Wed, 28 Jun 2023 20:07:52 +0200
improve mempool implementation
1 ---
2 title: UCX Features
3 ---
5 <div id="modules">
7 ------------------------ ------------------------- ------------------- ---------------------------------
8 [Allocator](#allocator) [String](#string) [Buffer](#buffer) [Memory Pool](#memory-pool)
9 [Iterator](#iterator) [Collection](#collection) [List](#list) [Map](#map)
10 [Utilities](#utilities)
11 ------------------------ ------------------------- ------------------- ---------------------------------
13 </div>
15 ## Allocator
17 *Header file:* [allocator.h](api/allocator_8h.html)
19 The UCX allocator provides an interface for implementing an own memory allocation mechanism.
20 Various function in UCX provide an additional alternative signature that takes an allocator as
21 argument. A default allocator implementation using the stdlib memory management functions is
22 available via the global symbol `cxDefaultAllocator`.
24 If you want to define your own allocator, you need to initialize the `CxAllocator` structure
25 with a pointer to an allocator class (containing function pointers for the memory management
26 functions) and an optional pointer to an arbitrary memory region that can be used to store
27 state information for the allocator. An example is shown below:
29 ```c
30 struct my_allocator_state {
31 size_t total;
32 size_t avail;
33 char mem[];
34 };
36 static cx_allocator_class my_allocator_class = {
37 my_malloc_impl,
38 my_realloc_impl, // all these functions are somewhere defined
39 my_calloc_impl,
40 my_free_impl
41 };
43 CxAllocator create_my_allocator(size_t n) {
44 CxAllocator alloc;
45 alloc.cl = &my_allocator_class;
46 alloc.data = calloc(1, sizeof(struct my_allocator_state) + n);
47 return alloc;
48 }
50 void free_my_allocator(CxAllocator *alloc) {
51 free(alloc.data);
52 free(alloc);
53 }
54 ```
56 ## String
58 *Header file:* [string.h](api/string_8h.html)
60 UCX strings come in two variants: immutable (`cxstring`) and mutable (`cxmutstr`).
61 The functions of UCX are designed to work with immutable strings by default but in situations where it is necessary,
62 the API also provides alternative functions that work directly with mutable strings.
63 Functions that change a string in-place are, of course, only accepting mutable strings.
65 When you are using UCX functions, or defining your own functions, you are sometimes facing the "problem",
66 that the function only accepts arguments of type `cxstring` but you only have a `cxmutstr` at hand.
67 In this case you _should not_ introduce a wrapper function that accepts the `cxmutstr`,
68 but instead you should use the `cx_strcast()` function to cast the argument to the correct type.
70 In general, UCX strings are **not** necessarily zero-terminated. If a function guarantees to return zero-terminated
71 string, it is explicitly mentioned in the documentation of the respective function.
72 As a rule of thumb, you _should not_ pass the strings of a UCX string structure to another API without explicitly
73 ensuring that the string is zero-terminated.
75 ## Buffer
77 *Header file:* [buffer.h](api/buffer_8h.html)
79 Instances of this buffer implementation can be used to read from or write to memory like you would do with a stream.
80 This allows the use of `cx_stream_copy()` (see [Utilities](#utilities)) to copy contents from one buffer to another,
81 or from a file or network streams to the buffer and vice-versa.
83 More features for convenient use of the buffer can be enabled, like automatic memory management and automatic
84 resizing of the buffer space.
86 Since UCX 3.0, the buffer also supports automatic flushing of contents to another stream (or buffer) as an alternative
87 to automatically resizing the buffer space.
88 Please refer to the API doc for the fields prefixed with `flush_` to learn more.
90 ## Memory Pool
92 *Header file:* [mempool.h](api/mempool_8h.html)
94 ## Iterator
96 *Header file:* [iterator.h](api/iterator_8h.html)
98 ## Collection
100 *Header file:* [collection.h](api/collection_8h.html)
102 ## List
104 *Header file:* [list.h](api/list_8h.html)
106 ### Linked List
108 *Header file:* [linked_list.h](api/linked__list_8h.html)
110 ### Array List
112 *Header file:* [array_list.h](api/array__list_8h.html)
114 ## Map
116 *Header file:* [map.h](api/map_8h.html)
118 ### Hash Map
120 *Header file:* [hash_map.h](api/hash__map_8h.html)
122 ## Utilities
124 *Header file:* [utils.h](api/utils_8h.html)
126 UCX provides some utilities for routine tasks. Most of them are simple macros, like e.g. the `cx_for_n()` macro,
127 creating a `for` loop counting from zero to (n-1) which is extremely useful to traverse the indices of
128 an array.
130 But the most useful utilities are the *stream copy* functions, which provide a simple way to copy all - or a
131 bounded amount of - data from one stream to another. Since the read/write functions of a UCX buffer are
132 fully compatible with stream read/write functions, you can easily transfer data from file or network streams to
133 a UCX buffer or vice-versa.
135 The following example shows, how easy it is to read the contents of a file into a buffer:
136 ```c
137 FILE *inputfile = fopen(infilename, "r");
138 if (inputfile) {
139 CxBuffer fbuf;
140 cxBufferInit(&fbuf, NULL, 4096, NULL, CX_BUFFER_AUTO_EXTEND);
141 cx_stream_copy(inputfile, &fbuf,
142 (cx_read_func) fread,
143 (cx_write_func) cxBufferWrite);
144 fclose(inputfile);
146 // ... do something meaningful with the contents ...
148 cxBufferDestroy(&fbuf);
149 } else {
150 perror("Error opening input file");
151 if (fout != stdout) {
152 fclose(fout);
153 }
154 }
155 ```
157 ### Printf Functions
159 *Header file:* [printf.h](api/printf_8h.html)
161 In this utility header you can find `printf()`-like functions that can write the formatted output to an arbitrary
162 stream (or UCX buffer, resp.), or to memory allocated by an allocator within a single function call.
163 With the help of these convenience functions, you do not need to `snprintf` your string to a temporary buffer anymore,
164 plus you do not need to worry about too small buffer sizes, because the functions will automatically allocate enough
165 memory to contain the entire formatted string.
167 ### Compare Functions
169 *Header file:* [compare.h](api/compare_8h.html)
171 This header file contains a collection of compare functions for various data types.
172 Their signatures are designed to be compatible with the `cx_compare_func` function pointer type.