Merge bitcoin/bitcoin#19438: Introduce deploymentstatus

e48826ad87b4f92261f7433e84f48dac9bd9e5c3 tests: remove ComputeBlockVersion shortcut from versionbits tests (Anthony Towns)
c5f36725e877d8eb492383844f8ef7535466b366 [refactor] Move ComputeBlockVersion into VersionBitsCache (Anthony Towns)
4a69b4dbe0d7f504811b67c399da7e6d11e4f805 [move-only] Move ComputeBlockVersion from validation to versionbits (Anthony Towns)
0cfd6c6a8f929d5567ac41f95c21548f115efee5 [refactor] versionbits: make VersionBitsCache a full class (Anthony Towns)
8ee3e0bed5bf2cd3c7a68ca6ba6c65f7b9a72cca [refactor] rpc/blockchain.cpp: SoftForkPushBack (Anthony Towns)
92f48f360da5f425428b761219301f509826bec4 deploymentinfo: Add DeploymentName() (Anthony Towns)
ea68b3a5729f5d240e968388c4f88acffeb27228 [move-only] Rename versionbitsinfo to deploymentinfo (Anthony Towns)
c64b2c6a0f79369624ae96b2e3d579d50aae4de6 scripted-diff: rename versionbitscache (Anthony Towns)
de55304f6e7a8b607e6b3fc7436de50910747b0c [refactor] Add versionbits deployments to deploymentstatus.h (Anthony Towns)
2b0d291da8f479739ff394dd92801da8c40b9f8e [refactor] Add deploymentstatus.h (Anthony Towns)
eccd736f3dc231ac0306ca763c3b72cf8247230a versionbits: Use dedicated lock instead of cs_main (Anthony Towns)
36a4ba0aaaa9b35185d7178994e36bc02cca9887 versionbits: correct doxygen comments (Anthony Towns)

Pull request description:

  Introduces helper functions to make it easy to bury future deployments, along the lines of the suggestion from [11398](https://github.com/bitcoin/bitcoin/pull/11398#issuecomment-335599326) "I would prefer it if a buried deployment wouldn't require all code paths that check the BIP9 status to require changing".

  This provides three functions: `DeploymentEnabled()` which tests if a deployment can ever be active, `DeploymentActiveAt()` which checks if a deployment should be enforced in the given block, and `DeploymentActiveAfter()` which checks if a deployment should be enforced in the block following the given block, and overloads all three to work both with buried deployments and versionbits deployments.

  This adds a dedicated lock for the versionbits cache, which is acquired internally by the versionbits functions, rather than relying on `cs_main`. It also moves moves versionbitscache into deploymentstatus to avoid a circular dependency with validation.

ACKs for top commit:
  jnewbery:
    ACK e48826ad87b4f92261f7433e84f48dac9bd9e5c3
  gruve-p:
    ACK https://github.com/bitcoin/bitcoin/pull/19438/commits/e48826ad87b4f92261f7433e84f48dac9bd9e5c3
  MarcoFalke:
    re-ACK e48826ad87b4f92261f7433e84f48dac9bd9e5c3 🥈

Tree-SHA512: c846ba64436d36f8180046ad551d8b0d9e20509b9bc185aa2639055fc28803dd8ec2d6771ab337e80da0b40009ad959590d5772f84a0bf6199b65190d4155bed

1 files changed, 55 insertions, 0 deletions

diff --git a/src/deploymentstatus.h b/src/deploymentstatus.h
new file mode 100644
index 0000000000..84c5e54698
--- /dev/null
+++ b/src/deploymentstatus.h
@@ -0,0 +1,55 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_DEPLOYMENTSTATUS_H
+#define BITCOIN_DEPLOYMENTSTATUS_H
+
+#include <chain.h>
+#include <versionbits.h>
+
+#include <limits>
+
+/** Global cache for versionbits deployment status */
+extern VersionBitsCache g_versionbitscache;
+
+/** Determine if a deployment is active for the next block */
+inline bool DeploymentActiveAfter(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::BuriedDeployment dep)
+{
+    assert(Consensus::ValidDeployment(dep));
+    return (pindexPrev == nullptr ? 0 : pindexPrev->nHeight + 1) >= params.DeploymentHeight(dep);
+}
+
+inline bool DeploymentActiveAfter(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos dep)
+{
+    assert(Consensus::ValidDeployment(dep));
+    return ThresholdState::ACTIVE == g_versionbitscache.State(pindexPrev, params, dep);
+}
+
+/** Determine if a deployment is active for this block */
+inline bool DeploymentActiveAt(const CBlockIndex& index, const Consensus::Params& params, Consensus::BuriedDeployment dep)
+{
+    assert(Consensus::ValidDeployment(dep));
+    return index.nHeight >= params.DeploymentHeight(dep);
+}
+
+inline bool DeploymentActiveAt(const CBlockIndex& index, const Consensus::Params& params, Consensus::DeploymentPos dep)
+{
+    assert(Consensus::ValidDeployment(dep));
+    return DeploymentActiveAfter(index.pprev, params, dep);
+}
+
+/** Determine if a deployment is enabled (can ever be active) */
+inline bool DeploymentEnabled(const Consensus::Params& params, Consensus::BuriedDeployment dep)
+{
+    assert(Consensus::ValidDeployment(dep));
+    return params.DeploymentHeight(dep) != std::numeric_limits<int>::max();
+}
+
+inline bool DeploymentEnabled(const Consensus::Params& params, Consensus::DeploymentPos dep)
+{
+    assert(Consensus::ValidDeployment(dep));
+    return params.vDeployments[dep].nTimeout != 0;
+}
+
+#endif // BITCOIN_DEPLOYMENTSTATUS_H