#include "error.h"#include "scope.h"#include "salloc.h"#include "statement.h"#include <string.h>typedef struct tuple{    char	 *key;    Declaration	 *decl;    struct tuple *next;}Tuple;#define HASH_ENTRIES	32struct scope{    Scope *parent_scope;    Tuple *hash_table [HASH_ENTRIES];	int wordcounter;};static unsigned hash_index(const char *string){    unsigned index = 0;    if (string == NULL)		return 0;    while (*string != '\0')	index += *string++;    return index % HASH_ENTRIES;}static Declaration *search(const Scope *scope, const char *key, unsigned index){    Tuple *tuple;    for (tuple = scope->hash_table [index]; tuple != 0; tuple = tuple->next)		if (strcmp(tuple->key, key) == 0){			return tuple->decl;					}    return 0;}static void add_tuple(Scope *scope, const char *key, Declaration *decl,		      unsigned index){    Tuple *tuple 		= safe_malloc(sizeof(Tuple));    tuple->key			= safe_strdup(key);    tuple->decl			= decl;    tuple->next			= scope->hash_table [index];    scope->hash_table [index]	= tuple;}static void delete_tuple(Tuple *tuple){    free(tuple->key);    free(tuple);}Scope *current_scope = 0, *global_scope;Scope *new_scope(void){    Scope    *scope	= safe_malloc(sizeof(Scope));    unsigned i;    scope->parent_scope = current_scope;    current_scope	= scope;    for (i = 0; i < HASH_ENTRIES; i ++)	scope->hash_table [i] = 0;    return scope;}void leave_scope(void){    current_scope = current_scope->parent_scope;}void delete_scope(Scope *scope){    if (scope != 0)    {	unsigned i;	Tuple	 *tuple, *next_tuple;	for (i = 0; i < HASH_ENTRIES; i ++)	    for (tuple = scope->hash_table [i]; tuple != 0; tuple = next_tuple)	    {		next_tuple = tuple->next;		delete_tuple(tuple);	    }	free(scope);    }}void declare(const char *key, Declaration *decl){    unsigned index = hash_index(key);    if (search(current_scope, key, index) != 0)	error(0, "%s already declared in this scope", key);    else	add_tuple(current_scope, key, decl, index);}Declaration *lookup(const Scope *scope, const char *key){    unsigned	index = hash_index(key);    Declaration	*decl;    do	if ((decl = search(scope, key, index)) != 0)	    return decl;    while ((scope = scope->parent_scope) != 0);    return 0;}Declaration *lookup_in_this_scope(const Scope *scope, const char *key){    return search(scope, key, hash_index(key));}