Sdo_pc pointcloud blob in SDO_PC_BLK type

Question

docs say:
POINTS BLOB BLOB containing the points. Consists of an array of
points, with the following information for each point:
■ d 8-byte IEEE doubles, where d is the PC_TOT_
DIMENSIONS value
■ 4-byte big-endian integer for the BLK_ID value
■ 4-byte big-endian integer for the PT_ID value
!!! blk_Id comes BEFORE point_id !!!
-- takes a block
-- output is x/y/z/...
function get_pc_points(p_blob blob) return base_t_PCArray
PIPELINED is
v_result base_t_PC;
v_curr_x number;
v_curr_y number;
v_curr_z number;
v_curr_block_id number;
v_curr_point_id number;
v_buffer_x raw(8);
v_buffer_y raw(8);
v_buffer_z raw(8);
v_buffer_block_id raw(4);
v_buffer_point_id raw(4);
v_size_double pls_integer := 8;
v_size_integer pls_integer := 4;
v_read_offset pls_integer := 1;
begin
--read current point
--read x (8 bytes)
dbms_lob.read(p_blob, v_size_double, v_read_offset, v_buffer_x);
--read y (8 bytes)
dbms_lob.read(p_blob, v_size_double, v_read_offset + 8, v_buffer_y);
--read y (8 bytes)
dbms_lob.read(p_blob, v_size_double, v_read_offset + 16, v_buffer_z);
--read block_id (4 bytes)
dbms_lob.read(p_blob,
v_size_integer,
v_read_offset + 20,
v_buffer_block_id);
--read point_id (4 bytes)
dbms_lob.read(p_blob,
v_size_integer,
v_read_offset + 24,
v_buffer_point_id);
v_result := base_t_PC(x => UTL_RAW.CAST_TO_BINARY_DOUBLE(v_buffer_x),
y => UTL_RAW.CAST_TO_BINARY_DOUBLE(v_buffer_y),
z => UTL_RAW.CAST_TO_BINARY_DOUBLE(v_buffer_z),
blk_id => UTL_RAW.cast_to_binary_integer(v_buffer_block_id),
pt_id => UTL_RAW.cast_to_binary_integer(v_buffer_point_id));
--result to caller
pipe row(v_result);
end get_pc_points;
select * from
table(mdp_laserscan.get_pc_points(
(select b.points from pointcloud_blk b where rownum <= 1)
rownum, x, y, z, blk_id, pt_id
1     586803,035     5365655,411     236,529     -1855425872     10178
it says:
blk_id = -1855425872
pt_id = 10178
--so i check my blocks for the block-id
select b.blk_id from pointcloud_blk b where rownum <= 1
--it says this is a block-id, not a point-id
10178
(yes i know rownum might deliver the wrong block. i checked that too)
-->> Here are TWO STRANGE findings.
1) blk_id and pt_id dont appear in the order as stated in the documentation (i havent found an error in my code)?
2) why do i get a negative number for pt_id?
UTL_RAW.cast_to_binary_integer seems to work ok for the other 4byte (according to docs) value?

Answer 1

I am not sure you are reading the blob right.
Your offsets are a bit off for the ptn_id.
X is at 0 (read 8 bytes)
Y is at 8 (read 8 bytes)
Z is at 16 (read 8 bytes)
block_id is at 24 (read 4 bytes)
pt_id is at 28 (read 4 bytes)
Since you are reading the pt_id from offset 24 you are getting the block id there.
siva