[PATCH bpf-next 3/6] bpftool: don't print empty key/value for maps

[Stanislav Fomichev]

When doing dump or lookup, don't print key if key_size == 0 or value if
value_size == 0. The initial usecase is queue and stack, where we have
only values.

This is for regular output only, json still has all the fields.

Before:
bpftool map create /sys/fs/bpf/q type queue value 4 entries 10 name q
bpftool map update pinned /sys/fs/bpf/q value 0 1 2 3
bpftool map lookup pinned /sys/fs/bpf/q
key:   value: 00 01 02 03

After:
bpftool map create /sys/fs/bpf/q type queue value 4 entries 10 name q
bpftool map update pinned /sys/fs/bpf/q value 0 1 2 3
bpftool map lookup pinned /sys/fs/bpf/q
value: 00 01 02 03

Signed-off-by: Stanislav Fomichev <s...@google.com>
---
 tools/bpf/bpftool/map.c | 47 ++++++++++++++++++++++++-----------------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 4256842f9664..3f599399913b 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -285,16 +285,21 @@ static void print_entry_plain(struct bpf_map_info *info, 
unsigned char *key,
                single_line = info->key_size + info->value_size <= 24 &&
                        !break_names;
 
-               printf("key:%c", break_names ? '\n' : ' ');
-               fprint_hex(stdout, key, info->key_size, " ");
+               if (info->key_size) {
+                       printf("key:%c", break_names ? '\n' : ' ');
+                       fprint_hex(stdout, key, info->key_size, " ");
 
-               printf(single_line ? "  " : "\n");
+                       printf(single_line ? "  " : "\n");
+               }
 
-               printf("value:%c", break_names ? '\n' : ' ');
-               if (value)
-                       fprint_hex(stdout, value, info->value_size, " ");
-               else
-                       printf("<no entry>");
+               if (info->value_size) {
+                       printf("value:%c", break_names ? '\n' : ' ');
+                       if (value)
+                               fprint_hex(stdout, value, info->value_size,
+                                          " ");
+                       else
+                               printf("<no entry>");
+               }
 
                printf("\n");
        } else {
@@ -303,19 +308,23 @@ static void print_entry_plain(struct bpf_map_info *info, 
unsigned char *key,
                n = get_possible_cpus();
                step = round_up(info->value_size, 8);
 
-               printf("key:\n");
-               fprint_hex(stdout, key, info->key_size, " ");
-               printf("\n");
-               for (i = 0; i < n; i++) {
-                       printf("value (CPU %02d):%c",
-                              i, info->value_size > 16 ? '\n' : ' ');
-                       if (value)
-                               fprint_hex(stdout, value + i * step,
-                                          info->value_size, " ");
-                       else
-                               printf("<no entry>");
+               if (info->key_size) {
+                       printf("key:\n");
+                       fprint_hex(stdout, key, info->key_size, " ");
                        printf("\n");
                }
+               if (info->value_size) {
+                       for (i = 0; i < n; i++) {
+                               printf("value (CPU %02d):%c",
+                                      i, info->value_size > 16 ? '\n' : ' ');
+                               if (value)
+                                       fprint_hex(stdout, value + i * step,
+                                                  info->value_size, " ");
+                               else
+                                       printf("<no entry>");
+                               printf("\n");
+                       }
+               }
        }
 }
 
-- 
2.20.1.97.g81188d93c3-goog