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• How to display consistent background image

  - by Tofu_Craving_Redish_BlueDragon

  Drawing a large background is relatively slow in PyGame. In order to avoid drawing BG every frame, you could draw it once, then do nothing. However, if something is overdrawn onto the surface and keeps moving, you will need to redraw the background in order to "erase" the color pixels left by moving object; otherwise, you will have "traces" of the moving object. I have a moving object in my PyGame. However, I do not want to "clear the color buffer" by redrawing the background image. Redrawing the background image every frame is slow. My solution : I will "clear" only required portions (where the "traces" of moving object are left) of the "buffer" by redrawing portions of background. Is there any other better way to have a consistent background?

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• Deterministic/Consistent Unique Masking

  - by Dinesh Rajasekharan-Oracle

  One of the key requirements while masking data in large databases or multi database environment is to consistently mask some columns, i.e. for a given input the output should always be the same. At the same time the masked output should not be predictable. Deterministic masking also eliminates the need to spend enormous amount of time spent in identifying data relationships, i.e. parent and child relationships among columns defined in the application tables. In this blog post I will explain different ways of consistently masking the data across databases using Oracle Data Masking and Subsetting The readers of post should have minimal knowledge on Oracle Enterprise Manager 12c, Application Data Modeling, Data Masking concepts. For more information on these concepts, please refer to Oracle Data Masking and Subsetting document Oracle Data Masking and Subsetting 12c provides four methods using which users can consistently yet irreversibly mask their inputs. 1. Substitute 2. SQL Expression 3. Encrypt 4. User Defined Function SUBSTITUTE The substitute masking format replaces the original value with a value from a pre-created database table. As the method uses a hash based algorithm in the back end the mappings are consistent. For example consider DEPARTMENT_ID in EMPLOYEES table is replaced with FAKE_DEPARTMENT_ID from FAKE_TABLE. The substitute masking transformation that all occurrences of DEPARTMENT_ID say ‘101’ will be replaced with ‘502’ provided same substitution table and column is used , i.e. FAKE_TABLE.FAKE_DEPARTMENT_ID. The following screen shot shows the usage of the Substitute masking format with in a masking definition: Note that the uniqueness of the masked value depends on the number of columns being used in the substitution table i.e. if the original table contains 50000 unique values, then for the masked output to be unique and deterministic the substitution column should also contain 50000 unique values without which only consistency is maintained but not uniqueness. SQL EXPRESSION SQL Expression replaces an existing value with the output of a specified SQL Expression. For example while masking an EMPLOYEES table the EMAIL_ID of an employee has to be in the format EMPLOYEE’s [email protected] while FIRST_NAME and LAST_NAME are the actual column names of the EMPLOYEES table then the corresponding SQL Expression will look like %FIRST_NAME%||’.’||%LAST_NAME%||’@COMPANY.COM’. The advantage of this technique is that if you are masking FIRST_NAME and LAST_NAME of the EMPLOYEES table than the corresponding EMAIL ID will be replaced accordingly by the masking scripts. One of the interesting aspect’s of a SQL Expressions is that you can use sub SQL expressions, which means that you can write a nested SQL and use it as SQL Expression to address a complex masking business use cases. SQL Expression can also be used to consistently replace value with hashed value using Oracle’s PL/SQL function ORA_HASH. The following SQL Expression will help in the previous example for replacing the DEPARTMENT_IDs with a hashed number ORA_HASH (%DEPARTMENT_ID%, 1000) The following screen shot shows the usage of encrypt masking format with in the masking definition: ORA_HASH takes three arguments: 1. Expression which can be of any data type except LONG, LOB, User Defined Type [nested table type is allowed]. In the above example I used the Original value as expression. 2. Number of hash buckets which can be number between 0 and 4294967295. The default value is 4294967295. You can also co-relate the number of hash buckets to a range of numbers. In the above example above the bucket value is specified as 1000, so the end result will be a hashed number in between 0 and 1000. 3. Seed, can be any number which decides the consistency, i.e. for a given seed value the output will always be same. The default seed is 0. In the above SQL Expression a seed in not specified, so it to 0. If you have to use a non default seed then the function will look like. ORA_HASH (%DEPARTMENT_ID%, 1000, 1234 The uniqueness depends on the input and the number of hash buckets used. However as ORA_HASH uses a 32 bit algorithm, considering birthday paradox or pigeonhole principle there is a 0.5 probability of collision after 232-1 unique values. ENCRYPT Encrypt masking format uses a blend of 3DES encryption algorithm, hashing, and regular expression to produce a deterministic and unique masked output. The format of the masked output corresponds to the specified regular expression. As this technique uses a key [string] to encrypt the data, the same string can be used to decrypt the data. The key also acts as seed to maintain consistent outputs for a given input. The following screen shot shows the usage of encrypt masking format with in the masking definition: Regular Expressions may look complex for the first time users but you will soon realize that it’s a simple language. There are many resources in internet, oracle documentation, oracle learning library, my oracle support on writing a Regular Expressions, out of all the following My Oracle Support document helped me to get started with Regular Expressions: Oracle SQL Support for Regular Expressions[Video](Doc ID 1369668.1) USER DEFINED FUNCTION [UDF] User Defined Function or UDF provides flexibility for the users to code their own masking logic in PL/SQL, which can be called from masking Defintion. The standard format of an UDF in Oracle Data Masking and Subsetting is: Function udf_func (rowid varchar2, column_name varchar2, original_value varchar2) returns varchar2; Where • rowid is the row identifier of the column that needs to be masked • column_name is the name of the column that needs to be masked • original_value is the column value that needs to be masked You can achieve deterministic masking by using Oracle’s built in hash functions like, ORA_HASH, DBMS_CRYPTO.MD4, DBMS_CRYPTO.MD5, DBMS_UTILITY. GET_HASH_VALUE.Please refers to the Oracle Database Documentation for more information on the Oracle Hash functions. For example the following masking UDF generate deterministic unique hexadecimal values for a given string input: CREATE OR REPLACE FUNCTION RD_DUX (rid varchar2, column_name varchar2, orig_val VARCHAR2) RETURN VARCHAR2 DETERMINISTIC PARALLEL_ENABLE IS stext varchar2 (26); no_of_characters number(2); BEGIN no_of_characters:=6; stext:=substr(RAWTOHEX(DBMS_CRYPTO.HASH(UTL_RAW.CAST_TO_RAW(text),1)),0,no_of_characters); RETURN stext; END; The uniqueness depends on the input and length of the string and number of bits used by hash algorithm. In the above function MD4 hash is used [denoted by argument 1 in the DBMS_CRYPTO.HASH function which is a 128 bit algorithm which produces 2^128-1 unique hashed values , however this is limited by the length of the input string which is 6, so only 6^6 unique values will be generated. Also do not forget about the birthday paradox/pigeonhole principle mentioned earlier in this post. An another example is to consistently replace characters or numbers preserving the length and special characters as shown below: CREATE OR REPLACE FUNCTION RD_DUS(rid varchar2,column_name varchar2,orig_val VARCHAR2) RETURN VARCHAR2 DETERMINISTIC PARALLEL_ENABLE IS stext varchar2(26); BEGIN DBMS_RANDOM.SEED(orig_val); stext:=TRANSLATE(orig_val,'ABCDEFGHILKLMNOPQRSTUVWXYZ',DBMS_RANDOM.STRING('U',26)); stext:=TRANSLATE(stext,'abcdefghijklmnopqrstuvwxyz',DBMS_RANDOM.STRING('L',26)); stext:=TRANSLATE(stext,'0123456789',to_char(DBMS_RANDOM.VALUE(1,9))); stext:=REPLACE(stext,'.','0'); RETURN stext; END; The following screen shot shows the usage of an UDF with in a masking definition: To summarize, Oracle Data Masking and Subsetting helps you to consistently mask data across databases using one or all of the methods described in this post. It saves the hassle of identifying the parent-child relationships defined in the application table. Happy Masking

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• Keeping a domain model consistent with actual data

  - by fstuijt

  Recently domain driven design got my attention, and while thinking about how this approach could help us I came across the following problem. In DDD the common approach is to retrieve entities (or better, aggregate roots) from a repository which acts as a in-memory collection of these entities. After these entities have been retrieved, they can be updated or deleted by the user, however after retrieval they are essentially disconnected from the data source and one must actively inform the repository to update the data source and make is consistent again with our in-memory representation. What is the DDD approach to retrieving entities that should remain connected to the data source? For example, in our situation we retrieve a series of sensors that have a specific measurement during retrieval. Over time, these measurement values may change and our business logic in the domain model should respond to these changes properly. E.g., domain events may be raised if a sensor value exceeds a predefined threshold. However, using the repository approach, these sensor values are just snapshots, and are disconnected from the data source. Does any of you have an idea on how to solve this following the DDD approach?

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• Data Aggregation of CSV files java

  - by royB

  I have k csv files (5 csv files for example), each file has m fields which produce a key and n values. I need to produce a single csv file with aggregated data. I'm looking for the most efficient solution for this problem, speed mainly. I don't think by the way that we will have memory issues. Also I would like to know if hashing is really a good solution because we will have to use 64 bit hashing solution to reduce the chance for a collision to less than 1% (we are having around 30000000 rows per aggregation). For example file 1: f1,f2,f3,v1,v2,v3,v4 a1,b1,c1,50,60,70,80 a3,b2,c4,60,60,80,90 file 2: f1,f2,f3,v1,v2,v3,v4 a1,b1,c1,30,50,90,40 a3,b2,c4,30,70,50,90 result: f1,f2,f3,v1,v2,v3,v4 a1,b1,c1,80,110,160,120 a3,b2,c4,90,130,130,180 algorithm that we thought until now: hashing (using concurentHashTable) merge sorting the files DB: using mysql or hadoop or redis. The solution needs to be able to handle Huge amount of data (each file more than two million rows) a better example: file 1 country,city,peopleNum england,london,1000000 england,coventry,500000 file 2: country,city,peopleNum england,london,500000 england,coventry,500000 england,manchester,500000 merged file: country,city,peopleNum england,london,1500000 england,coventry,1000000 england,manchester,500000 The key is: country,city. This is just an example, my real key is of size 6 and the data columns are of size 8 - total of 14 columns. We would like that the solution will be the fastest in regard of data processing.

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• What's the recommended hashing algorithm to use for stored passwords?

  - by Hissohathair

  Given the known weaknesses of MD5 and the recent (May 2009) weaknesses discussed in SHA1, how should new programs be salting & hashing their passwords? I've seen SHA-256 and SHA-512 suggested. Programming predominately in Ruby on Rails and using PostgreSQL -- but other languages and environments might also have to calculate password hashes.

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• TC hashing filters - single rule deletion

  - by exa

  For traffic shaping I'm currently using a setup that looks exactly like the setup from LARTC, on this page: http://lartc.org/howto/lartc.adv-filter.hashing.html I have a simple problem with that - everytime I want to modify something in the hash table (like assign a IP to different flowid), I need to delete the whole filter table and add it again filter by filter. (I actually don't do it by hand, I have a nice program that does it for me... but still...) There is a problem - I got roughly 10k filters allocated this way and deleting and refilling the whole filtertable can get pretty lengthy, which is not exactly good for traffic shaping. My program could easily manage to delete only the rules that need to be deleted (thus reducing the whole problem to several commands and miliseconds), but I simply don't know the command that deletes only the one hashing rule. My tc filter show: filter parent 1: protocol ip pref 1 u32 filter parent 1: protocol ip pref 1 u32 fh 2: ht divisor 256 filter parent 1: protocol ip pref 1 u32 fh 2:a:800 order 2048 key ht 2 bkt a flowid 1:101 match 0a0a0a0a/ffffffff at 16 filter parent 1: protocol ip pref 1 u32 fh 2:c:800 order 2048 key ht 2 bkt c flowid 1:102 match 0a0a0a0c/ffffffff at 16 filter parent 1: protocol ip pref 1 u32 fh 800: ht divisor 1 filter parent 1: protocol ip pref 1 u32 fh 800::800 order 2048 key ht 800 bkt 0 link 2: match 00000000/00000000 at 16 hash mask 000000ff at 16 The wish: 'tc filter del ...' command that removes only one specific filter (for example the 0a0a0a0a IP match (IP address 10.10.10.10)). Removal of some small subgroup would also be good - for example I could still recreate a bucket (bkt a) pretty fast. My attempts: I tried to number all the filters using prio, but with no help -- they just create something unusuable (but deletable) below, but the bucketed filters remain there after that gets deleted. Any ideas? edit - I'm adding a simplified tl;dr description of the problem: I created hash filter on some interfce just like in this http://lartc.org/howto/lartc.adv-filter.hashing.html I want to find a command that deletes one rule (e.g. 1.2.1.123) from the table, leaving the rest untouched and working.

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• Design considerations on JSON schema for scalars with a consistent attachment property

  - by casperOne

  I'm trying to create a JSON schema for the results of doing statistical analysis based on disparate pieces of data. The current schema I have looks something like this: { // Basic key information. video : "http://www.youtube.com/watch?v=7uwfjpfK0jo", start : "00:00:00", end : null, // For results of analysis, to be populated: // *** This is where it gets interesting *** analysis : { game : { value: "Super Street Fighter 4: Arcade Edition Ver. 2012", confidence: 0.9725 } teams : [ { player : { value : "Desk", confidence: 0.95, } characters : [ { value : "Hakan", confidence: 0.80 } ] } ] } } The issue is the tuples that are used to store a value and the confidence related to that value (i.e. { value : "some value", confidence : 0.85 }), populated after the results of the analysis. This leads to a creep of this tuple for every value. Take a fully-fleshed out value from the characters array: { name : { value : "Hakan", confidence: 0.80 } ultra : { value: 1, confidence: 0.90 } } As the structures that represent the values become more and more detailed (and more analysis is done on them to try and determine the confidence behind that analysis), the nesting of the tuples adds great deal of noise to the overall structure, considering that the final result (when verified) will be: { name : "Hakan", ultra : 1 } (And recall that this is just a nested value) In .NET (in which I'll be using to work with this data), I'd have a little helper like this: public class UnknownValue<T> { T Value { get; set; } double? Confidence { get; set; } } Which I'd then use like so: public class Character { public UnknownValue<Character> Name { get; set; } } While the same as the JSON representation in code, it doesn't have the same creep because I don't have to redefine the tuple every time and property accessors hide the appearance of creep. Of course, this is an apples-to-oranges comparison, the above is code while the JSON is data. Is there a more formalized/cleaner/best practice way of containing the creep of these tuples in JSON, or is the approach above an accepted approach for the type of data I'm trying to store (and I'm just perceiving it the wrong way)? Note, this is being represented in JSON because this will ultimately go in a document database (something like RavenDB or elasticsearch). I'm not concerned about being able to serialize into the object above, because I can always use data transfer objects to facilitate getting data into/out of my underlying data store.

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• Consistent Flash Player Crash ONLY on YouTube

  - by Aiman Mueller

  It could be similar to one of the bugs listed on LaunchPad (#689158), but may not be. Basically, I used to occasionally get a crash on YouTube and opening a new browser or rebooting (don't remember which) took care of the problem. However, now, EVERY time I try to open a video on YouTube, I get the frowning block and the message, "The Adobe Flash plugin has crashed." However, Hulu would also call for Adobe, right? But I can see videos there.

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• MINSCN?Cache Fusion Read Consistent

  - by Liu Maclean(???)

  ????? ???Ask Maclean Home ???  RAC ? Past Image PI????, ?????????,???11.2.0.3 2 Node RAC??????????: SQL> select * from v$version; BANNER -------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production PL/SQL Release 11.2.0.3.0 - Production CORE 11.2.0.3.0 Production TNS for Linux: Version 11.2.0.3.0 - Production NLSRTL Version 11.2.0.3.0 - Production SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- www.oracledatabase12g.com SQL> drop table test purge; Table dropped. SQL> alter system flush buffer_cache; System altered. SQL> create table test(id number); insert into test values(1); insert into test values(2); commit; /* ???? rowid??TEST????2????????? */ select dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_relative_fno(rowid) from test; DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID) ------------------------------------ ------------------------------------                                89233                                    1                                89233                                    1 SQL> alter system flush buffer_cache; System altered. Instance 1 Session A ??UPDATE??: SQL> update test set id=id+1 where id=1; 1 row updated. Instance 1 Session B ??x$BH buffer header?? ?? ??Buffer??? SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0;      STATE CR_SCN_BAS ---------- ----------          1          0          3    1227595 X$BH ??? STATE????Buffer???, ???????: STATE NUMBER KCBBHFREE 0 buffer free KCBBHEXLCUR 1 buffer current (and if DFS locked X) KCBBHSHRCUR 2 buffer current (and if DFS locked S) KCBBHCR 3 buffer consistant read KCBBHREADING 4 Being read KCBBHMRECOVERY 5 media recovery (current & special) KCBBHIRECOVERY 6 Instance recovery (somewhat special) ????????????? : state =1 Xcurrent ? state=2 Scurrent ? state=3 CR ??? Instance 2  ?? ????????????? ,???? gc current block 2 way  ??Current Block ??? Instance 2, ?? Instance 1 ??”Current Block” Convert ? Past Image: Instance 2 Session C SQL> update test set id=id+1 where id=2; 1 row updated. Instance 2 Session D SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1227641 3 1227638 STATE =1 ?Xcurrent block???? Instance 2 , ??? Instance 1 ??? GC??: Instance 1 Session B SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0;      STATE CR_SCN_BAS ---------- ----------          3    1227641          3    1227638          8          0          3    1227595 ???????, ??????Instance 1??session A????TEST??SELECT??? ,????? 3? State=3?CR ? ??????1?: Instance 1 session A ?????UPDATE? session SQL> alter session set events '10046 trace name context forever,level 8:10708 trace name context forever,level 103: trace[rac.*] disk high'; Session altered. SQL> select * from test;         ID ----------          2          2 select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0;       STATE CR_SCN_BAS ---------- ----------          3    1227716          3    1227713          8          0 ?????????v$BH ????CR????,?????SELECT??? CR????????,???????? ?????????? ??X$BH?????? , ?????CR??SCN Version???: 1227641?1227638?1227595, ?SELECT?????? 2???SCN version?CR? 1227716? 1227713 ???, Oracle????????? ?????????SELECT??????event 10708? rac.*???TRACE,??????TRACE??: PARSING IN CURSOR #140444679938584 len=337 dep=1 uid=0 oct=3 lid=0 tim=1335698913632292 hv=3345277572 ad='bc0e68c8' sqlid='baj7tjm3q9sn4' SELECT /* OPT_DYN_SAMP */ /*+ ALL_ROWS IGNORE_WHERE_CLAUSE NO_PARALLEL(SAMPLESUB) opt_param('parallel_execution_enabled', 'false') NO_PARALLEL_INDEX(SAMPLESUB) NO_SQL_TUNE */ NVL(SUM(C1),0), NVL(SUM(C2),0) FROM (SELECT /*+ NO_PARALLEL("TEST") FULL("TEST") NO_PARALLEL_INDEX("TEST") */ 1 AS C1, 1 AS C2 FROM "SYS"."TEST" "TEST") SAMPLESUB END OF STMT PARSE #140444679938584:c=1000,e=27630,p=0,cr=0,cu=0,mis=1,r=0,dep=1,og=1,plh=1950795681,tim=1335698913632252 EXEC #140444679938584:c=0,e=44,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,plh=1950795681,tim=1335698913632390 *** 2012-04-29 07:28:33.632 kclscrs: req=0 block=1/89233 *** 2012-04-29 07:28:33.632 kclscrs: bid=1:3:1:0:7:80:1:0:4:0:0:0:1:2:4:1:26:0:0:0:70:1a:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:4:3:2:1:2:0:3f:0:1c:86:2d:4:0:0:0:0:a2:3c:7c:b:70:1a:0:0:0:0:1:0:7a:f8:76:1d:1:2:dc:5:a9:fe:17:75:0:0:0:0:0:0:0:0:0:0:0:0:63:e5:0:0:0:0:0:0:10:0:0:0 2012-04-29 07:28:33.632578 : kjbcrc[0x15c91.1 76896.0][9] 2012-04-29 07:28:33.632616 : GSIPC:GMBQ: buff 0xba1e8f90, queue 0xbb79f278, pool 0x60013fa0, freeq 1, nxt 0xbb79f278, prv 0xbb79f278 2012-04-29 07:28:33.632634 : kjbmscrc(0x15c91.1)seq 0x2 reqid=0x1c(shadow 0xb4bb4458,reqid x1c)mas@2(infosz 200)(direct 1) 2012-04-29 07:28:33.632654 : kjbsentscn[0x0.12bbc1][to 2] 2012-04-29 07:28:33.632669 : GSIPC:SENDM: send msg 0xba1e9000 dest x20001 seq 24026 type 32 tkts xff0000 mlen x17001a0 2012-04-29 07:28:33.633385 : GSIPC:KSXPCB: msg 0xba1e9000 status 30, type 32, dest 2, rcvr 1 *** 2012-04-29 07:28:33.633 kclwcrs: wait=0 tm=689 *** 2012-04-29 07:28:33.633 kclwcrs: got 1 blocks from ksxprcv WAIT #140444679938584: nam='gc cr block 2-way' ela= 689 p1=1 p2=89233 p3=1 obj#=76896 tim=1335698913633418 2012-04-29 07:28:33.633490 : kjbcrcomplete[0x15c91.1 76896.0][0] 2012-04-29 07:28:33.633510 : kjbrcvdscn[0x0.12bbc1][from 2][idx 2012-04-29 07:28:33.633527 : kjbrcvdscn[no bscn <= rscn 0x0.12bbc1][from 2] *** 2012-04-29 07:28:33.633 kclwcrs: req=0 typ=cr(2) wtyp=2hop tm=689 ??TRACE???? ?????????TEST??????, ???????Dynamic Sampling?????,???????TEST?? CR???,???????’gc cr block 2-way’ ??: 2012-04-29 07:28:33.632654 : kjbsentscn[0x0.12bbc1][to 2] 12bbc1= 1227713  ???X$BH????CR???,kjbsentscn[0x0.12bbc1][to 2] ????? ? Instance 2 ???SCN=12bbc1=1227713   DBA=0x15c91.1 76896.0 ?  CR Request(obj#=76896) ??kjbrcvdscn????? [no bscn <= rscn 0x0.12bbc1][from 2] ,??? ??receive? SCN Version =12bbc1 ???Best Version CR Server Arch ??????????????????SELECT??: PARSING IN CURSOR #140444682869592 len=18 dep=0 uid=0 oct=3 lid=0 tim=1335698913635874 hv=1689401402 ad='b1a188f0' sqlid='c99yw1xkb4f1u' select * from test END OF STMT PARSE #140444682869592:c=4999,e=34017,p=0,cr=7,cu=0,mis=1,r=0,dep=0,og=1,plh=1357081020,tim=1335698913635870 EXEC #140444682869592:c=0,e=23,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=1357081020,tim=1335698913635939 WAIT #140444682869592: nam='SQL*Net message to client' ela= 7 driver id=1650815232 #bytes=1 p3=0 obj#=0 tim=1335698913636071 *** 2012-04-29 07:28:33.636 kclscrs: req=0 block=1/89233 *** 2012-04-29 07:28:33.636 kclscrs: bid=1:3:1:0:7:83:1:0:4:0:0:0:1:2:4:1:26:0:0:0:70:1a:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:4:3:2:1:2:0:2:0:1c:86:2d:4:0:0:0:0:a2:3c:7c:b:70:1a:0:0:0:0:1:0:7d:f8:76:1d:1:2:dc:5:a9:fe:17:75:0:0:0:0:0:0:0:0:0:0:0:0:63:e5:0:0:0:0:0:0:10:0:0:0 2012-04-29 07:28:33.636209 : kjbcrc[0x15c91.1 76896.0][9] 2012-04-29 07:28:33.636228 : GSIPC:GMBQ: buff 0xba0e5d50, queue 0xbb79f278, pool 0x60013fa0, freeq 1, nxt 0xbb79f278, prv 0xbb79f278 2012-04-29 07:28:33.636244 : kjbmscrc(0x15c91.1)seq 0x3 reqid=0x1d(shadow 0xb4bb4458,reqid x1d)mas@2(infosz 200)(direct 1) 2012-04-29 07:28:33.636252 : kjbsentscn[0x0.12bbc4][to 2] 2012-04-29 07:28:33.636358 : GSIPC:SENDM: send msg 0xba0e5dc0 dest x20001 seq 24029 type 32 tkts xff0000 mlen x17001a0 2012-04-29 07:28:33.636861 : GSIPC:KSXPCB: msg 0xba0e5dc0 status 30, type 32, dest 2, rcvr 1 *** 2012-04-29 07:28:33.637 kclwcrs: wait=0 tm=865 *** 2012-04-29 07:28:33.637 kclwcrs: got 1 blocks from ksxprcv WAIT #140444682869592: nam='gc cr block 2-way' ela= 865 p1=1 p2=89233 p3=1 obj#=76896 tim=1335698913637294 2012-04-29 07:28:33.637356 : kjbcrcomplete[0x15c91.1 76896.0][0] 2012-04-29 07:28:33.637374 : kjbrcvdscn[0x0.12bbc4][from 2][idx 2012-04-29 07:28:33.637389 : kjbrcvdscn[no bscn <= rscn 0x0.12bbc4][from 2] *** 2012-04-29 07:28:33.637 kclwcrs: req=0 typ=cr(2) wtyp=2hop tm=865 ???, “SELECT * FROM TEST”??????’gc cr block 2-way’??:2012-04-29 07:28:33.637374 : kjbrcvdscn[0x0.12bbc4][from 2][idx 2012-04-29 07:28:33.637389 : kjbrcvdscn[no bscn ??Foreground Process? Remote LMS??got?? SCN=1227716 Version?CR, ??? ?????X$BH ?????scn??? ??????????Instance 1????2?SCN???CR?, ???????????Instance 1 Buffer Cache?? ??SCN Version ???CR ??????? ?????????: SQL> alter system set "_enable_minscn_cr"=false scope=spfile; System altered. SQL> alter system set "_db_block_max_cr_dba"=20 scope=spfile; System altered. SQL> startup force; ORA-32004: obsolete or deprecated parameter(s) specified for RDBMS instance ORACLE instance started. Total System Global Area 1570009088 bytes Fixed Size 2228704 bytes Variable Size 989859360 bytes Database Buffers 570425344 bytes Redo Buffers 7495680 bytes Database mounted. Database opened. ???? “_enable_minscn_cr”=false ? “_db_block_max_cr_dba”=20 ???RAC????, ??????: ?Instance 2 Session C ?update??????? ?????Instance 1 ????? ,????Instance 1?Request CR SQL> update test set id=id+1 where id=2; -- Instance 2 1 row updated. SQL> select * From test; -- Instance 1 ID ---------- 1 2 ??? Instance 1? X$BH?? select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0;  STATE CR_SCN_BAS ---------- ---------- 3 1273080 3 1273071 3 1273041 3 1273039 8 0 SQL> update test set id=id+1 where id=3; 1 row updated. SQL> select * From test; ID ---------- 1 2 SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1273091 3 1273080 3 1273071 3 1273041 3 1273039 8 0 ................... SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1273793 3 1273782 3 1273780 3 1273769 3 1273734 3 1273715 3 1273691 3 1273679 3 1273670 3 1273643 3 1273635 3 1273623 3 1273106 3 1273091 3 1273080 3 1273071 3 1273041 3 1273039 3 1273033 19 rows selected. SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1274993 ????? ???? “_enable_minscn_cr”(enable/disable minscn optimization for CR)=false ? “_db_block_max_cr_dba”=20 (Maximum Allowed Number of CR buffers per dba) 2? ??? ????? Instance 1 ??????????? ?? 19????CR?? “_enable_minscn_cr”?11g??????????,???Oracle????CR????SCN,?Foreground Process Receive????????????(SCN??)?SCN Version CR Block??????CBC?? SCN??????CR? , ?????????Buffer Cache??????? ????SCN Version?CR????,????? ?????????? ?????Snap_Scn ?? SCN?? ?????????Current SCN, ??????CR??????????????????????, ????Buffer Cache? ?????????? CR?????????, ?????? “_db_block_max_cr_dba” ???????, ???????????20 ,??????Buffer Cache?????19????CR?; ???”_db_block_max_cr_dba” ???????6 , ?????Buffer cache????????CR ???????6?? ??”_enable_minscn_cr” ??CR???MINSCN ??????, ?????????CR???????, ????? Foreground Process??????CR Request , ?? Holder Instance LMS ?build?? BEST CR ??, ?????????

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• Alsa version numbers not consistent

  - by user69245

  I've recently moved from 10.04 to 12.04 and have problems with crackles on audio when the screen changes (especially obvious in a Skype conversation with video). !!Kernel Information !!------------------ Kernel release: 3.2.0-26-generic-pae Operating System: GNU/Linux Architecture: i686 Processor: i686 SMP Enabled: Yes !!ALSA Version !!------------ Driver version: 1.0.24 Library version: 1.0.25 Utilities version: 1.0.25 Running through the SoundTroubleShooting procedures I got the above details at Step 3. Is the mismatch between the Driver version (1.0.24) and the Library and Utilities versions (1.0.25) the cause of my problem, or should I be looking elsewhere? In answers to the question "Will ALSA 1.0.25 version have time to enter 12.04?" I read that 1.0.25 would be part of the new kernel, but my kernel version appears to be newer than the original release.

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• A* PathFinding Not Consistent

  - by RedShft

  I just started trying to implement a basic A* algorithm in my 2D tile based game. All of the nodes are tiles on the map, represented by a struct. I believe I understand A* on paper, as I've gone through some pseudo code, but I'm running into problems with the actual implementation. I've double and tripled checked my node graph, and it is correct, so I believe the issue to be with my algorithm. This issue is, that with the enemy still, and the player moving around, the path finding function will write "No Path" an astounding amount of times and only every so often write "Path Found". Which seems like its inconsistent. This is the node struct for reference: struct Node { bool walkable; //Whether this node is blocked or open vect2 position; //The tile's position on the map in pixels int xIndex, yIndex; //The index values of the tile in the array Node*[4] connections; //An array of pointers to nodes this current node connects to Node* parent; int gScore; int hScore; int fScore; } Here is the rest: http://pastebin.com/cCHfqKTY This is my first attempt at A* so any help would be greatly appreciated.

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• ec2-consistent-snapshot volume does not exist?

  - by mpaler

  Does anybody know why this might happen? me@ip-10-176-234-62:/$ ec2-describe-volumes VOLUME vol-994ec1fd 8 snap-2971f04d us-west-1a in-use 2012-05-14T18:57:01+0000 ATTACHMENT vol-994ec1fd i-a49a2ae2 /dev/sda1 attached 2012-08-31T18:39:18+0000 me@ip-10-176-234-62:/$ ec2-consistent-snapshot vol-994ec1fd --aws-access-key-id xxxx --aws-secret-access-key xxxxx ec2-consistent-snapshot: ERROR: The volume 'vol-994ec1fd' does not exist.

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• Hi, I have a C hashing routine which is behaving strangely?

  - by aks

  Hi, In this hashing routine: 1.) I am able to add strings. 2.) I am able to view my added strings. 3.) When i try to add a duplicate string, it throws me an error saying already present. 4.) But, when i try to delete the same string which is already present in hash table, then the lookup_routine calls hash function to get an index. At this time, it throws a different hash index to the one it was already added. Hence, my delete routine is failing? I am able to understand the reason why for same string, hash fucntion calculates a different index each time (whereas the same logic works in view hash table routine)? Can someone help me? This is the Output, i am getting: $ ./a Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 1 Please enter the string :gaura enters in add_string DEBUG purpose in hash function: str passed = gaura Hashval returned in hash func= 1 hashval = 1 enters in lookup_string str in lookup_string = gaura DEBUG purpose in hash function: str passed = gaura Hashval returned in hash func= 1 hashval = 1 DEBUG ERROR :element not found in lookup string DEBUG Purpose NULL Inserting... DEBUG1 : enters here hashval = 1 String added successfully Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 1 Please enter the string :ayu enters in add_string DEBUG purpose in hash function: str passed = ayu Hashval returned in hash func= 1 hashval = 1 enters in lookup_string str in lookup_string = ayu DEBUG purpose in hash function: str passed = ayu Hashval returned in hash func= 1 hashval = 1 returns NULL in lookup_string DEBUG Purpose NULL Inserting... DEBUG2 : enters here hashval = 1 String added successfully Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 1 Please enter the string :gaurava enters in add_string DEBUG purpose in hash function: str passed = gaurava Hashval returned in hash func= 7 hashval = 7 enters in lookup_string str in lookup_string = gaurava DEBUG purpose in hash function: str passed = gaurava Hashval returned in hash func= 7 hashval = 7 DEBUG ERROR :element not found in lookup string DEBUG Purpose NULL Inserting... DEBUG1 : enters here hashval = 7 String added successfully Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 4 Index : i = 1 String = gaura ayu Index : i = 7 String = gaurava Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: 2 Please enter the string you want to delete :gaura String entered = gaura enters in delete_string DEBUG purpose in hash function: str passed = gaura Hashval returned in hash func= 0 hashval = 0 enters in lookup_string str in lookup_string = gaura DEBUG purpose in hash function: str passed = gaura Hashval returned in hash func= 0 hashval = 0 DEBUG ERROR :element not found in lookup string DEBUG Purpose Item not present. So, cannot be deleted Item found in list: Deletion failed Press 1 to add an element to the hashtable Press 2 to delete an element from the hashtable Press 3 to search the hashtable Press 4 to view the hashtable Press 5 to exit Please enter your choice: My routine is pasted below: include include struct list { char *string; struct list *next; }; struct hash_table { int size; /* the size of the table */ struct list *table; / the table elements */ }; struct hash_table * hashtable = NULL; struct hash_table *create_hash_table(int size) { struct hash_table *new_table; int i; if (size<1) return NULL; /* invalid size for table */ /* Attempt to allocate memory for the table structure */ if ((new_table = malloc(sizeof(struct hash_table))) == NULL) { return NULL; } /* Attempt to allocate memory for the table itself */ if ((new_table->table = malloc(sizeof(struct list *) * size)) == NULL) { return NULL; } /* Initialize the elements of the table */ for(i=0; i<size; i++) new_table->table[i] = '\0'; /* Set the table's size */ new_table->size = size; return new_table; } unsigned int hash(struct hash_table *hashtable, char *str) { printf("\n DEBUG purpose in hash function:\n"); printf("\n str passed = %s", str); unsigned int hashval = 0; int i = 0; for(; *str != '\0'; str++) { hashval += str[i]; i++; } hashval = hashval % 10; printf("\n Hashval returned in hash func= %d", hashval); return hashval; } struct list *lookup_string(struct hash_table *hashtable, char *str) { printf("\n enters in lookup_string \n"); printf("\n str in lookup_string = %s",str); struct list * new_list; unsigned int hashval = hash(hashtable, str); printf("\n hashval = %d \n", hashval); if(hashtable->table[hashval] == NULL) { printf("\n DEBUG ERROR :element not found in lookup string \n"); return NULL; } /* Go to the correct list based on the hash value and see if str is * in the list. If it is, return return a pointer to the list element. * If it isn't, the item isn't in the table, so return NULL. */ for(new_list = hashtable->table[hashval]; new_list != NULL;new_list = new_list->next) { if (strcmp(str, new_list->string) == 0) return new_list; } printf("\n returns NULL in lookup_string \n"); return NULL; } int add_string(struct hash_table *hashtable, char *str) { printf("\n enters in add_string \n"); struct list *new_list; struct list *current_list; unsigned int hashval = hash(hashtable, str); printf("\n hashval = %d", hashval); /* Attempt to allocate memory for list */ if ((new_list = malloc(sizeof(struct list))) == NULL) { printf("\n enters here \n"); return 1; } /* Does item already exist? */ current_list = lookup_string(hashtable, str); if (current_list == NULL) { printf("\n DEBUG Purpose \n"); printf("\n NULL \n"); } /* item already exists, don't insert it again. */ if (current_list != NULL) { printf("\n Item already present...\n"); return 2; } /* Insert into list */ printf("\n Inserting...\n"); new_list->string = strdup(str); new_list->next = NULL; //new_list->next = hashtable->table[hashval]; if(hashtable->table[hashval] == NULL) { printf("\n DEBUG1 : enters here \n"); printf("\n hashval = %d", hashval); hashtable->table[hashval] = new_list; } else { printf("\n DEBUG2 : enters here \n"); printf("\n hashval = %d", hashval); struct list * temp_list = hashtable->table[hashval]; while(temp_list->next!=NULL) temp_list = temp_list->next; temp_list->next = new_list; // hashtable->table[hashval] = new_list; } return 0; } int delete_string(struct hash_table *hashtable, char *str) { printf("\n enters in delete_string \n"); struct list *new_list; struct list *current_list; unsigned int hashval = hash(hashtable, str); printf("\n hashval = %d", hashval); /* Does item already exist? */ current_list = lookup_string(hashtable, str); if (current_list == NULL) { printf("\n DEBUG Purpose \n"); printf("\n Item not present. So, cannot be deleted \n"); return 1; } /* item exists, delete it. */ if (current_list != NULL) { struct list * temp = hashtable->table[hashval]; if(strcmp(temp->string,str) == 0) { if(temp->next == NULL) { hashtable->table[hashval] = NULL; free(temp); } else { hashtable->table[hashval] = temp->next; free(temp); } } else { struct list * temp1; while(temp->next != NULL) { temp1 = temp; if(strcmp(temp->string, str) == 0) { break; } else { temp = temp->next; } } if(temp->next == NULL) { temp1->next = NULL; free(temp); } else { temp1->next = temp->next; free(temp); } } } return 0; } void free_table(struct hash_table *hashtable) { int i; struct list *new_list, *temp_list; if (hashtable==NULL) return; /* Free the memory for every item in the table, including the * strings themselves. */ for(i=0; i<hashtable->size; i++) { new_list = hashtable->table[i]; while(new_list!=NULL) { temp_list = new_list; new_list = new_list->next; free(temp_list->string); free(temp_list); } } /* Free the table itself */ free(hashtable->table); free(hashtable); } void view_hashtable(struct hash_table * hashtable) { int i = 0; if(hashtable == NULL) return; for(i =0; i < hashtable->size; i++) { if((hashtable->table[i] == 0) || (strcmp(hashtable->table[i]->string, "*") == 0)) { continue; } printf(" Index : i = %d\t String = %s",i, hashtable->table[i]->string); struct list * temp = hashtable->table[i]->next; while(temp != NULL) { printf("\t %s",temp->string); temp = temp->next; } printf("\n"); } } int main() { hashtable = create_hash_table(10); if(hashtable == NULL) { printf("\n Memory allocation failure during creation of hash table \n"); return 0; } int flag = 1; while(flag) { int choice; printf("\n Press 1 to add an element to the hashtable\n"); printf("\n Press 2 to delete an element from the hashtable\n"); printf("\n Press 3 to search the hashtable\n"); printf("\n Press 4 to view the hashtable\n"); printf("\n Press 5 to exit \n"); printf("\n Please enter your choice: "); scanf("%d",&choice); if(choice == 5) flag = 0; else if(choice == 1) { char str[20]; printf("\n Please enter the string :"); scanf("%s",&str); int i; i = add_string(hashtable,str); if(i == 1) { printf("\n Memory allocation failure:Choice 1 \n"); return 0; } else if(i == 2) { printf("\n String already prsent in hash table : Couldnot add it again\n"); return 0; } else { printf("\n String added successfully \n"); } } else if(choice == 2) { int i; struct list * temp_list; char str[20]; printf("\n Please enter the string you want to delete :"); scanf("%s",&str); printf("\n String entered = %s", str); i = delete_string(hashtable,str); if(i == 0) { printf("\n Item found in list: Deletion success \n"); } else printf("\n Item found in list: Deletion failed \n"); } else if(choice == 3) { struct list * temp_list; char str[20]; printf("\n Please enter the string :"); scanf("%s",&str); temp_list = lookup_string(hashtable,str); if(!temp_list) { printf("\n Item not found in list: Deletion failed \n"); return 0; } printf("\n Item found: Present in Hash Table \n"); } else if(choice == 4) { view_hashtable(hashtable); } else if(choice == 5) { printf("\n Exiting ...."); return 0; } else printf("\n Invalid choice:"); }; free_table(hashtable); return 0; }

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• How can I create consistent snapshots of tmpfs?

  - by netvope

  How can I create consistent snapshots of tmpfs or any RAM disks?

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• Secure hash and salt for PHP passwords

  - by luiscubal

  It is currently said that MD5 is partially unsafe. Taking this into consideration, I'd like to know which mechanism to use for password protection. Is “double hashing” a password less secure than just hashing it once? Suggests that hashing multiple times may be a good idea. How to implement password protection for individual files? Suggests using salt. I'm using PHP. I want a safe and fast password encryption system. Hashing a password a million times may be safer, but also slower. How to achieve a good balance between speed and safety? Also, I'd prefer the result to have a constant number of characters. The hashing mechanism must be available in PHP It must be safe It can use salt (in this case, are all salts equally good? Is there any way to generate good salts?) Also, should I store two fields in the database(one using MD5 and another one using SHA, for example)? Would it make it safer or unsafer? In case I wasn't clear enough, I want to know which hashing function(s) to use and how to pick a good salt in order to have a safe and fast password protection mechanism. EDIT: The website shouldn't contain anything too sensitive, but still I want it to be secure. EDIT2: Thank you all for your replies, I'm using hash("sha256",$salt.":".$password.":".$id) Questions that didn't help: What's the difference between SHA and MD5 in PHP Simple Password Encryption Secure methods of storing keys, passwords for asp.net How would you implement salted passwords in Tomcat 5.5

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• MD5 and SHA1 checksum uses for downloading

  - by Zac

  I notice that when downloading a lot of open source tools (Eclipse, etc.) there are links for MD5 and SHA1 checksums, and didn't know what these were or what their purpose was. I know these are hashing algorithms, and I do understand hashing, so my only guess is that these are used for hashing some component of the download targets, and to compare them with "official" hash strings stored server-side. Perhaps that way it can be determined whether or not the targets have been modified from their correct version (for security and other purposes). Am I close or completely wrong, and if wrong, what are they?!?! Thanks!

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• hashing password giving different results

  - by geoff

  I am taking over a system that a previous developer wrote. The system has an administrator approve a user account and when they do that the system uses the following method to hash a password and save it to the database. It sends the unhashed password to the user. When the user logs in the system uses the exact same method to hash what the user enters and compares it to the database value. We've run into a couple of times when the database entry doesn't match the user's entry whey they should. So it appears that the method isn't always hashing the value the same. Does anyone know if this method of hashing isn't reliable and how to make it reliable? Thanks. private string HashPassword(string password) { string hashedPassword = string.Empty; // Convert plain text into a byte array. byte[] plainTextBytes = Encoding.UTF8.GetBytes(password); // Allocate array, which will hold plain text and salt. byte[] plainTextWithSaltBytes = new byte[plainTextBytes.Length + SALT.Length]; // Copy plain text bytes into resulting array. for(int i = 0; i < plainTextBytes.Length; i++) plainTextWithSaltBytes[i] = plainTextBytes[i]; // Append salt bytes to the resulting array. for(int i = 0; i < SALT.Length; i++) plainTextWithSaltBytes[plainTextBytes.Length + i] = SALT[i]; // Because we support multiple hashing algorithms, we must define // hash object as a common (abstract) base class. We will specify the // actual hashing algorithm class later during object creation. HashAlgorithm hash = new SHA256Managed(); // Compute hash value of our plain text with appended salt. byte[] hashBytes = hash.ComputeHash(plainTextWithSaltBytes); // Create array which will hold hash and original salt bytes. byte[] hashWithSaltBytes = new byte[hashBytes.Length + SALT.Length]; // Copy hash bytes into resulting array. for(int i = 0; i < hashBytes.Length; i++) hashWithSaltBytes[i] = hashBytes[i]; // Append salt bytes to the result. for(int i = 0; i < SALT.Length; i++) hashWithSaltBytes[hashBytes.Length + i] = SALT[i]; // Convert result into a base64-encoded string. hashedPassword = Convert.ToBase64String(hashWithSaltBytes); return hashedPassword; }

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• Can I save & store a user's submission in a way that proves that the data has not been altered, and that the timestamp is accurate?

  - by jt0dd

  There are many situations where the validity of the timestamp attached to a certain post (submission of information) might be invaluable for the post owner's legal usage. I'm not looking for a service to achieve this, as requested in this great question, but rather a method for the achievement of such a service. For the legal (in most any law system) authentication of text content and its submission time, the owner of the content would need to prove: that the timestamp itself has not been altered and was accurate to begin with. that the text content linked to the timestamp had not been altered I'd like to know how to achieve this via programming (not a language-specific solution, but rather the methodology behind the solution). Can a timestamp be validated to being accurate to the time that the content was really submitted? Can data be stored in a form that it can be read, but not written to, in a proven way? In other words, can I save & store a user's submission in a way that proves that the data has not been altered, and that the timestamp is accurate? I can't think of any programming method that would make this possible, but I am not the most experienced programmer out there. Based on MidnightLightning's answer to the question I cited, this sort of thing is being done. Clarification: I'm looking for a method (hashing, encryption, etc) that would allow an average guy like me to achieve the desired effect through programming. I'm interested in this subject for the purpose of Defensive Publication. I'd like to learn a method that allows an every-day programmer to pick up his computer, write a program, pass information through it, and say: I created this text at this moment in time, and I can prove it. This means the information should be protected from the programmer who writes the code as well. Perhaps a 3rd party API would be required. I'm ok with that.

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• Hash Algorithm Randomness Visualization

  - by clstroud

  I'm curious if anyone here has any idea how the images were generated as shown in this response: Which hashing algorithm is best for uniqueness and speed? Ian posted a very well-received response but I can't seem to understand how he went about making the images. I hate to make a new question dedicated to this, but I can't find any means to ask him more directly. On the other hand, perhaps someone has an alternative perspective. The best I can personally come up with would be to have it almost like a bar graph, which would illustrate how evenly the buckets of the hash table are being generated. I have a working Cocoa program that does this, but it can't generate anything like what he showed there. So the question is two fold I suppose: A) How does one truly interpret the data he shows? Is it more than "less whitespace = better"? B) How does one generate such an image based on some set of inputs, a hash, and an index? Perhaps I'm misunderstanding entirely, but I really would like to know more about this particular visualization technique. Or maybe I'm mis-applying this to hash tables rather than just hashes in general, but in that case I don't know how it would be "bounded" for the image.

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• nginx hashing on GET parameter

  - by Sparsh Gupta

  I have two Varnish servers and I plan to add more varnish servers. I am using a nginx load balancer to divide traffic to these varnish servers. To utilize maximum RAM of each varnish server, I need that same request reaches same varnish server. Same request can be identified by one GET parameter in the request URL say 'a' In a normal code, I would do something like- (if I need to divide all traffic between 2 Varnish servers) if($arg_a % 2 == 0) { proxy_pass varnish1; } if($arg_a % 2 == 1) { proxy_pass varnish2; } This is basically doing a even / odd check on GET parameter a and then deciding which upstream pool to send the request. My question are- What is the nginx equivalent of such a code. I dont know if nginx accepts modulas Is there a better/ efficient hashing function built in with nginx (0.8.54) which I can possibly use. In future I want to add more upstream pools so I need not to change %2 to %3 %4 and so on Any other alternate way to solve this problem

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• Automate hashing for each file in a folder?

  - by Kennie R.

  I have quite a few FTP folders, and I add a few each month and prefer to leave some sort of method of verifying their integrity, for example the files MD5SUMS, SHA256SUMS, ... which I could create using a script. Take for example: find ./ -type f -exec md5sum $1 {} \; This works fine, but when I run it each time for each shaxxx sum afterwards, it creates a sum of the MD5SUMs file which is really not wanted. Is there a simpler way, or script, or common way of hashing all the files in to their sums file without causing problems like that? I could really use a better option.

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• sequentially-consistent atomic load on x86

  - by axe

  Hello all, I'm interested in sequentially-consistent load operation on x86. As far as I see from assembler listing, generated by compiler it is implemented as a plain load on x86, however plain loads as far as I know guaranteed to have acquire semantics, while plain stores are guaranteed to have release. Sequentially-consistent store is implemented as locked xchg, while load as plain load. That sounds strange to me, could you please explain this in details? added Just found in internet, that sequentially-consistent atomic load could be done as simple mov as long as store is done with locked xchg, but there was no prove and no links to documentation. Do you know where can I read about that? Thanks in advance.

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• Using hashing to group similar records

  - by Neil Dobson

  I work for a fulfillment company and we have to pack and ship many orders from our warehouse to customers. To improve efficiency we would like to group identical orders and pack these in the most optimum way. By identical I mean having the same number of order lines containing the same SKUs and same order quantities. To achieve this I was thinking about hashing each order. We can then group by hash to quickly see which orders are the same. We are moving from an Access database to a PostgreSQL database and we have .NET based systems for data loading and general order processing systems, so we can either do the hashing during the data loading or hand this task over to the DB. My question firstly is should the hashing be managed by DB, possibly using triggers, or should the hash be created on-the-fly using a view or something? And secondly would it be best to calculate a hash for each order line and then to combine these to find an order-level hash for grouping, or should I just use a trigger for all CRUD operations on the order lines table which re-calculates a single hash for the entire order and store the value in the orders table? TIA

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• CentOS 6 - YUM Local Repo - Ensure consistent package distribution

  - by Mike Purcell

  I've read a few guides outlining how to setup a local YUM repo, but none of them explicitly stated an answer to my question; If I set up a local YUM repo, does that mean that any CentOS servers which pull from said repo will never be "ahead" of the local YUM repo? I want to ensure a consistent package distribution across all my servers. Right now, when I do a yum update, even on a daily basis, the servers can be out of alignment. For example if I run YUM update on my dev server in the morning, then run YUM update on one of my production servers in the afternoon, the production server may have picked up a new version of a package that the dev server did not pick up, due to the time window between the update commands. Rather, I'd prefer that I run yum update from my dev server which has access to remote upstream yum repos, then let it sit for 2 weeks, after which I run yum update on my production servers against the local repo on my dev server.

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• Can't get Postfix Admin to use Dovecot password hashing

  - by Paul

  I'm setting up Postfix Admin 2.91 and trying to use dovecot:SHA512-CRYPT for password hashing. In config.inc.php I have set: // dovecot:CRYPT-METHOD = use dovecotpw -s 'CRYPT-METHOD'. Example: dovecot:CRAM-MD5 // (WARNING: don't use dovecot:* methods that include the username in the hash - you won't be able to login to PostfixAdmin in this case) $CONF['encrypt'] = 'dovecot:SHA512-CRYPT'; // If you use the dovecot encryption method: where is the dovecotpw binary located? // for dovecot 1.x // $CONF['dovecotpw'] = "/usr/sbin/dovecotpw"; // for dovecot 2.x (dovecot 2.0.0 - 2.0.7 is not supported!) $CONF['dovecotpw'] = "/usr/sbin/doveadm pw"; I have also tried SHA256-CRYPT and MD5-CRYPT with same results (as I understand it, these do not include usernames in the hash) In running setup.php, I get the following message when trying to create an admin account: can't encrypt password with dovecotpw, see error log for details Server error log reports: 1624#0: *6 FastCGI sent in stderr: "PHP message: dovecotpw password encryption failed. PHP message: STDERR output: sh: 1: /usr/sbin/doveadm: not found" while reading response header from upstream <...> upstream: "fastcgi://unix:/var/run/php5-fpm.sock:" <...> A couple quick checks: # ll /usr/sbin/doveadm -rwxr-xr-x 1 root root 423264 Feb 13 23:23 /usr/bin/doveadm* # doveadm pw -l CRYPT MD5 MD5-CRYPT SHA SHA1 SHA256 SHA512 SMD5 SSHA SSHA256 SSHA512 PLAIN CLEAR CLEARTEXT PLAIN-TRUNC CRAM-MD5 SCRAM-SHA-1 HMAC-MD5 DIGEST-MD5 PLAIN-MD4 PLAIN-MD5 LDAP-MD5 LANMAN NTLM OTP SKEY RPA SHA256-CRYPT SHA512-CRYPT # doveadmin pw -s SHA512-CRYPT Enter new password: Retype new password: {SHA512-CRYPT}$6$<long string here>/ Using Dovecot 2.2, PHP 5.5, MariaDB 10, Postfix 2.11, nginx 1.6.0, Ubuntu 12.04.

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