array.c

机器学习作者tom mitchell的书上代码

/* Implementation of arrays that can grow. */

/* Copyright (C) 1997, 1998, 1999 Andrew McCallum

   Written by:  Andrew Kachites McCallum <[e-mail]>

   This file is part of the Bag-Of-Words Library, `libbow'.

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License
   as published by the Free Software Foundation, version 2.
   
   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA */

#include <bow/libbow.h>
#include <assert.h>

/* The magic-string written at the beginning of archive files, so that
   we can verify we are in the right place for when reading. */
#define HEADER_STRING "bow_array\n"

int bow_array_default_capacity = 1024;
int bow_array_default_growth_factor = 2;

/* Allocate, initialize and return a new array structure. */
bow_array *
bow_array_new (int capacity, int entry_size, void (*free_func)())
{
  bow_array *ret;

  ret = bow_malloc (sizeof (bow_array));
  bow_array_init (ret, capacity, entry_size, free_func);
  return ret;
}

/* Initialize an already allocated array structure. */
void
bow_array_init (bow_array *array, int capacity, 
		int entry_size, void (*free_func)())
{
  if (capacity == 0)
    capacity = bow_array_default_capacity;
  array->size = capacity;
  array->length = 0;
  array->entry_size = entry_size;
  array->free_func = free_func;
  array->growth_factor = 2;
  array->entries = bow_malloc (array->size * entry_size);
}

#define ADDR_ENTRY_AT_INDEX(ARRAY, INDEX)	\
(((char*)((ARRAY)->entries)) + (INDEX * (ARRAY)->entry_size))

/* Append an entry to the array.  Return its index. */
int
bow_array_append (bow_array *array, void *entry)
{
  if (array->length >= array->size)
    {
      /* The array must grow to accommodate the new entry. */
      array->size *= array->growth_factor;
      array->size /= array->growth_factor - 1;
      array->entries = bow_realloc (array->entries, 
				    array->size * array->entry_size);
    }
  memcpy (ADDR_ENTRY_AT_INDEX (array, array->length), entry,
	  array->entry_size);
  return (array->length)++;
}

/* Append an entry to the array by reading from fp.  Return its index,
   or -1 if there are no more entries to be read. */
int
bow_array_append_from_fp_inc (bow_array *array, 
			      int (*read_func)(void*,FILE*), 
			      FILE *fp)
{
  int c = fgetc(fp);

  if (feof(fp))  
    return -1; /* we've hit eof -- bail out */
  ungetc(c, fp);
 
  if (array->length >= array->size)
    {
      /* The array must grow to accommodate the new entry. */
      array->size *= array->growth_factor;
      array->size /= array->growth_factor - 1;
      array->entries = bow_realloc (array->entries, 
				    array->size * array->entry_size);
    }
  (*read_func) (ADDR_ENTRY_AT_INDEX (array, array->length), fp);

  return (array->length)++;
}

/* Return what will be the index of the next entry to be appended */
int
bow_array_next_index (bow_array *array)
{
  return array->length;
}

/* Return a pointer to the array entry at index INDEX. */
void *
bow_array_entry_at_index (bow_array *array, int index)
{
  assert (index < array->length);
  return ADDR_ENTRY_AT_INDEX (array, index);
}

/* Write the array ARRAY to the file-pointer FP, using the function
   WRITE_FUNC to write each of the entries in ARRAY. */
void
bow_array_write (bow_array *array, int (*write_func)(void*,FILE*), FILE *fp)
{
  int i;

  fprintf (fp, HEADER_STRING);
  bow_fwrite_int (array->length, fp);
  bow_fwrite_int (array->entry_size, fp);
  for (i = 0; i < array->length; i++)
    (*write_func) (ADDR_ENTRY_AT_INDEX (array, i), fp);
}

/* Write the incremental format header to the file-pointer FP */
void
bow_array_write_header_inc (bow_array *array, FILE *fp)
{
  bow_fwrite_int (array->entry_size, fp);
  fflush (fp);
}

/* Write one entry in incremental format to the file-pointer FP, using the function
   WRITE_FUNC. It will fseek to the appropriate location to write. */
void
bow_array_write_entry_inc (bow_array *array, int i, int (*write_func)(void*,FILE*), FILE *fp)
{
  fseek (fp, sizeof (int) + array->entry_size * i, SEEK_SET);
 (*write_func) (ADDR_ENTRY_AT_INDEX (array, i), fp);
 fflush (fp);
}

/* Return a new array, created by reading file-pointer FP, and using
   the function READ_FUNC to read each of the array entries. The
   returned array will have entry-freeing-function FREE_FUNC. */
bow_array *
bow_array_new_from_fp_inc (int (*read_func)(void*,FILE*), 
			   void (*free_func)(),
			   FILE *fp)
{
  int entry_size;
  bow_array *ret;

  bow_fread_int (&entry_size, fp);
  ret = bow_array_new (0, entry_size, free_func);
 
  while (bow_array_append_from_fp_inc (ret, read_func, fp) != -1)
    ;

  return ret;
}

/* Return a new array, created by reading file-pointer FP, and using
   the function READ_FUNC to read each of the array entries.  The
   array entries will have size MIN_ENTRY_SIZE, or larger, if
   indicated by the data in FP; this is useful when a structure is
   re-defined to be larger.  The returned array will have
   entry-freeing-function FREE_FUNC.  */
bow_array *
bow_array_new_with_entry_size_from_data_fp (int min_entry_size,
					    int (*read_func)(void*,FILE*), 
					    void (*free_func)(),
					    FILE *fp)
{
  int length;
  int entry_size;
  bow_array *ret;
  int i;

  /* Make sure the FP is positioned corrected to read a bow_int4str.
     Look for the magic string we are expecting. */
  {
    const char *magic = HEADER_STRING;
    while (*magic)
      {
	if (*magic != fgetc (fp))
	  bow_error ("Proper header not found in file.");
	magic++;
      }
  }

  bow_fread_int (&length, fp);
  bow_fread_int (&entry_size, fp);
  if (entry_size < min_entry_size)
    entry_size = min_entry_size;
  ret = bow_array_new (length, entry_size, free_func);
  for (i = 0; i < length; i++)
    (*read_func) (ADDR_ENTRY_AT_INDEX (ret, i), fp);
  ret->length = length;
  return ret;
}

/* Return a new array, created by reading file-pointer FP, and using
   the function READ_FUNC to read each of the array entries.  The
   returned array will have entry-freeing-function FREE_FUNC. */
bow_array *
bow_array_new_from_data_fp (int (*read_func)(void*,FILE*), 
			    void (*free_func)(),
			    FILE *fp)
{
  return bow_array_new_with_entry_size_from_data_fp (0, read_func,
						     free_func, fp);
}

#if 0
/* Define an iterator over a cdocs array */

struct bow_cdocs_iterator_context {
  bow_array *cdocs;
  int ci;
  int di;
}
#define CONTEXT ((struct bow_cdocs_iterator_context*)context)

static void
cdocs_iterator_reset (int ignored, void *context)
{
  CONTEXT->di = 0;
}

static int
array_iterator_advance_to_next (void *context)
{
  bow_cdoc *cdoc;
  if (CONTEXT->di >= CONTEXT->array->length)
    return 0;
  while (CONTEXT->di < CONTEXT->cdocs->length)
    {
      CONTEXT->di++;
      cdoc = bow_array_entry_at_index (CONTEXT->cdocs, CONTEXT->di)
      if (cdoc->class == CONTEXT->ci)
	break;
    }
  if (CONTEXT->di >= CONTEXT->cdocs->length)
    return 0;
  return 1;
}

static int
cdocs_iterator_index (void *context)
{
  if (CONTEXT->di >= CONTEXT->cdocs->length)
    return INT_MIN;
  return CONTEXT->di;
}

static double
cdocs_iterator_count_for_doc (void *context)
{
  bow_cdocs *cdocs;
  if (CONTEXT->di >= CONTEXT->cdocs->length)
    return 0.0/0;		/* NaN */
  cdoc = bow_array_entry_at_index (CONTEXT->cdocs, CONTEXT->di)
  return cdoc->word_count;
}


bow_iterator_double *
bow_array_iterator_for_ci_new (bow_array *array, int ci)
{
  bow_iterator_double *ret;
  void *context;

  ret = bow_malloc (sizeof (bow_iterator_double) + 
		    sizeof (struct bow_array_iterator_context));
  ret->reset = array_iterator_reset_at_wi;
  ret->advance = array_iterator_advance_to_next_di;
  ret->index = array_iterator_doc_index;
  ret->value = array_iterator_count_for_doc;
  context = ret->context = (char*)ret + sizeof (bow_iterator_double);
  CONTEXT->array = array;
  CONTEXT->ci = ci;
  CONTEXT->dv = NULL;
  CONTEXT->dvi = 0;
  return ret;
}
#undef CONTEXT
#endif

/* Free the memory held by the array ARRAY. */
void
bow_array_free (bow_array *array)
{
  if (array->free_func)
    {
      while ((array->length)--)
	(*(array->free_func)) (ADDR_ENTRY_AT_INDEX (array, array->length));
    }
  bow_free (array->entries);
  bow_free (array);
}