[PATCH 2/4] os/log: Add LogVHdrMessageVerb and friends

[Daniel Kurtz]

LogVHdrMessageVerb allows a custom header to be inserted in a log message,
between the Log system's MessageType string, and a formatted variable
message body. The custom header can itself be a formatted variable string.

These functions can be used, for example, by driver abstraction layers to
format specific driver messages in a standard format, but do it in a way
that is efficient, obeys the log-layers verbosity settings, and is safe
to use in signal handlers (because they don't call malloc), even for
types besides X_NONE.

Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>
---
 include/os.h |   13 +++++++++++++
 os/log.c     |   55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 0 deletions(-)

diff --git a/include/os.h b/include/os.h
index 506dc5d..a86c3d4 100644
--- a/include/os.h
+++ b/include/os.h
@@ -518,6 +518,19 @@ extern _X_EXPORT void LogMessageVerb(MessageType type, int verb, const char *for
 			   ...) _X_ATTRIBUTE_PRINTF(3,4);
 extern _X_EXPORT void LogMessage(MessageType type, const char *format, ...)
 			_X_ATTRIBUTE_PRINTF(2,3);
+
+extern _X_EXPORT void LogVHdrMessageVerb(MessageType type, int verb,
+			    const char *msg_format, va_list msg_args,
+			    const char *hdr_format, va_list hdr_args)
+			_X_ATTRIBUTE_PRINTF(3,0) _X_ATTRIBUTE_PRINTF(5,0);
+extern _X_EXPORT void LogHdrMessageVerb(MessageType type, int verb,
+			    const char *msg_format, va_list msg_args,
+			    const char *hdr_format, ...)
+			_X_ATTRIBUTE_PRINTF(3,0) _X_ATTRIBUTE_PRINTF(5,6);
+extern _X_EXPORT void LogHdrMessage(MessageType type, const char *msg_format,
+			    va_list msg_args, const char *hdr_format, ...)
+			_X_ATTRIBUTE_PRINTF(2,0) _X_ATTRIBUTE_PRINTF(4,5);
+
 extern _X_EXPORT void FreeAuditTimer(void);
 extern _X_EXPORT void AuditF(const char *f, ...) _X_ATTRIBUTE_PRINTF(1,2);
 extern _X_EXPORT void VAuditF(const char *f, va_list args) _X_ATTRIBUTE_PRINTF(1,0);
diff --git a/os/log.c b/os/log.c
index 93d4763..41bd33b 100644
--- a/os/log.c
+++ b/os/log.c
@@ -412,6 +412,61 @@ LogMessage(MessageType type, const char *format, ...)
     va_end(ap);
 }
 
+
+void
+LogVHdrMessageVerb(MessageType type, int verb, const char *msg_format,
+		   va_list msg_args, const char *hdr_format, va_list hdr_args)
+{
+    const char *type_str;
+    char tmpFormat[1024];
+    char *tmpFormat_end = &tmpFormat[sizeof(tmpFormat)];
+    char *p = tmpFormat;
+    int left;
+
+    type_str = LogMessageTypeVerbString(type, verb);
+    if (!type_str)
+	return;
+
+    /* if type_str is not "", prepend it, and ' ', to hdr_format */
+    left = tmpFormat_end - p;
+    if (strlen(type_str))
+	p += snprintf(p, left, "%s ", type_str);
+
+    /* append header string to tmpBuf */
+    left = tmpFormat_end - p;
+    if (left > 1)
+	p += vsnprintf(p, left, hdr_format, hdr_args);
+
+    /* if still room in tmpBuf copy as much of msg_format as will fit */
+    left = tmpFormat_end - p;
+    if (left > 1)
+	snprintf(p, left, "%s", msg_format);
+
+    LogVWrite(verb, tmpFormat, msg_args);
+}
+
+void
+LogHdrMessageVerb(MessageType type, int verb, const char *msg_format,
+		  va_list msg_args, const char *hdr_format, ...)
+{
+    va_list hdr_args;
+
+    va_start(hdr_args, hdr_format);
+    LogVHdrMessageVerb(type, verb, msg_format, msg_args, hdr_format, hdr_args);
+    va_end(hdr_args);
+}
+
+void
+LogHdrMessage(MessageType type, const char *msg_format, va_list msg_args,
+	      const char *hdr_format, ...)
+{
+    va_list hdr_args;
+
+    va_start(hdr_args, hdr_format);
+    LogVHdrMessageVerb(type, 1, msg_format, msg_args, hdr_format, hdr_args);
+    va_end(hdr_args);
+}
+
 void
 AbortServer(void) _X_NORETURN;
 
-- 
1.7.3.1