path: root/README.md

![STC](docs/pics/containers.jpg)

STC - Smart Template Containers for C
=====================================

News: Version 3.6 released (April 2022)
---------------------------------------
- See [Changes version 3.6](#changes-version-36)

Introduction
------------
STC is a *modern*, *templated*, *user-friendly*, *type-safe*, *very fast* and *compact* container library for C99.
The API is fairly similar to c++ STL, but a bit more uniform across the containers and takes
inspiration from Rust and Python too. It is an advantage to know how these containers work in other languages, like
Java, C# or C++, but it's not required.

This library allows you to manage both trivial to very complex data in a wide variety of containers
without the need for boilerplate code. You may specify element-cloning, -comparison, -destruction and
more on complex container hierarchies without resorting to cumbersome function pointers with type casting.
Usage with trivial data types is simple to use compared to most generic container libraries for C because
of its type safety with an intuitive and consistent API.

Three standout features of STC are
1. the centralized analysis of template arguments: It assigns good defaults to non-specified templates.
You may specify a number of "standard" template arguments for each container, but as minimum only one is
required (two for maps). In the latter case, STC assumes the elements are basic types. For more complex types,
additional template arguments must be defined.
2. the general "heterogeneous lookup"-like feature: Allows specification of an alternative type to use
for lookup in containers. E.g. for containers with string type (**cstr**) elements, `const char*` may be used
as lookup type. It will then use the input `const char*` directly when comparing with the string data in the
container. This avoids the construction of a new `cstr` (which possible allocates memory) for the lookup. 
Finally, destruction of the lookup key (i.e. string literal) after usage is not needed (or allowed), which 
is convenient in C. The alternative lookup type may also be used for adding entries into containers by using 
the *emplace*-functions. E.g. `MyCStrVec_emplace_back(&vec, "Hello")`, which further simplifies usage of STC.
3. the design of iterators: All container can be iterated the same way, and uses the
same element access syntax. E.g. `c_foreach (it, IntContainer, container) printf(" %d", *it.ref);` will work for
every type of container defined as `IntContainer` with `int` elements. Also the form `c_foreach (it, IntContainer, it1, it2)`
may be used to iterate from `it1` up to `it2`.

The library is mature and well tested, so you may use it in projects. However, minor breaking API changes may
still happen. The main development of this project is finished, but I will handle PRs with bugs and improvements
in the future, and do minor modifications.

Contents
--------
- [***ccommon*** - RAII and iterator macros](docs/ccommon_api.md)
- [***carc*** - **std::shared_ptr** alike support](docs/carc_api.md)
- [***carr2/3*** - **2d** and **3d** dynamic **array** type](docs/carray_api.md)
- [***cbits*** - **std::bitset** alike type](docs/cbits_api.md)
- [***cbox*** - **std::unique_ptr** alike type](docs/cbox_api.md)
- [***cdeq*** - **std::deque** alike type](docs/cdeq_api.md)
- [***clist*** - **std::forward_list** alike type](docs/clist_api.md)
- [***cmap*** - **std::unordered_map** alike type](docs/cmap_api.md)
- [***cpque*** - **std::priority_queue** alike type](docs/cpque_api.md)
- [***cqueue*** - **std::queue** alike type](docs/cqueue_api.md)
- [***cset*** - **std::unordered_set** alike type](docs/cset_api.md)
- [***csmap*** - **std::map** sorted map alike type](docs/csmap_api.md)
- [***csset*** - **std::set** sorted set alike type](docs/csset_api.md)
- [***cstack*** - **std::stack** alike type](docs/cstack_api.md)
- [***cstr*** - **std::string** alike type](docs/cstr_api.md)
- [***csview*** - **std::string_view** alike type](docs/csview_api.md)
- [***cvec*** - **std::vector** alike type](docs/cvec_api.md)

Others:
- [***crandom*** - A novel very fast *PRNG* named **stc64**](docs/crandom_api.md)
- [***coption*** - Command line options scanner](docs/coption_api.md)
- [***threads*** - Mimic **C11-threads** (by Marcus Geelnard)](include/threads.h)

Highlights
----------
- **User friendly** - Just include the headers and you are good. The API and functionality is very close to c++ STL, and is fully listed in the docs. 
- **Templates** - Use `#define i_{arg}` to specify container template arguments. There are templates for element-*type*, -*comparison*, -*destruction*, -*cloning*, -*conversion types*, and more.
- **Unparalleled performance** - Some containers are much faster than the c++ STL containers, the rest are about equal in speed.
- **Fully memory managed** - All containers will destruct keys/values via destructor defined as macro parameters before including the container header. Also, shared pointers are supported and can be stored in containers, see ***carc***.
- **Fully type safe** - Because of templating, it avoids error-prone casting of container types and elements back and forth from the containers.
- **Uniform, easy-to-learn API** - Methods to ***construct***, ***initialize***, ***iterate*** and ***destruct*** have uniform and intuitive usage across the various containers.
- **Small footprint** - Small source code and generated executables. The executable from the example below with six different containers is *22 kb in size* compiled with gcc -Os on linux.
- **Dual mode compilation** - By default it is a simple header-only library with inline and static methods only, but you can easily switch to create a traditional library with shared symbols, without changing existing source files. See the Installation section.
- **No callback functions** - All passed template argument functions/macros are directly called from the implementation, no slow callbacks which requires storage.
- **Compiles with C++ and C99** - C code can be compiled with C++ (container element types must be POD).
- **Container prefix and forward declaration** - Templated containers may have user defined prefix, e.g. myvec_push_back(). They may also be forward declared without including the full API/implementation. See documentation below.

Performance
-----------
![Benchmark](benchmarks/pics/benchmark.gif)

Benchmark notes:
- The barchart shows average test times over three platforms: Mingw64 10.30, Win-Clang 12, VC19. CPU: Ryzen 7 2700X CPU @4Ghz.
- Containers uses value types `uint64_t` and pairs of `uint64_t` for the maps.
- Black bars indicates performance variation between various platforms/compilers.
- Iterations are repeated 4 times over n elements.
- **find()**: not executed for *forward_list*, *deque*, and *vector* because these c++ containers does not have native *find()*.
- **deque**: *insert*: n/3 push_front(), n/3 push_back()+pop_front(), n/3 push_back().
- **map and unordered map**: *insert*: n/2 random numbers, n/2 sequential numbers. *erase*: n/2 keys in the map, n/2 random keys.

Usage
-----
The usage of the containers is similar to the c++ standard containers in STL, so it should be easy if you
are familiar with them. All containers are generic/templated, except for **cstr** and **cbits**.
No casting is used, so containers are type-safe like templates in c++. A basic usage example:
```c
#define i_type FVec    // if not defined, vector type would be cvec_float
#define i_val float    // element type
#include <stc/cvec.h>  // defines the FVec type

int main(void) {
    FVec vec = FVec_init();
    FVec_push_back(&vec, 10.f);
    FVec_push_back(&vec, 20.f);
    FVec_push_back(&vec, 30.f);

    for (size_t i = 0; i < FVec_size(vec); ++i)
        printf(" %g", vec.data[i]);
    FVec_drop(&vec); // free memory
}
```
An alternative and often preferred way to write this code with STL is:
```c
int main(void) {
    c_auto (FVec, vec) // RAII - specify create and destruct at one place.
    {
        c_apply(v, FVec_push_back(&vec, *v), float, {10.f, 20.f, 30.f});

        c_foreach (i, FVec, vec) // generic iteration and element access
            printf(" %g", *i.ref);
    }
}
```
In order to include two **cvec**s with different element types, include cvec.h twice. For struct, a `i_cmp`
compare function is required to enable sorting and searching (`<` and `==` operators is default and works
for integral types only). Alternatively, `#define i_opt c_no_cmp` to disable methods using comparison.

Similarly, if a destructor `i_valdrop` is defined, either define a `i_valclone` clone function
or `#define i_opt c_no_clone` to disable cloning and emplace methods. Unless these requirements are met,
compile errors are generated.
```c
#define i_val struct One
#define i_opt c_no_cmp
#define i_tag one
#include <stc/cvec.h>

#define i_val struct Two
#define i_opt c_no_cmp
#define i_tag two
#include <stc/cvec.h>
...
cvec_one v1 = cvec_one_init();
cvec_two v2 = cvec_two_init();
```

With six different containers:
```c
#include <stdio.h>
#include <stc/ccommon.h>

struct Point { float x, y; };

int Point_cmp(const struct Point* a, const struct Point* b) {
    int cmp = c_default_cmp(&a->x, &b->x);
    return cmp ? cmp : c_default_cmp(&a->y, &b->y);
}

#define i_key int
#include <stc/cset.h>  // cset_int: unordered set

#define i_val struct Point
#define i_cmp Point_cmp
#define i_tag pnt
#include <stc/cvec.h>  // cvec_pnt: vector of struct Point

#define i_val int
#include <stc/cdeq.h>  // cdeq_int: deque of int

#define i_val int
#include <stc/clist.h> // clist_int: singly linked list

#define i_val int
#include <stc/cstack.h>

#define i_key int
#define i_val int
#include <stc/csmap.h> // csmap_int: sorted map int => int

int main(void) {
    // define six containers with automatic call of init and drop (destruction after scope exit)
    c_auto (cset_int, set)
    c_auto (cvec_pnt, vec)
    c_auto (cdeq_int, deq)
    c_auto (clist_int, lst)
    c_auto (cstack_int, stk)
    c_auto (csmap_int, map)
    {
        // add some elements to each container
        c_apply(v, cset_int_insert(&set, *v), int, {10, 20, 30});
        c_apply(v, cvec_pnt_push_back(&vec, *v), struct Point, { {10, 1}, {20, 2}, {30, 3} });
        c_apply(v, cdeq_int_push_back(&deq, *v), int, {10, 20, 30});
        c_apply(v, clist_int_push_back(&lst, *v), int, {10, 20, 30});
        c_apply(v, cstack_int_push(&stk, *v), int, {10, 20, 30});
        c_apply(v, csmap_int_insert(&map, c_pair(v)), 
            csmap_int_raw, { {20, 2}, {10, 1}, {30, 3} });

        // add one more element to each container
        cset_int_insert(&set, 40);
        cvec_pnt_push_back(&vec, (struct Point){40, 4});
        cdeq_int_push_front(&deq, 5);
        clist_int_push_front(&lst, 5);
        cstack_int_push(&stk, 40);
        csmap_int_insert(&map, 40, 4);

        // find an element in each container
        cset_int_iter i1 = cset_int_find(&set, 20);
        cvec_pnt_iter i2 = cvec_pnt_find(&vec, (struct Point){20, 2});
        cdeq_int_iter i3 = cdeq_int_find(&deq, 20);
        clist_int_iter i4 = clist_int_find(&lst, 20);
        csmap_int_iter i5 = csmap_int_find(&map, 20);
        printf("\nFound: %d, (%g, %g), %d, %d, [%d: %d]\n", *i1.ref, i2.ref->x, i2.ref->y,
                                                            *i3.ref, *i4.ref,
                                                            i5.ref->first, i5.ref->second);
        // erase the elements found
        cset_int_erase_at(&set, i1);
        cvec_pnt_erase_at(&vec, i2);
        cdeq_int_erase_at(&deq, i3);
        clist_int_erase_at(&lst, i4);
        csmap_int_erase_at(&map, i5);

        printf("After erasing elements found:");
        printf("\n set:"); c_foreach (i, cset_int, set) printf(" %d", *i.ref);
        printf("\n vec:"); c_foreach (i, cvec_pnt, vec) printf(" (%g, %g)", i.ref->x, i.ref->y);
        printf("\n deq:"); c_foreach (i, cdeq_int, deq) printf(" %d", *i.ref);
        printf("\n lst:"); c_foreach (i, clist_int, lst) printf(" %d", *i.ref);
        printf("\n stk:"); c_foreach (i, cstack_int, stk) printf(" %d", *i.ref);
        printf("\n map:"); c_foreach (i, csmap_int, map) printf(" [%d: %d]", i.ref->first,
                                                                             i.ref->second);
    }
}
```

Output
```
Found: 20, (20, 2), 20, 20, [20: 2]
After erasing elements found:
 set: 10 30 40
 vec: (10, 1) (30, 3) (40, 4)
 deq: 5 10 30
 lst: 5 10 30
 stk: 10 20 30 40
 map: [10: 1] [30: 3] [40: 4]
```

Installation
------------
Because it is headers-only, headers can simply be included in your program. By default, functions are static
(some inlined). You may add the *include* folder to the **CPATH** environment variable to
let GCC, Clang, and TinyC locate the headers.

If containers are used across several translation units with common instantiated container types, it is 
recommended to build as a "library" with external linking to minimize executable size. To enable this,
specify `-DSTC_HEADER` as compiler option in your build environment. Next, place all the instantiations
of the containers used inside a single C-source file as in the example below, and `#define STC_IMPLEMENT` at top. 
You may also cherry-pick external linking mode on individual containers by `#define i_opt c_header` and
`#define i_opt c_implement`, or force static symbols by `#define i_opt c_static` before container includes.
```c
// stc_libs.c
#define STC_IMPLEMENT
#include <stc/cstr.h>
#include "Point.h"

#define i_key int
#define i_val int
#define i_tag ii
#include <stc/cmap.h>  // cmap_ii: int => int

#define i_key int64_t
#define i_tag ix
#include <stc/cset.h>  // cset_ix

#define i_val int
#include <stc/cvec.h>  // cvec_int

#define i_val Point
#define i_tag pnt
#include <stc/clist.h> // clist_pnt
```

Specifying template parameters
------------------------------
Each templated type requires one `#include`, even if it's the same container base type, as described earlier.
The template parameters are given by a `#define i_xxxx` statement, where *xxxx* is the parameter name.
The list of template parameters:

- `i_key`     - Element key type for map/set only. **[required]**.
- `i_val`     - Element value type. **[required for]** cmap/csmap, it is the mapped value type.
- `i_cmp`     - Three-way comparison of two *i_keyraw*\* or *i_valraw*\* - **[required for]** non-integral *i_keyraw* types unless *i_opt* is defined with *c_no_cmp*.
- `i_hash`    - Hash function taking *i_keyraw*\* - defaults to *c_default_hash*. **[required for]** non-POD keyraw types.
- `i_eq`      - Equality comparison of two *i_keyraw*\* - defaults to *!i_cmp*. Companion with *i_hash*.

Properties:
- `i_tag`     - Container type name tag. Defaults to *i_key* name.
- `i_type`    - Full container type name. Alternative to *i_tag*.
- `i_opt`     - Boolean properties: may combine *c_no_cmp*, *c_no_clone*, *c_no_atomic*, *c_is_fwd*, *c_static*, *c_header* with the *|* separator.

Key:
- `i_keydrop` - Destroy map/set key func - defaults to empty destructor.
- `i_keyclone` - **[required if]** *i_keydrop* is defined (not required for **carc**). 
- `i_keyraw`  - Convertion "raw" type - defaults to *i_key*.
- `i_keyfrom` - Convertion func *i_key* <- *i_keyraw*. **[required if]** *i_keyraw* is defined
- `i_keyto`   - Convertion func *i_key*\* -> *i_keyraw*.

Val:
- `i_valdrop` - Destroy mapped or value func - defaults to empty destruct.
- `i_valclone` - **[required if]** *i_valdrop* is defined. 
- `i_valraw`  - Convertion "raw" type - defaults to *i_val*.
- `i_valfrom` - Convertion func *i_val* <- *i_valraw*.
- `i_valto`   - Convertion func *i_val*\* -> *i_valraw*.

Specials:
- `i_key_str` - Define key type *cstr* and container i_tag = *str*. It binds type convertion from/to *const char*\*, and the ***cmp***, ***eq***, ***hash***, and ***keydrop*** functions.
- `i_key_ssv` - Define key type *cstr* and container i_tag = *ssv*. It binds type convertion from/to *csview*, and its ***cmp***, ***eq***, ***hash***, and ***keydrop*** functions.
- `i_key_arcbox TYPE` - Define container key type where TYPE is a smart pointer **carc** or **cbox**. NB: not to be used when defining carc/cbox types themselves.
- `i_key_bind TYPE` - General version of the two above - will auto-bind to standard named functions: *TYPE_clone*, *TYPE_drop*, *TYPE_cmp*, *TYPE_eq*, *TYPE_hash*. If `i_keyraw` is defined, *TYPE_toraw* func. is bound to `i_keyto`. Only functions required by the particular container need to be defined. E.g., only **cmap** and **cset** and smart pointers uses *TYPE_hash* and *TYPE_eq*. **cstack** does not use *TYPE_cmp*. *TYPE_clone* is not used if *#define i_opt c_no_clone* is specified. Likewise, *TYPE_cmp* is not used if *#define i_opt c_no_cmp* is specified.
- `i_val_str`, `i_val_bind`, `i_val_arcbox` - Similar rules as for ***key***.

**Notes**:
- Instead of defining `i_cmp`, you may define *i_opt c_no_cmp* to disable searching and sorting functions.
- Instead of defining `i_*clone`, you may define *i_opt c_no_clone* to disable emplace and clone-functions.
- `i_keyraw RAWTYPE` - If defined along with *i_key_bind*, the two functions *TYPE TYPE_from(RAWTYPE)* and *RAWTYPE TYPE_toraw(TYPE\*)* are expected in addition to *TYPE TYPE_clone(TYPE)*. Note the signature for ***cmp***, ***eq***, ***hash*** now: *int RAWTYPE_cmp(const RAWTYPE\*, const RAWTYPE\*)*, and similar for the two others.

The *emplace* versus non-emplace container methods
--------------------------------------------------
STC, like c++ STL, has two sets of methods for adding elements to containers. One set begins
with **emplace**, e.g. *cvec_X_emplace_back()*. This is a convenient alternative to
*cvec_X_push_back()* when dealing non-trivial container elements, e.g. strings, shared pointers or
other elements using dynamic memory or shared resources.

The **emplace** methods ***constructs*** or ***clones*** the given elements when they are added
to the container. In contrast, the *non-emplace* methods ***moves*** the given elements into the
container. 

**Note**: For containers with integral/trivial element types, or when neither `i_keyraw/i_valraw` is defined,
the **emplace** functions are ***not*** available (or needed), as it can easier lead to mistakes.

| non-emplace: Move          | emplace: Embedded copy         | Container                                   |
|:---------------------------|:-------------------------------|:--------------------------------------------|
| insert(), push()           | emplace()                      | cmap, csmap, cset, csset                    |
| insert_or_assign()         | emplace_or_assign()            | cmap, csmap                                 |
| push()                     | emplace()                      | cqueue, cpque, cstack                       |
| push_back(), push()        | emplace_back()                 | cdeq, clist, cvec                           |
| push_front()               | emplace_front()                | cdeq, clist                                 |

Strings are the most commonly used non-trivial data type. STC containers have proper pre-defined
definitions for cstr container elements, so they are fail-safe to use both with the **emplace**
and non-emplace methods:
```c
#define i_val_str       // special macro to enable container of cstr
#include <stc/cvec.h>   // vector of string (cstr)
...
c_auto (cvec_str, vec)  // declare and call cvec_str_init() and defer cvec_str_drop(&vec)
c_autovar (cstr s = cstr_new("a string literal"), cstr_drop(&s))  // c_autovar is a more general c_auto.
{
    const char* hello = "Hello";
    cvec_str_push_back(&vec, cstr_from(hello);    // construct and add string from const char*
    cvec_str_push_back(&vec, cstr_clone(s));      // clone and append a cstr

    cvec_str_emplace_back(&vec, "Yay, literal");  // internally constructs cstr from const char*
    cvec_str_emplace_back(&vec, cstr_clone(s));   // <-- COMPILE ERROR: expects const char*
    cvec_str_emplace_back(&vec, cstr_str(&s));    // Ok: const char* input type.
}
```
This is made possible because the type configuration may be given an optional
conversion/"rawvalue"-type as template parameter, along with a back and forth conversion
methods to the container value type.

Rawvalues are primarily beneficial for **lookup** and **map insertions**, however the
**emplace** methods constructs `cstr`-objects from the rawvalues, but only when required:
```c
cmap_str_emplace(&map, "Hello", "world");
// Two cstr-objects were constructed by emplace

cmap_str_emplace(&map, "Hello", "again");
// No cstr was constructed because "Hello" was already in the map.

cmap_str_emplace_or_assign(&map, "Hello", "there");
// Only cstr_new("there") constructed. "world" was destructed and replaced.

cmap_str_insert(&map, cstr_new("Hello"), cstr_new("you"));
// Two cstr's constructed outside call, but both destructed by insert
// because "Hello" existed. No mem-leak but less efficient.

it = cmap_str_find(&map, "Hello");
// No cstr constructed for lookup, although keys are cstr-type.
```
Apart from strings, maps and sets are normally used with trivial value types. However, the
last example on the **cmap** page demonstrates how to specify a map with non-trivial keys.

Erase methods
-------------
| Name                      | Description                  | Container                                   |
|:--------------------------|:-----------------------------|:--------------------------------------------|
| erase()                   | key based                    | csmap, csset, cmap, cset, cstr              |
| erase_at()                | iterator based               | csmap, csset, cmap, cset, cvec, cdeq, clist |
| erase_range()             | iterator based               | csmap, csset, cvec, cdeq, clist             |
| erase_n()                 | index based                  | cvec, cdeq, cstr                            |
| remove()                  | remove all matching values   | clist                                       |

Forward declaring containers
----------------------------
It is possible to forward declare containers. This is useful when a container is part of a struct, 
but still not expose or include the full implementation / API of the container.
```c
// Header file
#include <stc/forward.h> // only include data structures
forward_cstack(cstack_pnt, struct Point); // declare cstack_pnt and cstack_pnt_value, cstack_pnt_iter;
                                          // the element may be forward declared type as well
typedef struct Dataset {
    cstack_pnt vertices;
    cstack_pnt colors;
} Dataset;

...
// Implementation
#define c_opt c_is_fwd                    // flag that the container was forward declared.
#define i_val struct Point
#define i_tag pnt
#include <stc/cstack.h>
```

User-defined container type name
--------------------------------
Define `i_type` instead of `i_tag`:
```c
#define i_type MyVec
#define i_val int
#include <stc/cvec.h>

myvec vec = MyVec_init();
MyVec_push_back(&vec, 1);
...
```

Memory efficiency
-----------------
- **cstr**, **cvec**: Type size: 1 pointer. The size and capacity is stored as part of the heap allocation that also holds the vector elements.
- **clist**: Type size: 1 pointer. Each node allocates a struct which stores the value and next pointer.
- **cdeq**:  Type size: 2 pointers. Otherwise like *cvec*.
- **cmap**: Type size: 4 pointers. *cmap* uses one table of keys+value, and one table of precomputed hash-value/used bucket, which occupies only one byte per bucket. The closed hashing has a default max load factor of 85%, and hash table scales by 1.6x when reaching that.
- **csmap**: Type size: 1 pointer. *csmap* manages its own array of tree-nodes for allocation efficiency. Each node uses only two 32-bit ints for child nodes, and one byte for `level`.
- **carr2**, **carr3**: Type size: 1 pointer plus dimension variables. Arrays are allocated as one contiguous block of heap memory, and one allocation for pointers of indices to the array.
- **carc**: Type size: 2 pointers, one for the data and one for the reference counter.

# Version 3

## Changes version 3.6
- Swapped to new **cstr** (*short string optimized*, aka SSO). Note that `cstr_str(&s)` must be used, `s.str` is no longer usable.
- Removed *redundant* size argument to `i_hash` template parameter and `c_default_hash`. Please update your code.
- Added general `i_keyclone/i_valclone` template parameter: containers of smart pointers (**carc**, **cbox**) now correctly cloned.
- Allows for `i_key*` template parameters instead of `i_val*` for all containers, not only for **cset** and **csset**.
- Optimized *c_default_hash()*. Therefore *c_hash32()* and *c_hash64()* are removed (same speed).
- Added *.._push()* and *.._emplace()* function to all containers to allow for more generic coding.
- Renamed global PRNGs *stc64_random()* and *stc64_srandom()* to *crandom()* and *csrandom()*.
- Added some examples and benchmarks for SSO and heterogenous lookup comparison with c++20 (string_bench_*.cpp).

## Brief summary of changes from version 2.x to 3.0
- Renamed: all ***_del*** to `_drop` (like destructors in Rust).
- Renamed: all ***_compare*** to `_cmp`
- Renamed: ***i_equ*** to `i_eq`, and ***_equalto*** to `_eq`.
- Renamed: ***i_cnt*** to `i_type` for defining the complete container type name.
- Renamed: type **csptr** to [**carc**](docs/carc_api.md) (atomic reference counted) smart pointer.
- Renamed: ***i_key_csptr*** / ***i_val_csptr*** to `i_key_arcbox` / `i_val_arcbox` for specifying **carc** and **cbox** values in containers.
- Renamed: *csptr_X_make()* to `carc_X_from()`.
- Renamed: *cstr_lit()* to `cstr_new(literal)`, and *cstr_assign_fmt()* to `cstr_printf()`.
- Renamed: *c_default_fromraw()* to `c_default_from()`.
- Changed: the [**c_apply**](docs/ccommon_api.md) macros API.
- Replaced: *csview_first_token()* and *csview_next_token()* with one function: `csview_token()`.
- Added: **checkauto** tool for checking that c-source files uses `c_auto*` macros correctly.
- Added: general `i_key_bind` / `i_val_bind` template parameters which auto-binds template functions.
- Added: `i_opt` template parameter: compile-time options: `c_no_cmp`, `c_no_clone`, `c_no_atomic`, `c_is_fwd`; may be combined with `|`
- Added: [**cbox**](docs/cbox_api.md) type: smart pointer, similar to [Rust Box](https://doc.rust-lang.org/rust-by-example/std/box.html) and [std::unique_ptr](https://en.cppreference.com/w/cpp/memory/unique_ptr).
- Added: [**c_forpair**](docs/ccommon_api.md) macro: for-loop with "structured binding"

## Migration guide from version 2 to 3
Replace (regular expression) globally in code base (VS Code):
- `_del\b` ⟶ `_drop`
- `_compare\b` ⟶ `_cmp`
- `_rawvalue\b` ⟶ `_raw`
- `_equ\b` ⟶ `_eq`

Replace (whole word + match case):
- `i_keydel` ⟶ `i_keydrop`
- `i_valdel` ⟶ `i_valdrop`
- `i_cnt` ⟶ `i_type`
- `cstr_lit` ⟶ `cstr_new`
- `i_key_sptr` ⟶ `i_key_arcbox`
- `i_val_sptr` ⟶ `i_val_arcbox`

Non-regex, global match case replace:
- `csptr` ⟶ `carc`