Ch9.13.1: String View Operations Reference

Overview

This appendix documents all string-view-specific operations. Most of these are also available on string (see Appendix §9.12.1). Return here when you need a particular feature.

1. npos

::fast_io::containers::npos (= SIZE_MAX) is returned by all find* operations when the search fails, and serves as the default count parameter meaning “to the end”.


#include <fast_io_dsal/string_view.h>
#include <fast_io.h>
using ::fast_io::containers::npos;

int main() {
    ::fast_io::string_view sv{"Hello, World!"};

    // npos as "not found"
    auto pos = sv.find_character('z');
    if (pos == npos) {
        ::fast_io::io::println("'z' not found");
    }

    // npos as "to end"
    auto tail = sv.subview(7zu); // default count = npos → "World!"
}

2. Subview Operations

Operation	Description	Example
`subview(pos, count=npos)`	View of `count` characters starting at `pos`.	`sv.subview(7zu)` → from index 7 to end
`subview_front(count)`	View of the first `count` characters.	`sv.subview_front(5zu)` → "Hello"
`subview_back(count)`	View of the last `count` characters.	`sv.subview_back(6zu)` → "World!"
`copy(dest, count, pos=0)`	Copy `count` characters to raw buffer `dest`.	`sv.copy(buf, 5zu)`

All subview* methods have _unchecked variants that skip bounds checking.

3. Search / Find Operations

Same API as string (see §9.12.1). All return npos when the target is not found.

Operation	Description	Example
`find_character(ch, pos=0)`	Find first occurrence of character.	`sv.find_character('W')` → 7
`find_not_character(ch, pos=0)`	Find first character that is not `ch`.	`sv.find_not_character('H')` → 1
`rfind_character(ch, pos=npos)`	Find last occurrence of character.	`sv.rfind_character('l')` → 10
`rfind_not_character(ch, pos=npos)`	Find last character that is not `ch`.	`sv.rfind_not_character('!')` → 11
`find(view, pos=0)`	Find first occurrence of substring.	`sv.find("World")` → 7
`rfind(view, pos=0)`	Find last occurrence of substring.	`sv.rfind("l")` → 10
`find_first_of(view, pos)`	Find first character matching any in `view`.	`sv.find_first_of("aeiou")` → 1 ('e')
`find_first_not_of(view, pos)`	Find first character not matching any in `view`.	`sv.find_first_not_of("Helo")` → 5 (',')
`find_last_of(view, pos)`	Find last character matching any in `view`.	`sv.find_last_of("aeiou")` → 8 ('o')
`find_last_not_of(view, pos)`	Find last character not matching any in `view`.	`sv.find_last_not_of(" !")` → 11 ('d')
`contains_character(ch)`	Returns `true` if character exists.	`sv.contains_character('W')` → true
`contains(view)`	Returns `true` if substring exists.	`sv.contains("World")` → true

4. starts_with / ends_with

Operation	Description	Example
`starts_with(view)`	Returns `true` if view begins with `view`.	`sv.starts_with("Hello")` → true
`starts_with_character(ch)`	Returns `true` if first character is `ch`.	`sv.starts_with_character('H')` → true
`ends_with(view)`	Returns `true` if view ends with `view`.	`sv.ends_with("!")` → true
`ends_with_character(ch)`	Returns `true` if last character is `ch`.	`sv.ends_with_character('!')` → true

5. Trim Operations (view-only)

These return a new view with characters removed — they do not modify the underlying data.

Operation	Description
`trim_subview_c_space()`	Return view with leading and trailing whitespace removed.
`trim_prefix_subview_c_space()`	Return view with leading whitespace removed.
`trim_suffix_subview_c_space()`	Return view with trailing whitespace removed.

Generic trim_subview(), trim_prefix_subview(), trim_suffix_subview() overloads accept a character category trait.

6. remove_prefix / remove_suffix

These shrink the view by advancing the start or reducing the end. They modify the view itself (not the underlying data).

Operation	Description	Example
`remove_prefix(n)`	Advance the start by `n` characters.	`sv.remove_prefix(6zu);`
`remove_suffix(n)`	Shrink the end by `n` characters.	`sv.remove_suffix(1zu);`
`clear()`	Reset view to null pointer and size 0.	`sv.clear();`

Both have _unchecked variants that skip bounds checking.

7. Comparison

String views support == and <=> (C++20 three-way comparison). Comparison is lexicographic.


::fast_io::string_view a{"abc"};
::fast_io::string_view b{"abd"};

bool eq = (a == b);          // false
auto cmp = (a <=> b);       // std::strong_ordering::less