Merge bitcoin/bitcoin#21966: Remove double serialization; use software encoder for fee estimation

66545da2008cd9e806e41b74522ded259cd64f86 Remove support for double serialization (Pieter Wuille)
fff1cae43af959a601cf2558cb3c77f3c2b1aa80 Convert uses of double-serialization to {En,De}codeDouble (Pieter Wuille)
afd964d70b6f7583ecf89c380f80db07f5b66a60 Convert existing float encoding tests (Pieter Wuille)
bda33f98e2f32f2411fb0a8f5fb4f0a32abdf7d4 Add unit tests for serfloat module (Pieter Wuille)
2be4cd94f4c7d92a4287971233a20d68db81c9c9 Add platform-independent float encoder/decoder (Pieter Wuille)
e40224d0c77674348bf0a518365208bc118f39a4 Remove unused float serialization (MarcoFalke)

Pull request description:

  Based on #21981.

  This adds a software-based platform-independent float/double encoder/decoder (platform independent in the sense that it only uses arithmetic and library calls, but never inspects the binary representation). This should strengthen our guarantee that encoded float/double values are portable across platforms. It then removes the functionality to serialize doubles from serialize.h, and replaces its only (non-test) use for fee estimation data serialization with the software encoder.

  At least on x86/ARM, the only difference should be how certain NaN values are encoded/decoded (but not *whether* they are NaN or not).

  It comes with tests that verify on is_iec559 platforms (which are the only ones we support, at least for now) that the serialized bytes exactly match the binary representation of floats in memory (for non-NaN).

ACKs for top commit:
  laanwj:
    Code review re-ACK 66545da2008cd9e806e41b74522ded259cd64f86
  practicalswift:
    cr re-ACK 66545da2008cd9e806e41b74522ded259cd64f86

Tree-SHA512: 62ad9adc26e28707b2eb12a919feefd4fd10cf9032652dbb1ca1cc97638ac21de89e240858e80d293d5112685c623e58affa3d316a9783ff0e6d291977a141f5

2 files changed, 14 insertions, 25 deletions

diff --git a/src/test/fuzz/float.cpp b/src/test/fuzz/float.cpp
index d18a87d177..adef66a3ee 100644
--- a/src/test/fuzz/float.cpp
+++ b/src/test/fuzz/float.cpp
@@ -3,14 +3,14 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <memusage.h>
-#include <serialize.h>
-#include <streams.h>
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
+#include <util/serfloat.h>
 #include <version.h>
 
 #include <cassert>
-#include <cstdint>
+#include <cmath>
+#include <limits>
 
 FUZZ_TARGET(float)
 {
@@ -19,24 +19,17 @@ FUZZ_TARGET(float)
     {
         const double d = fuzzed_data_provider.ConsumeFloatingPoint<double>();
         (void)memusage::DynamicUsage(d);
-        assert(ser_uint64_to_double(ser_double_to_uint64(d)) == d);
 
-        CDataStream stream(SER_NETWORK, INIT_PROTO_VERSION);
-        stream << d;
-        double d_deserialized;
-        stream >> d_deserialized;
-        assert(d == d_deserialized);
-    }
-
-    {
-        const float f = fuzzed_data_provider.ConsumeFloatingPoint<float>();
-        (void)memusage::DynamicUsage(f);
-        assert(ser_uint32_to_float(ser_float_to_uint32(f)) == f);
-
-        CDataStream stream(SER_NETWORK, INIT_PROTO_VERSION);
-        stream << f;
-        float f_deserialized;
-        stream >> f_deserialized;
-        assert(f == f_deserialized);
+        uint64_t encoded = EncodeDouble(d);
+        if constexpr (std::numeric_limits<double>::is_iec559) {
+            if (!std::isnan(d)) {
+                uint64_t encoded_in_memory;
+                std::copy((const unsigned char*)&d, (const unsigned char*)(&d + 1), (unsigned char*)&encoded_in_memory);
+                assert(encoded_in_memory == encoded);
+            }
+        }
+        double d_deserialized = DecodeDouble(encoded);
+        assert(std::isnan(d) == std::isnan(d_deserialized));
+        assert(std::isnan(d) || d == d_deserialized);
     }
 }
diff --git a/src/test/fuzz/util.h b/src/test/fuzz/util.h
index 86b203c6b5..36b1d5035c 100644
--- a/src/test/fuzz/util.h
+++ b/src/test/fuzz/util.h
@@ -513,8 +513,6 @@ void WriteToStream(FuzzedDataProvider& fuzzed_data_provider, Stream& stream) noe
                 WRITE_TO_STREAM_CASE(uint32_t, fuzzed_data_provider.ConsumeIntegral<uint32_t>()),
                 WRITE_TO_STREAM_CASE(int64_t, fuzzed_data_provider.ConsumeIntegral<int64_t>()),
                 WRITE_TO_STREAM_CASE(uint64_t, fuzzed_data_provider.ConsumeIntegral<uint64_t>()),
-                WRITE_TO_STREAM_CASE(float, fuzzed_data_provider.ConsumeFloatingPoint<float>()),
-                WRITE_TO_STREAM_CASE(double, fuzzed_data_provider.ConsumeFloatingPoint<double>()),
                 WRITE_TO_STREAM_CASE(std::string, fuzzed_data_provider.ConsumeRandomLengthString(32)),
                 WRITE_TO_STREAM_CASE(std::vector<char>, ConsumeRandomLengthIntegralVector<char>(fuzzed_data_provider)));
         } catch (const std::ios_base::failure&) {
@@ -545,8 +543,6 @@ void ReadFromStream(FuzzedDataProvider& fuzzed_data_provider, Stream& stream) no
                 READ_FROM_STREAM_CASE(uint32_t),
                 READ_FROM_STREAM_CASE(int64_t),
                 READ_FROM_STREAM_CASE(uint64_t),
-                READ_FROM_STREAM_CASE(float),
-                READ_FROM_STREAM_CASE(double),
                 READ_FROM_STREAM_CASE(std::string),
                 READ_FROM_STREAM_CASE(std::vector<char>));
         } catch (const std::ios_base::failure&) {