ack/lang/cem/libcc.ansi/stdlib/setenv.c

/*
 * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
 * See the copyright notice in the ACK home directory, in the file "Copyright".
 */
/* $Id$ */

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

extern char* _findenv(const char* name, int* offset);
extern char **environ;

/*
 * setenv(name,value,rewrite)
 *	Set the value of the environmental variable "name" to be
 *	"value".  If rewrite is set, replace any current value.
 */
int setenv(register const char* name, register const char* value, int rewrite)
{
    static int  alloced = 0;        /* if allocated space before */
    register char   *C;
    int l_value,
        offset;

    if (*value == '=')          /* no `=' in value */
        ++value;
    l_value = strlen(value);
    if ((C = _findenv(name,&offset))) { /* find if already exists */
        if (!rewrite)
            return(0);
        if (strlen(C) >= l_value) { /* old larger; copy over */
            while (*C++ = *value++);
            return(0);
        }
    }
    else {                  /* create new slot */
        register int    cnt = 0;
        register char   **P;

		if (environ)
			for (P = environ;*P;++P,++cnt);
        if (alloced) {          /* just increase size */
            environ = (char **)realloc((char *)environ,
                (unsigned)(sizeof(char *) * (cnt + 2)));
            if (!environ)
                return(-1);
        }
        else {              /* get new space */
            alloced = 1;        /* copy old entries into it */
            P = (char **)malloc((unsigned)(sizeof(char *) *
                (cnt + 2)));
            if (!P)
                return(-1);
            if (environ)
				bcopy(environ,P,cnt * sizeof(char *));
            environ = P;
        }
        environ[cnt + 1] = NULL;
        offset = cnt;
    }
    for (C = name;*C && *C != '=';++C); /* no `=' in name */
    if (!(environ[offset] =         /* name + `=' + value */
        malloc((unsigned)((int)(C - name) + l_value + 2))))
        return(-1);
    for (C = environ[offset];(*C = *name++) && *C != '=';++C);
    for (*C++ = '=';*C++ = *value++;);
    return(0);
}

/*
 * unsetenv(name) --
 *	Delete environmental variable "name".
 */
int
unsetenv(const char* name)
{
    register char   **P;
    int offset;

    while (_findenv(name,&offset))      /* if set multiple times */
        for (P = &environ[offset];;++P)
            if (!(*P = *(P + 1)))
                break;

    return 0;
}