Use ReadLE64 in uint256::GetUint64 instead of duplicating logic #26105
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ACK 04fee75 The existing code assumes host endianness. |
jonatack
reviewed
Sep 16, 2022
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ACK 04fee75 review, this use of ReadLE64() is similar to the existing invocation by Num3072::Num3072(), sanity checked that before and after this change GetUint64() returns the same result (debug build, clang 13)
--- a/src/uint256.h
+++ b/src/uint256.h
@@ -7,6 +7,7 @@
#include <crypto/common.h>
+#include <logging.h>
#include <span.h>
@@ -85,7 +86,20 @@ public:
uint64_t GetUint64(int pos) const
{
- return ReadLE64(m_data + pos * 8);
+ const uint8_t* ptr = m_data + pos * 8;
+ uint64_t x = ((uint64_t)ptr[0]) | \
+ ((uint64_t)ptr[1]) << 8 | \
+ ((uint64_t)ptr[2]) << 16 | \
+ ((uint64_t)ptr[3]) << 24 | \
+ ((uint64_t)ptr[4]) << 32 | \
+ ((uint64_t)ptr[5]) << 40 | \
+ ((uint64_t)ptr[6]) << 48 | \
+ ((uint64_t)ptr[7]) << 56;
+ LogPrintf("GetUint64 old: %s\n", x);
+
+ const auto y = ReadLE64(m_data + pos * 8);
+ LogPrintf("GetUint64 new: %s\n", y);
+
+ assert(x == y);
+ return y;
}2022-09-16T09:13:53Z GetUint64 old: 2830827502690553650
2022-09-16T09:13:53Z GetUint64 new: 2830827502690553650
2022-09-16T09:13:53Z GetUint64 old: 13427380872610120290
2022-09-16T09:13:53Z GetUint64 new: 13427380872610120290
2022-09-16T09:13:53Z GetUint64 old: 12183277635375193944
2022-09-16T09:13:53Z GetUint64 new: 12183277635375193944
2022-09-16T09:13:53Z GetUint64 old: 16580367070613284548
2022-09-16T09:13:53Z GetUint64 new: 16580367070613284548
2022-09-16T09:13:53Z GetUint64 old: 16949092074016075712
2022-09-16T09:13:53Z GetUint64 new: 16949092074016075712
2022-09-16T09:13:53Z GetUint64 old: 14891467430351852074
2022-09-16T09:13:53Z GetUint64 new: 14891467430351852074
2022-09-16T09:13:53Z GetUint64 old: 2319828850847527094
2022-09-16T09:13:53Z GetUint64 new: 2319828850847527094
2022-09-16T09:13:53Z GetUint64 old: 921024485749193602
2022-09-16T09:13:53Z GetUint64 new: 921024485749193602
No, it does not. Both the old and new code interpret the bytes as little-endian. |
Right, I meant that the old code interprets the bytes as little endian and stores them as little endian, even if the host machine is big-endian. |
sidhujag
pushed a commit
to syscoin/syscoin
that referenced
this pull request
Sep 20, 2022
…plicating logic 04fee75 Use ReadLE64 in uint256::GetUint64() instead of duplicating logic (Pieter Wuille) Pull request description: No need to have a (naive) copy of the `ReadLE64` logic inside `uint256::GetUint64`, when we have an optimized function for exactly that. ACKs for top commit: davidgumberg: ACK 04fee75 jonatack: ACK 04fee75 review, this use of ReadLE64() is similar to the existing invocation by Num3072::Num3072(), sanity checked that before and after this change GetUint64() returns the same result (debug build, clang 13) Tree-SHA512: 0fc2681536a18d82408411bcc6d5c6445fb96793fa43ff4021cd2933d46514c725318da35884f428d1799023921f33f8af091ef428ceb96a50866ac53a345356
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No need to have a (naive) copy of the
ReadLE64logic insideuint256::GetUint64, when we have an optimized function for exactly that.