(DecodeError::ExhaustedInput)? as u16) << 8);
+ inst.length += 2;
+ Operand::A16(imm as u16)
+ }
+ OperandSpec::D16 => {
+ let imm =
+ (iter.next().ok_or(DecodeError::ExhaustedInput)? as u16) |
+ ((iter.next().ok_or(DecodeError::ExhaustedInput)? as u16) << 8);
+ inst.length += 2;
+ Operand::D16(imm as u16)
+ }
+ OperandSpec::SPWithOffset => {
+ let imm = iter.next().ok_or(DecodeError::ExhaustedInput)?;
+ inst.length += 1;
+ Operand::SPWithOffset(imm as i8)
+ }
+
+ OperandSpec::Imm(u) => {
+ Operand::D8(u)
+ }
+ OperandSpec::Bit(u) => {
+ Operand::Bit(u)
+ }
+
+ OperandSpec::CondC => Operand::CondC,
+ OperandSpec::CondNC => Operand::CondNC,
+ OperandSpec::CondZ => Operand::CondZ,
+ OperandSpec::CondNZ => Operand::CondNZ,
+
+ OperandSpec::Nothing => Operand::Nothing,
+ };
+ Ok(operand)
+}