Add tracecmd_read_cpu_first() and last()

Add a interface to get the first and last item per CPU.

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

3 files changed, 92 insertions, 0 deletions

diff --git a/trace-cmd.h b/trace-cmd.h
index 9fbd475..e67cdef 100644
--- a/trace-cmd.h
+++ b/trace-cmd.h
@@ -75,6 +75,10 @@ tracecmd_read_at(struct tracecmd_input *handle, unsigned long long offset,
 struct record *
 tracecmd_translate_data(struct tracecmd_input *handle,
                         void *ptr, int size);
+struct record *
+tracecmd_read_cpu_first(struct tracecmd_input *handle, int cpu);
+struct record *
+tracecmd_read_cpu_last(struct tracecmd_input *handle, int cpu);
 
 int tracecmd_set_cpu_to_timestamp(struct tracecmd_input *handle,
                                   int cpu, unsigned long long ts);
diff --git a/trace-input.c b/trace-input.c
index 7051709..3747680 100644
--- a/trace-input.c
+++ b/trace-input.c
@@ -585,6 +585,14 @@ static int get_page(struct tracecmd_input *handle, int cpu,
                 return -1;
         }
 
+        if (offset < handle->cpu_data[cpu].file_offset ||
+            offset > handle->cpu_data[cpu].file_offset +
+            handle->cpu_data[cpu].file_size) {
+                errno = -EINVAL;
+                die("bad page offset %llx", offset);
+                return -1;
+        }
+
         handle->cpu_data[cpu].offset = offset;
         handle->cpu_data[cpu].size = (handle->cpu_data[cpu].file_offset +
                                       handle->cpu_data[cpu].file_size) -
@@ -796,6 +804,39 @@ tracecmd_read_at(struct tracecmd_input *handle, unsigned long long offset,
                 return find_and_read_event(handle, offset, pcpu);
 }
 
+struct record *
+tracecmd_read_cpu_first(struct tracecmd_input *handle, int cpu)
+{
+        get_page(handle, cpu, handle->cpu_data[cpu].file_offset);
+
+        return tracecmd_read_data(handle, cpu);
+}
+
+struct record *
+tracecmd_read_cpu_last(struct tracecmd_input *handle, int cpu)
+{
+        struct record *record;
+        off64_t offset;
+
+        offset = handle->cpu_data[cpu].file_offset +
+                handle->cpu_data[cpu].file_size;
+
+        if (offset & (handle->page_size - 1))
+                offset &= ~(handle->page_size - 1);
+        else
+                offset -= handle->page_size;
+
+        get_page(handle, cpu, offset);
+
+        do {
+                record = tracecmd_read_data(handle, cpu);
+                if (record)
+                        offset = record->offset;
+        } while (record);
+
+        return tracecmd_read_at(handle, offset, NULL);
+}
+
 int
 tracecmd_set_cpu_to_timestamp(struct tracecmd_input *handle, int cpu,
                               unsigned long long ts)
diff --git a/trace-read.c b/trace-read.c
index 48c9510..492aab1 100644
--- a/trace-read.c
+++ b/trace-read.c
@@ -133,6 +133,53 @@ static void test_save(struct record *record, int cpu)
 }
 #endif /* TEST_AT_TIMESTAMP */
 
+#define TEST_FIRST_LAST 1
+#if TEST_FIRST_LAST
+#define DO_TEST
+static void show_test(struct tracecmd_input *handle)
+{
+        struct pevent *pevent;
+        struct record *record;
+        struct trace_seq s;
+        int cpu = 0;
+
+        pevent = tracecmd_get_pevent(handle);
+
+        record = tracecmd_read_cpu_first(handle, cpu);
+        if (!record) {
+                printf("No first record?\n");
+                return;
+        }
+
+        printf("\nHERE'S THE FIRST RECORD with offset %p\n",
+               (void *)record->offset);
+        trace_seq_init(&s);
+        pevent_print_event(pevent, &s, cpu, record->data, record->size, record->ts);
+        trace_seq_do_printf(&s);
+        printf("\n");
+
+        free(record);
+
+        record = tracecmd_read_cpu_last(handle, cpu);
+        if (!record) {
+                printf("No last record?\n");
+                return;
+        }
+
+        printf("\nHERE'S THE LAST RECORD with offset %p\n",
+               (void *)record->offset);
+        trace_seq_init(&s);
+        pevent_print_event(pevent, &s, cpu, record->data, record->size, record->ts);
+        trace_seq_do_printf(&s);
+        printf("\n");
+
+        free(record);
+}
+static void test_save(struct record *record, int cpu)
+{
+}
+#endif /* TEST_FIRST_LAST */
+
 #ifndef DO_TEST
 static void show_test(struct tracecmd_input *handle)
 {