keep track of buffer full

The trace_seq buffer might fill up, and right now
one needs to check the return value of each printf
into the buffer to check for that.

Instead, have the buffer keep track of whether it
is full or not, and reject more input if it is full
or would have overflowed with an input that wasn't
added.

Also simplify the buffer output function and have
it print [truncated] when that is the case.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

2 files changed, 24 insertions, 24 deletions

diff --git a/parse-events.h b/parse-events.h
index c0dbc60..9c6d89f 100644
--- a/parse-events.h
+++ b/parse-events.h
@@ -23,6 +23,7 @@ struct trace_seq {
         char                    buffer[TRACE_SEQ_SIZE];
         unsigned int            len;
         unsigned int            readpos;
+        int                     full;
 };
 
 static inline void
@@ -30,6 +31,7 @@ trace_seq_init(struct trace_seq *s)
 {
         s->len = 0;
         s->readpos = 0;
+        s->full = 0;
 }
 
 extern int trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
diff --git a/trace-seq.c b/trace-seq.c
index 3e3e059..3143bbb 100644
--- a/trace-seq.c
+++ b/trace-seq.c
@@ -32,7 +32,7 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
         va_list ap;
         int ret;
 
-        if (!len)
+        if (s->full || !len)
                 return 0;
 
         va_start(ap, fmt);
@@ -40,8 +40,10 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
         va_end(ap);
 
         /* If we can't write it all, don't bother writing anything */
-        if (ret >= len)
+        if (ret >= len) {
+                s->full = 1;
                 return 0;
+        }
 
         s->len += ret;
 
@@ -65,14 +67,16 @@ trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
         int len = (TRACE_SEQ_SIZE - 1) - s->len;
         int ret;
 
-        if (!len)
+        if (s->full || !len)
                 return 0;
 
         ret = vsnprintf(s->buffer + s->len, len, fmt, args);
 
         /* If we can't write it all, don't bother writing anything */
-        if (ret >= len)
+        if (ret >= len) {
+                s->full = 1;
                 return 0;
+        }
 
         s->len += ret;
 
@@ -93,8 +97,13 @@ int trace_seq_puts(struct trace_seq *s, const char *str)
 {
         int len = strlen(str);
 
-        if (len > ((TRACE_SEQ_SIZE - 1) - s->len))
+        if (s->full)
+                return 0;
+
+        if (len > ((TRACE_SEQ_SIZE - 1) - s->len)) {
+                s->full = 1;
                 return 0;
+        }
 
         memcpy(s->buffer + s->len, str, len);
         s->len += len;
@@ -104,8 +113,13 @@ int trace_seq_puts(struct trace_seq *s, const char *str)
 
 int trace_seq_putc(struct trace_seq *s, unsigned char c)
 {
-        if (s->len >= (TRACE_SEQ_SIZE - 1))
+        if (s->full)
+                return 0;
+
+        if (s->len >= (TRACE_SEQ_SIZE - 1)) {
+                s->full = 1;
                 return 0;
+        }
 
         s->buffer[s->len++] = c;
 
@@ -114,22 +128,6 @@ int trace_seq_putc(struct trace_seq *s, unsigned char c)
 
 int trace_seq_do_printf(struct trace_seq *s)
 {
-        char *buf;
-        int ret;
-
-        if (!s->len)
-                return 0;
-
-        if (s->len < TRACE_SEQ_SIZE) {
-                s->buffer[s->len] = 0;
-                return printf("%s", s->buffer);
-        }
-
-        buf = malloc_or_die(s->len + 1);
-        memcpy(buf, s->buffer, s->len);
-        buf[s->len] = 0;
-        ret = printf("%s", buf);
-        free(buf);
-
-        return ret;
+        return printf("%.*s%s", s->len, s->buffer,
+                        s->full ? "[truncated]" : "");
 }