有大佬熟悉 ffi 么，如何从 ffi 获取 array 返回值

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#[no_mangle]
pub extern "C" fn decode(raw: *const libc::c_char) -> *mut u32 {
    let str_raw = unsafe { CStr::from_ptr(raw) }.to_str().unwrap().to_string();
    let bytes_raw = hex::decode(str_raw).unwrap();
    let mut u8_fixed: [u32; 6] = Decode::decode(&mut &bytes_raw[..]).unwrap();
    let ptr = u8_fixed.as_mut_ptr();
    std::mem::forget(u8_fixed);
    ptr
}

nodejs code


let libm = ffi.Library(rootPath, {
   'decode': [ref.refType("uint"), ['string']],
}
let value = libm.decode("010000000200000003000000040000000500000006000000")

decode 的 value 返回值应该是 []uint{1,2,3,4,5,6} ,现在打印出 value 看起来像是个 buffer, 不知道怎么解析这个 buffer

8 replies • 2024-01-07 17:58:39 +08:00

nomagick

Aug 7, 2022

https://www.npmjs.com/package/ref-array-di

freehere

Aug 8, 2022

@nomagick 看过了 example 和 test ，测试了一下，还是没有搞出来

nomagick

Aug 8, 2022

@freehere 你这个函数返回的是 ref(array(uint)), 第一层是个指针，你拿到的 buffer 是指针的值，把它 deref(), 才是 array(uint)

freehere

Aug 8, 2022

@nomagick 试了一下，只返回了第一个 value, test 在这里 https://github.com/gmajor-encrypt/scale-codec-comparator/blob/main/polkadot-js/test/base.spec.ts#L167

k1263

Aug 26, 2022

Decode::decode 哪里来的？自己定义的吗？

freehere

Aug 31, 2022

@k1263 这个地方 https://github.com/gmajor-encrypt/scale-codec-comparator/blob/main/src/lib.rs#L6

k1263

Sep 7, 2022

@freehere
我的这一步会出错，CStr::from_ptr(raw).to_str()，你的出错吗？

#[no_mangle]
pub extern "C" fn decode(raw: *const libc::c_char) -> *mut u32 {
if raw.is_null() {
return ptr::null_mut();
}
if let Ok(str_raw) = unsafe { CStr::from_ptr(raw).to_str() } {
println!("str_raw: {:?}", str_raw);
let bytes_raw = hex::decode(str_raw).unwrap();
let mut u8_fixed: [u32; 6] = Decode::decode(&mut &bytes_raw[..]).unwrap();
let ptr = u8_fixed.as_mut_ptr();
std::mem::forget(u8_fixed);
ptr
} else {
println!("str_raw fail");
return ptr::null_mut();
}

}

pub fn main() {
let raw = "010000000200000003000000040000000500000006000000";
let aa = decode(raw.as_ptr() as *const i8);
println!("{:?}", aa);
}

zhangyuang

Jan 7, 2024

用 ffi-rs,https://github.com/zhangyuang/node-ffi-rs