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git/string-list.c
Derrick Stolee 19716b21a4 cleanup: fix possible overflow errors in binary search 
A common mistake when writing binary search is to allow possible
integer overflow by using the simple average:

	mid = (min + max) / 2;

Instead, use the overflow-safe version:

	mid = min + (max - min) / 2;

This translation is safe since the operation occurs inside a loop
conditioned on "min < max". The included changes were found using
the following git grep:

	git grep '/ *2;' '*.c'

Making this cleanup will prevent future review friction when a new
binary search is contructed based on existing code.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-10 08:57:24 +09:00

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#include "cache.h"
#include "string-list.h"
void string_list_init(struct string_list *list, int strdup_strings)
{
memset(list, 0, sizeof(*list));
list->strdup_strings = strdup_strings;
}
/* if there is no exact match, point to the index where the entry could be
* inserted */
static int get_entry_index(const struct string_list *list, const char *string,
int *exact_match)
{
int left = -1, right = list->nr;
compare_strings_fn cmp = list->cmp ? list->cmp : strcmp;
while (left + 1 < right) {
int middle = left + (right - left) / 2;
int compare = cmp(string, list->items[middle].string);
if (compare < 0)
right = middle;
else if (compare > 0)
left = middle;
else {
*exact_match = 1;
return middle;
}
}
*exact_match = 0;
return right;
}
/* returns -1-index if already exists */
static int add_entry(int insert_at, struct string_list *list, const char *string)
{
int exact_match = 0;
int index = insert_at != -1 ? insert_at : get_entry_index(list, string, &exact_match);
if (exact_match)
return -1 - index;
ALLOC_GROW(list->items, list->nr+1, list->alloc);
if (index < list->nr)
MOVE_ARRAY(list->items + index + 1, list->items + index,
list->nr - index);
list->items[index].string = list->strdup_strings ?
xstrdup(string) : (char *)string;
list->items[index].util = NULL;
list->nr++;
return index;
}
struct string_list_item *string_list_insert(struct string_list *list, const char *string)
{
int index = add_entry(-1, list, string);
if (index < 0)
index = -1 - index;
return list->items + index;
}
void string_list_remove(struct string_list *list, const char *string,
int free_util)
{
int exact_match;
int i = get_entry_index(list, string, &exact_match);
if (exact_match) {
if (list->strdup_strings)
free(list->items[i].string);
if (free_util)
free(list->items[i].util);
list->nr--;
MOVE_ARRAY(list->items + i, list->items + i + 1, list->nr - i);
}
}
int string_list_has_string(const struct string_list *list, const char *string)
{
int exact_match;
get_entry_index(list, string, &exact_match);
return exact_match;
}
int string_list_find_insert_index(const struct string_list *list, const char *string,
int negative_existing_index)
{
int exact_match;
int index = get_entry_index(list, string, &exact_match);
if (exact_match)
index = -1 - (negative_existing_index ? index : 0);
return index;
}
struct string_list_item *string_list_lookup(struct string_list *list, const char *string)
{
int exact_match, i = get_entry_index(list, string, &exact_match);
if (!exact_match)
return NULL;
return list->items + i;
}
void string_list_remove_duplicates(struct string_list *list, int free_util)
{
if (list->nr > 1) {
int src, dst;
compare_strings_fn cmp = list->cmp ? list->cmp : strcmp;
for (src = dst = 1; src < list->nr; src++) {
if (!cmp(list->items[dst - 1].string, list->items[src].string)) {
if (list->strdup_strings)
free(list->items[src].string);
if (free_util)
free(list->items[src].util);
} else
list->items[dst++] = list->items[src];
}
list->nr = dst;
}
}
int for_each_string_list(struct string_list *list,
string_list_each_func_t fn, void *cb_data)
{
int i, ret = 0;
for (i = 0; i < list->nr; i++)
if ((ret = fn(&list->items[i], cb_data)))
break;
return ret;
}
void filter_string_list(struct string_list *list, int free_util,
string_list_each_func_t want, void *cb_data)
{
int src, dst = 0;
for (src = 0; src < list->nr; src++) {
if (want(&list->items[src], cb_data)) {
list->items[dst++] = list->items[src];
} else {
if (list->strdup_strings)
free(list->items[src].string);
if (free_util)
free(list->items[src].util);
}
}
list->nr = dst;
}
static int item_is_not_empty(struct string_list_item *item, void *unused)
{
return *item->string != '\0';
}
void string_list_remove_empty_items(struct string_list *list, int free_util) {
filter_string_list(list, free_util, item_is_not_empty, NULL);
}
void string_list_clear(struct string_list *list, int free_util)
{
if (list->items) {
int i;
if (list->strdup_strings) {
for (i = 0; i < list->nr; i++)
free(list->items[i].string);
}
if (free_util) {
for (i = 0; i < list->nr; i++)
free(list->items[i].util);
}
free(list->items);
}
list->items = NULL;
list->nr = list->alloc = 0;
}
void string_list_clear_func(struct string_list *list, string_list_clear_func_t clearfunc)
{
if (list->items) {
int i;
if (clearfunc) {
for (i = 0; i < list->nr; i++)
clearfunc(list->items[i].util, list->items[i].string);
}
if (list->strdup_strings) {
for (i = 0; i < list->nr; i++)
free(list->items[i].string);
}
free(list->items);
}
list->items = NULL;
list->nr = list->alloc = 0;
}
void print_string_list(const struct string_list *p, const char *text)
{
int i;
if ( text )
printf("%s\n", text);
for (i = 0; i < p->nr; i++)
printf("%s:%p\n", p->items[i].string, p->items[i].util);
}
struct string_list_item *string_list_append_nodup(struct string_list *list,
char *string)
{
struct string_list_item *retval;
ALLOC_GROW(list->items, list->nr + 1, list->alloc);
retval = &list->items[list->nr++];
retval->string = string;
retval->util = NULL;
return retval;
}
struct string_list_item *string_list_append(struct string_list *list,
const char *string)
{
return string_list_append_nodup(
list,
list->strdup_strings ? xstrdup(string) : (char *)string);
}
static int cmp_items(const void *a, const void *b, void *ctx)
{
compare_strings_fn cmp = ctx;
const struct string_list_item *one = a;
const struct string_list_item *two = b;
return cmp(one->string, two->string);
}
void string_list_sort(struct string_list *list)
{
QSORT_S(list->items, list->nr, cmp_items,
list->cmp ? list->cmp : strcmp);
}
struct string_list_item *unsorted_string_list_lookup(struct string_list *list,
const char *string)
{
struct string_list_item *item;
compare_strings_fn cmp = list->cmp ? list->cmp : strcmp;
for_each_string_list_item(item, list)
if (!cmp(string, item->string))
return item;
return NULL;
}
int unsorted_string_list_has_string(struct string_list *list,
const char *string)
{
return unsorted_string_list_lookup(list, string) != NULL;
}
void unsorted_string_list_delete_item(struct string_list *list, int i, int free_util)
{
if (list->strdup_strings)
free(list->items[i].string);
if (free_util)
free(list->items[i].util);
list->items[i] = list->items[list->nr-1];
list->nr--;
}
int string_list_split(struct string_list *list, const char *string,
int delim, int maxsplit)
{
int count = 0;
const char *p = string, *end;
if (!list->strdup_strings)
die("internal error in string_list_split(): "
"list->strdup_strings must be set");
for (;;) {
count++;
if (maxsplit >= 0 && count > maxsplit) {
string_list_append(list, p);
return count;
}
end = strchr(p, delim);
if (end) {
string_list_append_nodup(list, xmemdupz(p, end - p));
p = end + 1;
} else {
string_list_append(list, p);
return count;
}
}
}
int string_list_split_in_place(struct string_list *list, char *string,
int delim, int maxsplit)
{
int count = 0;
char *p = string, *end;
if (list->strdup_strings)
die("internal error in string_list_split_in_place(): "
"list->strdup_strings must not be set");
for (;;) {
count++;
if (maxsplit >= 0 && count > maxsplit) {
string_list_append(list, p);
return count;
}
end = strchr(p, delim);
if (end) {
*end = '\0';
string_list_append(list, p);
p = end + 1;
} else {
string_list_append(list, p);
return count;
}
}
}
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