neo-decompiler 0.10.2

Neo N3 NEF decompiler: parse, disassemble, lift bytecode to high-level pseudocode and C# skeletons, with a CLI, JSON reports, and optional WebAssembly bindings.
Documentation 
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use std::collections::BTreeSet;

use crate::instruction::{Instruction, OpCode, Operand};

pub(in super::super::super) fn collect_control_flow_edges(
    instructions: &[Instruction],
    known_offsets: &BTreeSet<usize>,
) -> Vec<(usize, usize)> {
    let mut edges = Vec::new();
    for instruction in instructions {
        match instruction.opcode {
            OpCode::Jmp
            | OpCode::Jmp_L
            | OpCode::Jmpif
            | OpCode::Jmpif_L
            | OpCode::Jmpifnot
            | OpCode::Jmpifnot_L
            | OpCode::JmpEq
            | OpCode::JmpEq_L
            | OpCode::JmpNe
            | OpCode::JmpNe_L
            | OpCode::JmpGt
            | OpCode::JmpGt_L
            | OpCode::JmpGe
            | OpCode::JmpGe_L
            | OpCode::JmpLt
            | OpCode::JmpLt_L
            | OpCode::JmpLe
            | OpCode::JmpLe_L
            | OpCode::Endtry
            | OpCode::EndtryL => {
                if let Some(target) = relative_target(instruction, known_offsets) {
                    edges.push((instruction.offset, target));
                }
            }
            OpCode::Try => {
                if let Some(Operand::Bytes(bytes)) = &instruction.operand {
                    if bytes.len() == 2 {
                        for delta in [bytes[0] as i8 as isize, bytes[1] as i8 as isize] {
                            if let Some(target) =
                                relative_target_with_delta(instruction.offset, delta, known_offsets)
                            {
                                edges.push((instruction.offset, target));
                            }
                        }
                    }
                }
            }
            OpCode::TryL => {
                if let Some(Operand::Bytes(bytes)) = &instruction.operand {
                    if bytes.len() == 8 {
                        let catch_delta =
                            i32::from_le_bytes(bytes[0..4].try_into().expect("slice length"))
                                as isize;
                        let finally_delta =
                            i32::from_le_bytes(bytes[4..8].try_into().expect("slice length"))
                                as isize;
                        for delta in [catch_delta, finally_delta] {
                            if let Some(target) =
                                relative_target_with_delta(instruction.offset, delta, known_offsets)
                            {
                                edges.push((instruction.offset, target));
                            }
                        }
                    }
                }
            }
            _ => {}
        }
    }
    edges
}

pub(in super::super::super) fn relative_target(
    instruction: &Instruction,
    known_offsets: &BTreeSet<usize>,
) -> Option<usize> {
    let delta = match &instruction.operand {
        Some(Operand::Jump(value)) => *value as isize,
        Some(Operand::Jump32(value)) => *value as isize,
        _ => return None,
    };
    relative_target_with_delta(instruction.offset, delta, known_offsets)
}

fn relative_target_with_delta(
    base: usize,
    delta: isize,
    known_offsets: &BTreeSet<usize>,
) -> Option<usize> {
    let target = base as isize + delta;
    if target < 0 {
        return None;
    }
    let target = target as usize;
    known_offsets.contains(&target).then_some(target)
}