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permute_tx: fix horrible thinko.

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Map needs to be inverted, otherwise non-trivial shuffles get confused.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2015-06-08 08:29:53 +09:30
parent 4dd6b8e385
commit a25ba452f3
1 changed files with 19 additions and 0 deletions
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19
permute_tx.c
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@@ -45,6 +45,21 @@ static void init_map(size_t *map, size_t len)
map[i] = i; map[i] = i;
} }
/* This map says where things ended up, eg. 0 might be in slot 3. we
* want to change it so map[0] = 3. */
static void invert_map(size_t *map, size_t len)
{
if (map) {
size_t i, newmap[len];
memset(newmap, 0, sizeof(newmap));
for (i = 0; i < len; i++) {
newmap[map[i]] = i;
}
memcpy(map, newmap, sizeof(newmap));
}
}
static bool input_better(const struct bitcoin_tx_input *a, static bool input_better(const struct bitcoin_tx_input *a,
const struct bitcoin_tx_input *b) const struct bitcoin_tx_input *b)
{ {
@@ -117,6 +132,8 @@ void permute_inputs(uint64_t seed1, uint64_t seed2, uint64_t tx_num,
size_t r = get_next_rand(&h, &randidx) % (num_inputs - i - 1); size_t r = get_next_rand(&h, &randidx) % (num_inputs - i - 1);
swap_inputs(inputs, map, i, i + 1 + r); swap_inputs(inputs, map, i, i + 1 + r);
} }
invert_map(map, num_inputs);
} }
static void swap_outputs(struct bitcoin_tx_output *outputs, size_t *map, static void swap_outputs(struct bitcoin_tx_output *outputs, size_t *map,
@@ -183,4 +200,6 @@ void permute_outputs(uint64_t seed1, uint64_t seed2, size_t tx_num,
size_t r = get_next_rand(&h, &randidx) % (num_outputs - i - 1); size_t r = get_next_rand(&h, &randidx) % (num_outputs - i - 1);
swap_outputs(outputs, map, i, i + 1 + r); swap_outputs(outputs, map, i, i + 1 + r);
} }
invert_map(map, num_outputs);
} }