add session id generator

src/id_generator/id_generator.cpp

@@ -0,0 +1,80 @@
+#include <string.h>
+
+#include "id_generator.h"
+#include "stellar.h"
+#include "timestamp.h"
+
+struct id_generator
+{
+    uint8_t device_base;   // 5bit  [0, 31]
+    uint8_t device_offset; // 7bit  [0, 127]
+    uint64_t device_id;    // 12bit [0, 4095] ( base << 7 | offset )
+    uint64_t thread_volatile[MAX_THREAD_NUM];
+};
+
+struct id_generator global_id_generator;
+
+/*
+ * device_base   (5bit)  : [0, 31]
+ * device_offset (7bit)  : [0, 127]
+ * device_id     (12bit) : (base << 7 | offset)
+ *
+ * return  0: success
+ * return -1: failed
+ */
+int id_generator_init(uint8_t device_base, uint8_t device_offset)
+{
+    memset(&global_id_generator, 0, sizeof(struct id_generator));
+
+    if (device_base > 31)
+    {
+        ID_GENERATOR_LOG_ERROR("device_base %u is invalid, range [0, 31]", device_base);
+        return -1;
+    }
+
+    if (device_offset > 127)
+    {
+        ID_GENERATOR_LOG_ERROR("device_offset %u is invalid, range [0, 127]", device_offset);
+        return -1;
+    }
+
+    global_id_generator.device_base = device_base;
+    global_id_generator.device_offset = device_offset;
+    global_id_generator.device_id = ((global_id_generator.device_base << 7) | global_id_generator.device_offset) & 0xFFF;
+
+    ID_GENERATOR_LOG_DEBUG("device_base: %u, device_offset: %u, device_id: %u",
+                           global_id_generator.device_base,
+                           global_id_generator.device_offset,
+                           global_id_generator.device_id);
+    return 0;
+}
+
+void id_generator_free()
+{
+    memset(&global_id_generator, 0, sizeof(struct id_generator));
+}
+
+/*
+ * 高位 --- 低位
+ *
+ * +------+------------------+----------------+------------------------+---------------------------+
+ * | 1bit |  12bit device_id | 8bit thread_id | 28bit timestamp in sec | 15bit sequence per thread |
+ * +------+------------------+----------------+------------------------+---------------------------+
+ */
+uint64_t id_generator_get()
+{
+#define MAX_ID_PER_THREAD (32768)
+#define MAX_ID_BASE_TIME (268435456L)
+
+    uint64_t global_id = 0;
+    uint64_t thread_index = stellar_get_current_thread_index();
+
+    uint64_t id_per_thread = (global_id_generator.thread_volatile[thread_index]++) % MAX_ID_PER_THREAD;
+    uint64_t id_base_time = timestamp_get_sec() % MAX_ID_BASE_TIME;
+    global_id = (global_id_generator.device_id << 51) |
+                (thread_index << 43) |
+                (id_base_time << 15) |
+                (id_per_thread);
+
+    return global_id;
+}