Kernel: Implement PoC FFI

Also add a C binary and a Python script to exercise it.

.gitignore

@@ -10,6 +10,7 @@ src/bitcoin-node
 src/bitcoin-tx
 src/bitcoin-util
 src/bitcoin-chainstate
+src/bitcoin-chainstate_c
 src/bitcoin-wallet
 src/test/fuzz/fuzz
 src/test/test_bitcoin
@@ -136,6 +137,7 @@ test/lint/test_runner/target/
 
 /doc/doxygen/
 
+libbitcoinkernel.pc
 contrib/devtools/split-debug.sh
 
 # Output from running db4 installation

Makefile.am

@@ -14,6 +14,11 @@ endif
 .PHONY: deploy FORCE
 .INTERMEDIATE: $(COVERAGE_INFO)
 
+if BUILD_BITCOIN_KERNEL_LIB
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA = libbitcoinkernel.pc
+endif
+
 BITCOIND_BIN=$(top_builddir)/src/$(BITCOIN_DAEMON_NAME)$(EXEEXT)
 BITCOIN_QT_BIN=$(top_builddir)/src/qt/$(BITCOIN_GUI_NAME)$(EXEEXT)
 BITCOIN_TEST_BIN=$(top_builddir)/src/test/$(BITCOIN_TEST_NAME)$(EXEEXT)

configure.ac

@@ -1553,6 +1553,10 @@ AC_MSG_RESULT($build_bitcoin_chainstate)
 
 AM_CONDITIONAL([BUILD_BITCOIN_KERNEL_LIB], [test "$build_experimental_kernel_lib" != "no" && ( test "$build_experimental_kernel_lib" = "yes" || test "$build_bitcoin_chainstate" = "yes" )])
 
+if test "$build_bitcoin_kernel_lib" = "yes"; then
+  AC_CONFIG_FILES([libbitcoinkernel.pc:libbitcoinkernel.pc.in])
+fi
+
 AC_LANG_POP
 
 if test "$use_ccache" != "no"; then

libbitcoinkernel.pc.in

@@ -0,0 +1,10 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: @PACKAGE_NAME@ kernel library
+Description: Library for the Bitcoin chain validation.
+Version: @PACKAGE_VERSION@
+Libs: -L${libdir} -lbitcoinkernel
+Cflags: -I${includedir}

src/Makefile.am

@@ -16,6 +16,7 @@ AM_LIBTOOLFLAGS = --preserve-dup-deps
 PTHREAD_FLAGS = $(PTHREAD_CFLAGS) $(PTHREAD_LIBS)
 EXTRA_LIBRARIES =
 
+include_HEADERS =
 lib_LTLIBRARIES =
 noinst_LTLIBRARIES =
 
@@ -110,6 +111,7 @@ endif
 
 if BUILD_BITCOIN_CHAINSTATE
   bin_PROGRAMS += bitcoin-chainstate
+  bin_PROGRAMS += bitcoin-chainstate_c
 endif
 
 .PHONY: FORCE check-symbols check-security
@@ -124,6 +126,7 @@ BITCOIN_CORE_H = \
   base58.h \
   bech32.h \
   bip324.h \
+  bitcoinkernel.h \
   blockencodings.h \
   blockfilter.h \
   chain.h \
@@ -888,6 +891,13 @@ bitcoin_util_LDADD = \
   $(LIBSECP256K1)
 #
 
+# bitcoin-chainstate C binary #
+bitcoin_chainstate_c_SOURCES = bitcoin-chainstate.c
+bitcoin_chainstate_c_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(BOOST_CPPFLAGS)
+bitcoin_chainstate_c_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+bitcoin_chainstate_c_LDFLAGS = $(RELDFLAGS) $(LIBTOOL_APP_LDFLAGS) $(AM_LDFLAGS) $(PTHREAD_FLAGS)
+bitcoin_chainstate_c_LDADD = $(LIBBITCOINKERNEL)
+
 # bitcoin-chainstate binary #
 bitcoin_chainstate_SOURCES = bitcoin-chainstate.cpp
 bitcoin_chainstate_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) $(BOOST_CPPFLAGS)
@@ -904,6 +914,7 @@ bitcoin_chainstate_LDADD += $(LIBSECP256K1)
 # bitcoinkernel library #
 if BUILD_BITCOIN_KERNEL_LIB
 lib_LTLIBRARIES += $(LIBBITCOINKERNEL)
+include_HEADERS += bitcoinkernel.h
 
 libbitcoinkernel_la_LDFLAGS = $(AM_LDFLAGS) -no-undefined $(RELDFLAGS) $(PTHREAD_FLAGS)
 libbitcoinkernel_la_LIBADD = $(LIBBITCOIN_CRYPTO) $(LIBLEVELDB) $(LIBMEMENV) $(LIBSECP256K1)
@@ -945,6 +956,7 @@ libbitcoinkernel_la_SOURCES = \
   kernel/disconnected_transactions.cpp \
   kernel/mempool_persist.cpp \
   kernel/mempool_removal_reason.cpp \
+  bitcoin-chainstate-wrapper.cpp \
   logging.cpp \
   node/blockstorage.cpp \
   node/chainstate.cpp \