Signed-off-by: Ben Pfaff <b...@nicira.com>
---
lib/meta-flow.c | 16 ++++++++++++----
1 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/lib/meta-flow.c b/lib/meta-flow.c
index a8cfd74..84ba88b 100644
--- a/lib/meta-flow.c
+++ b/lib/meta-flow.c
@@ -2262,19 +2262,27 @@ mf_write_subfield(const struct mf_subfield *sf, const
union mf_subvalue *x,
bitwise_one ( &mask, field->n_bytes, sf->ofs, sf->n_bits);
mf_set(field, &value, &mask, rule);
}
+
+/* Makes subfield 'sf' within 'rule' exactly match the 'sf->n_bits'
+ * least-significant bits of 'x'.
+ *
+ * Example: suppose that 'sf->field' is originally the following 2-byte field
+ * in 'rule':
*
* value == 0xe00a == 2#1110000000001010
* mask == 0xfc3f == 2#1111110000111111
*
- * The call mf_set_subfield(mf, 0x55, 8, 7, rule) would have the following
- * effect (note that 0x55 is 2#1010101):
+ * The call mf_set_subfield(sf, 0x55, 8, 7, rule), where sf->ofs == 8 and
+ * sf->n_bits == 7 would have the following effect (note that 0x55 is
+ * 2#1010101):
*
* value == 0xd50a == 2#1101010100001010
* mask == 0xff3f == 2#1111111100111111
+ * ^^^^^^^ affected bits
*
* The caller is responsible for ensuring that the result will be a valid
- * wildcard pattern for 'mf'. The caller is responsible for ensuring that
- * 'rule' meets 'mf''s prerequisites. */
+ * wildcard pattern for 'sf->field'. The caller is responsible for ensuring
+ * that 'rule' meets 'sf->field''s prerequisites. */
void
mf_set_subfield(const struct mf_subfield *sf, uint64_t x,
struct cls_rule *rule)
--
1.7.2.5
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