This is an alternative to #13242 which keeps the ReadLE64 part, but moves the crypto/common.h dependency into crypto/common.h as a function outside of uint256.
Reason: this change will remove dependencies for uint256 to crypto/common.h, compat/endian.h, and compat/byteswap.h.
This PR removes the need to update tests to be endian-aware/-independent, but keeps the (arguably dubious) ReadLE64 part (which was only introduced to fix the tests, not for any functionality).
All the GetCheapHash calls are relative to CHashWriter and BlockHasher, how about putting it higher up?
I’m not crazy about the template approach because it’s overly general and doesn’t guarantee that there are 64 bits there to read.
I’m not crazy about the template approach because it’s overly general and doesn’t guarantee that there are 64 bits there to read.
Yeah, but a uint256 does not guarantee it is random, either, so you still have to use this cautiously, even before this patch.
Putting it in CHashWriter may be a better idea, for sure. I’ll try that and see what it looks like.
GetHash().GetCheapHash() which will do double-double-SHA256, instead of double-SHA256. Considering the limited use, I think that gotcha is acceptable.
7@@ -8,25 +8,26 @@
8 #include <hash.h>
9 #include <serialize.h>
10 #include <streams.h>
11+#include <crypto/common.h>
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138@@ -138,7 +139,7 @@ static const int DEFAULT_STOPATHEIGHT = 0;
139
140 struct BlockHasher
141 {
142- size_t operator()(const uint256& hash) const { return hash.GetCheapHash(); }
143+ size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
GetCheapHash to explain the implementation.
138@@ -138,6 +139,18 @@ class CHashWriter
139 return result;
140 }
141
142+ /** A cheap hash function that just returns 64 bits from the result, it can be
17@@ -18,6 +18,7 @@
18 #include <script/script_error.h>
19 #include <sync.h>
20 #include <versionbits.h>
21+#include <crypto/common.h> // for ReadLE64
