/* varlib.c * * a simple storage system to store name=value pairs * with facility to mark items as part of the environment * * interface: *     VLstore( name, value )    returns 1 for 0k, 0 for no *     VLlookup( name )          returns string or NULL if not there *     VLlist()			 prints out current table * * environment-related functions *     VLexport( name )		 adds name to list of env vars *     VLtable2environ()	 copy from table to environ *     VLenviron2table()         copy from environ to table * * details: *	the table is stored as an array of structs that *	contain a flag for `global' and a single string of *	the form name=value.  This allows EZ addition to the *	environment.  It makes searching pretty easy, as *	long as you search for "name="  * */#include	<stdio.h>#include	<stdlib.h>#include	"varlib.h"#include	<string.h>#define	MAXVARS	200		/* a linked list would be nicer */struct var {		char *str;		/* name=val string	*/		int  global;		/* a boolean		*/	};static struct var tab[MAXVARS];			/* the table	*/static char *new_string( char *, char *);	/* private methods	*/static struct var *find_item(char *, int);int VLstore( char *name, char *val )/* * traverse list, if found, replace it, else add at end * since there is no delete, a blank one is a free one * return 1 if trouble, 0 if ok (like a command) */{	struct var *itemp;	char	*s;	int	rv = 1;	/* find spot to put it              and make new string */	if ((itemp=find_item(name,1))!=NULL && (s=new_string(name,val))!=NULL) 	{		if ( itemp->str )		/* has a val?	*/			free(itemp->str);	/* y: remove it	*/		itemp->str = s;		rv = 0;				/* ok! */	}	return rv;}char * new_string( char *name, char *val )/* * returns new string of form name=value or NULL on error */{	char	*retval;	retval = malloc( strlen(name) + strlen(val) + 2 );	if ( retval != NULL )		sprintf(retval, "%s=%s", name, val );	return retval;}char * VLlookup( char *name )/* * returns value of var or empty string if not there */{	struct var *itemp;	if ( (itemp = find_item(name,0)) != NULL )		return itemp->str + 1 + strlen(name);	return "";}int VLexport( char *name )/* * marks a var for export, adds it if not there * returns 1 for no, 0 for ok */{	struct var *itemp;	int	rv = 1;	if ( (itemp = find_item(name,0)) != NULL ){		itemp->global = 1;		rv = 0;	}	else if ( VLstore(name, "") == 1 )		rv = VLexport(name);	return rv;}static struct var * find_item( char *name , int first_blank )/* * searches table for an item * returns ptr to struct or NULL if not found * OR if (first_blank) then ptr to first blank one */{	int	i;	int	len = strlen(name);	char	*s;	for( i = 0 ; i<MAXVARS && tab[i].str != NULL ; i++ )	{		s = tab[i].str;		if ( strncmp(s,name,len) == 0 && s[len] == '=' ){			return &tab[i];		}	}	if ( i < MAXVARS && first_blank )		return &tab[i];	return NULL;}void VLlist()/* * performs the shell's  `set'  command * Lists the contents of the variable table, marking each * exported variable with the symbol  '*'  */{	int	i;	for(i = 0 ; i<MAXVARS && tab[i].str != NULL ; i++ )	{		if ( tab[i].global )			printf("  * %s\n", tab[i].str);		else			printf("    %s\n", tab[i].str);	}}int VLenviron2table(char *env[])/* * initialize the variable table by loading array of strings * return 1 for ok, 0 for not ok */{	int     i;	char	*newstring;	for(i = 0 ; env[i] != NULL ; i++ )	{		if ( i == MAXVARS )			return 0;		newstring = malloc(1+strlen(env[i]));		if ( newstring == NULL )			return 0;		strcpy(newstring, env[i]);		tab[i].str = newstring;		tab[i].global = 1;	}	while( i < MAXVARS ){		/* I know we don't need this	*/		tab[i].str = NULL ;	/* static globals are nulled	*/		tab[i++].global = 0;	/* by default			*/	}	return 1;}char ** VLtable2environ()/* * build an array of pointers suitable for making a new environment * note, you need to free() this when done to avoid memory leaks */{	int	i,			/* index			*/		j,			/* another index		*/		n = 0;			/* counter			*/	char	**envtab;		/* array of pointers		*/	/*	 * first, count the number of global variables	 */	for( i = 0 ; i<MAXVARS && tab[i].str != NULL ; i++ )		if ( tab[i].global == 1 )			n++;	/* then, allocate space for that many variables	*/	envtab = (char **) malloc( (n+1) * sizeof(char *) );	if ( envtab == NULL )		return NULL;	/* then, load the array with pointers		*/	for(i = 0, j = 0 ; i<MAXVARS && tab[i].str != NULL ; i++ )		if ( tab[i].global == 1 )			envtab[j++] = tab[i].str;	envtab[j] = NULL;	return envtab;}