Keep the file handle open for future write operations for extra perfo…

…rmance

README.md

@@ -73,11 +73,11 @@ slog_enable(SLOG_TRACE);
 slog_disable(SLOG_FLAGS_ALL);
 ```
 
-Deinitialization needed only if the thread safety flag is greater than zero (nTdSafe > 0) while initialization.
+Deinitialization needed only if the `nTdSafe` and/or `nKeepOpen` flags are greater than zero while initialization.
 ```c
 slog_destroy();
 ```
-Function destroys the mutex context and resets thread safety flag to zero.
+Function destroys the mutex context, closes output file and resets thread safety flag to zero.
 
 
 ### Print and log something in the file
@@ -177,6 +177,7 @@ logCallback  | slog_cb_t         | NULL              | Log callback function to
 pCallbackCtx | void*             | NULL              | User data pointer passed to log callback.
 eColorFormat | slog_coloring_t   | SLOG_COLORING_TAG | Output coloring format control.
 eDateControl | slog_date_ctrl_t  | SLOG_TIME_ONLY    | Time and date control in log output.
+nKeepOpen    | uint8_t           | 0 (disabled)      | Keep the file handle open for future writes.
 nTraceTid    | uint8_t           | 0 (disabled)      | Trace thread ID and display in output.
 nToScreen    | uint8_t           | 1 (enabled)       | Enable or disable screen logging.
 nNewLine     | uint8_t           | 1 (enabled)       | Enable or disable new line ending.
@@ -197,6 +198,7 @@ slgCfg.eColorFormat = SLOG_COLORING_TAG;
 slgCfg.eDateControl = SLOG_TIME_ONLY;
 strcpy(slgCfg.sFileName, "myproject");
 strcpy(slgCfg.sFilePath, "./logs/");
+slgCfg.nKeepOpen = 1;
 slgCfg.nTraceTid = 1;
 slgCfg.nToScreen = 1;
 slgCfg.nNewLine = 1;

example/example.c

@@ -45,7 +45,7 @@ int main()
     greet();
 
     /* Initialize slog and allow only error and not tagged output */
-    slog_init("example", nLogFlags, 0);
+    slog_init("example", SLOG_FLAGS_ALL, 0);
     slog_config_get(&cfg);
 
     /* Disable time and date in output */
@@ -100,6 +100,7 @@ int main()
     /* Enable file logger and color the whole log output instead of coloring only tags*/
     cfg.eColorFormat = SLOG_COLORING_FULL;
     cfg.nToFile = 1;
+    cfg.nKeepOpen = 1;
     slog_config_set(&cfg);
 
     /* Print message and save log in the file */
@@ -131,5 +132,6 @@ int main()
     slog_trace();
     slog_debug("Above we traced source location without output message");
 
+    slog_destroy();
     return 0;
 }

src/slog.c

@@ -51,9 +51,11 @@
 #endif
 
 typedef struct slog {
-    unsigned int nTdSafe:1;
     pthread_mutex_t mutex;
     slog_config_t config;
+    uint8_t nStartDay;
+    uint8_t nTdSafe;
+    FILE *pLogFile;
 } slog_t;
 
 typedef struct XLogCtx {
@@ -161,6 +163,35 @@ static const char* slog_get_color(slog_flag_t eFlag)
     return SLOG_EMPTY;
 }
 
+static void slog_close_file()
+{
+    if (g_slog.pLogFile != NULL)
+    {
+        fclose(g_slog.pLogFile);
+        g_slog.pLogFile = NULL;
+    }
+}
+
+static uint8_t slog_open_file(const slog_config_t *pCfg, const slog_date_t *pDate)
+{
+    slog_close_file();
+
+    char sFilePath[SLOG_PATH_MAX + SLOG_NAME_MAX + SLOG_DATE_MAX];
+    snprintf(sFilePath, sizeof(sFilePath), "%s/%s-%04d-%02d-%02d.log",
+        pCfg->sFilePath, pCfg->sFileName, pDate->nYear, pDate->nMonth, pDate->nDay);
+
+    g_slog.pLogFile = fopen(sFilePath, "a");
+    if (g_slog.pLogFile == NULL)
+    {
+        printf("<%s:%d> %s: [ERROR] Failed to open file: %s (%s)\n",
+            __FILE__, __LINE__, __func__, sFilePath, strerror(errno));
+
+        return 0;
+    }
+
+    return 1;
+}
+
 uint16_t slog_get_usec()
 {
     struct timeval tv;
@@ -236,10 +267,18 @@ static void slog_display_message(const slog_context_t *pCtx, const char *pInfo,
         size_t nLength = 0;
         char *pLog = NULL;
 
-        nLength += asprintf(&pLog, "%s%s%s%s%s", pInfo, pSeparator, pMessage, pReset, pNewLine);
+        nLength += asprintf(&pLog, "%s%s%s%s%s", pInfo,
+            pSeparator, pMessage, pReset, pNewLine);
+
         if (pLog != NULL)
         {
-            nCbVal = pCfg->logCallback(pLog, nLength, pCtx->eFlag, pCfg->pCallbackCtx);
+            nCbVal = pCfg->logCallback (
+                pLog,
+                nLength,
+                pCtx->eFlag,
+                pCfg->pCallbackCtx
+            );
+
             free(pLog);
         }
     }
@@ -253,15 +292,15 @@ static void slog_display_message(const slog_context_t *pCtx, const char *pInfo,
     if (!pCfg->nToFile || nCbVal < 0) return;
     const slog_date_t *pDate = &pCtx->date;
 
-    char sFilePath[SLOG_PATH_MAX + SLOG_NAME_MAX + SLOG_DATE_MAX];
-    snprintf(sFilePath, sizeof(sFilePath), "%s/%s-%04d-%02d-%02d.log", 
-        pCfg->sFilePath, pCfg->sFileName, pDate->nYear, pDate->nMonth, pDate->nDay);
+    if ((g_slog.pLogFile == NULL ||
+         g_slog.nStartDay != pDate->nDay) &&
+         !slog_open_file(pCfg, pDate)) return;
 
-    FILE *pFile = fopen(sFilePath, "a");
-    if (pFile == NULL) return;
+    fprintf(g_slog.pLogFile, "%s%s%s%s%s", pInfo,
+        pSeparator, pMessage, pReset, pNewLine);
 
-    fprintf(pFile, "%s%s%s%s%s", pInfo, pSeparator, pMessage, pReset, pNewLine);
-    fclose(pFile);
+    if (pCfg->nFlush) fflush(g_slog.pLogFile);
+    if (!pCfg->nKeepOpen) slog_close_file();
 }
 
 static int slog_create_info(const slog_context_t *pCtx, char* pOut, size_t nSize)
@@ -275,7 +314,7 @@ static int slog_create_info(const slog_context_t *pCtx, char* pOut, size_t nSize
     if (pCfg->eDateControl == SLOG_TIME_ONLY)
     {
         snprintf(sDate, sizeof(sDate), "%02d:%02d:%02d.%03d ",
-            pDate->nHour,pDate->nMin, pDate->nSec, pDate->nUsec);
+            pDate->nHour, pDate->nMin, pDate->nSec, pDate->nUsec);
     }
     else if (pCfg->eDateControl == SLOG_DATE_FULL)
     {
@@ -378,6 +417,15 @@ void slog_config_get(slog_config_t *pCfg)
 void slog_config_set(slog_config_t *pCfg)
 {
     slog_lock(&g_slog);
+    slog_config_t *pOldCfg = &g_slog.config;
+
+    if (strncmp(pOldCfg->sFilePath, pCfg->sFilePath, sizeof(pOldCfg->sFilePath)) ||
+        strncmp(pOldCfg->sFileName, pCfg->sFileName, sizeof(pOldCfg->sFileName)))
+    {
+        /* Log function will open it again */
+        slog_close_file();
+    }
+
     g_slog.config = *pCfg;
     slog_unlock(&g_slog);
 }
@@ -458,6 +506,7 @@ void slog_init(const char* pName, uint16_t nFlags, uint8_t nTdSafe)
     pCfg->sSeparator[1] = '\0';
     pCfg->sFilePath[0] = '.';
     pCfg->sFilePath[1] = '\0';
+    pCfg->nKeepOpen = 0;
     pCfg->nTraceTid = 0;
     pCfg->nToScreen = 1;
     pCfg->nNewLine = 1;
@@ -470,6 +519,9 @@ void slog_init(const char* pName, uint16_t nFlags, uint8_t nTdSafe)
     const char *pFileName = (pName != NULL) ? pName : SLOG_NAME_DEFAULT;
     snprintf(pCfg->sFileName, sizeof(pCfg->sFileName), "%s", pFileName);
 
+    g_slog.pLogFile = NULL;
+    g_slog.nStartDay = 0;
+
 #ifdef WIN32
     /* Enable color support */
     HANDLE hOutput = GetStdHandle(STD_OUTPUT_HANDLE);
@@ -487,9 +539,12 @@ void slog_init(const char* pName, uint16_t nFlags, uint8_t nTdSafe)
 void slog_destroy()
 {
     slog_lock(&g_slog);
+
     memset(&g_slog.config, 0, sizeof(g_slog.config));
     g_slog.config.pCallbackCtx = NULL;
     g_slog.config.logCallback = NULL;
+    slog_close_file();
+
     slog_unlock(&g_slog);
 
     if (g_slog.nTdSafe)

src/slog.h

@@ -36,7 +36,7 @@ extern "C" {
 /* SLog version information */
 #define SLOG_VERSION_MAJOR      1
 #define SLOG_VERSION_MINOR      8
-#define SLOG_BUILD_NUM          31
+#define SLOG_BUILD_NUM          32
 
 /* Supported colors */
 #define SLOG_COLOR_NORMAL       "\x1B[0m"
@@ -156,14 +156,15 @@ typedef struct SLogConfig {
     slog_cb_t logCallback;              // Log callback to collect logs
     void* pCallbackCtx;                 // Data pointer passed to log callback
 
-    uint8_t nTraceTid;                // Trace thread ID and display in output
-    uint8_t nToScreen;                // Enable screen logging
-    uint8_t nNewLine;                 // Enable new line ending
-    uint8_t nUseHeap;                 // Use dynamic allocation
-    uint8_t nToFile;                  // Enable file logging
-    uint8_t nIndent;                  // Enable indentations
-    uint8_t nFlush;                   // Flush stdout after screen log
-    uint16_t nFlags;                  // Allowed log level flags
+    uint8_t nKeepOpen;                  // Keep file handle open for next file writes
+    uint8_t nTraceTid;                  // Trace thread ID and display in output
+    uint8_t nToScreen;                  // Enable screen logging
+    uint8_t nNewLine;                   // Enable new line ending
+    uint8_t nUseHeap;                   // Use dynamic allocation
+    uint8_t nToFile;                    // Enable file logging
+    uint8_t nIndent;                    // Enable indentations
+    uint8_t nFlush;                     // Flush stdout after screen log
+    uint16_t nFlags;                    // Allowed log level flags
 
     char sSeparator[SLOG_NAME_MAX];     // Separator between info and log
     char sFileName[SLOG_NAME_MAX];      // Output file name for logs
@@ -184,7 +185,7 @@ void slog_disable(slog_flag_t eFlag);
 
 void slog_init(const char* pName, uint16_t nFlags, uint8_t nTdSafe);
 void slog_display(slog_flag_t eFlag, const char *pFormat, ...);
-void slog_destroy(); // Required only if the slog_init() called with nTdSafe > 0
+void slog_destroy(); // Required only if (nTdSafe > 0 || nKeepOpen > 0)
 
 #ifdef __cplusplus
 }