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  • please explain my fio results - is O_SYNC|O_DIRECT misbehaving on linux?

    - by Zoltan
    I'm going mad over figuring out what the problem could be with one of our storage boxes. With a simple fio script I'm testing random writes using bs=1M and direct=1. The SSD is a Samsung 840pro attached to an LSI HBA (3Gbit/s ports). This is the result I'm getting under FreeBSD 9.1: WRITE: io=13169MB, aggrb=224743KB/s, minb=224743KB/s, maxb=224743KB/s, mint=60002msec, maxt=60002msec This is regardless of sync being set to 0 or 1. On linux, this is the result with sync=0: WRITE: io=14828MB, aggrb=253060KB/s, minb=253060KB/s, maxb=253060KB/s, mint=60001msec, maxt=60001msec and with sync=1: WRITE: io=6360.0MB, aggrb=108542KB/s, minb=108542KB/s, maxb=108542KB/s, mint=60001msec, maxt=60001msec My understanding is that since I'm operating on the raw block device, O_SYNC should not make any difference - there's no filesystem, any barrier, anything between the writes and the drive itself. Especially with O_DIRECT|O_SYNC set. Any ideas? For reference, here's the fio script I'm testing with: [global] bs=1M ioengine=sync iodepth=4 size=16g direct=1 runtime=60 filename=/dev/sdh sync=1 [rand-write] rw=randwrite stonewall

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  • Can someone explain the fascination with twitter.com? [closed]

    - by raven
    I don't get it. WTF do people see in this? I'm trying to figure it out, but I can't. Have you seen what people post? Let's use Jeff Atwood as an example. What does he gain by posting (with disturbing frequency) all those, well... posts (I find the term "tweets" disgusting). What is a "follower" supposed to get from these posts? I know many of you are thinking, "Just don't use it!". Yes, I know I don't have to use it, but it's like asking me not to look at the space shuttle that just crashed in my front yard. The rest of the world thinks it's the greatest thing since sliced bread. I'm just trying to understand what people see in it.

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  • Can anyone explain these differences between two similar i7 processors? [closed]

    - by Brian Frost
    I have two systems I've just built. They both have i7 processors and Asus P8Z77 motherboards. When I run a simple processor loop benchmark that I wrote in Delphi some time back I get one machine showing nealry twice as fast as the other. I then used CPU-Z to dump me the details of the hardware and I see that the fast machine shows: Processor 1 ID = 0 Number of cores 4 (max 8) Number of threads 8 (max 16) Name Intel Core i7 2700K Codename Sandy Bridge Specification Intel(R) Core(TM) i7-2700K CPU @ 3.50GHz Package (platform ID) Socket 1155 LGA (0x1) CPUID 6.A.7 Extended CPUID 6.2A Core Stepping D2 Technology 32 nm TDP Limit 95 Watts Core Speed 3610.7 MHz Multiplier x FSB 36.0 x 100.3 MHz Stock frequency 3500 MHz the slow machine shows: Processor 1 ID = 0 Number of cores 4 (max 8) Number of threads 8 (max 16) Name Intel Core i7 2600K Codename Sandy Bridge Specification Intel(R) Core(TM) i7-2600K CPU @ 3.40GHz Package (platform ID) Socket 1155 LGA (0x1) CPUID 6.A.7 Extended CPUID 6.2A Core Stepping D2 Technology 32 nm TDP Limit 95 Watts Core Speed 1648.2 MHz Multiplier x FSB 16.0 x 103.0 MHz Stock frequency 3400 MHz i.e the slow machine has a 2600k to the fast machine 2700k. The very different "Multiplier x FSB" must be significant but I dont understand how two processors with a very 'similar' number can be so different. To get the machines the same must I copy the processors or is there some clever setting that I can change? Thanks for any help. Brian.

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  • What could explain my partitions disappearing on a new SSD with Windows 7?

    - by charlesrandall
    So this morning, I had a fresh install of Windows 7 pro, on a new SSD (Patriot TorqX 128gb), which I just put in to a new Dell Studio XPS 9000. Everything was fine. I booted to windows, no problem. I go to work. 8 hours later, I come home, and I'm greeted by my boot screen complaining about no bootable devices. Windows repair from the Windows 7 pro disk says it can't fix the problem. It doesn't see any windows installs. I boot up GParted, and my SSD is completely unallocated. No space used, no partitions. Perhaps this is related to allowing windows 7 to create a utility partition when I installed? Only thing I can think of. Is there some kind of known hardware issue that can result in an SSD completely wiping itself?

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  • Can someone explain the physical architecture of RAID 10 in complete layman's terms?

    - by Hank
    I am a newbie in the world of storage and I am having a hard time digesting the physical architecture of some of the RAID levels. I am particularly interested in RAID 10, and 50. I asked the question specifically about RAID 10, because I feel if I understand that, I'll understand the other. So, I get the definition of RAID 10 - "minimum 4 disks, a striped array whose segments are mirrored". If I've got 4 disks and Disks 1 and 2 are a mirrored pair, and Disks 3 and 4 are a mirrored pair - where does the data get striped? Thanks.

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  • Can you explain how to understand what the 'iwconfig' command displays in Ubuntu-9.04?

    - by Shawn
    I'm having trouble making my wireless connection work, and I realized I don't really know how to use the tools I have, in this case, the iwconfig command in Ubuntu-9.04. Here is what I get: ***iwconfig*** - lo no wireless extensions. eth0 no wireless extensions. wmaster0 no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"Network" Mode:Managed Frequency:2.412 GHz Access Point: Not-Associated Tx-Power=20 dBm Retry min limit:7 RTS thr:off Fragment thr=2352 B Power Management:off Link Quality:0 Signal level:0 Noise level:0 Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 vboxnet0 no wireless extensions. pan0 no wireless extensions. "Network" is the name of my wireless network, btw. But what does this all mean? How can this information help me aquire a working wireless connection? When I try associating a key using sudo iwconfig wlan0 key s:my_key I get the following error message: Error for wireless request "Set Encode" (8B2A) : SET failed on device wlan0 ; Invalid argument. I do have the right key though, so what's the problem?

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  • Can someone please explain these Network Activity entries are? (resource monitor windows 7)

    - by Keyes
    The first one is the address microsoftword.com.br. What is this? I noticed when I connected windows to the internet briefly, and it went away soon after. when I typed the address into my tablet, it redirected to bing with the search "microsoftword com" with MSSRPD at the end of the address. The other unknowns seemed to appear when my brothers laptop was connected to the network. Is that normal? Usually if I disconnected and reconnected they would appear, but I noticed when I had disconnected and reconnected to try it didn't happen as he wasn't connected. I'm concerned about the microsoftword one is. Is it legitimate? The svchost that associated with is a legit svchost image.

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  • Can you explain how to understand what the 'iwconfig' command displays in Ubuntu-9.04?

    - by Shawn
    I'm having trouble making my wireless connection work, and I realized I don't really know how to use the tools I have, in this case, the iwconfig command in Ubuntu-9.04. Here is what I get: ***iwconfig*** - lo no wireless extensions. eth0 no wireless extensions. wmaster0 no wireless extensions. wlan0 IEEE 802.11bgn ESSID:"Network" Mode:Managed Frequency:2.412 GHz Access Point: Not-Associated Tx-Power=20 dBm Retry min limit:7 RTS thr:off Fragment thr=2352 B Power Management:off Link Quality:0 Signal level:0 Noise level:0 Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 vboxnet0 no wireless extensions. pan0 no wireless extensions. "Network" is the name of my wireless network, btw. But what does this all mean? How can this information help me aquire a working wireless connection? When I try associating a key using sudo iwconfig wlan0 key s:my_key I get the following error message: Error for wireless request "Set Encode" (8B2A) : SET failed on device wlan0 ; Invalid argument. I do have the right key though, so what's the problem?

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  • What trivial real-life example do you use to explain programming to total non-programmers?

    - by anon
    Programmers seem to live in a world of their own (as this site indicates), with their own vibrant culture - and their own premises and vocabulary. Once we've been in the field for a bit, we take a lot of things for granted. But I'm often faced with the question "What do you do?" Or "What is programming?" I generally try to answer this with a small, often trivial, real-world example of how programming is prevalent in our everyday lives and keeps things running. The example I use most often is an elevator - someone has to program the logic of that... And I've seen elevators that are "smart" and ones that are quite backwards and foolish. (And you can easily understand if/decision and looping from that... incorporates a lot of important programming concepts in a very small example.) I've sometimes heard people use traffic lights as an example. What example do you / would you use to explain the concept of programming to someone completely clueless?

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  • Java binary files writeUTF... explain specifications...

    - by user69514
    I'm studying Java on my own. One of the exercises is the following, however I do not really understand what it is asking to.... any smart java gurus out there that could explain this in more detail and simple words? Thanks Suppose that you have a binary file that contains numbers whos type is either int or double. You dont know the order of the numbers in the file, but their order is recorded in a string at the begining of the file. The string is composed of the letters i for int, and d for double, in the order of the types of the subsequent numbers. The string is written using the method writeUTF. For example the string "iddiiddd" indicated that the file contains eight values, as follows: one integer, followed by two doubles, followed by two integers, followed by three doubles. Read this binary file and create a new text file of the values written one to a line.

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  • Can someone explain the ivy.xml dependency's conf attribute?

    - by tieTYT
    I can't find any thorough explanation of the ivy dependency tag's conf attribute: <dependency org="hibernate" name="hibernate" rev="3.1.3" conf="runtime, standalone -> runtime(*)"/> See that conf attribute? I can't find any explanation (that I can understand) about the right hand side of the - symbol. PLEASE keep in mind I don't know the first thing about maven so please explain this attribute with that consideration. Yes, I've already looked at this: http://ant.apache.org/ivy/history/latest-release/ivyfile/dependency.html Thanks, Dan

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  • Can someone explain this "endian-ness" function for me?

    - by Mike
    Write a program to determine whether a computer is big-endian or little-endian. bool endianness() { int i = 1; char *ptr; ptr = (char*) &i; return (*ptr); } So I have the above function. I don't really get it. ptr = (char*) &i, which I think means a pointer to a character at address of where i is sitting, so if an int is 4 bytes, say ABCD, are we talking about A or D when you call char* on that? and why? Would some one please explain this in more detail? Thanks. So specifically, ptr = (char*) &i; when you cast it to char*, what part of &i do I get?

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  • Someone explain to me the meanings behind the naming conventions used in .net?

    - by IbrarMumtaz
    I need someone to explain the following names; Asynchronous Delegates. Asynchronous methods. Asynchronous events. I'm currently going over this for my 70-536 exam and I am covering all my bases so far. The threading chapter and online resources have been good to me on my second read through. Still though, the names used above mean absolutely nothing to me? I would really appreciate the meaning behind the word 'Asynchronous' and its relevance to Delegates, methods and events. Feel free to go into as much detail as you like. Thanks, Ibrar

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  • I need someone for explain this ASP function to me.

    - by Ronnie Chester Lynwood
    Hello! I've got an ASP document that 5 years old. Actually I'm working with PHP but I must use ASP for a Windows Application. So I need someone to explain this function to me. Thanks anyway. //DNS SETTINGS ARE INCLUDED ALREADY. function Check_Is_Web_Locked() dim cmdDB , Ret OpenDatabase Set cmdDB = Server.CreateObject("ADODB.Command") With cmdDB .ActiveConnection = DBCon .CommandText = "TICT_CHECK_WEB_STATUS" .CommandType = adCmdStoredProc .Parameters.Append .CreateParameter("RETURN_VALUE", adInteger, adParamReturnValue, 0) .Execute,,adExecuteNoRecords Ret = Trim(.Parameters("RETURN_VALUE")) End With Set cmdDB = Nothing CloseDatabase Check_Is_Web_Locked = Ret end function What does this functions do? Is "TICT_CHECK_WEB_STATUS" a StoredProcedure? If it's what are the coulumns that function looking for?

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  • How can I explain to a programmer that CSS positioning has many benefits over table based layouts?

    - by Pat
    I have a friend who wishes to work as a freelance web developer, but insists that tables are the way forwards for layouts. Several points he maintains in favour of tables: 1 This is what was taught at the beginning of 10 years of programming & computer science degrees. 2 Large companies use tables to achieve 'technical' things. 3 It saves time I have coded him some examples of CSS exactly matching table based layouts, and provided many links to articles explaining SEO and accessibility benefits. From the perspective of a client, I have been explaining to him that I wouldn't hire someone using outdated methods as their main strategy for layout. As he is my friend and I wish him every success, I believe it is important for him to gain the best start when pitching for work. The question again: How can I explain to a programmer that CSS positioning has many benefits over table based layouts?

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  • Can someone please explain to me the basic function of Intents in the Android OS?

    - by K-RAN
    I'm new to programming applications for the Android OS. As far as general architecture of the OS goes, I understand that processes are implemented as Linux processes and that each one is sandboxed. However, I'm utterly confused on the IPCs and syscalls (if any) used. I know that the IBinder is a form of this; parcels are sent back and forth between processes and Bundles are array forms of parcels (?). But even that is still unfamiliar to me. Same with Intents. All in all, I don't understand what kinds of IPCs are implemented and how. Could someone briefly explain to me the specific methods used by user level applications in Android OS to communicate with each other and the OS? I've done kernel programming and played with various IPCs in Linux (Ubuntu and Debian) so it would help immensely if this was all explained in relation to what I'm familiar with... Thanks in advance!

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  • SRAM Cell Diagram - Can someone explain this a bit more clearly? ( From COMP1917 @ UNSW: Lecture 2 o

    - by Kristina
    I've begun watching a series of first year lectures from the University of New South Wales (UNSW) in Australia, and I'm a bit perplexed by the instructors explanation of how an SRAM gate works. I realize this isn't exactly "programming-related" but since it comes from a series of lectures relating to computing and programming, I thought StackOverflow may be able to help (reddit failed me entirely). In this lecture beginning at around 32:12, Richard (the lecturer) tries to explain how a "latch gate" works within SRAM. Although his students seem to keep up, I feel I'm missing something crucial which is preventing the concept from really "clicking" in my brain. For convenience, I've added the image from the video below: Thanks in advance for any help you can provide, but if this question doesn't fit your view of "programming-related" could you please provide an alternate forum for this in a comment when you cast your close vote? Thanks!

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  • How to explain to users the advantages of dumb primary key?

    - by Hao
    Primary key attractiveness I have a boss(and also users) that wants primary key to be sophisticated/smart/attractive control number(sort of like Social Security number, or credit card number format) I just padded the primary key(in Views) with zeroes to appease their desire to make the control number sophisticated,smart and attractive. But they wanted it as: first 2 digits as client code, then 4 digits as year year, then last 4 digits as transaction number on that client on a given year, then reset the transaction number of client to 1 when next year flows. Each client's transaction starts with 1. e.g. WM20090001, WM20090002, BB2009001, WM20100001, BB20100001 But as I wanted to make things as simple as possible, I forgo embedding their suggested smartness in primary key, I just keep the primary key auto increments regardless of client and year. But to make it not dull-looking(they really are adamant to make the primary key as smart control number), I made the primary key appears to them smart, on view query, I put the client code and four digit year code on front of the eight-zero padded autoincrement key, i.e. WM200900000001. Sort of slug-like information on autoincremented primary key. Keeping primary key autoincrement regardless of any other information, we are able keep other potential side effects problem when they edit a record, for example, if they made a mistake of entering the transaction on WM, then they edit the client code to BB, if we use smart primary key, the primary keys of WM customer will have gaps in their control number. Or worse yet, instead of letting the control numbers have gaps/holes, the user will request that subsequent records of that gap should shift up to that gap and have their subsequent primary keys re-adjust(decremented). How do you deal with these user requests(reasonable or otherwise)? Do you yield to their request? Or just continue using dumb primary key and explain them the repercussions of having a very smart/sophisticated primary key and educate them the significant advantages of having a dumb primary key? P.S. quotable quote(http://articles.techrepublic.com.com/5100-10878_11-1044961.html): "If you hold your tongue the first time users ask what is for them a reasonable request, things will work a lot better in the end."

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  • Explain this C# code: byte* p = (byte*) (void*) Scan0;

    - by qulzam
    I found the code from the net in which i cant understand this line:- byte* p = (byte*)(void*)Scan0; There Scan0 is System.IntPtr. It is code of C#.Net. Plz Explain the above line. The complete code is given below. this is code to convert a image in grayscale. public static Image GrayScale(Bitmap b) { BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe { byte* p = (byte*)(void*)Scan0; int nOffset = stride - b.Width * 3; byte red, green, blue; for (int y = 0; y < b.Height; ++y) { for (int x = 0; x < b.Width; ++x) { blue = p[0]; green = p[1]; red = p[2]; p[0] = p[1] = p[2] = (byte)(.299 * red + .587 * green + .114 * blue); p += 3; } p += nOffset; } } b.UnlockBits(bmData); return (Image)b; } I understand all the code but only have the problem on this line. byte* p = (byte*)(void*)Scan0;

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  • To what extent should code try to explain fatal exceptions?

    - by Andrzej Doyle
    I suspect that all non-trivial software is likely to experience situations where it hits an external problem it cannot work around and thus needs to fail. This might be due to bad configuration, an external server being down, disk full, etc. In these situations, especially if the software is running in non-interactive mode, I expect that all one can really do is log an error and wait for the admin to read the logs and fix the problem. If someone happens to interact with the software in the meantime, e.g. a request comes in to a server that failed to initialize properly, then perhaps an appropriate hint can be given to check the logs and maybe even the error can be echoed (depending on whether you can tell if they're a technical guy as opposed to a business user). For the moment though let's not think too hard about this part. My question is, to what extent should the software be responsible for trying to explain the meaning of the fatal error? In general, how much competence/knowledge are you allowed to presume on administrators of the software, and how much should you include troubleshooting information and potential resolution steps when logging fatal errors? Of course if there's something that's unique to the runtime context this should definitely be logged; but lets assume your software needs to talk to Active Directory via LDAP and gets back an error "[LDAP: error code 49 - 80090308: LdapErr: DSID-0C090334, comment: AcceptSecurityContext error, data 525, vece]". Is it reasonable to assume that the maintainers will be able to Google the error code and work out what it means, or should the software try to parse the error code and log that this is caused by an incorrect user DN in the LDAP config? I don't know if there is a definitive best-practices answer for this, so I'm keen to hear a variety of views.

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  • Running 32 bit assembly code on a 64 bit Linux & 64 bit Processor : Explain the anomaly.

    - by claws
    Hello, I'm in an interesting problem.I forgot I'm using 64bit machine & OS and wrote a 32 bit assembly code. I don't know how to write 64 bit code. This is the x86 32-bit assembly code for Gnu Assembler (AT&T syntax) on Linux. //hello.S #include <asm/unistd.h> #include <syscall.h> #define STDOUT 1 .data hellostr: .ascii "hello wolrd\n"; helloend: .text .globl _start _start: movl $(SYS_write) , %eax //ssize_t write(int fd, const void *buf, size_t count); movl $(STDOUT) , %ebx movl $hellostr , %ecx movl $(helloend-hellostr) , %edx int $0x80 movl $(SYS_exit), %eax //void _exit(int status); xorl %ebx, %ebx int $0x80 ret Now, This code should run fine on a 32bit processor & 32 bit OS right? As we know 64 bit processors are backward compatible with 32 bit processors. So, that also wouldn't be a problem. The problem arises because of differences in system calls & call mechanism in 64-bit OS & 32-bit OS. I don't know why but they changed the system call numbers between 32-bit linux & 64-bit linux. asm/unistd_32.h defines: #define __NR_write 4 #define __NR_exit 1 asm/unistd_64.h defines: #define __NR_write 1 #define __NR_exit 60 Anyway using Macros instead of direct numbers is paid off. Its ensuring correct system call numbers. when I assemble & link & run the program. $cpp hello.S hello.s //pre-processor $as hello.s -o hello.o //assemble $ld hello.o // linker : converting relocatable to executable Its not printing helloworld. In gdb its showing: Program exited with code 01. I don't know how to debug in gdb. using tutorial I tried to debug it and execute instruction by instruction checking registers at each step. its always showing me "program exited with 01". It would be great if some on could show me how to debug this. (gdb) break _start Note: breakpoint -10 also set at pc 0x4000b0. Breakpoint 8 at 0x4000b0 (gdb) start Function "main" not defined. Make breakpoint pending on future shared library load? (y or [n]) y Temporary breakpoint 9 (main) pending. Starting program: /home/claws/helloworld Program exited with code 01. (gdb) info breakpoints Num Type Disp Enb Address What 8 breakpoint keep y 0x00000000004000b0 <_start> 9 breakpoint del y <PENDING> main I tried running strace. This is its output: execve("./helloworld", ["./helloworld"], [/* 39 vars */]) = 0 write(0, NULL, 12 <unfinished ... exit status 1> Explain the parameters of write(0, NULL, 12) system call in the output of strace? What exactly is happening? I want to know the reason why exactly its exiting with exitstatus=1? Can some one please show me how to debug this program using gdb? Why did they change the system call numbers? Kindly change this program appropriately so that it can run correctly on this machine. EDIT: After reading Paul R's answer. I checked my files claws@claws-desktop:~$ file ./hello.o ./hello.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped claws@claws-desktop:~$ file ./hello ./hello: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, not stripped All of my questions still hold true. What exactly is happening in this case? Can someone please answer my questions and provide an x86-64 version of this code?

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  • Can anyone explain why my crypto++ decrypted file 16 bytes short?

    - by Tom Williams
    I suspect it might be too much to hope for, but can anyone with experience with crypto++ explain why the "decrypted.out" file created by main() is 16 characters short (which probably not coincidentally is the block size)? I think the issue must be in CryptStreamBuffer::GetNextChar(), but I've been staring at it and the crypto++ documentation for hours. Any other comments about how crummy or naive my std::streambuf implementation are also welcome ;-) And I've just noticed I'm missing some calls to delete so you don't have to tell me about those. Thanks, Tom // Runtime Includes #include <iostream> // Crypto++ Includes #include "aes.h" #include "modes.h" // xxx_Mode< > #include "filters.h" // StringSource and // StreamTransformation #include "files.h" using namespace std; class CryptStreamBuffer: public std::streambuf { public: CryptStreamBuffer(istream& encryptedInput, CryptoPP::StreamTransformation& c); CryptStreamBuffer(ostream& encryptedOutput, CryptoPP::StreamTransformation& c); protected: virtual int_type overflow(int_type ch = traits_type::eof()); virtual int_type uflow(); virtual int_type underflow(); virtual int_type pbackfail(int_type ch); virtual int sync(); private: int GetNextChar(); int m_NextChar; // Buffered character CryptoPP::StreamTransformationFilter* m_StreamTransformationFilter; CryptoPP::FileSource* m_Source; CryptoPP::FileSink* m_Sink; }; // class CryptStreamBuffer CryptStreamBuffer::CryptStreamBuffer(istream& encryptedInput, CryptoPP::StreamTransformation& c) : m_NextChar(traits_type::eof()), m_StreamTransformationFilter(0), m_Source(0), m_Sink(0) { m_StreamTransformationFilter = new CryptoPP::StreamTransformationFilter(c); m_Source = new CryptoPP::FileSource(encryptedInput, false, m_StreamTransformationFilter); } CryptStreamBuffer::CryptStreamBuffer(ostream& encryptedOutput, CryptoPP::StreamTransformation& c) : m_NextChar(traits_type::eof()), m_StreamTransformationFilter(0), m_Source(0), m_Sink(0) { m_Sink = new CryptoPP::FileSink(encryptedOutput); m_StreamTransformationFilter = new CryptoPP::StreamTransformationFilter(c, m_Sink); } CryptStreamBuffer::int_type CryptStreamBuffer::overflow(int_type ch) { return m_StreamTransformationFilter->Put((byte)ch); } CryptStreamBuffer::int_type CryptStreamBuffer::uflow() { int_type result = GetNextChar(); // Reset the buffered character m_NextChar = traits_type::eof(); return result; } CryptStreamBuffer::int_type CryptStreamBuffer::underflow() { return GetNextChar(); } CryptStreamBuffer::int_type CryptStreamBuffer::pbackfail(int_type ch) { return traits_type::eof(); } int CryptStreamBuffer::sync() { if (m_Sink) { m_StreamTransformationFilter->MessageEnd(); } } int CryptStreamBuffer::GetNextChar() { // If we have a buffered character do nothing if (m_NextChar != traits_type::eof()) { return m_NextChar; } // If there are no more bytes currently available then pump the source // *** I SUSPECT THE PROBLEM IS HERE *** if (m_StreamTransformationFilter->MaxRetrievable() == 0) { m_Source->Pump(1024); } // Retrieve the next byte byte nextByte; size_t noBytes = m_StreamTransformationFilter->Get(nextByte); if (0 == noBytes) { return traits_type::eof(); } // Buffer up the next character m_NextChar = nextByte; return m_NextChar; } void InitKey(byte key[]) { key[0] = -62; key[1] = 102; key[2] = 78; key[3] = 75; key[4] = -96; key[5] = 125; key[6] = 66; key[7] = 125; key[8] = -95; key[9] = -66; key[10] = 114; key[11] = 22; key[12] = 48; key[13] = 111; key[14] = -51; key[15] = 112; } void DecryptFile(const char* sourceFileName, const char* destFileName) { ifstream ifs(sourceFileName, ios::in | ios::binary); ofstream ofs(destFileName, ios::out | ios::binary); byte key[CryptoPP::AES::DEFAULT_KEYLENGTH]; InitKey(key); CryptoPP::ECB_Mode<CryptoPP::AES>::Decryption decryptor(key, sizeof(key)); if (ifs) { if (ofs) { CryptStreamBuffer cryptBuf(ifs, decryptor); std::istream decrypt(&cryptBuf); int c; while (EOF != (c = decrypt.get())) { ofs << (char)c; } ofs.flush(); } else { std::cerr << "Failed to open file '" << destFileName << "'." << endl; } } else { std::cerr << "Failed to open file '" << sourceFileName << "'." << endl; } } void EncryptFile(const char* sourceFileName, const char* destFileName) { ifstream ifs(sourceFileName, ios::in | ios::binary); ofstream ofs(destFileName, ios::out | ios::binary); byte key[CryptoPP::AES::DEFAULT_KEYLENGTH]; InitKey(key); CryptoPP::ECB_Mode<CryptoPP::AES>::Encryption encryptor(key, sizeof(key)); if (ifs) { if (ofs) { CryptStreamBuffer cryptBuf(ofs, encryptor); std::ostream encrypt(&cryptBuf); int c; while (EOF != (c = ifs.get())) { encrypt << (char)c; } encrypt.flush(); } else { std::cerr << "Failed to open file '" << destFileName << "'." << endl; } } else { std::cerr << "Failed to open file '" << sourceFileName << "'." << endl; } } int main(int argc, char* argv[]) { EncryptFile(argv[1], "encrypted.out"); DecryptFile("encrypted.out", "decrypted.out"); return 0; }

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  • Can anyone explain why my crypto++ decrypted file is 16 bytes short?

    - by Tom Williams
    I suspect it might be too much to hope for, but can anyone with experience with crypto++ explain why the "decrypted.out" file created by main() is 16 characters short (which probably not coincidentally is the block size)? I think the issue must be in CryptStreamBuffer::GetNextChar(), but I've been staring at it and the crypto++ documentation for hours. Any other comments about how crummy or naive my std::streambuf implementation are also welcome ;-) And I've just noticed I'm missing some calls to delete so you don't have to tell me about those. Thanks, Tom // Runtime Includes #include <iostream> // Crypto++ Includes #include "aes.h" #include "modes.h" // xxx_Mode< > #include "filters.h" // StringSource and // StreamTransformation #include "files.h" using namespace std; class CryptStreamBuffer: public std::streambuf { public: CryptStreamBuffer(istream& encryptedInput, CryptoPP::StreamTransformation& c); CryptStreamBuffer(ostream& encryptedOutput, CryptoPP::StreamTransformation& c); protected: virtual int_type overflow(int_type ch = traits_type::eof()); virtual int_type uflow(); virtual int_type underflow(); virtual int_type pbackfail(int_type ch); virtual int sync(); private: int GetNextChar(); int m_NextChar; // Buffered character CryptoPP::StreamTransformationFilter* m_StreamTransformationFilter; CryptoPP::FileSource* m_Source; CryptoPP::FileSink* m_Sink; }; // class CryptStreamBuffer CryptStreamBuffer::CryptStreamBuffer(istream& encryptedInput, CryptoPP::StreamTransformation& c) : m_NextChar(traits_type::eof()), m_StreamTransformationFilter(0), m_Source(0), m_Sink(0) { m_StreamTransformationFilter = new CryptoPP::StreamTransformationFilter(c); m_Source = new CryptoPP::FileSource(encryptedInput, false, m_StreamTransformationFilter); } CryptStreamBuffer::CryptStreamBuffer(ostream& encryptedOutput, CryptoPP::StreamTransformation& c) : m_NextChar(traits_type::eof()), m_StreamTransformationFilter(0), m_Source(0), m_Sink(0) { m_Sink = new CryptoPP::FileSink(encryptedOutput); m_StreamTransformationFilter = new CryptoPP::StreamTransformationFilter(c, m_Sink); } CryptStreamBuffer::int_type CryptStreamBuffer::overflow(int_type ch) { return m_StreamTransformationFilter->Put((byte)ch); } CryptStreamBuffer::int_type CryptStreamBuffer::uflow() { int_type result = GetNextChar(); // Reset the buffered character m_NextChar = traits_type::eof(); return result; } CryptStreamBuffer::int_type CryptStreamBuffer::underflow() { return GetNextChar(); } CryptStreamBuffer::int_type CryptStreamBuffer::pbackfail(int_type ch) { return traits_type::eof(); } int CryptStreamBuffer::sync() { if (m_Sink) { m_StreamTransformationFilter->MessageEnd(); } } int CryptStreamBuffer::GetNextChar() { // If we have a buffered character do nothing if (m_NextChar != traits_type::eof()) { return m_NextChar; } // If there are no more bytes currently available then pump the source // *** I SUSPECT THE PROBLEM IS HERE *** if (m_StreamTransformationFilter->MaxRetrievable() == 0) { m_Source->Pump(1024); } // Retrieve the next byte byte nextByte; size_t noBytes = m_StreamTransformationFilter->Get(nextByte); if (0 == noBytes) { return traits_type::eof(); } // Buffer up the next character m_NextChar = nextByte; return m_NextChar; } void InitKey(byte key[]) { key[0] = -62; key[1] = 102; key[2] = 78; key[3] = 75; key[4] = -96; key[5] = 125; key[6] = 66; key[7] = 125; key[8] = -95; key[9] = -66; key[10] = 114; key[11] = 22; key[12] = 48; key[13] = 111; key[14] = -51; key[15] = 112; } void DecryptFile(const char* sourceFileName, const char* destFileName) { ifstream ifs(sourceFileName, ios::in | ios::binary); ofstream ofs(destFileName, ios::out | ios::binary); byte key[CryptoPP::AES::DEFAULT_KEYLENGTH]; InitKey(key); CryptoPP::ECB_Mode<CryptoPP::AES>::Decryption decryptor(key, sizeof(key)); if (ifs) { if (ofs) { CryptStreamBuffer cryptBuf(ifs, decryptor); std::istream decrypt(&cryptBuf); int c; while (EOF != (c = decrypt.get())) { ofs << (char)c; } ofs.flush(); } else { std::cerr << "Failed to open file '" << destFileName << "'." << endl; } } else { std::cerr << "Failed to open file '" << sourceFileName << "'." << endl; } } void EncryptFile(const char* sourceFileName, const char* destFileName) { ifstream ifs(sourceFileName, ios::in | ios::binary); ofstream ofs(destFileName, ios::out | ios::binary); byte key[CryptoPP::AES::DEFAULT_KEYLENGTH]; InitKey(key); CryptoPP::ECB_Mode<CryptoPP::AES>::Encryption encryptor(key, sizeof(key)); if (ifs) { if (ofs) { CryptStreamBuffer cryptBuf(ofs, encryptor); std::ostream encrypt(&cryptBuf); int c; while (EOF != (c = ifs.get())) { encrypt << (char)c; } encrypt.flush(); } else { std::cerr << "Failed to open file '" << destFileName << "'." << endl; } } else { std::cerr << "Failed to open file '" << sourceFileName << "'." << endl; } } int main(int argc, char* argv[]) { EncryptFile(argv[1], "encrypted.out"); DecryptFile("encrypted.out", "decrypted.out"); return 0; }

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