tauri中使用rust调用动态链接库例子（使用libloading库和libc库）

前言

当前采用桌面端框架位tauri，现在需要调用读卡器等硬件设备，硬件厂商提供了32位的动态链接库，现在记录例子，需要注意的点是使用libloading库和libc库，

[package]
name = "yyt-device-rust"
version = "0.0.1"
description = "yyt-device-rust"
authors = ["Alaia"]
license = ""
repository = ""
edition = "2021"# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html[build-dependencies]
tauri-build = { version = "1.2", features = [] }[dependencies]
tauri = { version = "1.2", features = [ "api-all"] }
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"
mac_address="*"
//重点依赖
libloading = "0.8"
encoding = "0.2.33"
libc = "0.2"[features]
# this feature is used for production builds or when `devPath` points to the filesystem
# DO NOT REMOVE!!
custom-protocol = ["tauri/custom-protocol"]

#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]use std::ffi::CString;
use libc::*;
use libloading::{Library, Symbol};
use encoding_rs::*;type DcInit = extern "stdcall" fn(port: c_int, baud: c_int) -> *mut c_int;
type DcFindSpeed = extern "stdcall" fn(icdev: *mut c_int) -> *mut c_int;
type DcCardInfo = extern "stdcall" fn(icdev: *mut c_int,typeNum: c_int,text_len: &c_int,text: *mut c_char,photo_len: &c_int,photo: *mut c_char,fingerprint_len: &c_int, fingerprint: *mut c_char,extra_len: &c_int,extra: *mut c_char,
) -> *mut c_int;
type DcParseTextInfo = extern "stdcall" fn(icdev: *mut c_int,typeNum: c_int,text_len: &c_int,text: *mut c_char,name: *mut c_char,sex: *mut c_char,nation: *mut c_char,birth_day: *mut c_char,address: *mut c_char,id_number: *mut c_char,department: *mut c_char,expire_start_day: *mut c_char,expire_end_day: *mut c_char,reserved: *mut c_char,
) -> *mut c_int;
type DcExit = extern "stdcall" fn(icdev: *mut c_int,
) -> *mut c_int;type PrintInput = extern "stdcall" fn(InInfo: *mut c_char,OutInfo: *mut c_char,
) -> *mut c_void;#[tauri::command]
fn get_mac_addr() -> Result<String, String> {let mac_result = mac_address::get_mac_address();if let Ok(Some(mac)) = mac_result {Ok(mac.to_string().into())} else {println!("Get Address Error");Err("Rust Get Address Error".into())}
}#[tauri::command]
fn print_tickertape(input: String) -> Result<String, String> {let res: String = call_dynamic(input).unwrap();println!("Hello, world! {:?}", res);return Ok(res);
}#[tauri::command]
fn read_id_card() -> Result<String, String> {let res: String = call_dynamic_card().unwrap();println!("Hello, world! {:?}", res);return Ok(res);
}fn call_dynamic_card() -> Result<String, Box<dyn std::error::Error>> {unsafe {let lib: libloading::Library = libloading::Library::new("lib/dekabig/idCard/dcrf32.dll")?;let dc_init: libloading::Symbol<DcInit> = lib.get(b"dc_init")?;let dc_find_i_d_speed: libloading::Symbol<DcFindSpeed> = lib.get(b"dc_find_i_d_speed")?;let dc_sam_aread_card_info: libloading::Symbol<DcCardInfo> = lib.get(b"dc_SamAReadCardInfo")?;let dc_parse_text_info: libloading::Symbol<DcParseTextInfo> = lib.get(b"dc_ParseTextInfo")?;let dc_exit: libloading::Symbol<DcExit> = lib.get(b"dc_exit")?;let device_no: *mut c_int = dc_init(100, 115200);let dc_find_i_d_speed = dc_find_i_d_speed(device_no);println!("{:?}", device_no);println!("{:?}", dc_find_i_d_speed);let mut text_len = 256i32;let mut photo_len = 1024i32;let mut fingerprint_len = 1024i32;let mut extra_len = 70i32;let mut into_text = [0u8; 256];let mut into_photo = [0u8; 1024];let mut into_fingerprint = [0u8; 1024];let mut into_extra = [0u8; 70];let dc_sam_aread_card_info = dc_sam_aread_card_info(device_no,3,&text_len,into_text.as_mut_ptr() as *mut i8,&photo_len,into_photo.as_mut_ptr() as *mut i8,&fingerprint_len,into_fingerprint.as_mut_ptr() as *mut i8,&extra_len,into_extra.as_mut_ptr() as *mut i8,);println!("{:?}", dc_sam_aread_card_info);let mut name = [0u8; 64];let mut sex = [0u8; 8];let mut nation = [0u8; 12];let mut birth_day = [0u8; 36];let mut address = [0u8; 144];let mut id_number = [0u8; 76];let mut department = [0u8; 64];let mut expire_start_day = [0u8; 36];let mut expire_end_day = [0u8; 36];let mut reserved = [0u8; 76];let dc_parse_text_info = dc_parse_text_info(device_no,0,&text_len,into_text.as_mut_ptr() as *mut i8,name.as_mut_ptr() as *mut i8,sex.as_mut_ptr() as *mut i8,nation.as_mut_ptr() as *mut i8,birth_day.as_mut_ptr() as *mut i8,address.as_mut_ptr() as *mut i8,id_number.as_mut_ptr() as *mut i8,department.as_mut_ptr() as *mut i8,expire_start_day.as_mut_ptr() as *mut i8,expire_end_day.as_mut_ptr() as *mut i8,reserved.as_mut_ptr() as *mut i8,);let nameC = &name[0..strlen(name.as_ptr() as *const i8)];let (nameutf, _, _) = GBK.decode(nameC);println!("nameutf: {}", nameutf);let dc_exit = dc_exit(device_no);println!("dc_exit: {:?}", dc_exit);return Ok("123".into());}
}fn call_dynamic(json: String) -> Result<String, Box<dyn std::error::Error>> {unsafe {let lib: libloading::Library = libloading::Library::new("lib/dekabig/tickertape/DC_Print.dll")?;let print_t: libloading::Symbol<PrintInput> = lib.get(b"Print_Input")?;let (json_out, _, _) = GBK.encode(&json);let cstring = CString::new(json_out).expect("cstring error");let mut output = [0u8; 1024];print_t(cstring.into_raw(), output.as_mut_ptr() as *mut i8,);let output_c: &[u8] = &output[0..strlen(output.as_ptr() as *const i8)];let (outputf, _, _)= GBK.decode(output_c);println!("nameutf: {}", outputf);return Ok(outputf.to_string());}
}fn main() {tauri::Builder::default().invoke_handler(tauri::generate_handler![get_mac_addr,print_tickertape,read_id_card]).run(tauri::generate_context!()).expect("error while running tauri application");
}

其他注意项：首先，对于只需要传值的字符串，很好解决，&str/ String都可以简单地传递就能使用。

对于需要提前分配的char*/char[]，简单办法就是使用固定长度数组作为参数。
获取返回值如果存的是字符串，使用strlen得到修改后的真正长度，然后构建vec，然后通过vec构建String。

如果是函数返回值char*则，简单方法使用CStr加载；也可以类似参数那样，使用strlen探测长度，然后构建vec然后转到String。

在libc中，c_char/c_int/c_float…都是i8/i32…的别名，所以，一般使用rust固有类型可能会更好理解。

回调函数也可以作为普通的指针传递就OK了。

参考例子

//参考例子extern crate libc;
extern crate libloading;use libc::*;
use libloading::{Library, Symbol};/*
// test_c.dll 接口内容SDK_API void test_normal(int a, float b, const char* c){printf("a: %d, b: %.2f, c: %s\n", a, b, c);
}SDK_API void test_p(int* a, float* b, char* c){printf("set *a=112233, *b=3.1415926, c='1234567890'\n");*a = 112233;*b = 3.1415926f;strcpy(c, "1234567890");
}typedef struct _TEST_OBJ
{int a;float* b;char c[256];
}TEST_OBJ;SDK_API void test_t(TEST_OBJ* arg){arg->a = 222;arg->b = NULL;strcpy(arg->c, u8"hello, world! 你好！~");
}
typedef  int(*CB_FUN)(int a);SDK_API int test_cb(CB_FUN p){printf("cb: %X, call p(10)\n", p);int a = p(10);return a;
}
*/type fn_test_normal = unsafe fn(c_int, c_float, &str);
type fn_test_p = unsafe fn(&c_int, &c_float, *mut c_char);#[repr(C)]
#[derive(Clone, Copy)]
struct fn_struct_t {a: c_int,b: *mut c_float,c: [u8; 256],
}type fn_test_t = unsafe fn(&mut fn_struct_t);type fn_test_cb = unsafe fn( fn(i32)->i32 ) -> i32;fn main() {let lib = Library::new("test_c.dll").unwrap();unsafe {let fun1: Symbol<fn_test_normal> = lib.get(b"test_normal").unwrap();fun1(1, 2.21, "Hello,world\0"); // rust 字符串没有结尾的\0,};println!();unsafe {let mut arg1 = 0i32;let mut arg2 = 0f32;let mut arg3 = [0u8; 256];  // 分配存储空间let fun2: Symbol<fn_test_p> = lib.get(b"test_p").unwrap();fun2(&arg1, &arg2, arg3.as_mut_ptr() as *mut i8); // set *a=112233, *b=3.1415926, c='1234567890'println!("{} {} {:?}", arg1, arg2, arg3[0]); // 112233 3.1415925 49
//        let s = String::from_raw_parts(arg3.as_mut_ptr() as *mut u8, strlen(arg3.as_ptr()), arg3.len());
//        println!("ret: {}", s); // ret: 1234567890, 有buf, 会导致下面的无输出，故使用3的方式构建字符串let sv = &arg3[0..strlen(arg3.as_ptr() as *const i8)]; // 通过strlen构造对应字符串的数组let s = String::from_utf8_unchecked(sv.to_vec()); // 字符串使用utf8编码的u8println!("ret: {}", s); // ret: 1234567890};println!();unsafe {let mut arg = fn_struct_t { a: 0, b: 0 as *mut f32, c: [0u8; 256] };let fun3: Symbol<fn_test_t> = lib.get(b"test_t").unwrap();fun3(&mut arg);println!("{} {:?} {:?}", arg.a, arg.b, arg.c[0]); // 222 0x0 104let sv = &arg.c[0..strlen(arg.c.as_ptr() as *const i8)]; // 通过strlen构造对应字符串的数组let s = String::from_utf8_unchecked(sv.to_vec()); // 字符串使用utf8编码的u8println!("ret: {}", s); // ret: hello, world! 你好！~};println!();unsafe {let arg = |arg:i32| {println!("arg cb called! arg is {}", arg); arg*10+123};let fun4: Symbol<fn_test_cb> = lib.get(b"test_cb").unwrap();let r = fun4(arg);println!("ret: {}", r); // 223};
}