I want to download a file to memory using curl.
I am currently using this and it looks like it works to a certain extent but corrupts my file.
I have used sigbench and it is around 20% different (while comparing original and downloaded)
The file I want to download is a binary so it won't work after it's modified.
I am currently testing with the x86 version of this.
original binary
downloaded binary
This is the code I am using to write it to a file:
ofstream stream = ofstream("test.dll");
stream.write(chunk.memory, chunk.size);
Opening the file like this:
ofstream stream = ofstream("test.dll");
will cause line-end characters to be adjusted to match your target system.
You should instead open the file in binary mode:
ofstream stream = ofstream("test.dll", std::ios::binary);
This will leave the characters that could be interpreted as line-endings unchanged.
Further reading: https://en.cppreference.com/w/cpp/io/c#Binary_and_text_modes
Related
So currently I am using a basic Http request to pull the exe data from my server weblink.com/Program.exe
it returns my program in .txt form but when I put it into a file it will not run.
I assume this is because I need metadata but have no clue how to find that process or even how to google something as specific as that... So I am either asking for a solution (how to add proper .exe metadata) or if there is a better way to download files like that in C++
*Note I cannot use basic windows functions such as DownloadToFileA or External Library's (Like LibCurl/Curl)
OutFile.open(XorStr("C:\\Users\\Program.exe").c_str(), std::ios::out);
if (OutFile.is_open())
{
OutFile << Output;
//Initialize .exe Meta Data???
}
OutFile.close();
You need to open your file in binary mode otherwise newline translation will screw up your executable:
OutFile.open(XorStr("C:\\Users\\Program.exe").c_str(), std::ios::out | std::ios::binary);
(My previous questions was closed as a duplicate of Are there binary memory streams in C++ which is ridiculous, since i can't change the implementation of the library I'm using)
I'm using a library (Poco) to create zip files. It takes ostream as an input and writes the data of the zip file into it. Something like:
std::ofstream ofs("file.zip", std::ios::binary);
Compress compress(ofs);
// add data to compress ...
compress.close();
// now file.zip contains added file
This works. But I want to be able to create a zip in memory without creating a file. I tried using stringstream instead of ofstream, i get additionl newline characters in the data in the zip file is corrupted. Is there any other stream i can use?
(If someone still thinks it's a duplicate, I'm gonna need an explanation, since I don't see how this other question is helpful for me)
Use a std::stringstream -- that will create an in-memory string that you can write to as an ostream, and WILL NOT add extra newlines. If you later copy the string to an fstream that was opened in text mode (such as std::cout), then that process may add extra CR characters that are not in the string (nor in the original output).
If you are seeing extra characters corrupting your stream, they are coming from somewhere else -- something besides you compress call/lib is writing to the stream, or something with how you are looking at your stream is doing something.
If you're on linux, how about creating an anonymous file using memfd_create? You can then open /proc/self/fd/<fd> and do your stuff. Some implementations of std::ofstream may even provide a constructor that takes a FILE*, you can check if that's the case on your system.
I am using the C++ streams to read in a bunch of files in a directory and then write them to another directory. Since these files may be of different types, I am using a the generic ios::binary flag when reading/writing these files.
Example code below:
std::fstream inf( "ex.txt", std::ios::in | std::ios::binary);
char c;
while( inf >> c ) {
// writing to another file in binary format
}
The issue I have is that in the case of files containing text, the end of line characters in these text files are not being written to the output file.
Edit: Or at least they do not appear to be as when the newly written file is opened, there is only a single continuous line of characters.
Edit again: The problem (of the continuous string) appears to persist even when the read / write is made in text mode.
Thus, I was wondering if there was a way to check if a file has text or binary and then read/write it appropriately. Else, is there any way to preserve the end of line characters even when opening the file in binary format?
Edit: I am using the g++ 4.8.2 compiler
When you want to manipulate bytes, you need to use read and write methods, not >> << operators.
You can get the intended behavior with inp.flags(inp.flags() & ~std::ios_base::skipws);, though.
I am a beginner C++ programmer.
I want to create a binary file, that is uncleared with the previous information that was in it. This is easy to do with RAM, simply by making an array, but how do I do this on a hard drive?
How do I create a uncleared file?
In other words how do I retrieve data that was not "cleared" but just marked "empty".
However, if the OS does not allow it, can I launch linux from USB and run my software?
To keep the content of a file to be written on, you can open a file in append mode with:
[ofstream ofs ("filename", ios::binary | ios::app);][1]
All output operations append at the end of the file. Alternatively, you could also use ios::ate so that the output position starts at the end of the file (but afterwards it's up to you).
With the usual read operations you can retrieve preexisting content, by first positionning yourself using seekp().
I'm trying to write a Huffman encoder but I'm getting some compression errors. I identified the problem as mismatches between characters that were put() to the ofstream and the characters read() from the same file.
One specific instance of this problem :
The put() writes ASCII character 10 (Line feed)
The read() reads ASCII character 13 (Carriage return)
I thought read and put read and write raw data ( no character translations ) I'm not sure why this is happening. Can someone help me out?
Here is the ofstream instance for writing the compressed file:
std::ofstream compressedFileStream(getCompressedFileName(),std::ios::binary||std::ios::ate);
and the ifstream instance for reading the same
std::ifstream fileInput(getFileName()+".huf",std::ios::binary);
The code is running on Windows 7 and all streams in the program are opened in binary mode.
Not opening in binary mode due to a typo:
std::ofstream compressedFileStream(getCompressedFileName(),std::ios::binary||std::ios::ate)
should be:
std::ofstream compressedFileStream(getCompressedFileName(),std::ios::binary|std::ios::ate)
// ^
|, not ||.
The symptoms show that you are creating the ofsteam with text mode or you are creating it using a filedesc that is opened in text mode.
You will want to pass ios::binary to it at construction time or it may run in text mode on Windows.
After you added the code, the reason proves to be a typo;
std::ios::binary||std::ios::ate
should be
std::ios::binary|std::ios::ate
On Windows, if you are writing binary data, you need to open the file with the appropriate attributes.
Similarly, if you are reading binary data, you need to open the file with the appropriate attributes.