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dynarr_init.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)