1 files changed, 105 insertions, 0 deletions
diff --git a/core/sql.c b/core/sql.c
new file mode 100644
index 0000000..59fc38e
--- /dev/null
+++ b/core/sql.c
@@ -0,0 +1,105 @@
+// file    : core/sql.c
+// project : Salis-VM
+// author  : Paul Oliver <contact@pauloliver.dev>
+
+// index:
+// [section] includes
+// [section] macros
+// [section] globals
+// [section] definitions
+
+// ----------------------------------------------------------------------------
+// [section] includes
+// ----------------------------------------------------------------------------
+#include <assert.h>
+#include <sqlite3.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "logger.h"
+#include "sql.h"
+
+// ----------------------------------------------------------------------------
+// [section] macros
+// ----------------------------------------------------------------------------
+#define DATA_PUSH_BUSY_TIMEOUT 600000
+
+// ----------------------------------------------------------------------------
+// [section] globals
+// ----------------------------------------------------------------------------
+sqlite3 *g_sim_db;
+
+// ----------------------------------------------------------------------------
+// [section] definitions
+// ----------------------------------------------------------------------------
+void sql_open(void) {
+    sqlite3_open(DATA_PUSH_PATH, &g_sim_db);
+    assert(g_sim_db);
+
+    // Install busy handler to retry transactions if DB is locked
+    sqlite3_busy_timeout(g_sim_db, DATA_PUSH_BUSY_TIMEOUT);
+
+    // Enable Write-Ahead Logging (WAL)
+    // This seems to help prevent DB locks when displaying live data.
+    // See: https://sqlite.org/wal.html
+    sql_exec(NULL, NULL, "pragma journal_mode=wal;");
+}
+
+void sql_close(void) {
+    assert(g_sim_db);
+    sqlite3_close(g_sim_db);
+}
+
+void sql_exec(void (*callback)(sqlite3_stmt *sql_stmt, void *data), void *data, const char *sql_format, ...) {
+    assert(sql_format);
+
+    va_list args;
+    va_start(args, sql_format);
+    int sql_len = vsnprintf(NULL, 0, sql_format, args) + 1;
+    char *sql_str = malloc(sql_len);
+    assert(sql_str);
+    va_end(args);
+
+    va_start(args, sql_format);
+    vsprintf(sql_str, sql_format, args);
+    va_end(args);
+
+    int sql_res;
+    sqlite3_stmt *sql_stmt;
+
+    sql_res = sqlite3_prepare_v2(g_sim_db, sql_str, -1, &sql_stmt, NULL);
+    assert(sql_res == SQLITE_OK);
+    free(sql_str);
+
+    while (true) {
+        sql_res = sqlite3_step(sql_stmt);
+
+        if (sql_res == SQLITE_ROW) {
+            if (callback) {
+                callback(sql_stmt, data);
+            }
+
+            continue;
+        }
+
+        if (sql_res == SQLITE_DONE) {
+            break;
+        }
+
+        log_attention("SQLite database returned error %d with message:", sql_res);
+        log_attention(sqlite3_errmsg(g_sim_db));
+
+        // Only handle SQLITE_BUSY error, in which case we retry the query.
+        // Setting 'journal_mode=wal;' should help prevent busy database errors.
+        if (sql_res == SQLITE_BUSY) {
+            log_info("Will retry query");
+            continue;
+        }
+
+        assert(false);
+    }
+
+    sqlite3_finalize(sql_stmt);
+}