aldb: the SQLite layer for settings, and later the caches

doc/ARCHITECTURE.md

@@ -5,6 +5,7 @@
 - **llmath** - Math primitives: vectors, matrices, quaternions, bounding boxes. Also includes meshoptimizer
 
 **Data/IO layer:**
+- **aldb** - SQLite files (`ALDatabase`): each file's writes are jobs a thread of its own commits together, each in a savepoint, so a job that fails is dropped alone and a failure that may pass is tried again; a profile by what losing the last writes would cost (Durable, Journal, Regenerable), tables made by migrations on `user_version`, a check after a crash that moves a damaged file aside and salvages it, and reads on a pool of read-only connections. `ALDbConnection` caches statements and reads a file from someone else with SQLite's defensive settings and limits. Depends on llcommon
 - **llfilesystem** - Virtual filesystem and asset cache
 - **llxml** - XML parsing utilities (depends on llfilesystem)
 - **llimage** - Image decoding/encoding (JPEG, PNG, TGA, J2C via OpenJPEG or KDU)

indra/CMakeLists.txt

@@ -571,6 +571,7 @@ if(AL_BUILD_TESTS)
     message(FATAL_ERROR "AL_REQUIRE_LSCRIPT: LL's LSL compiler and its tests are ${lscript_status}")
   endif()
 endif()
+add_subdirectory(aldb)
 add_subdirectory(alrender)
 add_subdirectory(llaudio)
 add_subdirectory(llappearance)

indra/aldb/CMakeLists.txt

@@ -0,0 +1,35 @@
+# -*- cmake -*-
+
+# SQLite database files, for what the viewer keeps: settings first, then the
+# cache's index and the chat logs. One writer thread a file, whose jobs are
+# written in batches, each in a savepoint of its own; a pool of readers;
+# migrations, with a copy kept before each; backups; and a damaged file moved
+# aside and salvaged with SQLite's recover API.
+
+set(aldb_SOURCES aldatabase.cpp aldbconnection.cpp aldbrecovery.cpp aldbwriter.cpp)
+
+set(aldb_HEADERS aldatabase.h aldbconnection.h aldbrecovery.h aldbwriter.h)
+
+add_library(aldb STATIC)
+target_sources(aldb PRIVATE ${aldb_SOURCES} PUBLIC FILE_SET HEADERS FILES ${aldb_HEADERS})
+
+target_link_libraries(aldb PRIVATE al::flags PUBLIC llcommon ll::sqlite3)
+
+target_precompile_headers(aldb REUSE_FROM llprecompiled)
+
+if(AL_BUILD_TESTS)
+  # A VFS over the platform's that fails or holds writes, or offers no shared
+  # memory, on request: for the tests of what the writer does when the disk
+  # does.
+  add_library(aldb_test_support OBJECT tests/aldbfaultvfs.cpp)
+  target_link_libraries(aldb_test_support PRIVATE al::flags al_test_support aldb)
+  set_target_properties(aldb_test_support PROPERTIES FOLDER "Tests/aldb")
+
+  al_add_test_binary(
+    aldb_tests
+    PROJECT aldb
+    SOURCES tests/aldatabase_test.cpp tests/aldbconnection_test.cpp tests/aldbrecovery_test.cpp
+    LIBRARIES aldb
+    SUPPORT aldb_test_support llcommon_test_checks
+  )
+endif()