touch fish 038

TLS Certificate Lifetimes Will Officially Reduce to 47 Days

• TLS Certificate Lifetimes Will Officially Reduce to 47 Days

47 days might seem like an arbitrary number, but it’s a simple cascade:

200 days = 6 maximal month (184 days) + 1/2 30-day month (15 days) + 1 day wiggle room

100 days = 3 maximal month (92 days) + ~1/4 30-day month (7 days) + 1 day wiggle room

47 days = 1 maximal month (31 days) + 1/2 30-day month (15 days) + 1 day wiggle room

Why are QR Codes with capital letters smaller than QR codes with lower-case letters?

• Why are QR Codes with capital letters smaller than QR codes with lower-case letters?

简单讲，qr code通过压缩数据将映射到不同的编码模式来提高存储效率

1. 数字模式(0-9)
2. 字母数字模式(A-Z, 0-9, space, $, %, *, +, -, ., /, :)
3. 8字节模式(AsicII)
4. kanji/kana模式(日文字符)

URL的编码规则下，大写字母（如A-Z）被直接映射到字母数字模式（11 bit两个字符），小写的会映射成ascii模式(1字节)

Performance Analysis and Tuning on Modern CPUs: Micro Arch

• Performance Analysis and Tuning on Modern CPUs: Micro Arch

有时间看看perf-ninja

Notes on Integer/Float Operations

• Notes on Integer/Float Operations

早年Integer & Endian

低レイヤを知りたい人のためのCコンパイラ作成入門

• 低レイヤを知りたい人のためのCコンパイラ作成入門

chibicc的配套书