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Jan 21st, 2009
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C++ character overflow help!!

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Hi
I am using Visual 6 C++ and try to retrieve a member's all closed trades. i declare a string as below:

char str[8000]={0};

But this declaration is ok and the program work fine if the member's record size does not exceed 8000bytes.


In order to be able to retrieve member's record where total size more than 8000, i have declare as below:

char *str = new char();

This declaration works fine but it hang my server. Whenever i execute this API with this declaration, my MT4 server will hang, and its service cannot restarted. We have to restart the server.

Is there any way or any example where i can return big volume data?


Thanks.


My main code to retrieve data as below:
C++ Syntax (Toggle Plain Text)
  1. trades=ExtServer->OrdersGetClosed(start, end,userlogins,1, &total);
  2.  
  3. //OrdersGetClosed(const time_t from,const time_t to,const int *logins,const int count,int* total);
  4.  
  5. // check orders
  6. for(j=0; j<total; j++)
  7. {
  8. if(strcmp(GetCmd(trades[j].cmd), "credit")!=0 && strcmp(GetCmd(trades[j].cmd), "balance")!=0)
  9. {
  10. sprintf(tmp,"%d",trades[j].order);
  11. strcat(str,tmp);
  12. strcat(str,",");
  13. sprintf(tmp,"%d",trades[j].login);
  14. strcat(str,tmp);
  15. strcat(str,",");
  16. FormatDateTime(trades[j].open_time,tmp,sizeof(tmp)-1,TRUE,TRUE);
  17. strcat(str,tmp);
  18. strcat(str,",");
  19. strcat(str, GetCmd(trades[j].cmd));
  20. strcat(str,",");
  21. COPY_STR(tmp, trades[j].symbol);
  22. _strlwr(tmp);
  23. strcat(str, tmp);
  24. strcat(str,",");
  25. sprintf(tmp,"%.2lf",trades[j].volume/100.0);
  26. strcat(str,tmp);
  27. strcat(str,",");
  28. ToSymExt(tmp, trades[j].open_price, trades[j].digits);
  29. strcat(str, tmp);
  30. strcat(str,",");
  31. FormatDateTime(trades[j].close_time,tmp,sizeof(tmp)-1,TRUE,TRUE);
  32. strcat(str,tmp);
  33. strcat(str,",");
  34. ToSym(tmp, trades[j].close_price, trades[j].digits);
  35. strcat(str, tmp);
  36. strcat(str,",");
  37.  
  38. strcat(str, ToMoney(trades[j].commission, 2, tmp, sizeof(tmp)-1));
  39. strcat(str,",");
  40. strcat(str, ToMoney(trades[j].taxes, 2, tmp, sizeof(tmp)-1));
  41. strcat(str,",");
  42. strcat(str, ToMoney(trades[j].commission_agent, 2, tmp, sizeof(tmp)-1));
  43. strcat(str,",");
  44. strcat(str, ToMoney(trades[j].storage, 2, tmp, sizeof(tmp)-1));
  45. strcat(str,",");
  46. strcat(str, ToMoney(trades[j].profit, 2, tmp, sizeof(tmp)-1));
  47. strcat(str,",");
  48. mul=Decimals(trades[j].digits);
  49. if(trades[j].cmd==OP_BUY)
  50. pips=NormalizeDouble(trades[j].close_price*mul,0)-NormalizeDouble(trades[j].open_price *mul,0);
  51. else
  52. pips=NormalizeDouble(trades[j].open_price *mul,0)-NormalizeDouble(trades[j].close_price*mul,0);
  53.  
  54. sprintf(tmp,"%d", int(pips));
  55. strcat(str, tmp);
  56. strcat(str,",");
  57. strcat(str, trades[j].comment);
  58.  
  59. strcat(str,"\n");
  60. }
  61.  
  62. }
  63. strcat(str,"end\r\n");
  64. //---- clear
  65. HEAP_FREE(trades); trades=NULL;
  66. if(strlen(str)==0)
  67. return _snprintf(buffer,size-1,"ERROR\r\nNo Orders for %d\r\nend\r\n", userlogin);
  68. else
  69. return _snprintf(buffer,size-1,"%s", str);


i am using native dll and cannot use MFC

any advise would be appreciated thanks
Last edited by Ancient Dragon; Jan 22nd, 2009 at 12:10 am. Reason: add code tags
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pacx is offline Offline
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Jan 22nd, 2009
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Re: C++ character overflow help!!

>>char *str = new char();

Do you really mean something like [icode]char *str = new char(Size);[/code] so that more than 1 character is allocated???

Can't really tell much from the code you posted because there are several undefined variables -- such as temp.
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Ancient Dragon is offline Offline
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Re: C++ character overflow help!!

hi

i am currently using
char str[8000]={0};

this program actually retrieve some data via api and i am suppose to return and 'massage' the values in the api via the variable str

the problem with this code is that when i try to return str that exceed 8000 characters, the program will hung...
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pacx is offline Offline
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Jan 22nd, 2009
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Re: C++ character overflow help!!

Do you need to return the whole result in a character buffer?

Could you return a vector of strings with one string per trade?
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Murtan is offline Offline
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Re: C++ character overflow help!!

hi


my application allow only native dlls.. i cant seem to use string to solve my problem..
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pacx is offline Offline
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Jan 22nd, 2009
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Re: C++ character overflow help!!

Can you use vector?

If not, you have a little more work cut out for you, but it can still be done. (I am presuming you have a heap and can allocate memory.)

I can fairly easily imagine a class where you can 'add' a C style string to it and it would keep an array of the strings. When you call the 'add' it could allocate enough space to hold the string and copy it in. It would then store the pointer to the new string in an array of character pointers. If you ran out of entries in the array of pointers, you could allocate a new array of pointers (some number of pointers bigger -- think 50 or 100) and copy the old pointers to it and release the old array.

This would provide functionality similar to vector<string> without using "non-native" code.

Once you have assembled all of the trade data, you would return this new object and the calling code could iterate the strings in the object to access all of the compiled data.
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Re: C++ character overflow help!!

Click to Expand / Collapse  Quote originally posted by pacx ...
hi


my application allow only native dlls.. i cant seem to use string to solve my problem..
if for some reason you cant use stl, you coulc have buffers that hold up to a set amount;in other words keep a large buffer aside that holds, say 4000 characters, as soon as it is full use the next 4000, and switch back and forth. Aside from having more thant 8000 characters at your disposal, anything more than that has to go somewhere if you are at a hard limit.
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seanhunt is offline Offline
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Jan 22nd, 2009
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Re: C++ character overflow help!!

any sample codes i can take a look ?
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This thread is more than three months old

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