From 797689ae27cb6d35e5911e6f2e9edd2e5201e877 Mon Sep 17 00:00:00 2001
From: Sheldon Lee <sheldon@sheldonlee.com>
Date: Tue, 12 Nov 2024 19:22:55 +0800
Subject: [PATCH] Add exponential backoff to logging

---
 log.c | 56 +++++++++++++++++++++++++++++++++++++++++++++-----------
 log.h |  2 ++
 2 files changed, 47 insertions(+), 11 deletions(-)

diff --git a/log.c b/log.c
index b2781c9..d08218b 100644
--- a/log.c
+++ b/log.c
@@ -1,5 +1,6 @@
 #include "log.h"
 #include <stdio.h>
+#include <string.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include <time.h>
@@ -16,6 +17,10 @@ const char* get_current_time()
 void log_message(LogLevel level, const char* format, ...)
 {
 	const char* level_strings[] = { "INFO", "WARNING", "ERROR" };
+	static char* last_message = NULL;
+	static unsigned int repeat_count = 0;
+	static unsigned int exp_count = 1;
+	char* message = NULL;
 
 	// Open the log file in append mode
 	FILE* log_file = fopen("logfile.txt", "a");
@@ -26,19 +31,48 @@ void log_message(LogLevel level, const char* format, ...)
 
 	va_list args;
 
-	// Write the log message to the file
 	va_start(args, format);
-	fprintf(log_file, "[%s] [%s] ", get_current_time(), level_strings[level]);
-	vfprintf(log_file, format, args);
-	fprintf(log_file, "\n");
-	va_end(args);
-	// Write to stdout
-	va_start(args, format);
-	printf("[%s] ", level_strings[level]);
-	vprintf(format, args);
-	printf("\n");
+	int message_size =  vsnprintf(NULL, 0, format, args) + 1;
 	va_end(args);
 
-	// Close the log file
+	va_start(args, format);
+	message = malloc(message_size);
+	vsnprintf(message, message_size, format, args);
+	va_end(args);
+
+	if (!last_message) goto output;
+	// If current and last messages different
+	if (strcmp(message, last_message)) {
+		repeat_count = 0;
+		exp_count = 1;
+		goto output;
+	}
+	repeat_count++;
+	if (repeat_count < LOG_MAX_REPEAT) goto output;
+
+	unsigned int bit_width = sizeof(exp_count) * 8; // Calculate the number of bits in an int
+	unsigned int leftmost_bit_mask = 1 << (bit_width - 1); // Create a mask with the
+	while (exp_count < repeat_count && exp_count < leftmost_bit_mask) exp_count = exp_count << 1;
+	if (repeat_count != exp_count && repeat_count != LOG_MAX_REPEAT) goto clean;
+
+	fprintf(log_file, "[%s] [%s] %s !! x%u !!\n", get_current_time(), level_strings[level], last_message, repeat_count);
+	printf("[%s] %s !! x%u !!\n", level_strings[level], last_message, repeat_count);
+
+	goto clean;
+output:
+	// Write the log message to the file
+	fprintf(log_file, "[%s] [%s] ", get_current_time(), level_strings[level]);
+	fprintf(log_file, "%s", message);
+	fprintf(log_file, "\n");
+	// Write to stdout
+	printf("[%s] ", level_strings[level]);
+	printf("%s", message);
+	printf("\n");
+	// Record last message
+	if (last_message) free(last_message);
+	last_message = malloc(message_size);
+	strcpy(last_message, message);
+clean:
+	free(message);
 	fclose(log_file);
 }
diff --git a/log.h b/log.h
index 1a312fa..e2d33ab 100644
--- a/log.h
+++ b/log.h
@@ -2,6 +2,8 @@
 #ifndef LOG_H
 #define LOG_H
 
+#define LOG_MAX_REPEAT 5
+
 typedef enum {
 	LOG_INFO,
 	LOG_WARNING,