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# STC [csview](../include/stc/csview.h): String View
The type **csview** is a ***null-terminated*** string view and refers to a constant contiguous sequence of
char-elements with the first element of the sequence at position zero. The implementation holds two
members: a pointer to constant char and a size. See [csubstr](csubstr_api.md) for a ***non null-terminated***
string view/span type.
Because **csview** is null-terminated, it can be a more efficient replacent for `const char*`. It never
allocates memory, and need therefore not be destructed. Its lifetime is limited by the source string
storage. It keeps the length of the string, and does not call *strlen()* when passing it around.
## Header file
All csview definitions and prototypes are available by including a single header file.
```c
#define i_implement
#include <stc/cstr.h>
#include <stc/csview.h> // after cstr.h: include extra cstr-csview functions
```
## Methods
```c
csview c_sv(const char literal_only[]); // construct from literal, no strlen()
csview c_sv(const char* str, intptr_t n); // construct from str and length n
csview csview_from(const char* str); // construct from const char*
csview csview_from_n(const char* str, intptr_t n); // alias for c_sv(str, n)
intptr_t csview_size(csview sv);
bool csview_empty(csview sv);
void csview_clear(csview* self);
bool csview_equals(csview sv, csview sv2);
intptr_t csview_find(csview sv, const char* str);
intptr_t csview_find_sv(csview sv, csview find);
bool csview_contains(csview sv, const char* str);
bool csview_starts_with(csview sv, const char* str);
bool csview_ends_with(csview sv, const char* str);
```
#### UTF8 methods
```c
intptr_t csview_u8_size(csview sv);
bool csview_valid_utf8(csview sv); // depends on src/utf8code.c
csview_iter csview_begin(const csview* self);
csview_iter csview_end(const csview* self);
void csview_next(csview_iter* it); // utf8 codepoint step, not byte!
csview_iter csview_advance(csview_iter it, intptr_t n);
// from utf8.h
intptr_t utf8_size(const char *s);
intptr_t utf8_size_n(const char *s, intptr_t nbytes); // number of UTF8 codepoints within n bytes
const char* utf8_at(const char *s, intptr_t index); // from UTF8 index to char* position
intptr_t utf8_pos(const char* s, intptr_t index); // from UTF8 index to byte index position
unsigned utf8_chr_size(const char* s); // UTF8 character size: 1-4
// implemented in src/utf8code.c:
bool utf8_valid(const char* s);
bool utf8_valid_n(const char* s, intptr_t nbytes);
uint32_t utf8_decode(utf8_decode_t *d, uint8_t byte); // decode next byte to utf8, return state.
unsigned utf8_encode(char *out, uint32_t codepoint); // encode unicode cp into out buffer
uint32_t utf8_peek(const char* s); // codepoint value of character at s
uint32_t utf8_peek_off(const char* s, int offset); // codepoint value at utf8 pos (may be negative)
```
#### Helper methods
```c
int csview_cmp(const csview* x, const csview* y);
int csview_icmp(const csview* x, const csview* y); // depends on src/utf8code.c:
bool csview_eq(const csview* x, const csview* y);
uint64_t csview_hash(const csview* x);
```
## Types
| Type name | Type definition | Used to represent... |
|:----------------|:-------------------------------------------|:-------------------------|
| `csview` | `struct { const char *str; intptr_t size; }` | The string view type |
| `csview_value` | `char` | The string element type |
| `csview_iter` | `struct { csview_value *ref; }` | UTF8 iterator |
## Example: UTF8 iteration and case conversion
```c
#define i_import
#include <stc/cstr.h>
#include <stc/csview.h>
int main(void)
{
cstr str = cstr_from("Liberté, égalité, fraternité.");
csview sv = cstr_sv(&str);
c_foreach (i, csview, sv)
printf("%.*s ", c_SS(i.u8.chr));
puts("");
cstr_uppercase(&str);
printf("%s\n", cstr_str(&str));
cstr_drop(&str);
}
```
Output:
```
L i b e r t é , é g a l i t é , f r a t e r n i t é .
LIBERTÉ, ÉGALITÉ, FRATERNITÉ.
```
### Example 2: UTF8 replace
```c
#define i_import // include dependent utf8 definitions.
#include <stc/cstr.h>
int main(void)
{
cstr s1 = cstr_lit("hell😀 w😀rld");
cstr_u8_replace_at(&s1, cstr_find(&s1, "😀rld"), 1, c_sv("ø"));
printf("%s\n", cstr_str(&s1));
c_foreach (i, cstr, s1)
printf("%.*s,", c_SS(i.u8.chr)); // u8.chr is a csubstr
cstr_drop(&s1);
}
```
Output:
```
hell😀 wørld
h,e,l,l,😀, ,w,ø,r,l,d,
```
|
