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|
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h> /* defines SIZE_MAX */
#include "../io/error.h"
#include "knowledge.h"
static ZoO_index pick_an_index
(
ZoO_index const occurrences,
const ZoO_index links_occurrences [const restrict static 1],
const ZoO_index links [const restrict static 1]
)
{
ZoO_index result, accumulator, random_number;
result = 0;
accumulator = links_occurrences[0];
random_number = (((ZoO_index) rand()) % occurrences);
while (accumulator < random_number)
{
/*
* Should be safe:
* result overflowing <-> sum('links_occurrences') > 'occurrences'
* and sum('links_occurrences') == 'occurrences'
*/
result += 1;
/*
* Should be safe:
* - sum('links_occurrences') == 'occurrences'.
* - 'occurrences' is safe.
* ----
* 'accumulator' is safe.
*/
accumulator += links_occurrences[result];
}
return links[result];
}
static unsigned char * extend_left
(
struct ZoO_knowledge k [const restrict static 1],
ZoO_index word_id,
ZoO_char current_sentence [static 1],
size_t sentence_size [const restrict static 1],
ZoO_index credits [const static 1]
)
{
size_t addition_size;
struct ZoO_knowledge_word * w;
ZoO_char * next_sentence;
w = (k->words + word_id);
if
(
(w->special == ZoO_WORD_STARTS_SENTENCE)
|| (w->occurrences == 0)
)
{
return current_sentence;
}
/* prevents current_sentence [restrict] */
next_sentence = current_sentence;
for (;;)
{
if (*credits == 0)
{
return current_sentence;
}
*credits -= 1;
word_id =
pick_an_index
(
w->occurrences,
w->backward_links_occurrences,
w->backward_links
);
w = (k->words + word_id);
switch (w->special)
{
case ZoO_WORD_HAS_NO_EFFECT:
/* FIXME: not overflow-safe. */
/* word also contains an '\0', which we will replace by a ' ' */
addition_size = w->word_size;
break;
case ZoO_WORD_ENDS_SENTENCE:
ZoO_S_WARNING("END OF LINE should not be prefixable.");
return current_sentence;
case ZoO_WORD_STARTS_SENTENCE:
return current_sentence;
case ZoO_WORD_REMOVES_LEFT_SPACE:
case ZoO_WORD_REMOVES_RIGHT_SPACE:
/* word also contains an '\0', which we will remove. */
addition_size = w->word_size - 1;
break;
}
if (*sentence_size > (SIZE_MAX - addition_size))
{
ZoO_S_WARNING
(
"Sentence construction aborted to avoid size_t overflow."
);
return current_sentence;
}
next_sentence =
(ZoO_char *) calloc
(
/* overflow-safe */
(*sentence_size + addition_size),
sizeof(ZoO_char)
);
if (next_sentence == (ZoO_char *) NULL)
{
ZoO_S_ERROR("Could not allocate memory to store new sentence.");
return current_sentence;
}
/* overflow-safe */
*sentence_size = (*sentence_size + addition_size);
switch (w->special)
{
case ZoO_WORD_HAS_NO_EFFECT:
snprintf
(
next_sentence,
*sentence_size,
" " ZoO_CHAR_STRING_SYMBOL ZoO_CHAR_STRING_SYMBOL,
w->word,
current_sentence
);
break;
case ZoO_WORD_REMOVES_LEFT_SPACE:
snprintf
(
next_sentence,
*sentence_size,
ZoO_CHAR_STRING_SYMBOL ZoO_CHAR_STRING_SYMBOL,
w->word,
current_sentence
);
break;
case ZoO_WORD_REMOVES_RIGHT_SPACE:
snprintf
(
next_sentence,
*sentence_size,
ZoO_CHAR_STRING_SYMBOL ZoO_CHAR_STRING_SYMBOL,
w->word,
/* Safe: strlen(current_sentence) >= 2 */
(current_sentence + 1)
);
break;
default:
/* TODO: PROGRAM LOGIC ERROR */
break;
}
free((void *) current_sentence);
/* prevents current_sentence [const] */
current_sentence = next_sentence;
}
}
static unsigned char * extend_right
(
struct ZoO_knowledge k [const restrict static 1],
ZoO_index word_id,
ZoO_char current_sentence [static 1],
size_t sentence_size [const restrict static 1],
ZoO_index credits [const static 1]
)
{
size_t addition_size;
struct ZoO_knowledge_word * w;
ZoO_char * next_sentence;
w = (k->words + word_id);
if
(
(w->special == ZoO_WORD_ENDS_SENTENCE)
|| (w->occurrences == 0)
)
{
return current_sentence;
}
/* prevents current_sentence [restrict] */
next_sentence = current_sentence;
for (;;)
{
if (*credits == 0)
{
return current_sentence;
}
*credits -= 1;
word_id =
pick_an_index
(
w->occurrences,
w->forward_links_occurrences,
w->forward_links
);
w = (k->words + word_id);
switch (w->special)
{
case ZoO_WORD_HAS_NO_EFFECT:
/* FIXME: Assumed to be overflow-safe. */
/* word also contains an '\0', which we will replace by a ' '. */
addition_size = w->word_size;
break;
case ZoO_WORD_ENDS_SENTENCE:
return current_sentence;
case ZoO_WORD_STARTS_SENTENCE:
ZoO_S_WARNING("START OF LINE should not be suffixable.");
return current_sentence;
case ZoO_WORD_REMOVES_LEFT_SPACE:
case ZoO_WORD_REMOVES_RIGHT_SPACE:
/* word also contains an '\0', which we will remove. */
addition_size = w->word_size - 1;
break;
}
if (*sentence_size > (SIZE_MAX - addition_size))
{
ZoO_S_WARNING
(
"Sentence construction aborted to avoid size_t overflow."
);
return current_sentence;
}
next_sentence =
(ZoO_char *) calloc
(
/* overflow-safe */
(*sentence_size + addition_size),
sizeof(ZoO_char)
);
if (next_sentence == (ZoO_char *) NULL)
{
ZoO_S_ERROR("Could not allocate memory to store new sentence.");
return current_sentence;
}
/* overflow-safe */
*sentence_size = (*sentence_size + addition_size);
switch (w->special)
{
case ZoO_WORD_REMOVES_LEFT_SPACE:
printf
(
"current sentence:'%s', pointing at '%c'.\n",
current_sentence,
current_sentence[*sentence_size - addition_size - 2]
);
current_sentence[*sentence_size - addition_size - 2] = '\0';
case ZoO_WORD_HAS_NO_EFFECT:
snprintf
(
next_sentence,
*sentence_size,
ZoO_CHAR_STRING_SYMBOL ZoO_CHAR_STRING_SYMBOL " ",
current_sentence,
w->word
);
break;
case ZoO_WORD_REMOVES_RIGHT_SPACE:
snprintf
(
next_sentence,
*sentence_size,
ZoO_CHAR_STRING_SYMBOL ZoO_CHAR_STRING_SYMBOL,
current_sentence,
w->word
);
break;
default:
/* TODO: PROGRAM LOGIC ERROR */
break;
}
free((void *) current_sentence);
/* prevents current_sentence [const] */
current_sentence = next_sentence;
}
}
int ZoO_knowledge_extend
(
struct ZoO_knowledge k [const static 1],
const struct ZoO_strings string [const static 1],
int const ignore_first_word,
ZoO_char * result [const static 1]
)
{
int word_found;
size_t sentence_size;
ZoO_index i, word_id, word_min_score, word_min_id, credits;
word_found = 0;
credits = ZoO_MAX_REPLY_WORDS;
if (ignore_first_word)
{
i = 1;
}
else
{
i = 0;
}
for (; i < string->words_count; ++i)
{
/* prevents k [restrict] */
if (ZoO_knowledge_find(k, string->words[i], &word_min_id) == 0)
{
word_found = 1;
word_min_score = k->words[word_min_id].occurrences;
break;
}
}
if (word_found == 0)
{
word_min_id = (rand() % k->words_count);
word_min_score = k->words[word_min_id].occurrences;
}
for (; i < string->words_count; ++i)
{
if
(
(ZoO_knowledge_find(k, string->words[i], &word_id) == 0)
&& (k->words[word_id].occurrences < word_min_score)
)
{
word_min_score = k->words[word_id].occurrences;
word_min_id = word_id;
}
}
/* 3: 2 spaces + '\0' */
/* FIXME: not overflow-safe */
switch (k->words[word_min_id].special)
{
case ZoO_WORD_REMOVES_LEFT_SPACE:
case ZoO_WORD_REMOVES_RIGHT_SPACE:
/* word + ' ' + '\0' */
sentence_size = (strlen(k->words[word_min_id].word) + 2);
break;
case ZoO_WORD_HAS_NO_EFFECT:
/* word + ' ' * 2 + '\0' */
sentence_size = (strlen(k->words[word_min_id].word) + 3);
break;
default:
ZoO_WARNING
(
"'%s' was unexpectedly selected as pillar.",
k->words[word_min_id].word
);
/* word + '[' + ']' + ' ' * 2 + '\0' */
sentence_size = (strlen(k->words[word_min_id].word) + 5);
break;
}
*result = (ZoO_char *) calloc(sentence_size, sizeof(ZoO_char));
if (*result == (ZoO_char *) NULL)
{
ZoO_S_ERROR("Could not allocate memory to start sentence.");
return -2;
}
switch (k->words[word_min_id].special)
{
case ZoO_WORD_REMOVES_LEFT_SPACE:
snprintf
(
*result,
sentence_size,
ZoO_CHAR_STRING_SYMBOL " ",
k->words[word_min_id].word
);
break;
case ZoO_WORD_REMOVES_RIGHT_SPACE:
snprintf
(
*result,
sentence_size,
" " ZoO_CHAR_STRING_SYMBOL,
k->words[word_min_id].word
);
break;
case ZoO_WORD_HAS_NO_EFFECT:
snprintf
(
*result,
sentence_size,
" " ZoO_CHAR_STRING_SYMBOL " ",
k->words[word_min_id].word
);
break;
default:
snprintf
(
*result,
sentence_size,
" [" ZoO_CHAR_STRING_SYMBOL "] ",
k->words[word_min_id].word
);
break;
}
if ((word_min_score == 0) || (credits == 0))
{
return 0;
}
--credits;
/* prevents result [restrict] */
*result = extend_left(k, word_min_id, *result, &sentence_size, &credits);
if (*result == (ZoO_char *) NULL)
{
return -2;
}
*result = extend_right(k, word_min_id, *result, &sentence_size, &credits);
if (*result == (ZoO_char *) NULL)
{
return -2;
}
return 0;
}
|
