Mercurial > hg > ucx / file revision

 ---

 title: Modules

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 UCX provides several modules for data structures and algorithms.

 You may choose to use specific modules by inclueding the corresponding header

 file.

 Please note, that some modules make use of other UCX modules.

 For instance, the [Allocator](#allocator) module is used by many other modules

 to allow flexible memory allocation.

 By default the header files are placed into an `ucx` directory within your

 systems include directory. In this case you can use a module by including it

 via `#include <ucx/MODULENAME.h>`.

 Required modules are included automatically.

 <div id="modules" align="center">

 ----------------------- ----------------------      ----------------------------     -------------------------

 [Allocator](#allocator) [AVL Tree](#avl-tree)  [Buffer](#buffer)                [List](#list)

 [Logging](#logging)     [Map](#map)                 [Memory Pool](#memory-pool) [Properties](#properties)

 [Stack](#stack)         [String](#string)           [Testing](#testing)              [Utilities](#utilities)

 ----------------------- ----------------------      ----------------------------     -------------------------

 </div>

 ## Allocator

 *Header file:* [allocator.h](api/allocator_8h.html)  

 *Required modules:* None.

 A UCX allocator consists of a pointer to the memory area / pool and four

 function pointers to memory management functions operating on this memory

 area / pool. These functions shall behave equivalent to the standard libc

 functions `malloc`, `calloc`, `realloc` and `free`.

 The signature of the memory management functions is based on the signature

 of the respective libc function but each of them takes the pointer to the

 memory area / pool as first argument.

 As the pointer to the memory area / pool can be arbitrarily chosen, any data

 can be provided to the memory management functions. One example is the

 [UCX Memory Pool](#memory-pool).

 ## AVL Tree

 *Header file:* [avl.h](api/avl_8h.html)  

 *Required modules:* [Allocator](#allocator)

 This binary search tree implementation allows average O(1) insertion and

 removal of elements (excluding binary search time).

 All common binary tree operations are implemented. Furthermore, this module

 provides search functions via lower and upper bounds.

 ### Filtering items with a time window

 Suppose you have a list of items which contain a `time_t` value and your task

 is to find all items within a time window `[t_start, t_end]`.

 With AVL Trees this is easy:

 ```C

 /* ---------------------

  * Somewhere in a header

  */

 typedef struct {

     time_t ts;

     // other important data

 } MyObject;

 /* -----------

  * Source code

  */

 UcxAVLTree* tree = ucx_avl_new(ucx_longintcmp);

 // ... populate tree with objects, use '& MyObject.ts' as key ...

 // Now find every item, with 30 <= ts <= 70

 time_t ts_start = 30;

 time_t ts_end = 70;

 printf("Values in range:\n");

 for (

         UcxAVLNode* node = ucx_avl_find_node(

             tree, (intptr_t) &ts_start,

             ucx_longintdist, UCX_AVL_FIND_LOWER_BOUNDED);

         node && (*(time_t*)node->key) <= ts_end;

         node = ucx_avl_succ(node)

     ) {

     printf(" ts: %ld\n", ((MyObject*)node->value)->ts);

 }

 ucx_avl_free_content(tree, free);

 ucx_avl_free(tree);

 ```

 ## Buffer

 *Header file:* [buffer.h](api/buffer_8h.html)  

 *Required modules:* None.

 Instances of this buffer implementation can be used to read from or to write to

 memory like you would do with a stream. This allows the use of

 `ucx_stream_copy()` from the [Utilities](#utilities) module to copy contents

 from one buffer to another or from file or network streams to the buffer and

 vice-versa.

 More features for convenient use of the buffer can be enabled, like automatic

 memory management and automatic resizing of the buffer space.

 See the documentation of the macro constants in the header file for more

 information.

 ### Add line numbers to a file

 When reading a file line by line, you have three options: first, you could limit

 the maximum supported line length.

 Second, you allocate a god buffer large

 enough for the most lines a text file could have.

 And third, undoubtedly the best option, you start with a small buffer, which

 adjusts on demand.

 An `UcxBuffer` can be created to do just that for you.

 Just pass the `UCX_BUFFER_AUTOEXTEND` option to the initialization function.

 Here is a full working program, which adds line numbers to a file.

 ```C

 #include <stdio.h>

 #include <ucx/buffer.h>

 #include <ucx/utils.h>

 int main(int argc, char** argv) {

     if (argc != 2) {

         fprintf(stderr, "Usage: %s <file>\n", argv[0]);

         return 1;

     }

     FILE* input = fopen(argv[1], "r");

     if (!input) {

         perror("Canno read input");

         return 1;

     }

     const size_t chunksize = 256;

     UcxBuffer* linebuf =

         ucx_buffer_new(

             NULL,       // the buffer should manage the memory area for us

             chunksize,  // initial buffer size should be the chunk size

             UCX_BUFFER_AUTOEXTEND); // the buffer will grow when necessary

     size_t lineno = 1;

     do {

         // read line chunk

         size_t read = ucx_stream_ncopy(

                 input, linebuf, fread, ucx_buffer_write, chunksize);

         if (read == 0) break;

         // handle line endings

         do {

             sstr_t bufstr = ucx_buffer_to_sstr(linebuf);

             sstr_t nl = sstrchr(bufstr, '\n');

             if (nl.length == 0) break;

             size_t linelen = bufstr.length - nl.length;

             sstr_t linestr = sstrsubsl(bufstr, 0, linelen);

             printf("%zu: %" PRIsstr "\n", lineno++, SFMT(linestr));

             // shift the buffer to the next line

             ucx_buffer_shift_left(linebuf, linelen+1);

         } while(1);

     } while(1);

     // print the 'noeol' line, if any

     sstr_t lastline = ucx_buffer_to_sstr(linebuf);

     if (lastline.length > 0) {

         printf("%zu: %" PRIsstr, lineno, SFMT(lastline));

     }

     fclose(input);

     ucx_buffer_free(linebuf);

     return 0;

 }

 ```

 ## List

 *Header file:* [list.h](api/list_8h.html)  

 *Required modules:* [Allocator](#allocator)

 This module provides the data structure and several functions for a doubly

 linked list. Among the common operations like insert, remove, search and sort,

 we allow convenient iteration via a special `UCX_FOREACH` macro.

 ## Logging

 *Header file:* [logging.h](api/logging_8h.html)  

 *Required modules:* [Map](#map), [String](#string)

 The logging module comes with some predefined log levels and allows some more

 customization. You may choose if you want to get timestamps or source file and

 line number logged automatically when outputting a message.

 ## Map

 *Header file:* [map.h](api/map_8h.html)  

 *Required modules:* [Allocator](#allocator), [String](#string)

 This module provides a hash map implementation using murmur hash 2 and separate

 chaining with linked lists. Similarly to the list module, we provide a

 `UCX_MAP_FOREACH` macro to conveniently iterate through the key/value pairs.

 ## Memory Pool

 *Header file:* [mempool.h](api/mempool_8h.html)  

 *Required modules:* [Allocator](#allocator)

 Here we have a concrete allocator implementation in the sense of a memory pool.

 This pool allows you to register destructor functions for the allocated memory,

 which are automatically called on the destruction of the pool.

 But you may also register *independent* destructor functions within a pool in

 case, some external library allocated memory for you, which you wish to be

 destroyed together with this pool.

 ## Properties

 *Header file:* [properties.h](api/properties_8h.html)  

 *Required modules:* [Map](#map)

 This module provides load and store function for `*.properties` files.

 The key/value pairs are stored within an UCX Map.

 ### Example: Loading properties from a file

 ```C

 // Open the file as usual

 FILE* file = fopen("myprops.properties", "r");

 if (!file) {

     // error handling

     return 1;

 }

 // Load the properties from the file

 UcxMap* myprops = ucx_map_new(16);

 if (ucx_properties_load(myprops, file)) {

     // error handling

     fclose(file);

     ucx_map_free(myprops);

     return 1;

 }

 // Print out the key/value pairs

 char* propval;

 UcxMapIterator propiter = ucx_map_iterator(myprops);

 UCX_MAP_FOREACH(key, propval, propiter) {

     printf("%s = %s\n", (char*)key.data, propval);

 }

 // Don't forget to free the values before freeing the map

 ucx_map_free_content(myprops, NULL);

 ucx_map_free(myprops);

 fclose(file);

 ```

 ## Stack

 *Header file:* [stack.h](api/stack_8h.html)  

 *Required modules:* [Allocator](#allocator)

 This concrete implementation of an UCX Allocator allows you to grab some amount

 of memory which is then handled as a stack.

 Please note, that the term *stack* only refers to the behavior of this

 allocator. You may still choose if you want to use stack or heap memory

 for the underlying space.

 A typical use case is an algorithm where you need to allocate and free large

 amounts of memory very frequently.

 ## String

 *Header file:* [string.h](api/string_8h.html)  

 *Required modules:* [Allocator](#allocator)

 This module provides a safe implementation of bounded string.

 Usually C strings do not carry a length. While for zero-terminated strings you

 can easily get the length with `strlen`, this is not generally possible for

 arbitrary strings.

 The `sstr_t` type of this module always carries the string and its length to

 reduce the risk of buffer overflows dramatically.

 ### Initialization

 There are several ways to create an `sstr_t`:

 ```C

 /* (1) sstr() uses strlen() internally, hence cstr MUST be zero-terminated */

 sstr_t a = sstr(cstr);

 /* (2) cstr does not need to be zero-terminated, if length is specified */

 sstr_t b = sstrn(cstr, len);

 /* (3) S() macro creates sstr_t from a string using sizeof() and using sstrn().

        This version is especially useful for function arguments */

 sstr_t c = S("hello");

 /* (4) ST() macro creates sstr_t struct literal using sizeof() */

 sstr_t d = ST("hello");

 ```

 You should not use the `S()` or `ST()` macro with string of unknown origin,

 since the `sizeof()` call might not coincide with the string length in those

 cases. If you know what you are doing, it can save you some performance,

 because you do not need the `strlen()` call.

 ### Finding the position of a substring

 The `sstrstr()` function gives you a new `sstr_t` object starting with the

 requested substring. Thus determining the position comes down to a simple

 subtraction.

 ```C

 sstr_t haystack = ST("Here we go!");

 sstr_t needle = ST("we");

 sstr_t result = sstrstr(haystack, needle);

 if (result.ptr)

     printf("Found at position %zd.\n", haystack.length-result.length);

 else

     printf("Not found.\n");

 ```

 ### Spliting a string by a delimiter

 The `sstrsplit()` function (and its allocator based version `sstrsplit_a()`) is

 very powerful and might look a bit nasty at a first glance. But it is indeed

 very simple to use. It is even more convenient in combination with a memory

 pool.

 ```C

 sstr_t test = ST("here::are::some::strings");

 sstr_t delim = ST("::");

 ssize_t count = 0; /* no limit */

 UcxMempool* pool = ucx_mempool_new_default();

 sstr_t* result = sstrsplit_a(pool->allocator, test, delim, &count);

 for (ssize_t i = 0 ; i < count ; i++) {

     /* don't forget to specify the length via the %*s format specifier */

     printf("%*s\n", result[i].length, result[i].ptr);

 }

 ucx_mempool_destroy(pool);

 ```

 The output is:

     here

     are

     some

     strings

 The memory pool ensures, that all strings are freed.

 ## Testing

 *Header file:* [test.h](api/test_8h.html)  

 *Required modules:* None.

 This module provides a testing framework which allows you to execute test cases

 within test suites.

 To avoid code duplication within tests, we also provide the possibility to

 define test subroutines.

 ## Utilities

 *Header file:* [utils.h](api/utils_8h.html)  

 *Required modules:* [Allocator](#allocator), [String](#string)

 In this module we provide very general utility function for copy and compare

 operations.

 We also provide several `printf` variants to conveniently print formatted data

 to streams or strings.

 ### A simple copy program

 The utilities package provides several stream copy functions.

 One of them has a very simple interface and can, for instance, be used to copy

 whole files in a single call.

 This is a minimal working example:

 ```C

 #include <stdio.h>

 #include <ucx/utils.h>

 int main(int argc, char** argv) {

     if (argc != 3) {

         fprintf(stderr, "Use %s <src> <dest>", argv[0]);

         return 1;

     }

     FILE *srcf = fopen(argv[1], "r");     // insert error handling on your own

     FILE *destf = fopen(argv[2], "w");

     size_t n =  ucx_stream_copy(srcf, destf, fread, fwrite);

     printf("%zu bytes copied.\n", n);

     fclose(srcf);

     fclose(destf);

     return 0;

 }

 ```

 ### Automatic allocation for formatted strings

 The UCX utility function `ucx_asprintf()` and it's convenient shortcut

 `ucx_sprintf` allow easy formatting of strings, without ever having to worry

 about the required space.

 ```C

 sstr_t mystring = ucx_sprintf("The answer is: %d!", 42);

 ```

 Still, you have to pass `mystring.ptr` to `free()` (or the free function of

 your allocator, if you use `ucx_asprintf`).

 If you don't have all the information ready to build your string, you can even

 use a [UcxBuffer](#buffer) as a target with the utility function

 `ucx_bprintf()`.

 ```C

 UcxBuffer* strbuffer = ucx_buffer_new(NULL, 512, UCX_BUFFER_AUTOEXTEND);

 for (unsigned int i = 2 ; i < 100 ; i++) {

         ucx_bprintf(strbuffer, "Integer %d is %s\n",

                         i, prime(i) ? "prime" : "not prime");

 }

 // print the result to stdout

 printf("%s", (char*)strbuffer->space);

 ucx_buffer_free(strbuffer);

 ```