typedef unsigned char uchar_t;
vector<uchar_t> data;
ifstream in("in_file.txt", ios_base::in | ios_base::binary);
ofsteram out("out_file.txt", ios_base::out | ios_base::binary);
// read the raw bytes from the file
copy(istream_iterator<uchar_t>(in), istream_iterator<uchar_t>(), back_inserter(data));
// transform the raw bytes
transform(data.begin(), data.end(), data.begin(), some_func);
// write the raw bytes to another file
copy(data.begin(), data.end(), ostream_iterator<uchar_t>(out));
istream_iterator for raw bytes?
Author
Is there not a way to read the raw bytes of a file using an istream_iterator? I would like to be able to read the raw bytes, modify them, and then write them to another file. I tried this, but it skips white space
Initialize the vector to the size of the file and use istream::read to read the binary data in one sweep. It's faster, and requires less code.
Author
Quote:Original post by ToohrVyk
Initialize the vector to the size of the file and use istream::read to read the binary data in one sweep. It's faster, and requires less code.
istream::read() takes a char*, not a vector<T>::iterator
The following snippit is from this thread:
http://www.gamedev.net/community/forums/topic.asp?topic_id=355078
I admit, it doesn't load it into a vector, but if I know my STL good enough, you shouldn't no problem replacing std::string with std::vector<char>
This function preserves whitespace and all the other bytes.
http://www.gamedev.net/community/forums/topic.asp?topic_id=355078
inline std::string loadtext(char * filename) { std::ifstream fin(filename); return std::string((std::istreambuf_iterator<char>(fin)), std::istreambuf_iterator<char>());}I admit, it doesn't load it into a vector, but if I know my STL good enough, you shouldn't no problem replacing std::string with std::vector<char>
This function preserves whitespace and all the other bytes.
Quote:Original post by scottdewaldQuote:Original post by ToohrVyk
Initialize the vector to the size of the file and use istream::read to read the binary data in one sweep. It's faster, and requires less code.
istream::read() takes a char*, not a vector<T>::iterator
std::vector guarantees that its storage is contiguous. Therefore, you can use &(*vector.begin()) as an argument to istream::read() (applying any required reinterpret casting if the type of the vector is not compatible with char*).
Author
Quote:Original post by ToohrVykQuote:Original post by scottdewaldQuote:Original post by ToohrVyk
Initialize the vector to the size of the file and use istream::read to read the binary data in one sweep. It's faster, and requires less code.
istream::read() takes a char*, not a vector<T>::iterator
std::vector guarantees that its storage is contiguous. Therefore, you can use &(*vector.begin()) as an argument to istream::read() (applying any required reinterpret casting if the type of the vector is not compatible with char*).
I've always read that vector does not guarantee contiguous storage, however, most libraries implement it that way. If I am wrong, could you please point me to the section in the standard that states that it used contiguous memory?
Quote:
vector - standard library template providing contiguous storage, re-sizing and the useful push_back() functions for adding elements at the end. Vector is the default container. See also: map, multimap, list, deque. TC++PL 3.7.1, 16.3.
I think that this guy knows! =)
Quote:Original post by scottdewald
Is there not a way to read the raw bytes of a file using an istream_iterator?
No. An istream is a formatter that lies on top of a stream. What you want is an istreambuf_iterator. That's just what it's designed for.
Quote:Original post by scottdewald
I've always read that vector does not guarantee contiguous storage, however, most libraries implement it that way. If I am wrong, could you please point me to the section in the standard that states that it used contiguous memory?
Quote:23.2.4 [lib.container.adaptors], paragraph 1:
The elements of a vector are stored contiguously, meaning that if v is a vector<T, Allocator> where T is some type other than bool, then it obeys the identity &v[n] == &v[0] + n for all 0 <= n < v.size().
It's been there since the 2003 Technical Corrigendum.
This topic is closed to new replies.
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