alloc(3) [redhat man page]

alloc(3)                                                     Library Functions Manual                                                     alloc(3)

NAME

       alloc - allocate memory

SYNTAX

       #include <alloc.h>

       char *alloc(new);

       void alloc_free(x);

       void alloc_re(&x,old,new);

       char *x;
       unsigned int old;
       unsigned int new;

DESCRIPTION

       alloc  allocates  enough  space  from the heap for new bytes of data, adequately aligned for any data type.  new may be 0.  alloc returns a
       pointer to the space.  If space is not available, alloc returns 0, setting errno appropriately.

       alloc_free returns space to the heap.

       alloc_re expands the space allocated to x from old bytes to new bytes.  It allocates new space, copies old bytes from the old space to  the
       new  space,  returns  the  old  space to the heap, and changes x to point to the new space.  It then returns 1.  If space is not available,
       alloc_re returns 0, leaving the old space alone.

SEE ALSO

       sbrk(2), malloc(3), error(3)

                                                                                                                                          alloc(3)

DYNARR(3pub)						       C Programmer's Manual						      DYNARR(3pub)

NAME

       dynarr, dynarr_init, dynarr_resize, dynarr_free - simple dynamic arrays

SYNOPSIS

       #include <publib.h>

       void dynarr_init(struct dynarr *da, size_t elsize);
       int dynarr_resize(struct dynarr *da, size_t newsize);
       void dynarr_free(struct dynarr *da);

DESCRIPTION

       These functions make it easier to use dynamic arrays, i.e., arrays that are allocated with malloc(3) and resized with realloc(3).  Below is
       a typical code fragment for implementing a dynamic array that is resized as more input is read.

	    char *p, *line;
	    size_t alloc, len;

	    len = 0;
	    alloc = 1024;
	    if ((line = malloc(alloc)) == NULL) abort();

	    while (fgets(line + len, alloc-len, stdin) != NULL) {
		 len = strlen(line);
		 alloc += 1024;
		 if ((p = realloc(alloc)) == NULL) abort();
		 alloc = p;
	    }

       (The error handling is intentionally simplified.)  Below is the above fragment with the dynarr(3).

	    struct dynarr da;

	    dynarr_init(&da);
	    while (fgets((char *)da.data + da.used, da.alloc-da.len, stdin) != NULL) {
		 da.used = strlen(da.data);
		 if (dynarr_resize(&da, da.alloc + 1024) == -1) abort();
	    }

       The code is a bit simpler, and all the memory allocation details and most of the error checking code is hidden away.

       The dynamic array is represented by a struct dynarr:

	    struct dynarr {
		void *data;
		size_t alloc, used;
	    };

       The interface to the dynamic allocation has intentionally been made unopaque.

       dynarr_init initializes a struct dynarr to be an empty array, dynarr_resize sets its size to be newsize, and dynarr_free  frees	the  array
       (it will become an empty array again).

RETURNS

       dynarr_resize returns -1 if it failed, 0 if it succeeded.  It does not change the array in any way if it failed.

SEE ALSO

       publib(3), malloc(3), realloc(3), strdup(3)

AUTHOR

       Lars Wirzenius (lars.wirzenius@helsinki.fi)

Publib							       C Programmer's Manual						      DYNARR(3pub)