Stream Functions

Introduction

The <utilities/stream.h> header supplies some utility functions that work on streams.

Reading from a Stream

std::string
utilities::read_line(std::istream &s,
1                     std::string_view comment_begin = "#");
std::size_t
utilities::read_line(std::istream &s, std::string &line,
2                     std::string_view comment_begin = "#");

1

This function reads a ‘line’ from a stream and returns that as a std::string.

2

Overwrites the ‘line’ argument with the contents from a stream s. Returns the number of characters placed into line.

These functions differ from std::getline in a few ways:

1. They ignore blank lines in the input stream.
2. They allow for long lines by assuming that lines that end with a “\” continue to the next.
3. They strip out comment lines and trailing comments.

Comment lines begin with “#” by default.

Related Functions

1std::istream & rewind(std::istream &is);

std::size_t
line_count(std::istream &is,
2           std::string_view comment_begin = "#");

1

This function rewinds an input stream to the start.

2

This function returns the number of non-comment lines in the stream.

If the comment start string is empty, line_count uses std::getline to read the lines. Otherwise, we use our read_line(...) function, so comment lines are excluded, etc.

These two functions only work with file streams, etc.