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istream_iterator for raw bytes?

scottdewald · 2006-09-15T08:00:58

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 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));

General and Gameplay Programming Programming

Started by scottdewald September 14, 2006 01:58 PM

11 comments, last by scottdewald 17 years, 7 months ago

scottdewald

163

Author

September 14, 2006 03:06 PM

Thanks for the clearing me up on vector being contiguous.

Are istreambuf_iterator's extremely slow? I ran some simple tests by reading in a file with istreambuf_iterator's and writing them out with ostream_iterator's vs. using fread() and fwrite() with a single char, and the latter was 5x faster. Is there any way to speed up iterators?

<a href="http://www.slimcalcs.com>www.slimcalcs.com

Zahlman

1,682

September 14, 2006 10:47 PM

Check your compiler settings. If you're using (certain versions of) MSVC, iterators are "checked" by default, even in release mode, but you can disable that.

scottdewald

163

Author

September 15, 2006 08:00 AM

Quote:Original post by Zahlman
Check your compiler settings. If you're using (certain versions of) MSVC, iterators are "checked" by default, even in release mode, but you can disable that.

Thanks. I didn't realize it, but with my compiler, I had to explicitly turn on inlining. After doing that and turning on optimizations (-O), I got much better performance.

<a href="http://www.slimcalcs.com>www.slimcalcs.com

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