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Re: Wmem has reached feature-parity with emem
From: Evan Huus <eapache () gmail com>
Date: Wed, 19 Jun 2013 11:52:34 -0700

On Wed, Jun 19, 2013 at 8:30 AM, Michal Labedzki
<michal.labedzki () tieto com> wrote:
Hi,
One more thing. What do you think about new API... In Bluetooth dissectors
there is a lot of code like this (little simplified):

        k_interface_id = interface_id;
        k_adapter_id   = adapter_id;
        k_chandle      = chandle;
        k_cid          = cid;
        k_frame_number = pinfo->fd->num;

        key[0].length = 1;
        key[0].key    = &k_interface_id;
        key[1].length = 1;
        key[1].key    = &k_adapter_id;
        key[2].length = 1;
        key[2].key    = &k_chandle;
        key[3].length = 1;
        key[3].key    = &k_cid;
        key[4].length = 1;
        key[4].key    = &k_frame_number;
        key[5].length = 0;
        key[5].key    = NULL;

        psm_data = (psm_data_t *)
wmem_tree_lookup32_array_le(cid_to_psm_table, key);
        if (!(psm_data && psm_data->interface_id == interface_id &&
                psm_data->adapter_id == adapter_id &&
                psm_data->chandle == chandle &&
                psm_data->scid == (scid | ((pinfo->p2p_dir == P2P_DIR_RECV)
? 0x00000000 : 0x80000000))))
            psm_data = NULL;

So I expected for every key expect last are equal, but last equal or less.
Currently I need to check all nodes. Maybe we can create for example:
wmem_tree_lookup32_array_cond() where we can control all the keys
conditions, for example:


        key[0].length = 1;
        key[0].key    = &k_interface_id;
        key[0].cond = COND_EQ;
        key[1].length = 1;
        key[1].key    = &k_adapter_id;
        key[1].cond = COND_EQ;
        key[2].length = 1;
        key[2].key    = &k_chandle;
        key[2].cond = COND_EQ;
        key[3].length = 1;
        key[3].key    = &k_cid;
        key[3].cond = COND_EQ; /* or COND_L, COND_G (possible?), COND_GE,
COND_NE (not equal)  */
        key[4].length = 1;
        key[4].key    = &k_frame_number;
        key[4].cond = COND_LE;
        key[5].length = 0;
        key[5].key    = NULL;

Or maybe other idea? (pack all session identifiers to one long length
identifier?)

lookup32_array_le and lookup32_le return the node with the given key
if it exists, or the next smallest node if it exists (regardless of
how much smaller), or NULL. I don't think mixing and matching
conditions is the correct way to do this.

What I think you can do (this code is not tested and I've never tried
anything like this, but I *think* it will work) is to make the key
with the first 4 entries (and not the k_frame_number value) and use it
in a lookup32_array. If the result of that isn't null, you can cast it
to a wmem_tree_t* and do a lookup32_le with just the frame number on
that subtree (so no need to build a key, just pass k_frame_number
directly to wmem_tree_lookup32_le).

Something like this:

        k_interface_id = interface_id;
        k_adapter_id   = adapter_id;
        k_chandle      = chandle;
        k_cid          = cid;

        key[0].length = 1;
        key[0].key    = &k_interface_id;
        key[1].length = 1;
        key[1].key    = &k_adapter_id;
        key[2].length = 1;
        key[2].key    = &k_chandle;
        key[3].length = 1;
        key[3].key    = &k_cid;
        key[4].length = 0;
        key[4].key    = NULL;

        wmem_tree_t *sub_tree = (wmem_tree_t *)
wmem_tree_lookup32_array(cid_to_psm_table, key);
        if (sub_tree) {
                psm_data = (psm_data_t *)
wmem_tree_lookup32_le(sub_tree, pinfo->fd->num);
        }

By the way.. key can be a string?

Yes, see wmem_tree_insert_string and wmem_tree_lookup_string. They
simply do the work of converting the string into an array and calling
wmem_tree_*32_array() for you.


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