symtab.c File Reference

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "symtab.h"
#include <limits.h>

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Defines
#define	HASH(x)   hash(x)
#define	BITS_IN_int   ( sizeof(int) * CHAR_BIT )
#define	THREE_QUARTERS   ((int) ((BITS_IN_int * 3) / 4))
#define	ONE_EIGHTH   ((int) (BITS_IN_int / 8))
#define	HIGH_BITS   ( ~((unsigned int)(~0) >> ONE_EIGHTH ))
Functions
unsigned int	HashPJW (const char *)
unsigned int	hash (const char *)
SYMTABLE *	new_symtable (unsigned int numentries)
int	hash_insert (SYMTABLE *table, void *node_val, char *tag)
HASHNODE *	hash_delete (SYMTABLE *table, char *tag)
HASHNODE *	hash_lookup (SYMTABLE *table, char *id)
HASHNODE *	search_hashlist (HASHNODE *list, char *id)
void	hash_dump (SYMTABLE *table, void(*dump_function)(char *, void *))

---

Define Documentation

#define BITS_IN_int   ( sizeof(int) * CHAR_BIT )

Definition at line 273 of file symtab.c.

#define HASH

(

x

)

hash(x)

Definition at line 22 of file symtab.c.

#define HIGH_BITS   ( ~((unsigned int)(~0) >> ONE_EIGHTH ))

Definition at line 276 of file symtab.c.

#define ONE_EIGHTH   ((int) (BITS_IN_int / 8))

Definition at line 275 of file symtab.c.

#define THREE_QUARTERS   ((int) ((BITS_IN_int * 3) / 4))

Definition at line 274 of file symtab.c.

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Function Documentation

unsigned int hash

(

const char *

str

)

Definition at line 248 of file symtab.c.

{
  int sum = 0;

  if (str == NULL)
    return 0;

  while (*str)
    sum += *str++;

  return sum;
}

HASHNODE* hash_delete	(	SYMTABLE *	table,
		char *	tag
	)

Definition at line 112 of file symtab.c.

{
  HASHNODE *list, *prev;
  int idx;

  if ((table == NULL) || (tag == NULL))
    return NULL;

  idx = HASH(tag) % table->num_entries;
  list = table->entry[idx];

  for (prev = NULL; list; list = list->next) {
    if (list->tag == NULL)
      prev = list;
    else if (!strcmp(list->tag, tag)) {
      if (prev)
    prev->next = list->next;
      else
    table->entry[idx] = list->next;

      table->num_items--;
      return (list);
    }

    prev = list;
  }

  return NULL;          /* Not in list. */
}

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void hash_dump	(	SYMTABLE *	table,
		void(*)(char *, void *)	dump_function
	)

Definition at line 219 of file symtab.c.

{
  HASHNODE *tmp;
  int i;

  for(i=0;i<table->num_entries;i++) {
    for(tmp = table->entry[i]; tmp != NULL; tmp = tmp->next) {
      dump_function(tmp->tag, tmp->item);
    }
  }

  return;
}

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int hash_insert	(	SYMTABLE *	table,
		void *	node_val,
		char *	tag
	)

Definition at line 76 of file symtab.c.

{
  HASHNODE *newnode;
  int idx;

  if ((table == NULL) || (tag == NULL))
    return -1;

  idx = HASH(tag) % table->num_entries;

  newnode = (HASHNODE *) malloc(sizeof(HASHNODE));
  if (!newnode)
    return -1;

  newnode->tag = tag;
  newnode->item = node_val;
  newnode->next = table->entry[idx];
  table->entry[idx] = newnode;

  table->num_items++;

  return 0;
}

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HASHNODE* hash_lookup	(	SYMTABLE *	table,
		char *	id
	)

Definition at line 156 of file symtab.c.

{
  int index;
  HASHNODE *hash_entry;

  if ((table == NULL) || (id == NULL))
    return NULL;

  index = HASH(id) % table->num_entries;

  hash_entry = search_hashlist(table->entry[index], id);
  if (hash_entry == NULL) {
#ifdef SYM_DEBUG
    printf("Not in table.\n");
#endif
    return NULL;
  } else {  /* Attempt to return the value pointed to by "type". */

#ifdef SYM_DEBUG
    printf("In table.\n");
#endif
    return (hash_entry);
  }
}

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unsigned int HashPJW

(

const char *

datum

)

Definition at line 279 of file symtab.c.

{
  unsigned int hash_value, i;
  for (hash_value = 0; *datum; ++datum) {
    hash_value = (hash_value << ONE_EIGHTH) + *datum;
    if ((i = hash_value & HIGH_BITS) != 0)
      hash_value = (hash_value ^ (i >> THREE_QUARTERS)) & ~HIGH_BITS;
  }
  return (hash_value);
}

SYMTABLE* new_symtable

(

unsigned int

numentries

)

Definition at line 40 of file symtab.c.

{
  SYMTABLE *newtable;
  newtable = (SYMTABLE *) malloc(sizeof(SYMTABLE));
  if (!newtable)
    return NULL;

  newtable->num_entries = numentries;
  newtable->num_items = 0;
  newtable->entry = (HASHNODE **) calloc(numentries, sizeof(HASHNODE *));

  if (!newtable->entry) {
    free(newtable);
    return NULL;
  }

  return (newtable);
}

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HASHNODE* search_hashlist	(	HASHNODE *	list,
		char *	id
	)

Definition at line 194 of file symtab.c.

{

  if (id == NULL)
    return NULL;

  for (; list; list = list->next) {
    if (list->tag == NULL)
      continue;
    if (!strcmp(list->tag, id))
      return (list);
  }

  return NULL;          /* Not in list. */
}

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