g_update_first是什么意思
时间: 2024-05-17 10:13:08 浏览: 12
我不知道上下文是什么,但是根据变量名字,g_update_first很可能是一个标志位或者开关,用来表示是否是第一次更新某个状态或者变量。在程序中,我们可能需要对某个状态或者变量进行更新,但是我们只需要在第一次更新的时候执行一些特殊的操作,之后的更新可以忽略这些操作。因此,我们可以使用一个标志位或者开关来记录是否是第一次更新,从而控制这些特殊的操作是否执行。
相关问题
go语言的爱心代码是什么
```
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<style>
* {
padding: 0;
margin: 0;
}
html,
body {
height: 100%;
padding: 0;
margin: 0;
background: #000;
}
canvas {
position: absolute;
width: 100%;
height: 100%;
}
.aa {
position: fixed;
left: 50%;
bottom: 10px;
color: #ccc;
}
</style>
<body>
<canvas id="pinkboard"></canvas>
<script>
/*
* Settings
*/
var settings = {
particles: {
length: 500, // maximum amount of particles
duration: 2, // particle duration in sec
velocity: 100, // particle velocity in pixels/sec
effect: -0.75, // play with this for a nice effect
size: 30 // particle size in pixels
}
};
/*
* RequestAnimationFrame polyfill by Erik M?ller
*/
(function () {
var b = 0;
var c = ["ms", "moz", "webkit", "o"];
for (var a = 0; a < c.length && !window.requestAnimationFrame; ++a) {
window.requestAnimationFrame = window[c[a] + "RequestAnimationFrame"];
window.cancelAnimationFrame =
window[c[a] + "CancelAnimationFrame"] ||
window[c[a] + "CancelRequestAnimationFrame"];
}
if (!window.requestAnimationFrame) {
window.requestAnimationFrame = function (h, e) {
var d = new Date().getTime();
var f = Math.max(0, 16 - (d - b));
var g = window.setTimeout(function () {
h(d + f);
}, f);
b = d + f;
return g;
};
}
if (!window.cancelAnimationFrame) {
window.cancelAnimationFrame = function (d) {
clearTimeout(d);
};
}
})();
/*
* Point class
*/
var Point = (function () {
function Point(x, y) {
this.x = typeof x !== "undefined" ? x : 0;
this.y = typeof y !== "undefined" ? y : 0;
}
Point.prototype.clone = function () {
return new Point(this.x, this.y);
};
Point.prototype.length = function (length) {
if (typeof length == "undefined")
return Math.sqrt(this.x * this.x + this.y * this.y);
this.normalize();
this.x *= length;
this.y *= length;
return this;
};
Point.prototype.normalize = function () {
var length = this.length();
this.x /= length;
this.y /= length;
return this;
};
return Point;
})();
/*
* Particle class
*/
var Particle = (function () {
function Particle() {
this.position = new Point();
this.velocity = new Point();
this.acceleration = new Point();
this.age = 0;
}
Particle.prototype.initialize = function (x, y, dx, dy) {
this.position.x = x;
this.position.y = y;
this.velocity.x = dx;
this.velocity.y = dy;
this.acceleration.x = dx * settings.particles.effect;
this.acceleration.y = dy * settings.particles.effect;
this.age = 0;
};
Particle.prototype.update = function (deltaTime) {
this.position.x += this.velocity.x * deltaTime;
this.position.y += this.velocity.y * deltaTime;
this.velocity.x += this.acceleration.x * deltaTime;
this.velocity.y += this.acceleration.y * deltaTime;
this.age += deltaTime;
};
Particle.prototype.draw = function (context, image) {
function ease(t) {
return --t * t * t + 1;
}
var size = image.width * ease(this.age / settings.particles.duration);
context.globalAlpha = 1 - this.age / settings.particles.duration;
context.drawImage(
image,
this.position.x - size / 2,
this.position.y - size / 2,
size,
size
);
};
return Particle;
})();
/*
* ParticlePool class
*/
var ParticlePool = (function () {
var particles,
firstActive = 0,
firstFree = 0,
duration = settings.particles.duration;
function ParticlePool(length) {
// create and populate particle pool
particles = new Array(length);
for (var i = 0; i < particles.length; i++)
particles[i] = new Particle();
}
ParticlePool.prototype.add = function (x, y, dx, dy) {
particles[firstFree].initialize(x, y, dx, dy);
// handle circular queue
firstFree++;
if (firstFree == particles.length) firstFree = 0;
if (firstActive == firstFree) firstActive++;
if (firstActive == particles.length) firstActive = 0;
};
ParticlePool.prototype.update = function (deltaTime) {
var i;
// update active particles
if (firstActive < firstFree) {
for (i = firstActive; i < firstFree; i++)
particles[i].update(deltaTime);
}
if (firstFree < firstActive) {
for (i = firstActive; i < particles.length; i++)
particles[i].update(deltaTime);
for (i = 0; i < firstFree; i++) particles[i].update(deltaTime);
}
// remove inactive particles
while (
particles[firstActive].age >= duration &&
firstActive != firstFree
) {
firstActive++;
if (firstActive == particles.length) firstActive = 0;
}
};
ParticlePool.prototype.draw = function (context, image) {
// draw active particles
if (firstActive < firstFree) {
for (i = firstActive; i < firstFree; i++)
particles[i].draw(context, image);
}
if (firstFree < firstActive) {
for (i = firstActive; i < particles.length; i++)
particles[i].draw(context, image);
for (i = 0; i < firstFree; i++) particles[i].draw(context, image);
}
};
return ParticlePool;
})();
/*
* Putting it all together
*/
(function (canvas) {
var context = canvas.getContext("2d"),
particles = new ParticlePool(settings.particles.length),
particleRate =
settings.particles.length / settings.particles.duration, // particles/sec
time;
// get point on heart with -PI <= t <= PI
function pointOnHeart(t) {
return new Point(
160 * Math.pow(Math.sin(t), 3),
130 * Math.cos(t) -
50 * Math.cos(2 * t) -
20 * Math.cos(3 * t) -
10 * Math.cos(4 * t) +
25
);
}
// creating the particle image using a dummy canvas
var image = (function () {
var canvas = document.createElement("canvas"),
context = canvas.getContext("2d");
canvas.width = settings.particles.size;
canvas.height = settings.particles.size;
// helper function to create the path
function to(t) {
var point = pointOnHeart(t);
point.x =
settings.particles.size / 2 +
(point.x * settings.particles.size) / 350;
point.y =
settings.particles.size / 2 -
(point.y * settings.particles.size) / 350;
return point;
}
// create the path
context.beginPath();
var t = -Math.PI;
var point = to(t);
context.moveTo(point.x, point.y);
while (t < Math.PI) {
t += 0.01; // baby steps!
point = to(t);
context.lineTo(point.x, point.y);
}
context.closePath();
// create the fill
context.fillStyle = "#ea80b0";
context.fill();
// create the image
var image = new Image();
image.src = canvas.toDataURL();
return image;
})();
// render that thing!
function render() {
// next animation frame
requestAnimationFrame(render);
// update time
var newTime = new Date().getTime() / 1000,
deltaTime = newTime - (time || newTime);
time = newTime;
// clear canvas
context.clearRect(0, 0, canvas.width, canvas.height);
// create new particles
var amount = particleRate * deltaTime;
for (var i = 0; i < amount; i++) {
var pos = pointOnHeart(Math.PI - 2 * Math.PI * Math.random());
var dir = pos.clone().length(settings.particles.velocity);
particles.add(
canvas.width / 2 + pos.x,
canvas.height / 2 - pos.y,
dir.x,
-dir.y
);
}
// update and draw particles
particles.update(deltaTime);
particles.draw(context, image);
}
// handle (re-)sizing of the canvas
function onResize() {
canvas.width = canvas.clientWidth;
canvas.height = canvas.clientHeight;
}
window.onresize = onResize;
// delay rendering bootstrap
setTimeout(function () {
onResize();
render();
}, 10);
})(document.getElementById("pinkboard"));
</script>
</body>
</html>
```
![示例图片](https://devbit-static.oss-cn-beijing.aliyuncs.com/devbit-static/img/heart.png)
nrf52832 2.4g获取设备rssi
要获取nrf52832设备的2.4G信号强度指示(RSSI),您需要在nrf52832上运行适当的代码并使用BLE协议栈 API。以下是一个示例代码片段,可以在nrf52832上获取连接设备的RSSI值:
```c
#include <stdbool.h>
#include <stdint.h>
#include "nrf_delay.h"
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_sdh.h"
#include "nrf_sdh_ble.h"
#include "ble.h"
#include "ble_gap.h"
// 定义一个 ble_gap_evt_handler_t 类型的函数,
// 用于处理 GAP (Generic Access Profile) 事件
void ble_gap_evt_handler(ble_gap_evt_t const * p_gap_evt, void * p_context)
{
switch (p_gap_evt->params.rssi_changed.rssi)
{
case BLE_GAP_RSSI_INVALID: // RSSI无效
NRF_LOG_INFO("RSSI无效");
break;
default: // RSSI有效
NRF_LOG_INFO("RSSI = %d dBm", p_gap_evt->params.rssi_changed.rssi);
break;
}
}
// 初始化 BLE Stack
static void ble_stack_init(void)
{
ret_code_t err_code;
err_code = nrf_sdh_enable_request();
APP_ERROR_CHECK(err_code);
// 等待 SoftDevice 启动
while (nrf_sdh_is_enabled() == false)
{
// Empty.
}
// 初始化 BLE Stack
err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &cfg);
APP_ERROR_CHECK(err_code);
err_code = nrf_sdh_ble_enable(&ram_start);
APP_ERROR_CHECK(err_code);
}
// 初始化 GAP (Generic Access Profile)
static void gap_params_init(void)
{
ret_code_t err_code;
ble_gap_conn_params_t gap_conn_params = {0};
ble_gap_conn_sec_mode_t sec_mode;
BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);
err_code = sd_ble_gap_device_name_set(&sec_mode, (const uint8_t *) DEVICE_NAME, strlen(DEVICE_NAME));
APP_ERROR_CHECK(err_code);
err_code = sd_ble_gap_appearance_set(BLE_APPEARANCE_GENERIC_TAG);
APP_ERROR_CHECK(err_code);
memset(&gap_conn_params, 0, sizeof(gap_conn_params));
gap_conn_params.min_conn_interval = MIN_CONN_INTERVAL;
gap_conn_params.max_conn_interval = MAX_CONN_INTERVAL;
gap_conn_params.slave_latency = SLAVE_LATENCY;
gap_conn_params.conn_sup_timeout = CONN_SUP_TIMEOUT;
err_code = sd_ble_gap_ppcp_set(&gap_conn_params);
APP_ERROR_CHECK(err_code);
}
// 初始化连接参数
static void conn_params_init(void)
{
ret_code_t err_code;
ble_conn_params_init_t conn_params_init;
memset(&conn_params_init, 0, sizeof(conn_params_init));
conn_params_init.p_conn_params = NULL;
conn_params_init.first_conn_params_update_delay = FIRST_CONN_PARAMS_UPDATE_DELAY;
conn_params_init.next_conn_params_update_delay = NEXT_CONN_PARAMS_UPDATE_DELAY;
conn_params_init.max_conn_params_update_count = MAX_CONN_PARAMS_UPDATE_COUNT;
conn_params_init.start_on_notify_cccd_handle = BLE_GATT_HANDLE_INVALID;
conn_params_init.disconnect_on_fail = true;
conn_params_init.evt_handler = NULL;
conn_params_init.error_handler = NULL;
err_code = ble_conn_params_init(&conn_params_init);
APP_ERROR_CHECK(err_code);
}
// 初始化服务
static void services_init(void)
{
ret_code_t err_code;
// 添加服务代码...
}
// 初始化广播
static void advertising_init(void)
{
ret_code_t err_code;
ble_advertising_init_t init;
memset(&init, 0, sizeof(init));
init.advdata.name_type = BLE_ADVDATA_FULL_NAME;
init.advdata.include_appearance = true;
init.advdata.flags = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;
init.advdata.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
init.advdata.uuids_complete.p_uuids = m_adv_uuids;
init.config.ble_adv_fast_enabled = true;
init.config.ble_adv_fast_interval = APP_ADV_INTERVAL;
init.config.ble_adv_fast_timeout = APP_ADV_DURATION;
init.evt_handler = NULL;
err_code = ble_advertising_init(&advdata, NULL);
APP_ERROR_CHECK(err_code);
}
int main(void)
{
// 初始化日志模块
ret_code_t err_code = NRF_LOG_INIT(NULL);
APP_ERROR_CHECK(err_code);
// 初始化 BLE Stack
ble_stack_init();
// 初始化 GAP (Generic Access Profile)
gap_params_init();
// 初始化连接参数
conn_params_init();
// 初始化服务
services_init();
// 初始化广播
advertising_init();
// 开始广播
err_code = ble_advertising_start(&m_advertising, BLE_ADV_MODE_FAST);
APP_ERROR_CHECK(err_code);
// 连接设备并获取 RSSI 值
err_code = sd_ble_gap_rssi_start(m_conn_handle, 5, 0);
APP_ERROR_CHECK(err_code);
// 进入主循环
while (true)
{
// 处理 BLE 事件
nrf_ble_qwr_on_ble_evt(&m_qwr, p_ble_evt);
ble_conn_params_on_ble_evt(p_ble_evt);
ble_advertising_on_ble_evt(p_ble_evt);
ble_nus_on_ble_evt(&m_nus, p_ble_evt);
on_ble_evt(p_ble_evt);
}
}
```
在上面的示例代码中,我们使用 `sd_ble_gap_rssi_start()` 函数来启动 RSSI 读取过程。该函数的第一个参数为连接句柄,第二个参数为 RSSI 读取周期,单位为 100 毫秒。在上面的示例代码中,我们设置周期为 5,即每 500 毫秒读取一次 RSSI。
当 RSSI 值发生变化时,`ble_gap_evt_handler()` 函数将被调用,从而可以获取 RSSI 值。注意,要在应用程序初始化期间注册 `ble_gap_evt_handler()` 以处理 GAP 事件。
希望这可以回答您的问题!