CODEWITHSUNDEEP
c++istream-iterator
Kadir Erdem Demir
Kadir Erdem Demir

Reputation: 3605

Some bytes are missing after reading an std::ifstream to a vector of lines

For copying what I read from input file to vector, I used std::copy() as recommended in Reading an std::ifstream to a vector of lines.

The problem occurs if I use: 

std::copy(std::istream_iterator<unsigned char>(inputfile),
          std::istream_iterator<unsigned char>(),
          std::back_inserter(myVector));

The 16th byte of my file is missing in the myVector variable.

But if I use the following code:

inputfile.read((char*)&myVector[0], sizeof(int)*getfilesize(nameOfFile));

Then the byte is not missing anymore.

I am trying to parse WAV files and I lost too much time on this, I hope I will learn something new out of this. Can you please tell me what is wrong with the first version of the code above?

Upvotes: 5

Views: 2048

Answers (3)

RiaD
RiaD

Reputation: 47658

istream_iterator uses operator >> to read elements, but operator >> skip whitespaces.

You may try using noskipws

inputfile >> noskipws;

§ 24.6.1 p1. (my emphasis)

The class template istream_iterator is an input iterator (24.2.3) that reads (using operator>>) successive elements from the input stream for which it was constructed....

Upvotes: 7

Konrad Rudolph
Konrad Rudolph

Reputation: 546073

Like RiaD said, istream_iterator performs formatted input via operator >>. The solution is to use unformatted reading on the underlying buffer. To do this, use istreambuf_iterator:

std::copy(std::istreambuf_iterator<char>(inputfile),
          std::istreambuf_iterator<char>(),
          std::back_inserter(myVector));

Upvotes: 6

nio
nio

Reputation: 5289

First of all wav file is a binary data, so you should treat it as such, you should open your file in binary mode:

ifstream ifs;
ifs.open ("test.wav", ifstream::in | ifstream::binary);

Then, you have to use ordinary read function that works as you stated.

ifstream documentation

Upvotes: 0

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