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transaction: avoid quadratic scaling when growing arrays #519

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transaction: avoid quadratic scaling when growing arrays #519

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34 changes: 28 additions & 6 deletions src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -619,8 +619,30 @@ int replace_bytes(const unsigned char *bytes, size_t bytes_len,
}


static size_t ceil2(size_t s)
{
--s;
s |= s >> 1;
s |= s >> 2;
s |= s >> 4;
#ifndef SIZE_MAX
# error SIZE_MAX not defined
#endif
#if SIZE_MAX > UINT8_MAX
s |= s >> 8;
#endif
#if SIZE_MAX > UINT16_MAX
s |= s >> 16;
#endif
#if SIZE_MAX > UINT32_MAX
s |= s >> 32;
#endif
++s;
return s + !s;
}

void *array_realloc(const void *src, size_t old_n, size_t new_n, size_t size)
/* Don't use this to build up an array iteratively! Use array_grow. */
static void *array_realloc(const void *src, size_t old_n, size_t new_n, size_t size)
{
unsigned char *p = wally_malloc(new_n * size);
if (!p)
Expand All @@ -631,17 +653,17 @@ void *array_realloc(const void *src, size_t old_n, size_t new_n, size_t size)
return p;
}

int array_grow(void **src, size_t num_items, size_t *allocation_len,
int array_grow(void **src, size_t num_items_needed, size_t *allocation_len,
size_t item_size)
{
if (num_items == *allocation_len) {
/* Array is full, allocate more space */
const size_t n = (*allocation_len == 0 ? 1 : *allocation_len) * 2;
if (num_items_needed > *allocation_len) {
/* Array needs grown; allocate more space */
const size_t n = ceil2(num_items_needed);
void *p = array_realloc(*src, *allocation_len, n, item_size);
if (!p)
return WALLY_ENOMEM;
/* Free and replace the old array with the new enlarged copy */
clear_and_free(*src, num_items * item_size);
clear_and_free(*src, *allocation_len * item_size);
*src = p;
*allocation_len = n;
}
Expand Down
4 changes: 1 addition & 3 deletions src/internal.h
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Expand Up @@ -101,9 +101,7 @@ bool clone_data(void **dst, const void *src, size_t len);
bool clone_bytes(unsigned char **dst, const unsigned char *src, size_t len);
int replace_bytes(const unsigned char *bytes, size_t bytes_len,
unsigned char **bytes_out, size_t *bytes_len_out);
void *array_realloc(const void *src, size_t old_n, size_t new_n, size_t size);

int array_grow(void **src, size_t num_items, size_t *allocation_len,
int array_grow(void **src, size_t num_items_needed, size_t *allocation_len,
size_t item_size);

struct ext_key;
Expand Down
2 changes: 1 addition & 1 deletion src/map.c
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Expand Up @@ -246,7 +246,7 @@ int map_add(struct wally_map *map_in,
return ignore_dups ? WALLY_OK : WALLY_EINVAL;
}

ret = array_grow((void *)&map_in->items, map_in->num_items,
ret = array_grow((void *)&map_in->items, map_in->num_items + 1,
&map_in->items_allocation_len, sizeof(struct wally_map_item));
if (ret == WALLY_OK) {
struct wally_map_item *new_item = map_in->items + map_in->num_items;
Expand Down
4 changes: 2 additions & 2 deletions src/psbt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1785,7 +1785,7 @@ int wally_psbt_add_tx_input_at(struct wally_psbt *psbt,
return ret;

if (psbt->num_inputs >= psbt->inputs_allocation_len &&
(ret = array_grow((void *)&psbt->inputs, psbt->num_inputs,
(ret = array_grow((void *)&psbt->inputs, psbt->num_inputs + 1,
&psbt->inputs_allocation_len,
sizeof(*psbt->inputs))) != WALLY_OK)
return ret;
Expand Down Expand Up @@ -1950,7 +1950,7 @@ int wally_psbt_add_tx_output_at(struct wally_psbt *psbt,
return ret;

if (psbt->num_outputs >= psbt->outputs_allocation_len &&
(ret = array_grow((void *)&psbt->outputs, psbt->num_outputs,
(ret = array_grow((void *)&psbt->outputs, psbt->num_outputs + 1,
&psbt->outputs_allocation_len,
sizeof(*psbt->outputs))) != WALLY_OK)
return ret;
Expand Down
53 changes: 17 additions & 36 deletions src/transaction.c
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Original file line number Diff line number Diff line change
Expand Up @@ -272,6 +272,7 @@ int wally_tx_witness_stack_set(struct wally_tx_witness_stack *stack, size_t inde
const unsigned char *witness, size_t witness_len)
{
unsigned char *new_witness = NULL;
int ret;

if (!is_valid_witness_stack(stack) || (!witness && witness_len))
return WALLY_EINVAL;
Expand All @@ -280,18 +281,12 @@ int wally_tx_witness_stack_set(struct wally_tx_witness_stack *stack, size_t inde
return WALLY_ENOMEM;

if (index >= stack->num_items) {
if (index >= stack->items_allocation_len) {
/* Expand the witness array */
struct wally_tx_witness_item *p;
p = array_realloc(stack->items, stack->items_allocation_len,
index + 1, sizeof(*stack->items));
if (!p) {
clear_and_free(new_witness, witness_len);
return WALLY_ENOMEM;
}
clear_and_free(stack->items, stack->num_items * sizeof(*stack->items));
stack->items = p;
stack->items_allocation_len = index + 1;
/* Expand the witness array if needed */
ret = array_grow((void *)&stack->items, index + 1,
&stack->items_allocation_len, sizeof(*stack->items));
if (ret != WALLY_OK) {
clear_and_free(new_witness, witness_len);
return ret;
}
stack->num_items = index + 1;
}
Expand Down Expand Up @@ -1198,18 +1193,11 @@ int wally_tx_add_input_at(struct wally_tx *tx, uint32_t index,
if (!is_valid_tx(tx) || index > tx->num_inputs || !is_valid_tx_input(input))
return WALLY_EINVAL;

if (tx->num_inputs >= tx->inputs_allocation_len) {
/* Expand the inputs array */
struct wally_tx_input *p;
p = array_realloc(tx->inputs, tx->inputs_allocation_len,
tx->num_inputs + 1, sizeof(*tx->inputs));
if (!p)
return WALLY_ENOMEM;

clear_and_free(tx->inputs, tx->num_inputs * sizeof(*tx->inputs));
tx->inputs = p;
tx->inputs_allocation_len += 1;
}
/* Expand the inputs array if needed */
ret = array_grow((void *)&tx->inputs, tx->num_inputs + 1,
&tx->inputs_allocation_len, sizeof(*tx->inputs));
if (ret != WALLY_OK)
return ret;

memmove(tx->inputs + index + 1, tx->inputs + index,
(tx->num_inputs - index) * sizeof(*input));
Expand Down Expand Up @@ -1427,18 +1415,11 @@ int wally_tx_add_output_at(struct wally_tx *tx, uint32_t index,
} else if (!is_valid_elements_tx_output(output))
return WALLY_EINVAL;

if (tx->num_outputs >= tx->outputs_allocation_len) {
/* Expand the outputs array */
struct wally_tx_output *p;
p = array_realloc(tx->outputs, tx->outputs_allocation_len,
tx->num_outputs + 1, sizeof(*tx->outputs));
if (!p)
return WALLY_ENOMEM;

clear_and_free(tx->outputs, tx->num_outputs * sizeof(*tx->outputs));
tx->outputs = p;
tx->outputs_allocation_len += 1;
}
/* Expand the outputs array if needed */
ret = array_grow((void *)&tx->outputs, tx->num_outputs + 1,
&tx->outputs_allocation_len, sizeof(*tx->outputs));
if (ret != WALLY_OK)
return ret;

memmove(tx->outputs + index + 1, tx->outputs + index,
(tx->num_outputs - index) * sizeof(*output));
Expand Down
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