wasmer/src/apis/emscripten/utils.rs

use byteorder::{ByteOrder, LittleEndian};
use crate::webassembly::module::Module;
use crate::webassembly::Instance;
use libc::stat;
use std::ffi::{CStr, CString};
use std::os::raw::c_char;
use std::slice;
use std::mem::size_of;

/// We check if a provided module is an Emscripten generated one
pub fn is_emscripten_module(module: &Module) -> bool {
    for (module, field) in &module.info.imported_funcs {
        if field == "_emscripten_memcpy_big" && module == "env" {
            return true;
        }
    }
    return false;
}

pub unsafe fn copy_cstr_into_wasm(instance: &Instance, cstr: *const c_char) -> u32 {
    let s = CStr::from_ptr(cstr).to_str().unwrap();
    let space_offset = (instance.emscripten_data.as_ref().unwrap().malloc)(s.len() as _, instance);
    let raw_memory = instance.memory_offset_addr(0, space_offset as _) as *mut u8;
    let slice = slice::from_raw_parts_mut(raw_memory, s.len());

    for (byte, loc) in s.bytes().zip(slice.iter_mut()) {
        *loc = byte;
    }
    space_offset
}

pub unsafe fn copy_cstr_array_into_wasm(array_count: u32, array: *mut *mut c_char, instance: &Instance) -> u32 {
    let array_offset = (instance.emscripten_data.as_ref().unwrap().malloc)((array_count as usize * size_of::<u32>()) as _, instance);

    let array_addr = instance.memory_offset_addr(0, array_offset as _) as *mut u32;
    for i in 0..array_count {
        let offset = copy_cstr_into_wasm(
            instance,
            *array.offset(i as isize)
        );
        *array_addr.offset(i as isize) = offset;
    }

    // let first_arg_addr = instance.memory_offset_addr(0, *array_addr.offset(0) as _) as *const i8;
    // debug!("###### argv[0] = {:?}", CStr::from_ptr(first_arg_addr));

    array_offset
}

pub unsafe fn copy_terminated_array_of_cstrs(
    _instance: &mut Instance,
    cstrs: *mut *mut c_char,
) -> u32 {
    let total_num = {
        let mut ptr = cstrs;
        let mut counter = 0;
        while !(*ptr).is_null() {
            counter += 1;
            ptr = ptr.add(1);
        }
        counter
    };
    debug!(
        "emscripten::copy_terminated_array_of_cstrs::total_num: {}",
        total_num
    );
    0
}

pub unsafe fn copy_stat_into_wasm(instance: &mut Instance, buf: u32, stat: &stat) {
    let buf_ptr = instance.memory_offset_addr(0, buf as _) as *mut u8;
    let buf = slice::from_raw_parts_mut(buf_ptr, 76);

    LittleEndian::write_u32(&mut buf[..], stat.st_dev as _);
    LittleEndian::write_u32(&mut buf[4..], 0);
    LittleEndian::write_u32(&mut buf[8..], stat.st_ino as _);
    LittleEndian::write_u32(&mut buf[12..], stat.st_mode as _);
    LittleEndian::write_u32(&mut buf[16..], stat.st_nlink as _);
    LittleEndian::write_u32(&mut buf[20..], stat.st_uid);
    LittleEndian::write_u32(&mut buf[24..], stat.st_gid);
    LittleEndian::write_u32(&mut buf[28..], stat.st_rdev as _);
    LittleEndian::write_u32(&mut buf[32..], 0);
    LittleEndian::write_u32(&mut buf[36..], stat.st_size as _);
    LittleEndian::write_u32(&mut buf[40..], 4096);
    LittleEndian::write_u32(&mut buf[44..], stat.st_blocks as _);
    LittleEndian::write_u32(&mut buf[48..], stat.st_atime as _);
    LittleEndian::write_u32(&mut buf[52..], 0);
    LittleEndian::write_u32(&mut buf[56..], stat.st_mtime as _);
    LittleEndian::write_u32(&mut buf[60..], 0);
    LittleEndian::write_u32(&mut buf[64..], stat.st_ctime as _);
    LittleEndian::write_u32(&mut buf[68..], 0);
    LittleEndian::write_u32(&mut buf[72..], stat.st_ino as _);
}

#[cfg(test)]
mod tests {
    use super::super::generate_emscripten_env;
    use super::is_emscripten_module;
    use crate::webassembly::instantiate;

    #[test]
    fn should_detect_emscripten_files() {
        let wasm_bytes = include_wast2wasm_bytes!("tests/is_emscripten_true.wast");
        let import_object = generate_emscripten_env();
        let result_object = instantiate(wasm_bytes, import_object).expect("Not compiled properly");
        assert!(is_emscripten_module(&result_object.module));
    }

    #[test]
    fn should_detect_non_emscripten_files() {
        let wasm_bytes = include_wast2wasm_bytes!("tests/is_emscripten_false.wast");
        let import_object = generate_emscripten_env();
        let result_object = instantiate(wasm_bytes, import_object).expect("Not compiled properly");
        assert!(!is_emscripten_module(&result_object.module));
    }
}