test that instruction lengths are correct

fix several instances of incorrect instruction lengths

* immediates for `mov reg, imm` and some other instructions were double-counted
* lengths for vex prefixes were wrong all over the place

2 files changed, 3 insertions, 3 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 9409ca9..500d59d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4757,7 +4757,6 @@ fn read_operands<T: Iterator<Item=u8>>(decoder: &InstDecoder, mut bytes_iter: T,
                 RegSpec::gp_from_parts(reg, instruction.prefixes.rex().b(), 1, instruction.prefixes.rex().present());
             instruction.imm =
                 read_imm_unsigned(&mut bytes_iter, 1, length)?;
-            *length += 1;
             instruction.operands[1] = OperandSpec::ImmU8;
             instruction.operand_count = 2;
         } else {
@@ -4774,7 +4773,6 @@ fn read_operands<T: Iterator<Item=u8>>(decoder: &InstDecoder, mut bytes_iter: T,
                 RegSpec::from_parts(reg, instruction.prefixes.rex().b(), bank);
             instruction.imm =
                 read_imm_ivq(&mut bytes_iter, opwidth, length)?;
-            *length += opwidth;
             instruction.operands[1] = match opwidth {
                 1 => OperandSpec::ImmI8,
                 2 => OperandSpec::ImmI16,
@@ -4947,7 +4945,6 @@ fn read_operands<T: Iterator<Item=u8>>(decoder: &InstDecoder, mut bytes_iter: T,
             instruction.operands[0] = mem_oper;
             let numwidth = if opwidth == 8 { 4 } else { opwidth };
             instruction.imm = read_imm_signed(&mut bytes_iter, numwidth, length)? as u64;
-            *length = numwidth;
             instruction.opcode = base_opcode_map((modrm >> 3) & 7);
             instruction.operands[1] = match opwidth {
                 1 => OperandSpec::ImmI8,
diff --git a/src/vex.rs b/src/vex.rs
index 99cee01..8a7434f 100644
--- a/src/vex.rs
+++ b/src/vex.rs
@@ -89,6 +89,7 @@ enum VEXOperandCode {
 pub(crate) fn three_byte_vex<T: Iterator<Item=u8>>(bytes: &mut T, instruction: &mut Instruction, mut length: u8) -> Result<(), DecodeError> {
     let vex_byte_one = bytes.next().ok_or(DecodeError::ExhaustedInput)?;
     let vex_byte_two = bytes.next().ok_or(DecodeError::ExhaustedInput)?;
+    length += 2;
     let p = vex_byte_two & 0x03;
     let p = match p {
         0x00 => VEXOpcodePrefix::None,
@@ -121,6 +122,7 @@ pub(crate) fn three_byte_vex<T: Iterator<Item=u8>>(bytes: &mut T, instruction: &
 
 pub(crate) fn two_byte_vex<T: Iterator<Item=u8>>(bytes: &mut T, instruction: &mut Instruction, mut length: u8) -> Result<(), DecodeError> {
     let vex_byte = bytes.next().ok_or(DecodeError::ExhaustedInput)?;
+    length += 1;
     let p = vex_byte & 0x03;
     let p = match p {
         0x00 => VEXOpcodePrefix::None,
@@ -553,6 +555,7 @@ fn read_vex_operands<T: Iterator<Item=u8>>(bytes: &mut T, instruction: &mut Inst
 
 fn read_vex_instruction<T: Iterator<Item=u8>>(opcode_map: VEXOpcodeMap, bytes: &mut T, instruction: &mut Instruction, length: &mut u8, p: VEXOpcodePrefix) -> Result<(), DecodeError> {
     let opc = bytes.next().ok_or(DecodeError::ExhaustedInput)?;
+    *length += 1;
 
     // the name of this bit is `L` in the documentation, so use the same name here.
     #[allow(non_snake_case)]