trace-cmd: Add tracecmd_get_cursor()

Add the helper routine tracecmd_get_cursor() that returns the offset
of the next tracecmd_read_data() or tracecmd_peek_data().

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 46 insertions, 0 deletions

diff --git a/trace-cmd.h b/trace-cmd.h
index df98fb3..5a2e96b 100644
--- a/trace-cmd.h
+++ b/trace-cmd.h
@@ -90,6 +90,8 @@ tracecmd_set_all_cpus_to_timestamp(struct tracecmd_input *handle,
 
 int tracecmd_set_cursor(struct tracecmd_input *handle,
                         int cpu, unsigned long long offset);
+unsigned long long
+tracecmd_get_cursor(struct tracecmd_input *handle, int cpu);
 
 int tracecmd_ftrace_overrides(struct tracecmd_input *handle);
 struct pevent *tracecmd_get_pevent(struct tracecmd_input *handle);
diff --git a/trace-input.c b/trace-input.c
index 3cf079d..306b7a5 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -1246,6 +1246,50 @@ int tracecmd_set_cursor(struct tracecmd_input *handle,
         return 0;
 }
 
+/**
+ * tracecmd_get_cursor - get the offset for the next tracecmd_read_data
+ * @handle: input handle for the trace.dat file
+ * @cpu: the CPU pointer to get the cursor from
+ *
+ * Returns the offset of the next record that would be read.
+ */
+unsigned long long
+tracecmd_get_cursor(struct tracecmd_input *handle, int cpu)
+{
+        struct cpu_data *cpu_data = &handle->cpu_data[cpu];
+        struct pevent *pevent;
+        int index;
+
+        if (cpu < 0 || cpu >= handle->cpus)
+                return 0;
+
+        /*
+         * Use the next pointer if it exists and matches the
+         * current timestamp.
+         */
+        if (cpu_data->next &&
+            cpu_data->next->ts == cpu_data->timestamp)
+                return cpu_data->next->offset;
+
+        /*
+         * Either the next point does not exist, or it does
+         * not match the timestamp. The next read will use the
+         * current page.
+         *
+         * If the offset is at the end, then return that.
+         */
+        if (cpu_data->offset >= cpu_data->file_offset +
+            cpu_data->file_size)
+                return cpu_data->offset;
+
+        pevent = handle->pevent;
+
+        index = cpu_data->index ? cpu_data->index :
+                pevent->header_page_data_offset;
+
+        return cpu_data->offset + index;
+}
+
 
 static unsigned int
 translate_data(struct tracecmd_input *handle,