Rust 笔记

// 这个地方有点疑惑，为什么必须是 `&mut frame`，去掉 `&mut` 会因两次可变借用而编译失败，进一步改为 `get` 后，会因可变借用和不可变借用同时发生而编译失败
if let Some(&mut frame) = self.transport.frames.get_mut(window_size as usize) {
    self.send_frame(frame.min_id, &frame.payload[0..frame.payload_len as usize], frame.payload_len).unwrap_or(0);
}

if let Some(frame) = self.transport.frames.get_mut(window_size as usize) {
                     --------------------- first mutable borrow occurs here
    self.send_frame(frame.min_id, &frame.payload[0..frame.payload_len as usize], frame.payload_len).unwrap_or(0);
    ^^^^            ------------ first borrow later used here
    |
    second mutable borrow occurs here

if let Some(frame) = self.transport.frames.get(window_size as usize) {
                     --------------------- immutable borrow occurs here
    self.send_frame(frame.min_id, &frame.payload[0..frame.payload_len as usize], frame.payload_len).unwrap_or(0);
    ^^^^^----------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |    |
    |    immutable borrow later used by call
    mutable borrow occurs here

use std::io::{self, Write};

print!("Hello");
io::stdout().flush().unwrap();

let hello = String::from("Hello");
let buf = hello.as_bytes();
assert_eq!(buf, [0x48, 0x65, 0x6c, 0x6c, 0x6f]);

#[allow(non_snake_case)]
#[repr(C)]
pub struct libusb_bos_dev_capability_descriptor {
    pub bLength: u8,
    pub bDescriptorType: u8,
    pub bDevCapabilityType: u8,
    // 这个位置应该是 Capability-Dependent 字段的数据
}

#[allow(non_snake_case)]
#[repr(C)]
pub struct libusb_bos_descriptor {
    pub bLength: u8,
    pub bDescriptorType: u8,
    pub wTotalLength: u16,
    pub bNumDeviceCaps: u8,
    // 这个位置应该是说有的能力描述符开始的内存区域
}

#[allow(non_snake_case)]
#[repr(C)]
pub struct libusb_bos_dev_capability_descriptor {
    pub bLength: u8,
    pub bDescriptorType: u8,
    pub bDevCapabilityType: u8,
    pub dev_capability_data: *const *const u8,
}

#[allow(non_snake_case)]
#[repr(C)]
pub struct libusb_bos_descriptor {
    pub bLength: u8,
    pub bDescriptorType: u8,
    pub wTotalLength: u16,
    pub bNumDeviceCaps: u8,
    pub dev_capability: *const *const libusb_bos_dev_capability_descriptor,
}

pub fn dev_capability(&self) -> Vec<BosDevCapabilityDescriptor> {
    unsafe {
        let mut v: Vec<BosDevCapabilityDescriptor> = Vec::new();
        for i in 0..self.num_device_caps() {
            // 先转换成指针
            let point = std::ptr::addr_of!((*self.descriptor).dev_capability).offset(i as _);
            // 在将指针转换为 *const *const libusb_bos_dev_capability_descriptor，然后解引用两次
            let dev_cap = &(*(*(point as * const *const libusb_bos_dev_capability_descriptor)));
            let cap = BosDevCapabilityDescriptor {
                addr: point as *const *const u8,
                bLength: dev_cap.bLength,
                bDescriptorType: dev_cap.bDescriptorType,
                bDevCapabilityType: dev_cap.bDevCapabilityType,
            };
            v.push(cap);
        }
        v
    }
}

pub struct libusb_bos_descriptor {
    pub bLength: u8,
    pub bDescriptorType: u8,
    pub wTotalLength: u16,
    pub bNumDeviceCaps: u8,
    // 错误是这一行引起的
    pub dev_capability: [*const libusb_bos_dev_capability_descriptor],
}

pub fn dev_capability(&self) -> Vec<libusb_bos_dev_capability_descriptor> {
    unsafe {
        let mut v: Vec<libusb_bos_dev_capability_descriptor> = Vec::new();
        for i in 0..self.num_device_caps() {
            println!("&dev_capability[{}]: {:p}", i, &(*self.descriptor).dev_capability[i as usize]);
            println!("dev_capability[{}]: {:p}", i, &(*((*self.descriptor).dev_capability)[i as usize]));
            let dev_cap = &(*(*self.descriptor).dev_capability[i as usize]);

            let cap = libusb_bos_dev_capability_descriptor {
                bLength: dev_cap.bLength,
                bDescriptorType: dev_cap.bDescriptorType,
                bDevCapabilityType: dev_cap.bDevCapabilityType,
                //dev_capability_data: dev_cap.dev_capability_data,
            };
            v.push(cap);
        }
        v
    }
}

for cap in bos_desc.dev_capability() {
    println!("      bLength:                 {}", cap.bLength);
    println!("      bDescriptorType:         {}", cap.bDescriptorType);
    println!("      bDevCapabilityType:      {}", cap.bDevCapabilityType);
    //println!("      dev_capability_data:     {}", cap.dev_capability_data);
}

pub struct libusb_bos_descriptor {
    pub bLength: u8,
    pub bDescriptorType: u8,
    pub wTotalLength: u16,
    pub bNumDeviceCaps: u8,
    // 错误是这一行引起的
    pub dev_capability: [*const libusb_bos_dev_capability_descriptor],
}

pub fn dev_capability(&self) -> &[*const libusb_bos_dev_capability_descriptor] {
    unsafe {
        &(*self.descriptor).dev_capability
    }
}

for cap in bos_desc.dev_capability() {
    unsafe {
        println!("      bLength:                 {}", (*(*cap)).bLength);
        println!("      bDescriptorType:         {}", (*(*cap)).bDescriptorType);
        println!("      bDevCapabilityType:      {}", (*(*cap)).bDevCapabilityType);
        //println!("      dev_capability_data:     {}", cap.dev_capability_data);
    }
}