From 3311960795ca30bfac4e5a3226909b0a79602bee Mon Sep 17 00:00:00 2001
From: Jef Driesen <jefdriesen@users.sourceforge.net>
Date: Sun, 19 Aug 2012 23:15:46 +0200
Subject: [PATCH] Add a convenience function for logging system errors.

The new convenience function provides a centralized and threadsafe
function for logging system errors. The previous functions are
deprecated and will be removed after the transition to the new context
based logging.
---
 configure.ac          |  1 +
 src/context-private.h |  4 ++++
 src/context.c         | 44 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/configure.ac b/configure.ac
index 78af57b..d08f2d7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -78,6 +78,7 @@ AC_CHECK_HEADERS([linux/serial.h])
 AC_CHECK_HEADERS([IOKit/serial/ioss.h])
 
 # Checks for library functions.
+AC_FUNC_STRERROR_R
 AC_CHECK_FUNCS([localtime_r gmtime_r])
 
 # Versioning.
diff --git a/src/context-private.h b/src/context-private.h
index 677eb09..c32fa1b 100644
--- a/src/context-private.h
+++ b/src/context-private.h
@@ -28,6 +28,7 @@
 extern "C" {
 #endif /* __cplusplus */
 
+#define SYSERROR(context, errcode) dc_context_syserror (context, DC_LOGLEVEL_ERROR, __FILE__, __LINE__, __FUNCTION__, errcode)
 #define ERROR(context, ...) dc_context_log (context, DC_LOGLEVEL_ERROR, __FILE__, __LINE__, __FUNCTION__, __VA_ARGS__)
 #define WARNING(context, ...) dc_context_log (context, DC_LOGLEVEL_WARNING, __FILE__, __LINE__, __FUNCTION__, __VA_ARGS__)
 #define INFO(context, ...) dc_context_log (context, DC_LOGLEVEL_INFO, __FILE__, __LINE__, __FUNCTION__, __VA_ARGS__)
@@ -36,6 +37,9 @@ extern "C" {
 dc_status_t
 dc_context_log (dc_context_t *context, dc_loglevel_t loglevel, const char *file, unsigned int line, const char *function, const char *format, ...);
 
+dc_status_t
+dc_context_syserror (dc_context_t *context, dc_loglevel_t loglevel, const char *file, unsigned int line, const char *function, int errcode);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/src/context.c b/src/context.c
index 2e0c62b..45f6800 100644
--- a/src/context.c
+++ b/src/context.c
@@ -24,6 +24,10 @@
 #include <stdarg.h>
 #include <string.h>
 
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
 #include "context-private.h"
 
 struct dc_context_t {
@@ -117,3 +121,43 @@ dc_context_log (dc_context_t *context, dc_loglevel_t loglevel, const char *file,
 
 	return DC_STATUS_SUCCESS;
 }
+
+dc_status_t
+dc_context_syserror (dc_context_t *context, dc_loglevel_t loglevel, const char *file, unsigned int line, const char *function, int errcode)
+{
+	const char *errmsg = NULL;
+
+#ifdef _WIN32
+	char buffer[256];
+
+	DWORD rc = FormatMessageA (FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+			NULL, errcode, 0, buffer, sizeof (buffer), NULL);
+
+	/* Remove the CRLF and period at the end of the error message. */
+	while (rc > 0 && (
+		buffer[rc - 1] == '\n' ||
+		buffer[rc - 1] == '\r' ||
+		buffer[rc - 1] == '.'))
+	{
+		buffer[rc - 1] = '\0';
+		rc--;
+	}
+
+	if (rc > 0)
+		errmsg = buffer;
+#elif defined (HAVE_STRERROR_R)
+	char buffer[256];
+
+	int rc = strerror_r (errcode, buffer, sizeof (buffer));
+	if (rc == 0)
+		errmsg = buffer;
+#else
+	/* Fallback to the non-threadsafe function. */
+	errmsg = strerror (errcode);
+#endif
+
+	if (errmsg == NULL)
+		errmsg = "Unknown system error";
+
+	return dc_context_log (context, loglevel, file, line, function, "%s (%d)", errmsg, errcode);
+}