Merge #19601: Refactoring CHashWriter & Get{Prevouts,Sequence,Outputs}Hash to SHA256 (Alternative to #18071)

9ab4cafabda227ccee5b241d7690fc67f9a27221 Refactor Get{Prevout,Sequence,Outputs}Hash to Get{Prevouts,Sequences,Outputs}SHA256. (Jeremy Rubin)
6510d0ff4173a7b01d6728051303c7c38eb34533 Add SHA256Uint256 helper functions (Jeremy Rubin)
b475d7d0fa000d5802caf3065b8b2abcea60719b Add single sha256 call to CHashWriter (Jeremy Rubin)

Pull request description:

  Opened as an alternative to #18071 to be more similar to #17977.

  I'm fine with either, deferring to others.

  cc jnewbery Sjors

ACKs for top commit:
  jnewbery:
    Code review ACK 9ab4cafabda227ccee5b241d7690fc67f9a27221
  jonatack:
    Tested ACK 9ab4caf
  fjahr:
    tested ACK 9ab4cafabda227ccee5b241d7690fc67f9a27221
  instagibbs:
    reACK https://github.com/bitcoin/bitcoin/pull/19601/commits/9ab4cafabda227ccee5b241d7690fc67f9a27221

Tree-SHA512: 93a7a47697f1657f027b18407bdcce16963f6b23d12372e7ac8fd4ee96769b3e2639369f9956fee669cc881b6338641cddfeeef1516c7104cb50ef4b880bb0a7

1 files changed, 24 insertions, 7 deletions

diff --git a/src/hash.h b/src/hash.h
index 71806483ff..c16bbb48ce 100644
--- a/src/hash.h
+++ b/src/hash.h
@@ -6,6 +6,7 @@
 #ifndef BITCOIN_HASH_H
 #define BITCOIN_HASH_H
 
+#include <attributes.h>
 #include <crypto/common.h>
 #include <crypto/ripemd160.h>
 #include <crypto/sha256.h>
@@ -98,7 +99,7 @@ inline uint160 Hash160(const T1& in1)
 class CHashWriter
 {
 private:
-    CHash256 ctx;
+    CSHA256 ctx;
 
     const int nType;
     const int nVersion;
@@ -110,13 +111,27 @@ public:
     int GetVersion() const { return nVersion; }
 
     void write(const char *pch, size_t size) {
-        ctx.Write({(const unsigned char*)pch, size});
+        ctx.Write((const unsigned char*)pch, size);
     }
 
-    // invalidates the object
+    /** Compute the double-SHA256 hash of all data written to this object.
+     *
+     * Invalidates this object.
+     */
     uint256 GetHash() {
         uint256 result;
-        ctx.Finalize(result);
+        ctx.Finalize(result.begin());
+        ctx.Reset().Write(result.begin(), CSHA256::OUTPUT_SIZE).Finalize(result.begin());
+        return result;
+    }
+
+    /** Compute the SHA256 hash of all data written to this object.
+     *
+     * Invalidates this object.
+     */
+    uint256 GetSHA256() {
+        uint256 result;
+        ctx.Finalize(result.begin());
         return result;
     }
 
@@ -124,9 +139,8 @@ public:
      * Returns the first 64 bits from the resulting hash.
      */
     inline uint64_t GetCheapHash() {
-        unsigned char result[CHash256::OUTPUT_SIZE];
-        ctx.Finalize(result);
-        return ReadLE64(result);
+        uint256 result = GetHash();
+        return ReadLE64(result.begin());
     }
 
     template<typename T>
@@ -181,6 +195,9 @@ uint256 SerializeHash(const T& obj, int nType=SER_GETHASH, int nVersion=PROTOCOL
     return ss.GetHash();
 }
 
+/** Single-SHA256 a 32-byte input (represented as uint256). */
+NODISCARD uint256 SHA256Uint256(const uint256& input);
+
 unsigned int MurmurHash3(unsigned int nHashSeed, Span<const unsigned char> vDataToHash);
 
 void BIP32Hash(const ChainCode &chainCode, unsigned int nChild, unsigned char header, const unsigned char data[32], unsigned char output[64]);