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Move the ctime part of choose_array_element_by_weight into di_ops
This way it gets the ctime options.
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@ -226,3 +226,48 @@ safe_mem_is_zero(const void *mem, size_t sz)
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return 1 & ((total - 1) >> 8);
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}
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/** Time-invariant 64-bit greater-than; works on two integers in the range
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* (0,INT64_MAX). */
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#if SIZEOF_VOID_P == 8
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#define gt_i64_timei(a,b) ((a) > (b))
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#else
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static inline int
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gt_i64_timei(uint64_t a, uint64_t b)
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{
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int64_t diff = (int64_t) (b - a);
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int res = diff >> 63;
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return res & 1;
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}
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#endif
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/**
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* Given an array of list of <b>n_entries</b> uint64_t values, whose sum is
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* <b>total</b>, find the first i such that the total of all elements 0...i is
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* greater than rand_val.
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*
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* Try to perform this operation in a constant-time way.
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*/
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int
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select_array_member_cumulative_timei(const uint64_t *entries, int n_entries,
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uint64_t total, uint64_t rand_val)
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{
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int i, i_chosen=-1, n_chosen=0;
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uint64_t total_so_far = 0;
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for (i = 0; i < n_entries; ++i) {
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total_so_far += entries[i];
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if (gt_i64_timei(total_so_far, rand_val)) {
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i_chosen = i;
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n_chosen++;
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/* Set rand_val to INT64_MAX rather than stopping the loop. This way,
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* the time we spend in the loop does not leak which element we chose. */
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rand_val = INT64_MAX;
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}
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}
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tor_assert(total_so_far == total);
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tor_assert(n_chosen == 1);
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tor_assert(i_chosen >= 0);
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tor_assert(i_chosen < n_entries);
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return i_chosen;
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}
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@ -42,6 +42,8 @@ void dimap_add_entry(di_digest256_map_t **map,
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const uint8_t *key, void *val);
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void *dimap_search(const di_digest256_map_t *map, const uint8_t *key,
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void *dflt_val);
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int select_array_member_cumulative_timei(const uint64_t *entries, int n_entries,
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uint64_t total, uint64_t rand_val);
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#endif
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@ -2103,20 +2103,6 @@ scale_array_elements_to_u64(uint64_t *entries_out, const double *entries_in,
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#undef SCALE_TO_U64_MAX
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}
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/** Time-invariant 64-bit greater-than; works on two integers in the range
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* (0,INT64_MAX). */
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#if SIZEOF_VOID_P == 8
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#define gt_i64_timei(a,b) ((a) > (b))
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#else
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static inline int
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gt_i64_timei(uint64_t a, uint64_t b)
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{
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int64_t diff = (int64_t) (b - a);
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int res = diff >> 63;
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return res & 1;
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}
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#endif
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/** Pick a random element of <b>n_entries</b>-element array <b>entries</b>,
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* choosing each element with a probability proportional to its (uint64_t)
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* value, and return the index of that element. If all elements are 0, choose
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@ -2125,8 +2111,7 @@ gt_i64_timei(uint64_t a, uint64_t b)
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STATIC int
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choose_array_element_by_weight(const uint64_t *entries, int n_entries)
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{
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int i, i_chosen=-1, n_chosen=0;
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uint64_t total_so_far = 0;
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int i;
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uint64_t rand_val;
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uint64_t total = 0;
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@ -2143,22 +2128,8 @@ choose_array_element_by_weight(const uint64_t *entries, int n_entries)
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rand_val = crypto_rand_uint64(total);
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for (i = 0; i < n_entries; ++i) {
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total_so_far += entries[i];
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if (gt_i64_timei(total_so_far, rand_val)) {
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i_chosen = i;
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n_chosen++;
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/* Set rand_val to INT64_MAX rather than stopping the loop. This way,
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* the time we spend in the loop does not leak which element we chose. */
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rand_val = INT64_MAX;
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}
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}
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tor_assert(total_so_far == total);
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tor_assert(n_chosen == 1);
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tor_assert(i_chosen >= 0);
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tor_assert(i_chosen < n_entries);
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return i_chosen;
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return select_array_member_cumulative_timei(
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entries, n_entries, total, rand_val);
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}
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/** When weighting bridges, enforce these values as lower and upper
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