|
- utarray: dynamic array macros for C
- ===================================
- Troy D. Hanson <tdh@tkhanson.net>
- v2.3.0, February 2021
-
- Here's a link back to the https://github.com/troydhanson/uthash[GitHub project page].
-
- Introduction
- ------------
- A set of general-purpose dynamic array macros for C structures are included with
- uthash in `utarray.h`. To use these macros in your own C program, just
- copy `utarray.h` into your source directory and use it in your programs.
-
- #include "utarray.h"
-
- The dynamic array supports basic operations such as push, pop, and erase on the
- array elements. These array elements can be any simple datatype or structure.
- The array <<operations,operations>> are based loosely on the C++ STL vector methods.
-
- Internally the dynamic array contains a contiguous memory region into which
- the elements are copied. This buffer is grown as needed using `realloc` to
- accommodate all the data that is pushed into it.
-
- Download
- ~~~~~~~~
- To download the `utarray.h` header file,
- follow the links on https://github.com/troydhanson/uthash to clone uthash or get a zip file,
- then look in the src/ sub-directory.
-
- BSD licensed
- ~~~~~~~~~~~~
- This software is made available under the
- link:license.html[revised BSD license].
- It is free and open source.
-
- Platforms
- ~~~~~~~~~
- The 'utarray' macros have been tested on:
-
- * Linux,
- * Mac OS X,
- * Windows, using Visual Studio 2008 and Visual Studio 2010
-
- Usage
- -----
-
- Declaration
- ~~~~~~~~~~~
-
- The array itself has the data type `UT_array`, regardless of the type of
- elements to be stored in it. It is declared like,
-
- UT_array *nums;
-
- New and free
- ~~~~~~~~~~~~
- The next step is to create the array using `utarray_new`. Later when you're
- done with the array, `utarray_free` will free it and all its elements.
-
- Push, pop, etc
- ~~~~~~~~~~~~~~
- The central features of the utarray involve putting elements into it, taking
- them out, and iterating over them. There are several <<operations,operations>>
- to pick from that deal with either single elements or ranges of elements at a
- time. In the examples below we will use only the push operation to insert
- elements.
-
- Elements
- --------
-
- Support for dynamic arrays of integers or strings is especially easy. These are
- best shown by example:
-
- Integers
- ~~~~~~~~
- This example makes a utarray of integers, pushes 0-9 into it, then prints it.
- Lastly it frees it.
-
- .Integer elements
- -------------------------------------------------------------------------------
- #include <stdio.h>
- #include "utarray.h"
-
- int main() {
- UT_array *nums;
- int i, *p;
-
- utarray_new(nums,&ut_int_icd);
- for(i=0; i < 10; i++) utarray_push_back(nums,&i);
-
- for(p=(int*)utarray_front(nums);
- p!=NULL;
- p=(int*)utarray_next(nums,p)) {
- printf("%d\n",*p);
- }
-
- utarray_free(nums);
-
- return 0;
- }
- -------------------------------------------------------------------------------
-
- The second argument to `utarray_push_back` is always a 'pointer' to the type
- (so a literal cannot be used). So for integers, it is an `int*`.
-
- Strings
- ~~~~~~~
- In this example we make a utarray of strings, push two strings into it, print
- it and free it.
-
- .String elements
- -------------------------------------------------------------------------------
- #include <stdio.h>
- #include "utarray.h"
-
- int main() {
- UT_array *strs;
- char *s, **p;
-
- utarray_new(strs,&ut_str_icd);
-
- s = "hello"; utarray_push_back(strs, &s);
- s = "world"; utarray_push_back(strs, &s);
- p = NULL;
- while ( (p=(char**)utarray_next(strs,p))) {
- printf("%s\n",*p);
- }
-
- utarray_free(strs);
-
- return 0;
- }
- -------------------------------------------------------------------------------
-
- In this example, since the element is a `char*`, we pass a pointer to it
- (`char**`) as the second argument to `utarray_push_back`. Note that "push" makes
- a copy of the source string and pushes that copy into the array.
-
- About UT_icd
- ~~~~~~~~~~~~
-
- Arrays be made of any type of element, not just integers and strings. The
- elements can be basic types or structures. Unless you're dealing with integers
- and strings (which use pre-defined `ut_int_icd` and `ut_str_icd`), you'll need
- to define a `UT_icd` helper structure. This structure contains everything that
- utarray needs to initialize, copy or destruct elements.
-
- typedef struct {
- size_t sz;
- init_f *init;
- ctor_f *copy;
- dtor_f *dtor;
- } UT_icd;
-
- The three function pointers `init`, `copy`, and `dtor` have these prototypes:
-
- typedef void (ctor_f)(void *dst, const void *src);
- typedef void (dtor_f)(void *elt);
- typedef void (init_f)(void *elt);
-
- The `sz` is just the size of the element being stored in the array.
-
- The `init` function will be invoked whenever utarray needs to initialize an
- empty element. This only happens as a byproduct of `utarray_resize` or
- `utarray_extend_back`. If `init` is `NULL`, it defaults to zero filling the
- new element using memset.
-
- The `copy` function is used whenever an element is copied into the array.
- It is invoked during `utarray_push_back`, `utarray_insert`, `utarray_inserta`,
- or `utarray_concat`. If `copy` is `NULL`, it defaults to a bitwise copy using
- memcpy.
-
- The `dtor` function is used to clean up an element that is being removed from
- the array. It may be invoked due to `utarray_resize`, `utarray_pop_back`,
- `utarray_erase`, `utarray_clear`, `utarray_done` or `utarray_free`. If the
- elements need no cleanup upon destruction, `dtor` may be `NULL`.
-
- Scalar types
- ~~~~~~~~~~~~
-
- The next example uses `UT_icd` with all its defaults to make a utarray of
- `long` elements. This example pushes two longs, prints them, and frees the
- array.
-
- .long elements
- -------------------------------------------------------------------------------
- #include <stdio.h>
- #include "utarray.h"
-
- UT_icd long_icd = {sizeof(long), NULL, NULL, NULL };
-
- int main() {
- UT_array *nums;
- long l, *p;
- utarray_new(nums, &long_icd);
-
- l=1; utarray_push_back(nums, &l);
- l=2; utarray_push_back(nums, &l);
-
- p=NULL;
- while( (p=(long*)utarray_next(nums,p))) printf("%ld\n", *p);
-
- utarray_free(nums);
- return 0;
- }
- -------------------------------------------------------------------------------
-
- Structures
- ~~~~~~~~~~
-
- Structures can be used as utarray elements. If the structure requires no
- special effort to initialize, copy or destruct, we can use `UT_icd` with all
- its defaults. This example shows a structure that consists of two integers. Here
- we push two values, print them and free the array.
-
- .Structure (simple)
- -------------------------------------------------------------------------------
- #include <stdio.h>
- #include "utarray.h"
-
- typedef struct {
- int a;
- int b;
- } intpair_t;
-
- UT_icd intpair_icd = {sizeof(intpair_t), NULL, NULL, NULL};
-
- int main() {
-
- UT_array *pairs;
- intpair_t ip, *p;
- utarray_new(pairs,&intpair_icd);
-
- ip.a=1; ip.b=2; utarray_push_back(pairs, &ip);
- ip.a=10; ip.b=20; utarray_push_back(pairs, &ip);
-
- for(p=(intpair_t*)utarray_front(pairs);
- p!=NULL;
- p=(intpair_t*)utarray_next(pairs,p)) {
- printf("%d %d\n", p->a, p->b);
- }
-
- utarray_free(pairs);
- return 0;
- }
- -------------------------------------------------------------------------------
-
- The real utility of `UT_icd` is apparent when the elements of the utarray are
- structures that require special work to initialize, copy or destruct.
-
- For example, when a structure contains pointers to related memory areas that
- need to be copied when the structure is copied (and freed when the structure is
- freed), we can use custom `init`, `copy`, and `dtor` members in the `UT_icd`.
-
- Here we take an example of a structure that contains an integer and a string.
- When this element is copied (such as when an element is pushed into the array),
- we want to "deep copy" the `s` pointer (so the original element and the new
- element point to their own copies of `s`). When an element is destructed, we
- want to "deep free" its copy of `s`. Lastly, this example is written to work
- even if `s` has the value `NULL`.
-
- .Structure (complex)
- -------------------------------------------------------------------------------
- #include <stdio.h>
- #include <stdlib.h>
- #include "utarray.h"
-
- typedef struct {
- int a;
- char *s;
- } intchar_t;
-
- void intchar_copy(void *_dst, const void *_src) {
- intchar_t *dst = (intchar_t*)_dst, *src = (intchar_t*)_src;
- dst->a = src->a;
- dst->s = src->s ? strdup(src->s) : NULL;
- }
-
- void intchar_dtor(void *_elt) {
- intchar_t *elt = (intchar_t*)_elt;
- if (elt->s) free(elt->s);
- }
-
- UT_icd intchar_icd = {sizeof(intchar_t), NULL, intchar_copy, intchar_dtor};
-
- int main() {
- UT_array *intchars;
- intchar_t ic, *p;
- utarray_new(intchars, &intchar_icd);
-
- ic.a=1; ic.s="hello"; utarray_push_back(intchars, &ic);
- ic.a=2; ic.s="world"; utarray_push_back(intchars, &ic);
-
- p=NULL;
- while( (p=(intchar_t*)utarray_next(intchars,p))) {
- printf("%d %s\n", p->a, (p->s ? p->s : "null"));
- }
-
- utarray_free(intchars);
- return 0;
- }
-
- -------------------------------------------------------------------------------
-
- [[operations]]
- Reference
- ---------
- This table lists all the utarray operations. These are loosely based on the C++
- vector class.
-
- Operations
- ~~~~~~~~~~
-
- [width="100%",cols="50<m,40<",grid="none",options="none"]
- |===============================================================================
- | utarray_new(UT_array *a, UT_icd *icd)| allocate a new array
- | utarray_free(UT_array *a) | free an allocated array
- | utarray_init(UT_array *a,UT_icd *icd)| init an array (non-alloc)
- | utarray_done(UT_array *a) | dispose of an array (non-allocd)
- | utarray_reserve(UT_array *a,int n) | ensure space available for 'n' more elements
- | utarray_push_back(UT_array *a,void *p) | push element p onto a
- | utarray_pop_back(UT_array *a) | pop last element from a
- | utarray_extend_back(UT_array *a) | push empty element onto a
- | utarray_len(UT_array *a) | get length of a
- | utarray_eltptr(UT_array *a,int j) | get pointer of element from index
- | utarray_eltidx(UT_array *a,void *e) | get index of element from pointer
- | utarray_insert(UT_array *a,void *p, int j) | insert element p to index j
- | utarray_inserta(UT_array *a,UT_array *w, int j) | insert array w into array a at index j
- | utarray_resize(UT_array *dst,int num) | extend or shrink array to num elements
- | utarray_concat(UT_array *dst,UT_array *src) | copy src to end of dst array
- | utarray_erase(UT_array *a,int pos,int len) | remove len elements from a[pos]..a[pos+len-1]
- | utarray_clear(UT_array *a) | clear all elements from a, setting its length to zero
- | utarray_sort(UT_array *a,cmpfcn *cmp) | sort elements of a using comparison function
- | utarray_find(UT_array *a,void *v, cmpfcn *cmp) | find element v in utarray (must be sorted)
- | utarray_front(UT_array *a) | get first element of a
- | utarray_next(UT_array *a,void *e) | get element of a following e (front if e is NULL)
- | utarray_prev(UT_array *a,void *e) | get element of a before e (back if e is NULL)
- | utarray_back(UT_array *a) | get last element of a
- |===============================================================================
-
- Notes
- ~~~~~
-
- 1. `utarray_new` and `utarray_free` are used to allocate a new array and free it,
- while `utarray_init` and `utarray_done` can be used if the UT_array is already
- allocated and just needs to be initialized or have its internal resources
- freed.
-
- 2. `utarray_reserve` takes the "delta" of elements to reserve, not the total
- desired capacity of the array. This differs from the C++ STL "reserve" notion.
-
- 3. `utarray_sort` expects a comparison function having the usual `strcmp`-like
- convention where it accepts two elements (a and b) and returns a negative
- value if a precedes b, 0 if a and b sort equally, and positive if b precedes a.
- This is an example of a comparison function:
-
- int intsort(const void *a, const void *b) {
- int _a = *(const int *)a;
- int _b = *(const int *)b;
- return (_a < _b) ? -1 : (_a > _b);
- }
-
- 4. `utarray_find` uses a binary search to locate an element having a certain value
- according to the given comparison function. The utarray must be first sorted
- using the same comparison function. An example of using `utarray_find` with
- a utarray of strings is included in `tests/test61.c`.
-
- 5. A 'pointer' to a particular element (obtained using `utarray_eltptr` or
- `utarray_front`, `utarray_next`, `utarray_prev`, `utarray_back`) becomes invalid whenever
- another element is inserted into the utarray. This is because the internal
- memory management may need to `realloc` the element storage to a new address.
- For this reason, it's usually better to refer to an element by its integer
- 'index' in code whose duration may include element insertion.
-
- 6. To override the default out-of-memory handling behavior (which calls `exit(-1)`),
- override the `utarray_oom()` macro before including `utarray.h`.
- For example,
-
- #define utarray_oom() do { longjmp(error_handling_location); } while (0)
- ...
- #include "utarray.h"
-
- // vim: set nowrap syntax=asciidoc:
|