Elementary string conversions

The growing number of data formats like JSON or XML require efficient string processing and manipulation. The maximum performance is especially crucial when such data formats are used to communicate over the network, where high throughput is the critical factor.

For example, you get the characters in a network packet, you deserialise it (convert strings into numbers), then process the data, and finally, it’s serialised back to the same file format (numbers into strings) and sent over the network as a response.

The Standard Library had bad luck in those areas. It’s usually perceived to be too slow for such advanced string processing. Often developers prefer custom solutions or third-party libraries.

The situation might change as with C++17 we get two sets of functions: from_chars and to_chars that allow for low-level string conversions.

Current Solutions Summaries Table #

Facility	Shortcomings
sprintf	format string, locale, buffer overrun
snprintf	format string, locale
sscanf	format string, locale
atol	locale, does not signal errors
strtol	locale, ignores whitespace and 0x prefix
strstream	locale, ignores whitespace
stringstream	locale, ignores whitespace, memory allocation
num_put / num_get facets	locale, virtual function
to_string	locale, memory allocation
stoi etc.	locale, memory allocation, ignores whitespace and 0x prefix, exceptions