macEnv.c

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/*************************************************************************\
* Copyright (c) 2009 UChicago Argonne LLC, as Operator of Argonne
*     National Laboratory.
* EPICS BASE is distributed subject to a Software License Agreement found
* in file LICENSE that is included with this distribution.
\*************************************************************************/
/*
 * Macro expansion of environment variables
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "errlog.h"
#include "epicsString.h"
#include "macLib.h"

char * epicsStdCall
macEnvExpand(const char *str)
{
    return macDefExpand(str, NULL);
}

char * epicsStdCall
macDefExpand(const char *str, MAC_HANDLE *macros)
{
    MAC_HANDLE *handle;
    static const char * pairs[] = { "", "environ", NULL, NULL };
    long destCapacity = 128;
    char *dest = NULL;
    int n;

    if (macros) {
        handle = macros;
    } else {
        if (macCreateHandle(&handle, pairs)){
            errlogMessage("macDefExpand: macCreateHandle failed.");
            return NULL;
        }
    }

    do {
        destCapacity *= 2;
        /*
         * Use free/malloc rather than realloc since there's no need to
         * keep the original contents.
         */
        free(dest);
        dest = malloc(destCapacity);
        if(!dest)
            goto done;

        n = macExpandString(handle, str, dest, destCapacity);
    } while (n >= (destCapacity - 1));

    if (n < 0) {
        free(dest);
        dest = NULL;
    } else {
        size_t unused = destCapacity - ++n;

        if (unused >= 20)
            dest = realloc(dest, n);
    }

done:
    if (macros == NULL) {
        if (macDeleteHandle(handle)) {
            errlogMessage("macDefExpand: macDeleteHandle failed.");
        }
    }
    return dest;
}