SDS
RE2
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SDS | RE2 | |
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48 | 49 | |
4,787 | 8,614 | |
- | 1.1% | |
0.0 | 8.9 | |
7 months ago | 16 days ago | |
C | C++ | |
BSD 2-clause "Simplified" License | BSD 3-clause "New" or "Revised" License |
Stars - the number of stars that a project has on GitHub. Growth - month over month growth in stars.
Activity is a relative number indicating how actively a project is being developed. Recent commits have higher weight than older ones.
For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.
SDS
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Strlcpy and strlcat added to glibc 2.38
Let me reframe this. What we're saying to do is stop using C string manipulation such as strcat, strcpy, etc. Particularly, I'm saying simply don't use C-style null terminated strings until you actually go to call a C ABI interface where it is necessary.
The argument against this is that you might call something that already does this. Yes, sure, that IS true, but what this betrays is the fact that you have to deal with that regardless of whether or not you add additional error-prone C string manipulation code on top of having to worry about memory ownership, mutation, etc. when passing blobs of memory to "untrusted" APIs.
It's not about passing the buck. Passing a blob of memory to an API that might do horrible things not defined by an API contract is not safe if you do strcat to construct the string or you clone it out of an std::string or you marshal it from Go or Rust. It's about not creating a bigger mess than you already have.
Okay fine, but what if someone hates C++ and Rust and Go and Zig? No problem. There are a slew of options for C that can all handle safer, less error-prone string manipulation, including interoperability with null-terminated C strings. Like this one used in Redis:
https://github.com/antirez/sds
And on top of everything else, it's quite ergonomic, so it seems silly to not consider it.
This entire line of thinking deeply reminds me of Technology Connection's video The LED Traffic Light and the Danger of "But Sometimes!".
https://youtube.com/watch?v=GiYO1TObNz8
I think hypothetically you can construct some scenarios where not using C strings for string manipulation requires more care, but justifying error prone C string manipulation with "well, I might call something that might do something unreasonable" as if that isn't still your problem regardless of how you get there makes zero sense to me.
And besides, these hypothetical incorrect APIs would crash horrifically on the DS9K anyways.
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Safest way to copy a string?
Even better, use a string handling library. Personally I am a big fan of (sds)[https://github.com/antirez/sds] from the Redis creator. It's not even a dependancy you can just copy the .c and .h to your project.
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New C features in GCC 13
One nice application is length-prefixed string literals to complement dynamic string libraries:
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Strlcpy and Strlcat – Consistent, Safe, String Copy and Concatenation (1999) [pdf]
The better answer would be to add data types like SDS[0] to the standard library, and use them as ADTs (Abstract Data Types) [1].
Unfortunely WG14 has proven in 30 years of existence, that it isn't something that they care to fix, and while 3rd party solutions exist, without vocabulary types on the stardard library adoption will never take off.
[0] - https://github.com/antirez/sds
[1] - https://en.wikipedia.org/wiki/Abstract_data_type
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C Strings and my slow descent to madness
With the woes of string.h being known, why not just use an alternative like https://github.com/antirez/sds ?
I’ve also been having a blast with C because writing C feels like being a god! But the biggest thing that I like about C is that the world is sort of written on it!
Just yesterday I needed to parse a JSON… found a bunch of libraries that do that and just picked one that I liked the API.
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How can i know for sure that i am allocating enough memory?
Please note that the discussion started with requirement for no dynamic allocation in critical code what virtually eliminates std::string. I agree that std::string code tends to be simpler but the main reason is that the standard C library sucks on strings. There are better alternatives like sds but they are ... not standard.
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str_header.h - A single header C string library
Another day, another post about a writing a bespoke string lib instead of using SDS
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C_dictionary: A simple dynamically typed and sized hashmap in C - feedback welcome
d) everything being a macro seems overkill for me (and possibly dangerous, see b)). Maybe implement more as static inline functions, see the sds header: https://github.com/antirez/sds/blob/master/sds.h (which does a similar thing with the header struct).
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Updated book to learn C
For example, you can use the C language with sds strings (see https://github.com/antirez/sds) if you want to have an easier time with string formatting and don't want to worry about using the famously unsafe string.h functions correctly. You'll still program in ISO C, but just not in the standard library. The same applies to pretty much all parts of the standard library, the only part unsurpassed is pretty much just printf and the math headers (math.h, fenv.h, tgmath.h, complex.h) imo, and the occasional call to exit. A good place to look for libraries if you want to go that route is the awesome-c collection: https://github.com/oz123/awesome-c
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Convenient Containers: A usability-oriented generic container library
One way around this problem is to declare the container as a pointer to the element type and then store the container’s metadata, alongside its elements, in the heap block to which the pointer points. This approach is already used for dynamic arrays in several container libraries, most notably stb_ds and sds. They place the metadata before the elements and provide the user with a pointer to the elements themselves (this has the nice effect that users can use the [] operator to access elements).
RE2
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C Is the Greenest Programming Language
Looking at the benchmark where C++ is worst compared to other languages, it's depending on the library used. I would guess if they used Google's re2 Regex library instead of Boost's, the result would be different.
https://github.com/google/re2
https://github.com/greensoftwarelab/Energy-Languages/blob/ma...
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what does this + do in the regular expression "(^A-Za-z)+"
That page says it just includes "some of the most common special characters", and following the link to the Examples page in turn includes a link to the full list.
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On a Great Interview Question
Python uses backtracking, so this probably isn't O(n), especially with the ability to choose the dictionary.
But with there are non-backtracking matchers which would make this O(n). Here's re2 from https://github.com/google/re2 :
>>> import re2
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RE2 VS hyperscan - a user suggested alternative
2 projects | 17 Mar 2023
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hyperscan VS RE2 - a user suggested alternative
2 projects | 17 Mar 2023
RE2 is a Google regular expression library
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Projects ideas to learn C++/OOP
google's regex library: https://github.com/google/re2
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Regex: is there a difference between * and {0,}, as well as + and {1,}?
I am currently working with Regex, specifically Re2, and was wondering if there is a real difference between the above expressions for repeated sub-regex.
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First release of SPVM::File::Spec - complex regular expressions, file tests, SPVM::Cwd, inheritance
I ported Google RE2, a regular expression library, to SPVM as Resource::Re2, and created SPVM::Regex, a wrapper for it.
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SPVM::File::Basename is released. This is the first module of SPVM using regular expressions.
I searched for I found that there is a Perl compatible regular expression called Google RE2. It is written in C++, and with Google RE2, I can use Perl-compatible regular expressions as a library.
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Ruby 3.2.0 Is from Another Dimension
Yes, but there is an interesting clarification here. RE2 has used the "caching" approach documented in the Ruby bug ticket linked for quite some time (since its birth?): https://github.com/google/re2/blob/954656f47fe8fb505d4818da1...
It is mentioned only briefly in Cox's article on regex matching in the wild. Look for the word "bitstate": https://swtch.com/~rsc/regexp/regexp3.html
I didn't know Perl had implemented this trick too.
The paper[1] cited in the Ruby bug ticket was published very recently. When I first read the Ruby bug ticket, I immediately wondered how they sidestepped the memory use problem. The paper's abstract seems to suggest there is some technique for doing so, as it rebuffs the idea of doing "full" memoization. Alas, I do not have access the paper. (Which is fucking ridiculous.)
[1]: https://ieeexplore.ieee.org/abstract/document/9519427
What are some alternatives?
Better String - The Better String Library
compile-time-regular-expressions - Compile Time Regular Expression in C++
Experimental Boost.MSM-lite - Boost.SML (formerly called Boost.MSM-lite)
semver.c - Semantic version in ANSI C
libcpuid - a small C library for x86 CPU detection and feature extraction
Boost.Signals - Boost.org signals2 module
ZXing - ZXing ("Zebra Crossing") barcode scanning library for Java, Android
libevil - The Evil License Manager
safestringlib
constexpr-8cc - Compile-time C Compiler implemented as C++14 constant expressions
stb - stb single-file public domain libraries for C/C++
Cppcheck - static analysis of C/C++ code