last-records response handler implemented

2 files changed, 30 insertions, 15 deletions

diff --git a/stm32f091/backlog.c b/stm32f091/backlog.c
index 3f21924..926ccad 100644
--- a/stm32f091/backlog.c
+++ b/stm32f091/backlog.c
@@ -2,33 +2,46 @@
 
 #include "backlog.h"
 
-ws_s_backlog_database* WS_G_BACKLOG_DATABASE = NULL;
+ws_s_backlog_database* g_ws_backlog_database = NULL;
 
 void ws_backlog_alloc(uint16_t record_amt) {
-	WS_G_BACKLOG_DATABASE = malloc(sizeof(ws_s_backlog_database) + sizeof(ws_s_backlog_record) * record_amt);
-	WS_G_BACKLOG_DATABASE->buffer_size = record_amt;
-	WS_G_BACKLOG_DATABASE->buffer_start = 0;
-	WS_G_BACKLOG_DATABASE->buffer_end = 0;
+	g_ws_backlog_database = malloc(sizeof(ws_s_backlog_database) + sizeof(ws_s_backlog_record) * record_amt);
+	g_ws_backlog_database->buffer_size = record_amt;
+	g_ws_backlog_database->buffer_start = 0;
+	g_ws_backlog_database->buffer_end = 0;
 }
 
 void ws_backlog_add_record(ws_s_backlog_record record) {
 	static uint16_t id = 0;
 
-	WS_G_BACKLOG_DATABASE->records[WS_G_BACKLOG_DATABASE->buffer_end].id = id++;
-	WS_G_BACKLOG_DATABASE->records[WS_G_BACKLOG_DATABASE->buffer_end].sens_atm_pressure = record.sens_atm_pressure;
-	WS_G_BACKLOG_DATABASE->records[WS_G_BACKLOG_DATABASE->buffer_end].sens_humidity = record.sens_humidity;
-	WS_G_BACKLOG_DATABASE->records[WS_G_BACKLOG_DATABASE->buffer_end].sens_temperature = record.sens_temperature;
+	g_ws_backlog_database->records[g_ws_backlog_database->buffer_end].id = id++;
+	g_ws_backlog_database->records[g_ws_backlog_database->buffer_end].sens_atm_pressure = record.sens_atm_pressure;
+	g_ws_backlog_database->records[g_ws_backlog_database->buffer_end].sens_humidity = record.sens_humidity;
+	g_ws_backlog_database->records[g_ws_backlog_database->buffer_end].sens_temperature = record.sens_temperature;
 
 	// shift buffer start/end
-	WS_G_BACKLOG_DATABASE->buffer_end = (WS_G_BACKLOG_DATABASE->buffer_end + 1) % WS_G_BACKLOG_DATABASE->buffer_size;
-	if (WS_G_BACKLOG_DATABASE->buffer_end == WS_G_BACKLOG_DATABASE->buffer_start)
-		WS_G_BACKLOG_DATABASE->buffer_start = (WS_G_BACKLOG_DATABASE->buffer_start + 1) % WS_G_BACKLOG_DATABASE->buffer_size;
+	g_ws_backlog_database->buffer_end = (g_ws_backlog_database->buffer_end + 1) % g_ws_backlog_database->buffer_size;
+	if (g_ws_backlog_database->buffer_end == g_ws_backlog_database->buffer_start)
+		g_ws_backlog_database->buffer_start = (g_ws_backlog_database->buffer_start + 1) % g_ws_backlog_database->buffer_size;
 }
 
 ws_s_backlog_record* ws_backlog_get_record(uint16_t record_index) {
-	return &WS_G_BACKLOG_DATABASE->records[record_index];
+	return &g_ws_backlog_database->records[record_index];
 }
 
 ws_s_backlog_record* ws_backlog_get_last_record(uint16_t record_offset) {
-	return ws_backlog_get_record((WS_G_BACKLOG_DATABASE->buffer_end - record_offset - 1) % WS_G_BACKLOG_DATABASE->buffer_size);
+	return ws_backlog_get_record((g_ws_backlog_database->buffer_end - record_offset - 1) % g_ws_backlog_database->buffer_size);
+}
+
+static uint16_t mod(uint16_t a, uint16_t b) {
+	uint16_t m = a % b;
+	return m < 0 ? (b < 0) ? m - b : m + b : m;
+}
+
+uint16_t ws_backlog_get_record_count() {
+	// add buffer_size to the result of the modulo operation if it's result is negative
+	// (only works when buffer_size is less than 2^15)
+	// this is a consequence of the way in which c handles negative numbers in modulo operations
+	int16_t mod = (g_ws_backlog_database->buffer_end - g_ws_backlog_database->buffer_start) % g_ws_backlog_database->buffer_size;
+	return mod < 0 ? mod + g_ws_backlog_database->buffer_size : mod;
 }
diff --git a/stm32f091/backlog.h b/stm32f091/backlog.h
index 465b3c0..c8ea019 100644
--- a/stm32f091/backlog.h
+++ b/stm32f091/backlog.h
@@ -30,7 +30,7 @@ typedef struct {
 #pragma pack(pop)
 
 /** @brief global record backlog database pointer */
-extern ws_s_backlog_database* WS_G_BACKLOG_DATABASE;
+extern ws_s_backlog_database* g_ws_backlog_database;
 
 /**
  * @brief add record to database
@@ -55,3 +55,5 @@ ws_s_backlog_record* ws_backlog_get_record(uint16_t record_index);
 /** @brief get pointer to last record with offset `record_offset` from the database */
 ws_s_backlog_record* ws_backlog_get_last_record(uint16_t record_offset);
 
+/** @brief return amount of valid records in database */
+uint16_t ws_backlog_get_record_count();