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  • procedure that swaps the bytes (low/high) of a Word variable

    - by Altar
    Hi. I have this procedure that swaps the bytes (low/high) of a Word variable (It does the same stuff as System.Swap function). The procedure works when the compiler optimization is OFF but not when it is ON. Can anybody help me with this? { UNSAFE! IT IS NOW WORKING WHEN COMPILER OPTIMIZATION IS ON ! } procedure SwapWord_NotWorking(VAR TwoBytes: word); asm Mov EBX, TwoBytes Mov AX, [EBX] XCHG AL,AH Mov [EBX], AX end;

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  • How to determine the port numbers for peripheral devices?

    - by smwikipedia
    I know that peripheral devices such as a hard driver, a floppy driver, etc are controlled by reading/writing certain control registers on their device controllers. I am wondering about the following questions: Is it true that when these peripheral devices are plugged onto the computer, the addresses(port numbers) of their control registers are thus determined by how they are attached to the address bus (i.e. the hard-wiring rules, not any soft things)? Who makes the scheme of the port number assignment? If I was given a naked computer(with no operating system and with many peripheral devices), how could I figure out the port number assignment so I can use them to control peripheral deveices. At last and as usual, thanks for your patience and reply. 8^)

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  • need to get computer speaking to a cell phone

    - by I__
    i have this super manual: http://www.arib.or.jp/IMT-2000/V710Dec08/5_Appendix/R99/27/27005-320.pdf i dont understand whether it is for every phone or just a certain subset i would like to know what i need to get started to have my computer speak to the phone i am ready to write in c#, c++, or what ever they need has anyone had experience writing AT commands?

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  • How to find the jmp address during a x86 function call?

    - by Bruce
    Suppose we have a call foo statement. So when the assembler encounters a call statement it breaks it down into - push ip + 6 jmp <addr of foo> I have the return address in a register ebx. Now I want to find out the "addr of foo". How do I do it? I want to confirm that the push statement is present before the jmp. Will the memory map look something like this? ------- push (what will be the value stored in this byte?? opcode ??) ------- jmp (what will be the value stored in this byte?? opcode ??) ------- jmp byte 1 ------- jmp byte 2 ------- jmp byte 3 ------- jmp byte 4 ------- return address stored in ebx ------- What are the opcodes for push and jmp?

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  • Instrumenting a string

    - by George Polevoy
    Somewhere in C++ era i have crafted a library, which enabled string representation of the computation history. Having a math expression like: TScalar Compute(TScalar a, TScalar b, TScalar c) { return ( a + b ) * c; } I could render it's string representation: r = Compute(VerbalScalar("a", 1), VerbalScalar("b", 2), VerbalScalar("c", 3)); Assert.AreEqual(9, r.Value); Assert.AreEqual("(a+b)*c==(1+2)*3", r.History ); C++ operator overloading allowed for substitution of a simple type with a complex self-tracking entity with an internal tree representation of everything happening with the objects. Now i would like to have the same possibility for NET strings, only instead of variable names i would like to see a stack traces of all the places in code which affected a string. And i want it to work with existing code, and existing compiled assemblies. Also i want all this to hook into visual studio debugger, so i could set a breakpoint, and see everything that happened with a string. Which technology would allow this kind of things? I know it sound like an utopia, but I think visual studio code coverage tools actually do the same kind of job while instrumenting the assemblies.

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  • How to determine the port numbers for peripherals devices?

    - by smwikipedia
    I know that peripheral devices such as a hard driver, a floppy driver, etc are controlled by reading/writing certain control registers on their device controllers. I am wondering about the following questions: Is it true that when these peripheral devices are plugged onto the computer, the addresses(port numbers) of their control registers are thus determined by how they are attached to the address bus (i.e. the hard-wiring)? Who makes the scheme of the port number assignment? If I was given a naked computer(with no operating system and with many peripheral devices), how could I figure out the port number assignment so I can use them to control peripheral deveices.

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  • Translate to MIPS

    - by user2334400
    HELP Translate A[i] = B[i-1] + B[i] + B[i+1] to MIPS the address of array A is $s1 the address of array B is $s2 the value of i is $s3 lb $s1,0($s3) # $s1=A[i] lb $s2,0($s3) # $s2=B[i] sb $s2,0($s3) # store s2 add $t0, $zero, $s2 #t0=B[i] addi $s3,$s3,-1 #i=i-1 lb $s2 0($s3) #$s2=B[i-1] add $t1,$zero,$s2 #t1=B[i-1] add $s1,$t0,$t1 #A[i]=B[i-1]+B[i] addi $s3,$s3,2 #i+1 lb $s2,0($s3) #s2=B[i+1] add $t2,$zero,$s2 #t2=B[i+1] add $s1,$s1,$t2 #A[i] = t1 + B[i+1] sb $s1 I know this is kind of mess, but it's the best i can write

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  • What does the Kernel Virtual Memory of each process contain?

    - by claws
    When say 3 programs (executables) are loaded into memory the layout might look something like this: I've following questions: Is the concept of Virtual Memory limited to user processes? Because, I am wondering where does the Operating System Kernel, Drivers live? How is its memory layout? I know its operating system specific make your choice (windows/linux). They say, on a 32 bit machine in a 4GB address space. Half of it (or more recently 1GB) is occupied by kernel. I can see in this diagram that "Kernel Virtual memory" is occupying 0xc0000000 - 0xffffffff (= 1 GB). Are they talking about this? or is it something else? Just want to confirm. What exactly does the Kernel Virtual Memory of each of these processes contain? What is its layout? When we do IPC we talk about shared memory. I don't see any memory shared between these processes. Where does it live? Resources (files, registries in windows) are global to all processes. So, the resource/file handle table must be in some global space. Which area would that be in? Where can I know more about this kernel side stuff.

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  • Where are the function literals c++?

    - by academicRobot
    First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one.

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  • functions in assembler

    - by stupid_idiot
    hi, i have philosophised about the purpose of stack a little bit and after some coding i figured out what is it's strength. The only thing that lies in my stomache is how does it work with functions? I tried to make some easy function for adding two numbers using universal registers but I suppose that's not how does it work in C for example.. where are all the parameters, local variables and where is the result stored? how would you rewrite this to assembler?(how would compiler for C rewrite it?) int function(int a, int &b, int *c){ return a*(b++)+(*c); } i know this example kinda sucks.. but this way i can understand all the possibilities

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  • How to move value from the stack to ST(0)?

    - by George Edison
    I am having trouble believing the following code is the most efficient way to move a value from the stack to ST(0): .data var dd 4.2 tmp dd ? .code mov EAX, var push EAX ; top of stack now contains a value ; move it to ST(0) pop EAX mov tmp, EAX fld tmp Is the temporary variable really necessary? Further, is there an easier way to get a value from the stack to ST(0)?

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  • Interrupt ?13 (ah=48) - don't working

    - by GLeBaTi
    mov dl,00h mov ah,08h int 13h this is code showing normal parameters of floppy disk. mov dl,80h mov ah,08h int 13h this is code, showing not valid parameters of hard disk(may be, my hard disk space is big (LBA)), And I've written this code: mov dl,80h mov ah,48h int 13h it is code doing cf = 1(error). How fix it? I want learn parameters of my hard disk. (http://lrs.uni-passau.de/support/doc/interrupt-57/RB-0677.HTM)

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  • Calling a non-exported function in a DLL

    - by Nilbert
    I have a program which loads DLLs and I need to call one of the non-exported functions it contains. Is there any way I can do this, via searching in a debugger or otherwise? Before anyone asks, yes I have the prototypes and stuff for the functions.

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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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  • Xcode debugger showing assembler for nested classes in a static library

    - by Massif
    I have a project A which creates a static library. I have a project B which uses this library. When I am debugging project B, certain functions within project A will display assembler when stepped into or when a breakpoint set inside them is hit. In the debug navigator, the line containing the function is grey instead of black. The strange part is that other functions in the same source file have no problems displaying. The thing that all these functions seem to have in common is that they belong to nested classes. However, I'm not totally convinced that this is the issue since functions from other nested classes display correctly. Does anyone know the cause of this?

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  • PC boot: dl register and drive number

    - by kikou
    I read somewhere in the internet that, before jumping to 0x7c00, the BIOS loads into %dl the "drive number" of the booted device. But what is this "drive number"? Each device attached to the computer is assigned a number by the BIOS? If so, how can I know which number is a given device assigned to? Reading GRUB's source code I found when %dl has bits 0x80 and 0x70 set, it overwrites the whole register with 0x80. Why is that? Here is the code: jmp 3f /* grub-setup may overwrite this jump */ testb $0x80, %dl jz 2f 3: /* Ignore %dl different from 0-0x0f and 0x80-0x8f. */ testb $0x70, %dl jz 1f 2: movb $0x80, %dl 1: By the way. Is there any detailed resource on the boot process of PC's in the web? Specially about what the BIOS does before giving the control to the bootloader and also the standard codes used to communicate with it (like that "drive numer"). I was hoping to write my own bootloader and everything I found is a bit too vague, not technical enough to the point of informing of the exact state of the computer when my bootloader starts to run.

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  • Interaction between for loops with clock function?!

    - by learningtolive
    Can someone explain me the exact interaction in context of delay between the two for loops with clock function. How does for1 interact with for2 on the cout statement(30 on 640000000)? start=clock(); cout<<endl<<start<<endl; for(delay=0; delay<30; delay++) for(i=0; i<640000000; i++); end=clock(); cout<<end<<endl; cout<<"Num of ticks for non reg-loop: "; cout<<end-start<<'\n';

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  • Can the .NET MethodInfo cache be cleared or disabled?

    - by Anton
    Per MSDN, calling Type.GetMethods() stores reflected method information in a MemberInfo cache so the expensive operation doesn't have to be performed again. I have an application that scans assemblies/types, looking for methods that match a given specification. The problem is that memory consumption increases significantly (especially with large numbers of referenced assemblies) since .NET hangs onto the method metadata. Is there any way to clear or disable this MemberInfo cache?

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  • Deeper function profiling/emulation

    - by Syntax_Error
    Hello everyone Merry Christmas I need an advice I have the following code: int main() { int k=5000000; int p; int sum=0; for (p=0;p<k;p++) { sum+=p; } return 0; } When I assemble it I get main: pushl %ebp movl %esp, %ebp subl $16, %esp movl $5000000, -4(%ebp) movl $0, -12(%ebp) movl $0, -8(%ebp) jmp .L2 .L3: movl -8(%ebp), %eax addl %eax, -12(%ebp) addl $1, -8(%ebp) .L2: movl -8(%ebp), %eax cmpl -4(%ebp), %eax jl .L3 movl $0, %eax leave ret If I run it through gprof I get that main executed the most, which is quite obvious! Yet I want to go a step further and be able to know if L2, or L3 executed the most. here it is obvious that L3 executed the most. yet is there some kind of profiler, emulator that can give me that data for an entire code?

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  • carry flag and subtraction issue!

    - by Zia ur Rahman
    If a large number is subtracted from a smaller number then borrow is needed. The carry flag plays the role of borrow during the subtraction operation. Now suppose we want to subtract 56 from 66, obviously the borrow is needed and carry flag will be set. Now how this subtraction is performed to get the result -10, how computer will distinguish that the result is going to be a negative number. Please explain the process.

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  • Within a DLL, how is the function table structured?

    - by Willi Ballenthin
    I've been looking into the implementation of a device library that doesn't explicitly support my operating system. In particular, I have a disassembled DLL, and a fair amount of supporting source code. Now, how is the function table/export table structured? My understanding is that the first structure of the .data section is a table of VRAs. Next is a table of strings linked by index to that first address table. This makes sense to me, as a linker could translate between symbols and addresses. How do functions referenced by ordinals fit into this picture? How does one know which function has such and such ordinal number, and how does the linker resolve this? In other words, given that some other DLL imports SOME_LIBRARY_ordinal_7, how does the linker know which function to work with? Thanks, all! edit More information... Im working with the FTDI libraries, and would like to resolve which function is being invoked. In particular, I see something like: extern FTD2XX_Ordinal_28: near how might I go about determining which function is being referenced, and how does the linker do this?

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