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comp_hash.c

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/****************************************************************************
 *  Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
 *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
 ****************************************************************************/

/*
 *    comp_hash.c --- Routines to deal with the hashtable of capability
 *                names.
 *
 */

#include <curses.priv.h>

#include <tic.h>
#include <hashsize.h>

#ifdef MAIN_PROGRAM
#include <ctype.h>
#undef  DEBUG
#define DEBUG(level, params)  /*nothing */
#endif

MODULE_ID("$Id: comp_hash.c,v 1.26 2003/11/08 21:58:36 tom Exp $")

static int hash_function(const char *);

/*
 *    _nc_make_hash_table()
 *
 *    Takes the entries in table[] and hashes them into hash_table[]
 *    by name.  There are CAPTABSIZE entries in table[] and HASHTABSIZE
 *    slots in hash_table[].
 *
 */

#ifdef MAIN_PROGRAM

#undef MODULE_ID
#define MODULE_ID(id)         /*nothing */
#include <tinfo/doalloc.c>

static void
_nc_make_hash_table(struct name_table_entry *table,
                struct name_table_entry **hash_table)
{
    int i;
    int hashvalue;
    int collisions = 0;

    for (i = 0; i < CAPTABSIZE; i++) {
      hashvalue = hash_function(table[i].nte_name);

      if (hash_table[hashvalue] != (struct name_table_entry *) 0)
          collisions++;

      if (hash_table[hashvalue] != 0)
          table[i].nte_link = (short) (hash_table[hashvalue] - table);
      hash_table[hashvalue] = &table[i];
    }

    DEBUG(4, ("Hash table complete: %d collisions out of %d entries",
            collisions, CAPTABSIZE));
}
#endif

/*
 *    int hash_function(string)
 *
 *    Computes the hashing function on the given string.
 *
 *    The current hash function is the sum of each consectutive pair
 *    of characters, taken as two-byte integers, mod HASHTABSIZE.
 *
 */

static
int
hash_function(const char *string)
{
    long sum = 0;

    DEBUG(9, ("hashing %s", string));
    while (*string) {
      sum += (long) (*string + (*(string + 1) << 8));
      string++;
    }

    DEBUG(9, ("sum is %ld", sum));
    return (int) (sum % HASHTABSIZE);
}

/*
 *    struct name_table_entry *
 *    find_entry(string)
 *
 *    Finds the entry for the given string in the hash table if present.
 *    Returns a pointer to the entry in the table or 0 if not found.
 *
 */

#ifndef MAIN_PROGRAM
NCURSES_EXPORT(struct name_table_entry const *)
_nc_find_entry
(const char *string, const struct name_table_entry *const *hash_table)
{
    int hashvalue;
    struct name_table_entry const *ptr;

    hashvalue = hash_function(string);

    if ((ptr = hash_table[hashvalue]) != 0) {
      while (strcmp(ptr->nte_name, string) != 0) {
          if (ptr->nte_link < 0)
            return 0;
          ptr = ptr->nte_link + hash_table[HASHTABSIZE];
      }
    }

    return (ptr);
}

/*
 *    struct name_table_entry *
 *    find_type_entry(string, type, table)
 *
 *    Finds the first entry for the given name with the given type in the
 *    given table if present (as distinct from find_entry, which finds the
 *    the last entry regardless of type).  You can use this if you detect
 *    a name clash.  It's slower, though.  Returns a pointer to the entry
 *    in the table or 0 if not found.
 */

NCURSES_EXPORT(struct name_table_entry const *)
_nc_find_type_entry
(const char *string,
 int type,
 const struct name_table_entry *table)
{
    struct name_table_entry const *ptr;

    for (ptr = table; ptr < table + CAPTABSIZE; ptr++) {
      if (ptr->nte_type == type && strcmp(string, ptr->nte_name) == 0)
          return (ptr);
    }

    return ((struct name_table_entry *) NULL);
}
#endif

#ifdef MAIN_PROGRAM
/*
 * This filter reads from standard input a list of tab-delimited columns,
 * (e.g., from Caps.filtered) computes the hash-value of a specified column and
 * writes the hashed tables to standard output.
 *
 * By compiling the hash table at build time, we're able to make the entire
 * set of terminfo and termcap tables readonly (and also provide some runtime
 * performance enhancement).
 */

#define MAX_COLUMNS BUFSIZ    /* this _has_ to be worst-case */

static char **
parse_columns(char *buffer)
{
    static char **list;

    int col = 0;

    if (list == 0 && (list = typeCalloc(char *, MAX_COLUMNS)) == 0)
        return (0);

    if (*buffer != '#') {
      while (*buffer != '\0') {
          char *s;
          for (s = buffer; (*s != '\0') && !isspace(UChar(*s)); s++)
            /*EMPTY */ ;
          if (s != buffer) {
            char mark = *s;
            *s = '\0';
            if ((s - buffer) > 1
                && (*buffer == '"')
                && (s[-1] == '"')) {      /* strip the quotes */
                buffer++;
                s[-1] = '\0';
            }
            list[col] = buffer;
            col++;
            if (mark == '\0')
                break;
            while (*++s && isspace(UChar(*s)))
                /*EMPTY */ ;
            buffer = s;
          } else
            break;
      }
    }
    return col ? list : 0;
}

int
main(int argc, char **argv)
{
    struct name_table_entry *name_table = typeCalloc(struct
                                         name_table_entry, CAPTABSIZE);
    struct name_table_entry **hash_table = typeCalloc(struct name_table_entry
                                          *, HASHTABSIZE);
    const char *root_name = "";
    int column = 0;
    int n;
    char buffer[BUFSIZ];

    static const char *typenames[] =
    {"BOOLEAN", "NUMBER", "STRING"};

    short BoolCount = 0;
    short NumCount = 0;
    short StrCount = 0;

    /* The first argument is the column-number (starting with 0).
     * The second is the root name of the tables to generate.
     */
    if (argc <= 2
      || (column = atoi(argv[1])) <= 0
      || (column >= MAX_COLUMNS)
      || *(root_name = argv[2]) == 0) {
      fprintf(stderr, "usage: make_hash column root_name\n");
      exit(EXIT_FAILURE);
    }

    /*
     * Read the table into our arrays.
     */
    for (n = 0; (n < CAPTABSIZE) && fgets(buffer, BUFSIZ, stdin);) {
      char **list, *nlp = strchr(buffer, '\n');
      if (nlp)
          *nlp = '\0';
      list = parse_columns(buffer);
      if (list == 0)          /* blank or comment */
          continue;
      name_table[n].nte_link = -1;  /* end-of-hash */
      name_table[n].nte_name = strdup(list[column]);
      if (!strcmp(list[2], "bool")) {
          name_table[n].nte_type = BOOLEAN;
          name_table[n].nte_index = BoolCount++;
      } else if (!strcmp(list[2], "num")) {
          name_table[n].nte_type = NUMBER;
          name_table[n].nte_index = NumCount++;
      } else if (!strcmp(list[2], "str")) {
          name_table[n].nte_type = STRING;
          name_table[n].nte_index = StrCount++;
      } else {
          fprintf(stderr, "Unknown type: %s\n", list[2]);
          exit(EXIT_FAILURE);
      }
      n++;
    }
    _nc_make_hash_table(name_table, hash_table);

    /*
     * Write the compiled tables to standard output
     */
    printf("static struct name_table_entry const _nc_%s_table[] =\n",
         root_name);
    printf("{\n");
    for (n = 0; n < CAPTABSIZE; n++) {
      sprintf(buffer, "\"%s\"",
            name_table[n].nte_name);
      printf("\t{ %15s,\t%10s,\t%3d, %3d }%c\n",
             buffer,
             typenames[name_table[n].nte_type],
             name_table[n].nte_index,
             name_table[n].nte_link,
             n < CAPTABSIZE - 1 ? ',' : ' ');
    }
    printf("};\n\n");

    printf("const struct name_table_entry * const _nc_%s_hash_table[%d] =\n",
         root_name,
         HASHTABSIZE + 1);
    printf("{\n");
    for (n = 0; n < HASHTABSIZE; n++) {
      if (hash_table[n] != 0) {
          sprintf(buffer, "_nc_%s_table + %3ld",
                root_name,
                (long) (hash_table[n] - name_table));
      } else {
          strcpy(buffer, "0");
      }
      printf("\t%s,\n", buffer);
    }
    printf("\t_nc_%s_table\t/* base-of-table */\n", root_name);
    printf("};\n\n");

    printf("#if (BOOLCOUNT!=%d)||(NUMCOUNT!=%d)||(STRCOUNT!=%d)\n",
         BoolCount, NumCount, StrCount);
    printf("#error\t--> term.h and comp_captab.c disagree about the <--\n");
    printf("#error\t--> numbers of booleans, numbers and/or strings <--\n");
    printf("#endif\n\n");

    return EXIT_SUCCESS;
}
#endif

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