Sane | Python interface to the SANE scanner and frame grabber
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kandi X-RAY | Sane Summary
Python interface to the SANE scanner and frame grabber
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QUESTION
I am trying to assign a value to a const char*
by using a pre-processor flag in the following way.
ANSWER
Answered 2022-Mar-14 at 11:51You don't have to use stringification macros when FLAG
is a string:
QUESTION
I'm trying to wrap my head around Rust's aliasing rules in the following situation:
Let's assume we have a memory allocation in C. We pass a pointer to this allocation to Rust. The Rust function does something with the allocation, and then calls back to C code (without any parameters), where another rust function is called with the same allocation as parameter. For now, let's assume that only the first Rust function gets a mutable reference.
The call stack would look like:
...ANSWER
Answered 2022-Jan-08 at 20:11Is the above code invoking undefined behaviour?
Yes, you've broken Rust's pointer aliasing rules. Relying on the Stacked Borrows rules is a bit dubious since, as you've hinted, I don't think it has been officially adopted as Rust's memory access model (even if it was just a formalization on the current semantics). However, something that is a practical and concrete ruling is LLVM's noalias
attribute, which the Rust compiler uses on &mut
arguments.
This indicates that memory locations accessed via pointer values based on the argument or return value are not also accessed, during the execution of the function, via pointer values not based on the argument or return value. ...
So since you access ints[1]
in another_rust_function
from a pointer that is not based based on the ints
in first_rust_function
during the execution of that function, it is a violation. In light of this undefined behavior, I believe the compiler is well within its rights to make the code print "Second value: 4".
Would the behaviour be well-defined if
called_from_rust()
would have the pointer as parameter and pass it forward:void called_from_rust(const int * i) { another_rust_function(i); }
?
Yes, that will make it well defined. You can see that because the Rust borrow checker can then see that the value can be used in called_from_rust()
and will prevent improper use of ints
around that call.
What if both Rust functions were using
&mut [c_int;3]
?
If you used the fix above, where the second borrow is based on the first, then there's no problem. If you didn't though, then it is way worse.
QUESTION
A fairly common data issue in some circles is coding an instrument, for example this one, where related items are separated in the instrument. The idea is to avoid cuing the respondent that all of these questions - say all those beginning with A or D in this example, are related.
...ANSWER
Answered 2022-Feb-05 at 19:37Consider using a named list. Is this what you want?
QUESTION
PHP has an ini-setting 'max_file_uploads' that prevents more files than the given number to be uploaded at once. Default is 20, can be changed into anything (I think).
What does this precisely prevent, given that there is also a 'post_max_size' and 'upload_max_filesize' in place? I mean, what security risks am I running into if I would change this limit into something huge like 999, so it gets out of the way, while keeping the other two limits at some sane level?
...ANSWER
Answered 2022-Jan-21 at 10:26You can think of this as defense in depth, an additional layer of protection against generic threats around file uploads.
One that directly comes to mind is an attacker uploading many very small (or 0 byte) files. Those would normally get stored in the temp directory (/tmp
usually), and on many filesystems there is limit to the number of files in a directory, and a lot of files can also affect filesystem performance.
This is a risk you can decide to accept, or implement other mitigations so this php setting doesn't "get in the way". Quite honestly, in many applications this would likely never cause an issue, but you need to be aware and make an informed decision. In some higher security applications increasing or removing this limitation might not be acceptable.
QUESTION
I am trying to establish WiFi connection on my Avenger96 (based on 96Boards STM32MP157) board. Goal is to automatically setup WiFi connection during boot time so that there is no need to manually configure WiFi after every boot.
Steps I have done:
Added
...network
section in wpa_supplicant.conf-sane as shown below:poky/meta/recipes-connectivity/wpa-supplicant/wpa-supplicant
:
ANSWER
Answered 2022-Jan-05 at 04:09The error unknown global field 'passphrase must be 8..63 characters'
is confusing.
If the passphrase is correct, then I think some configuration file consists of exactly the same string passphrase must be 8..63 characters
instead of some useful value and hence the error unknown global field 'passphrase must be 8..63 characters
.
You can search and validate the same using grep -rn "characters" /etc/
and remove the string from the configuration file that contains passphrase must be 8..63 characters
.
QUESTION
npm install
in the relevant react project folder, it gives back this error after installing node modules
...ANSWER
Answered 2021-Dec-07 at 06:54I had the same problem with literally the exact same number of vulnerabilities.
Check out the solution here
QUESTION
Suppose you have two collections (Vec
for simplicity here) of instances of T
, and a function to compute whether the elements in those collections appear in either or both of them:
ANSWER
Answered 2021-Dec-19 at 20:09Yes, it is sound. In fact, the official documentation for transmute()
says it can be used to extend lifetimes:
https://doc.rust-lang.org/stable/std/mem/fn.transmute.html#examples
Extending a lifetime, or shortening an invariant lifetime. This is advanced, very unsafe Rust!
QUESTION
I want to Hive-partition my dataset, but I don't quite know how to ensure the file counts in the splits are sane. I know I should roughly aim for files that are 128MB in size
How do I safely scale and control the row counts inside files of my Hive-partitioned dataset?
...ANSWER
Answered 2021-Nov-08 at 18:00For this answer, I'll assume you have correctly understood the reasons why you should and should not do Hive-style partitioning and won't be covering the backing theory.
In this case, it's important to ensure we not only correctly calculate the number of files needed inside our splits but also repartition our dataset based on these calculations. Failure to do repartitions before write-out on Hive-style partition datasets may result in your job attempting to write out millions of tiny files which will kill your performance.
In our case, the strategy we will use will be to create files that are at most N
rows per file, which will bound the size of each file. We can't easily limit the exact size of each file inside the splits, but we can use row counts as a good approximation.
The methodology we will use to accomplish this will be to create a synthetic column that describes which 'batch' a row will belong to, repartition the final dataset on both the Hive split column and this synthetic column, and use this result on write.
In order to ensure our synthetic column indicates the proper batch a row belongs to, we need to determine the number of rows inside each hive split, and 'sprinkle' the rows inside this split into the proper number of files.
The strategy in total will look something like this:
- Determine number of rows per Hive value
- Join this count against main dataframe
- Determine number of files in split by dividing row count per split by rows per file
- Create random index between 0 and the file count, essentially 'picking' the file the row will belong to
- Calculate number of unique combinations of Hive split columns and our synthetic column
- Repartition output dataset over both Hive column and synthetic column into the number of unique combinations. i.e. one file per combination, exactly what we want
Let's start by considering the following dataset:
QUESTION
I'm not experienced so I can't really pinpoint what is the problem. Thanks for the help.
I cloned this repo: https://github.com/flatlogic/react-native-starter.git
And was trying to follow the steps below:
Clone the repogit clone https://github.com/flatlogic/react-native-starter.git
Navigate to clonned folder and Install dependenciescd react-native-starter && yarn install
Install Podscd ios && pod install
When I got to the pod install I'm getting that error.
...ANSWER
Answered 2021-Jul-28 at 18:31I think your pod install
working fine and has done its job. You need to set up iPhone SDK on your mac then try to run cd ../ && react-native run-ios
.
Follow this guide : React Native Environment set up on Mac OS with Xcode and Android Studio
QUESTION
POSIX requires (I think) that function pointers can be stored in a variable of type void* and/or passed to functions expecting a void* argument, even though this is strictly non-standard.
My question is this: if I test such a variable/argument for NULL
-ness, if (!(variable or argument))
say, and the result is true
, does that necessarily mean that the function-pointer is NULL
? Could the bit pattern for a NULL void* data-pointer ever equate to a non-NULL function-pointer value? Would any sane implementation do this? Do any common implementations do this?
EDIT: this answer (to a different question admittedly) made me wonder if I had to cast the void* intermediate back to the original function pointer type before I could test NULL-ness, otherwise it's UB... is that true? Can those who posted answers weigh in on this question?
...ANSWER
Answered 2021-Dec-08 at 12:15This C11 Draft Standard suggests that, while not part of the core standard, casting function pointers to object pointers (for purposes of testing, as in your NULL
-check) falls under the category of "Common Extensions" (Annex J.5):
J.5.7 Function pointer casts1 A pointer to an object or to
void
may be cast to a pointer to a function, allowing data to be invoked as a function (6.5.4).2 A pointer to a function may be cast to a pointer to an object or to
void
, allowing a function to be inspected or modified (for example, by a debugger) (6.5.4)
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