rwasm 0.4.3

ZK-friendly WebAssembly runtime optimized for blockchain and zero-knowledge applications
Documentation 
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use crate::{ElementSegmentIdx, InstructionSet, TableIdx, TrapCode};
use rwasm_fuel_policy::{TABLE_ELEMS_PER_FUEL, TABLE_ELEMS_PER_FUEL_LOG2};

impl InstructionSet {
    pub const MSH_TABLE_INIT_CHECKED: u32 = 2;
    pub const MSH_TABLE_GROW_CHECKED: u32 = 2;
    pub const MSH_TABLE_FILL_CHECKED: u32 = 2;
    pub const MSH_TABLE_COPY_CHECKED: u32 = 2;

    /// Max stack height: 2
    pub fn op_table_init_checked(
        &mut self,
        segment_index: ElementSegmentIdx,
        table_index: TableIdx,
        length: u32,
        offset: u32,
        inject_fuel_check: bool,
    ) {
        // [d, s, n]
        self.op_local_get(1); // n
        self.op_local_get(3); // s
        self.op_i32_add(); // n+s
        self.op_i32_const(length); // length
        self.op_i32_gt_s(); // n+s>length
        self.op_br_if_eqz(2);
        self.op_trap(TrapCode::TableOutOfBounds);
        // we need to replace the offset on the stack with the new value
        if offset > 0 {
            self.op_i32_const(offset);
            self.op_local_get(3);
            self.op_i32_add();
            self.op_local_set(2);
        }
        // charge fuel for this call after all checks
        if inject_fuel_check {
            self.op_local_get(1); // n
            self.op_i32_const(TABLE_ELEMS_PER_FUEL - 1); // upper round
            self.op_i32_add();
            self.op_i32_const(TABLE_ELEMS_PER_FUEL_LOG2); // 2^4=16
            self.op_i32_shr_u(); // n/16
            self.op_consume_fuel_stack();
        }
        self.op_table_init(segment_index);
        self.op_table_get(table_index);
    }

    /// Max stack height: 2
    pub fn op_table_grow_checked(
        &mut self,
        table_idx: TableIdx,
        limit_check: Option<u32>,
        inject_fuel_check: bool,
    ) {
        // [init, delta]
        if let Some(limit) = limit_check {
            self.op_local_get(1); // n
            self.op_table_size(table_idx); // table_size
            self.op_i32_add(); // n+table_size
            self.op_i32_const(limit); // limit
            self.op_i32_gt_s(); // n+table_size>limit
            self.op_br_if_eqz(5);
            self.op_drop();
            self.op_drop();
            // we don't trap here, because, according to a wasm standard, we should put u32::MAX on
            // the top of the stack in case of overflow
            self.op_i32_const(u32::MAX);
            self.op_br(if inject_fuel_check { 8 } else { 2 });
        }
        if inject_fuel_check {
            self.op_local_get(1); // n
            self.op_i32_const(TABLE_ELEMS_PER_FUEL - 1); // upper round
            self.op_i32_add();
            self.op_i32_const(TABLE_ELEMS_PER_FUEL_LOG2); // 2^4=16
            self.op_i32_shr_u(); // n/16
            self.op_consume_fuel_stack();
        }
        self.op_table_grow(table_idx);
    }

    /// Max stack height: 2
    pub fn op_table_fill_checked(&mut self, table_idx: TableIdx, inject_fuel_check: bool) {
        if inject_fuel_check {
            self.op_local_get(1); // n
            self.op_i32_const(TABLE_ELEMS_PER_FUEL - 1); // upper round
            self.op_i32_add();
            self.op_i32_const(TABLE_ELEMS_PER_FUEL_LOG2); // 2^4=16
            self.op_i32_shr_u(); // n/16
            self.op_consume_fuel_stack();
        }
        self.op_table_fill(table_idx);
    }

    /// Max stack height: 2
    pub fn op_table_copy_checked(
        &mut self,
        dst_table_idx: TableIdx,
        src_table_idx: TableIdx,
        inject_fuel_check: bool,
    ) {
        if inject_fuel_check {
            self.op_local_get(1); // n
            self.op_i32_const(TABLE_ELEMS_PER_FUEL - 1); // upper round
            self.op_i32_add();
            self.op_i32_const(TABLE_ELEMS_PER_FUEL_LOG2); // 2^4=16
            self.op_i32_shr_u(); // n/16
            self.op_consume_fuel_stack();
        }
        self.op_table_copy(dst_table_idx, src_table_idx);
    }
}