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ble蓝牙的标识符怎么确定的 - App Inventor 2 中文网 - 清泛IT社区，为创新赋能！
这个里面ble蓝牙的服务UUID和特征UUID的标识符为什么是F000和F0011、UUID 背后的理念是，由于空间非常大（2^128，比宇宙中原子的估计数量还要多），随机选择两个 UUID 来标识事物时几乎不可能产生碰撞。如果您知道要连接的服务/...
Why is C so fast, and why aren't other languages as fast or faster? [closed]
... only day to write isn't worthwhile? What if that program needs to run 500,000,000+ times a day? Being twice as fast is incredibly significant. If it runs on thousands or millions of CPUs, the cost savings of the extra month of development to achieve twice the performance will be enormous. Basically...
“Full screen”
...isplay: block; /* iframes are inline by default */
background: #000;
border: none; /* Reset default border */
height: 100vh; /* Viewport-relative units */
width: 100vw;
}
<iframe></iframe>
This is supported in most modern browsers - suppo...
Bootstrap carousel multiple frames at once
...rouselExample" class="carousel slide" data-ride="carousel" data-interval="9000">
<div class="carousel-inner row w-100 mx-auto" role="listbox">
<div class="carousel-item col-md-4 active">
<img class="img-fluid mx-auto d-block" src="//placehold.it/...
Fast way of counting non-zero bits in positive integer
...00FF00FF00FF) + ((n & 0xFF00FF00FF00FF00) >> 8)
n = (n & 0x0000FFFF0000FFFF) + ((n & 0xFFFF0000FFFF0000) >> 16)
n = (n & 0x00000000FFFFFFFF) + ((n & 0xFFFFFFFF00000000) >> 32) # This last & isn't strictly necessary.
return n
This works for 64-bit pos...
Convert normal date to unix timestamp
...
new Date('2012.08.10').getTime() / 1000
Check the JavaScript Date documentation.
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Mysql ibdata 丢失或损坏如何通过frm&ibd 恢复数据 - 更多技术 - 清泛网 - ...
...点在什么位置。开始执行 import tablespace，报错 ERROR 1030 (HY000): Got error -1 from storage engine。找到mysql的错误日志，InnoDB: Error: tablespace id in file ‘.\test\weibo_qq0.ibd’ is 112, but in the InnoDB InnoDB: data dictionary it is 1. 因为 weibo_qq0 之前...
ActiveRecord: size vs count
...a query at all.
Consider one example:
in my database, one customer has 20,000 customer activities and I try to count the number of records of customer activities of that customer with each of count, length and size method. here below the benchmark report of all these methods.
user ...
Python loop counter in a for loop [duplicate]
... in xrange(len(s)))". Each of them averaged on 8.83 usec per loop over 100,000 loops. Other tests (too long for a comment) showed very slight (~2%) speed increases for xrange(len(s)) if it only needed to access the element on every 16 iterations.
– ArtOfWarfare
...
Understanding the Rails Authenticity Token
...ould just send an HTTP request to the server saying GET /transfer?amount=$1000000&account-to=999999, right?
Wrong. The hackers attack won't work. The server will basically think?
Huh? Who is this guy trying to initiate a transfer. It's not the owner of the account, that's for sure.
How ...