# Using ReadDirectoryChangesW() to get information about new files in a folder

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#### LUN2

##### Guest
LUN2 Asks: Using ReadDirectoryChangesW() to get information about new files in a folder
Good evening!

I need to get information about new files in certain directory (Windows 10, C++).

To do this (1) I call ReadDirectoryChangesW in overlapped mode and point an event to be signaled when ReadDirectoryChangesW will finish, (2) wait until event will be signalled (WaitForMultipleObjects), (3) call GetOverlappedResult to get ReadDirectoryChangesW info about new files.

All actions above are repeated in a loop.

It works well, but if I create two or more files simultaneously (copy several files and paste them in the Windows Explorer), then in the step (3) I get info about one file only.

But if I rename a file, then I correctly get from ReadDirectoryChangesW two records – about old and new file names.

Buffer (FILE_NOTIFY_INFORMATION) for ReadDirectoryChangesW likely does not overflow – I allocate 10 kb, information about new files is about 50-200 bytes (their paths and names are short enough).

If I do copy/paste 1 file, then 1 file etc, than each copying is reported normally.

It seems ReadDirectoryChangesW/GetOverlappedResult return info about 1 file only if new files appear "fast" (copy/paste several files), but how can I get info about other files ?

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#### What is the exact row-reduced echelon from R of A?

SherringFord69 Asks: What is the exact row-reduced echelon from R of A?
Suppose A is a 4 by 5 matrix and s = (4,5,2,1,0) is the only special solution for Ax = 0. What is the exact row-reduced echelon from R of A? Can Ax = b be solved for all b?

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#### Maximum matching for bipartite graph with category restriction.

picker Asks: Maximum matching for bipartite graph with category restriction.
The general maximum matching on bipartite graphs is extracted as follows: We have a bipartite graph G, which contains two sets of vertices without any connections within the two sets and several connections between the two sets. We want to find the maximum matching (number of connections) where there are no two selected edges connected to the same vertex.

Consider the following restriction. If the vertices on the left-hand side ${X}$ have one or several specific label, e.g., $x_1 = 1, x_2 = 2, x_3 = 2, x_4 = {1 and 3} ...$

If we want to achieve that, finally, the match has uniform label distribution. How can we design the algorithm to calculate the maximum matching number?

For example, we have two kinds of labels, 1 and 2. The final matching should have $\frac{k}{2}$ matchings with $label = 1$ and $\frac{k}{2}$ matchings with $label = 2$ if the final matching number is $k$.

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#### Is the converse of Vertically opposite angles true?

Apoorva Shukla Asks: Is the converse of Vertically opposite angles true?
When two straight lines intersect the vertically opposite angles are equal.

But, can we say that, if the vertically opposite angles of two lines are equal then the lines are straight?

The angles marked equal in orange, come after comparing the two congruent triangles, in the attached image.

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#### Intersection of conic sets

bosky2001 Asks: Intersection of conic sets
Question Prompt

How do I find the Intersection of C and C'?

and In addition to this, if I am given a set for C (C definition) , How do i construct the C' of it?

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#### How will you solve this integral? [closed]

Dhruv Mohta Asks: How will you solve this integral? [closed]
the question

we have to solve using only rectangular coordinates, nothing else

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#### Could a Legendre transform be equivalent to evaluation in a retarded time?

JM3 Asks: Could a Legendre transform be equivalent to evaluation in a retarded time?
We have the following function:

U = U(r(t), p(t)) = (α/r)·sqrt(1 - p^2/c^2)

being α and c positive constants, t a real variable 0 or positive, and p = dr/dt.

I would like to show that if we define

t'= t – r(t)/c

it is true that

U' = U - p·(∂U/∂p)

where the prime ' stands for evaluated at t'

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#### What is the sign of Ax where A is negative definite matrix and x > 0?

• Tomoki Matsumoto
• Mathematics
• Replies: 0
Tomoki Matsumoto Asks: What is the sign of Ax where A is negative definite matrix and x > 0?
Let A be a negative definite matrix and x is a vector whose elements are positive all, that is x > 0. Then, is the sign of all elements of the vector Ax negative?

Best regards,

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