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  • ask help: I need to create a demo application in Java to test my new designed Java Api

    - by Christophe
    A new programmer needs yourhelp. I'm working on a porject of re-developement of Java driver for the company's PIN pad terminals. the Java Api (CPXApplicationUpdate) will allow the applications in pinpads to be updated and to be downloaded at different speed (Baud rate). the Java Api was created. i followed the protocolto build the message. the message is to send to a RS-232 port. i'm trying to use setter and getter to let the code work as an API. import java.io.InputStream; import java.io.OutputStream; import java.util.Properties; public class CPXApplicationUpdate extends CPXCommand { private int speed; // TODO: temporary variable for baud rate test stub. // speed: baud rate of the maintenance application performing DL /** Creates a new instance of CPXApplicationUpdate */ public CPXApplicationUpdate() { speed = 9600; // no baud rate change CPXProcessor.logger.fine("-------CPXApplicationUpdate constructor"); // setParam("timeout", _cmdInfo.getDefaultParValue("timeout")); } public CPXApplicationUpdate(int speedinit) { speed = speedinit; // TODO: where to get the speed? wait for user input. CPXProcessor.logger.fine("-------CPXApplicationUpdate constructor"); // setParam("timeout", _cmdInfo.getDefaultParValue("timeout")); } public void setSpeed(int speed){ this.speed = speed; } protected void buildRequest() throws ElitePortException { String trans = ""; // build the full-qualified message trans = addToRequest(trans, (char) 0); trans = addToRequest(trans, (char) 5); trans = addToRequest(trans, (char) 6); trans = addToRequest(trans, (char) 0); trans = addToRequest(trans, (char) 0); trans = addToRequest(trans, (char) 2); switch (speed) { case 9600: trans = addToRequest(trans, (char) 0x09); break; case 19200: trans = addToRequest(trans, (char) 0x0A); break; case 115200: trans = addToRequest(trans, (char) 0x0E); break; default: // TODO: unexpected baud rate. throw(); break; } trans = EncryptBinary(trans); trans = "F0." + trans; wrapRequest(trans); } protected String addToRequest(String req, char c) { CPXProcessor.logger.fine("adding char to request: I-" + (int) c + " C-" + c + " H-" + Integer.toHexString((int) c)); return req + c; } protected String addToRequest(String req, String s) { CPXProcessor.logger.fine("adding String to request: S-" + s); return req + s; } protected String addToRequest(String req) { return req; } public void analyzeResponse() { String response_transaction, response; int absLen = _response.length(); if (absLen < 4) return; response = _response.substring(3); CPXProcessor.logger.fine("stripped response=[" + response + "]"); for (int i = 0; i < response.length(); i++) { char c = response.charAt(i); CPXProcessor.logger.fine("[" + i + "] = " + c + " <> " + Integer.toHexString((int) c)); } int status = (short) response.charAt(3); CPXProcessor.logger.fine("status = " + status); _outputValues.put("status", "" + status); } please help me to correct the code. Now, i need to create a demo application to test if this java driver (Java Api) works. the value of the speed can be input by users (command line), or creat property files. how can i do that?

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  • Call/Ret in x86 assembly embedded in C++

    - by SP658
    This is probably trivial, but for some reason I can't it to work. Its supposed to be a simple function that changes the last byte of a dword to 'AA' (10101010), but nothing happens when I call the function. It just returns my original dword __declspec(naked) long function(unsigned long inputDWord, unsigned long *outputDWord) { _asm{ mov ebx, dword ptr[esp+4] push ebx call SET_AA pop ebx mov eax, dword ptr[esp+8] mov dword ptr[eax], ebx } } __declspec(naked) unsigned long SET_AA( unsigned long inputDWord ) { __asm{ mov eax, [esp+4] mov al, 0xAA ret } }

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  • How to manually (bitwise) perform (float)x? (homework)

    - by Silver
    Now, here is the function header of the function I'm supposed to implement: /* * float_from_int - Return bit-level equivalent of expression (float) x * Result is returned as unsigned int, but * it is to be interpreted as the bit-level representation of a * single-precision floating point values. * Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while * Max ops: 30 * Rating: 4 */ unsigned float_from_int(int x) { ... } We aren't allowed to do float operations, or any kind of casting. Now I tried to implement the first algorithm given at this site: http://locklessinc.com/articles/i2f/ Here's my code: unsigned float_from_int(int x) { // grab sign bit int xIsNegative = 0; int absValOfX = x; if(x < 0){ xIsNegative = 1; absValOfX = -x; } // zero case if(x == 0){ return 0; } //int shiftsNeeded = 0; /*while(){ shiftsNeeded++; }*/ unsigned I2F_MAX_BITS = 15; unsigned I2F_MAX_INPUT = ((1 << I2F_MAX_BITS) - 1); unsigned I2F_SHIFT = (24 - I2F_MAX_BITS); unsigned result, i, exponent, fraction; if ((absValOfX & I2F_MAX_INPUT) == 0) result = 0; else { exponent = 126 + I2F_MAX_BITS; fraction = (absValOfX & I2F_MAX_INPUT) << I2F_SHIFT; i = 0; while(i < I2F_MAX_BITS) { if (fraction & 0x800000) break; else { fraction = fraction << 1; exponent = exponent - 1; } i++; } result = (xIsNegative << 31) | exponent << 23 | (fraction & 0x7fffff); } return result; } But it didn't work (see test error below): Test float_from_int(-2147483648[0x80000000]) failed... ...Gives 0[0x0]. Should be -822083584[0xcf000000] 4 4 0 float_times_four I don't know where to go from here. How should I go about parsing the float from this int?

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  • function to org-sort by three (3) criteria: due date / priority / title

    - by lawlist
    Is anyone aware of an org-sort function / modification that can refile / organize a group of TODO so that it sorts them by three (3) criteria: first sort by due date, second sort by priority, and third sort by by title of the task? EDIT: If anyone can please help me to modify this so that undated TODO are sorted last, that would be greatly appreciated -- at the present time, undated TODO are not being sorted: ;; multiple sort (defun org-sort-multi (&rest sort-types) "Multiple sorts on a certain level of an outline tree, or plain list items. SORT-TYPES is a list where each entry is either a character or a cons pair (BOOL . CHAR), where BOOL is whether or not to sort case-sensitively, and CHAR is one of the characters defined in `org-sort-entries-or-items'. Entries are applied in back to front order. Example: To sort first by TODO status, then by priority, then by date, then alphabetically (case-sensitive) use the following call: (org-sort-multi '(?d ?p ?t (t . ?a)))" (interactive) (dolist (x (nreverse sort-types)) (when (char-valid-p x) (setq x (cons nil x))) (condition-case nil (org-sort-entries (car x) (cdr x)) (error nil)))) ;; sort current level (defun lawlist-sort (&rest sort-types) "Sort the current org level. SORT-TYPES is a list where each entry is either a character or a cons pair (BOOL . CHAR), where BOOL is whether or not to sort case-sensitively, and CHAR is one of the characters defined in `org-sort-entries-or-items'. Entries are applied in back to front order. Defaults to \"?o ?p\" which is sorted by TODO status, then by priority" (interactive) (when (equal mode-name "Org") (let ((sort-types (or sort-types (if (or (org-entry-get nil "TODO") (org-entry-get nil "PRIORITY")) '(?d ?t ?p) ;; date, time, priority '((nil . ?a)))))) (save-excursion (outline-up-heading 1) (let ((start (point)) end) (while (and (not (bobp)) (not (eobp)) (<= (point) start)) (condition-case nil (outline-forward-same-level 1) (error (outline-up-heading 1)))) (unless (> (point) start) (goto-char (point-max))) (setq end (point)) (goto-char start) (apply 'org-sort-multi sort-types) (goto-char end) (when (eobp) (forward-line -1)) (when (looking-at "^\\s-*$") ;; (delete-line) ) (goto-char start) ;; (dotimes (x ) (org-cycle)) )))))

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  • Grading an algorithm: Readability vs. Compactness

    - by amiregelz
    Consider the following question in a test \ interview: Implement the strcpy() function in C: void strcpy(char *destination, char *source); The strcpy function copies the C string pointed by source into the array pointed by destination, including the terminating null character. Assume that the size of the array pointed by destination is long enough to contain the same C string as source, and does not overlap in memory with source. Say you were the tester, how would you grade the following answers to this question? 1) void strcpy(char *destination, char *source) { while (*source != '\0') { *destination = *source; source++; destionation++; } *destionation = *source; } 2) void strcpy(char *destination, char *source) { while (*(destination++) = *(source++)) ; } The first implementation is straightforward - it is readable and programmer-friendly. The second implementation is shorter (one line of code) but less programmer-friendly; it's not so easy to understand the way this code is working, and if you're not familiar with the priorities in this code then it's a problem. I'm wondering if the first answer would show more complexity and more advanced thinking, in the tester's eyes, even though both algorithms behave the same, and although code readability is considered to be more important than code compactness. It seems to me that since making an algorithm this compact is more difficult to implement, it will show a higher level of thinking as an answer in a test. However, it is also possible that a tester would consider the first answer not good because it's not readable. I would also like to mention that this is not specific to this example, but general for code readability vs. compactness when implementing an algorithm, specifically in tests \ interviews.

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  • Windows recv method usage

    - by vandamon taigi
    I'm making a multiplayer game and I have an issue with the recv function ( or the send one , not sure ). Server side code : char* UserName = new char[256]; ZeroMemory(UserName,256); recv(sConnect,UserName,256,0); // works char* Password = new char[256]; ZeroMemory(Password,256); recv(sConnect,Password,256,0); // works users[ ++usercount ] = new Client(UserName,Password,sConnect); if( users[usercount] ->GetLogInSuccesful() ) send(sConnect,"0x0001",6,0); // debugging shows it gets here and sends the data. Client side code : send(server->getsConnect(),User,256,0); // works send(server->getsConnect(),Pass,256,0); // works char* Response = new char[6]; ZeroMemory(Response,6); recv(server->getsConnect(),Response,6,0); // gets stuck here. Any ideea why does it get stuck on that recv ? I also tried by making response [256] or such.

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  • How should I group these variables?

    - by stariz77
    I have a shape that will be defined by: char s_type; char color; double height; double width; These variables are scanned in from a request string sent to my server and passed into my printing function, which then prints out the shape. Currently they are just local variables sitting in my main(); however, I was wondering if there would be any advantage in creating a struct containing these variables, and then passing the struct to my printing function? or how else might I improve my program's structure/style, would passing a struct by reference have any kind of performance benefit if there were many requests and therefore many printing function calls? printer(char st, char cr, double ht, double wd); int main() { // Other main functionality. char s_type; char color; double height; double width; sscanf (serv_req, "GET /%c/%c/%lf/%lf", &s_type, &color, &height, &width); printer(s_type, color, height, width); // Other main functionality. return 0; } It seemed "neater" if I had a struct or something that didn't leave me with declarations in the middle of everything else going on in main. I'm interested in structure/style as well as performance. EDIT: didn't mean to put printer declaration inside main.

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  • undefined reference to function, despite giving reference in c

    - by Jamie Edwards
    I'm following a tutorial, but when it comes to compiling and linking the code I get the following error: /tmp/cc8gRrVZ.o: In function `main': main.c:(.text+0xa): undefined reference to `monitor_clear' main.c:(.text+0x16): undefined reference to `monitor_write' collect2: ld returned 1 exit status make: *** [obj/main.o] Error 1 What that is telling me is that I haven't defined both 'monitor_clear' and 'monitor_write'. But I have, in both the header and source files. They are as follows: monitor.c: // monitor.c -- Defines functions for writing to the monitor. // heavily based on Bran's kernel development tutorials, // but rewritten for JamesM's kernel tutorials. #include "monitor.h" // The VGA framebuffer starts at 0xB8000. u16int *video_memory = (u16int *)0xB8000; // Stores the cursor position. u8int cursor_x = 0; u8int cursor_y = 0; // Updates the hardware cursor. static void move_cursor() { // The screen is 80 characters wide... u16int cursorLocation = cursor_y * 80 + cursor_x; outb(0x3D4, 14); // Tell the VGA board we are setting the high cursor byte. outb(0x3D5, cursorLocation >> 8); // Send the high cursor byte. outb(0x3D4, 15); // Tell the VGA board we are setting the low cursor byte. outb(0x3D5, cursorLocation); // Send the low cursor byte. } // Scrolls the text on the screen up by one line. static void scroll() { // Get a space character with the default colour attributes. u8int attributeByte = (0 /*black*/ << 4) | (15 /*white*/ & 0x0F); u16int blank = 0x20 /* space */ | (attributeByte << 8); // Row 25 is the end, this means we need to scroll up if(cursor_y >= 25) { // Move the current text chunk that makes up the screen // back in the buffer by a line int i; for (i = 0*80; i < 24*80; i++) { video_memory[i] = video_memory[i+80]; } // The last line should now be blank. Do this by writing // 80 spaces to it. for (i = 24*80; i < 25*80; i++) { video_memory[i] = blank; } // The cursor should now be on the last line. cursor_y = 24; } } // Writes a single character out to the screen. void monitor_put(char c) { // The background colour is black (0), the foreground is white (15). u8int backColour = 0; u8int foreColour = 15; // The attribute byte is made up of two nibbles - the lower being the // foreground colour, and the upper the background colour. u8int attributeByte = (backColour << 4) | (foreColour & 0x0F); // The attribute byte is the top 8 bits of the word we have to send to the // VGA board. u16int attribute = attributeByte << 8; u16int *location; // Handle a backspace, by moving the cursor back one space if (c == 0x08 && cursor_x) { cursor_x--; } // Handle a tab by increasing the cursor's X, but only to a point // where it is divisible by 8. else if (c == 0x09) { cursor_x = (cursor_x+8) & ~(8-1); } // Handle carriage return else if (c == '\r') { cursor_x = 0; } // Handle newline by moving cursor back to left and increasing the row else if (c == '\n') { cursor_x = 0; cursor_y++; } // Handle any other printable character. else if(c >= ' ') { location = video_memory + (cursor_y*80 + cursor_x); *location = c | attribute; cursor_x++; } // Check if we need to insert a new line because we have reached the end // of the screen. if (cursor_x >= 80) { cursor_x = 0; cursor_y ++; } // Scroll the screen if needed. scroll(); // Move the hardware cursor. move_cursor(); } // Clears the screen, by copying lots of spaces to the framebuffer. void monitor_clear() { // Make an attribute byte for the default colours u8int attributeByte = (0 /*black*/ << 4) | (15 /*white*/ & 0x0F); u16int blank = 0x20 /* space */ | (attributeByte << 8); int i; for (i = 0; i < 80*25; i++) { video_memory[i] = blank; } // Move the hardware cursor back to the start. cursor_x = 0; cursor_y = 0; move_cursor(); } // Outputs a null-terminated ASCII string to the monitor. void monitor_write(char *c) { int i = 0; while (c[i]) { monitor_put(c[i++]); } } void monitor_write_hex(u32int n) { s32int tmp; monitor_write("0x"); char noZeroes = 1; int i; for (i = 28; i > 0; i -= 4) { tmp = (n >> i) & 0xF; if (tmp == 0 && noZeroes != 0) { continue; } if (tmp >= 0xA) { noZeroes = 0; monitor_put (tmp-0xA+'a' ); } else { noZeroes = 0; monitor_put( tmp+'0' ); } } tmp = n & 0xF; if (tmp >= 0xA) { monitor_put (tmp-0xA+'a'); } else { monitor_put (tmp+'0'); } } void monitor_write_dec(u32int n) { if (n == 0) { monitor_put('0'); return; } s32int acc = n; char c[32]; int i = 0; while (acc > 0) { c[i] = '0' + acc%10; acc /= 10; i++; } c[i] = 0; char c2[32]; c2[i--] = 0; int j = 0; while(i >= 0) { c2[i--] = c[j++]; } monitor_write(c2); } monitor.h: // monitor.h -- Defines the interface for monitor.h // From JamesM's kernel development tutorials. #ifndef MONITOR_H #define MONITOR_H #include "common.h" // Write a single character out to the screen. void monitor_put(char c); // Clear the screen to all black. void monitor_clear(); // Output a null-terminated ASCII string to the monitor. void monitor_write(char *c); #endif // MONITOR_H common.c: // common.c -- Defines some global functions. // From JamesM's kernel development tutorials. #include "common.h" // Write a byte out to the specified port. void outb ( u16int port, u8int value ) { asm volatile ( "outb %1, %0" : : "dN" ( port ), "a" ( value ) ); } u8int inb ( u16int port ) { u8int ret; asm volatile ( "inb %1, %0" : "=a" ( ret ) : "dN" ( port ) ); return ret; } u16int inw ( u16int port ) { u16int ret; asm volatile ( "inw %1, %0" : "=a" ( ret ) : "dN" ( port ) ); return ret; } // Copy len bytes from src to dest. void memcpy(u8int *dest, const u8int *src, u32int len) { const u8int *sp = ( const u8int * ) src; u8int *dp = ( u8int * ) dest; for ( ; len != 0; len-- ) *dp++ =*sp++; } // Write len copies of val into dest. void memset(u8int *dest, u8int val, u32int len) { u8int *temp = ( u8int * ) dest; for ( ; len != 0; len-- ) *temp++ = val; } // Compare two strings. Should return -1 if // str1 < str2, 0 if they are equal or 1 otherwise. int strcmp(char *str1, char *str2) { int i = 0; int failed = 0; while ( str1[i] != '\0' && str2[i] != '\0' ) { if ( str1[i] != str2[i] ) { failed = 1; break; } i++; } // Why did the loop exit? if ( ( str1[i] == '\0' && str2[i] != '\0' || (str1[i] != '\0' && str2[i] =='\0' ) ) failed =1; return failed; } // Copy the NULL-terminated string src into dest, and // return dest. char *strcpy(char *dest, const char *src) { do { *dest++ = *src++; } while ( *src != 0 ); } // Concatenate the NULL-terminated string src onto // the end of dest, and return dest. char *strcat(char *dest, const char *src) { while ( *dest != 0 ) { *dest = *dest++; } do { *dest++ = *src++; } while ( *src != 0 ); return dest; } common.h: // common.h -- Defines typedefs and some global functions. // From JamesM's kernel development tutorials. #ifndef COMMON_H #define COMMON_H // Some nice typedefs, to standardise sizes across platforms. // These typedefs are written for 32-bit x86. typedef unsigned int u32int; typedef int s32int; typedef unsigned short u16int; typedef short s16int; typedef unsigned char u8int; typedef char s8int; void outb ( u16int port, u8int value ); u8int inb ( u16int port ); u16int inw ( u16int port ); #endif //COMMON_H main.c: // main.c -- Defines the C-code kernel entry point, calls initialisation routines. // Made for JamesM's tutorials <www.jamesmolloy.co.uk> #include "monitor.h" int main(struct multiboot *mboot_ptr) { monitor_clear(); monitor_write ( "hello, world!" ); return 0; } here is my makefile: C_SOURCES= main.c monitor.c common.c S_SOURCES= boot.s C_OBJECTS=$(patsubst %.c, obj/%.o, $(C_SOURCES)) S_OBJECTS=$(patsubst %.s, obj/%.o, $(S_SOURCES)) CFLAGS=-nostdlib -nostdinc -fno-builtin -fno-stack-protector -m32 -Iheaders LDFLAGS=-Tlink.ld -melf_i386 --oformat=elf32-i386 ASFLAGS=-felf all: kern/kernel .PHONY: clean clean: -rm -f kern/kernel kern/kernel: $(S_OBJECTS) $(C_OBJECTS) ld $(LDFLAGS) -o $@ $^ $(C_OBJECTS): obj/%.o : %.c gcc $(CFLAGS) $< -o $@ vpath %.c source $(S_OBJECTS): obj/%.o : %.s nasm $(ASFLAGS) $< -o $@ vpath %.s asem Hopefully this will help you understand what is going wrong and how to fix it :L Thanks in advance. Jamie.

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  • Doctrine Mssql uniqueidentifier isn't cast as char or nvarchar when retrieved from the database.

    - by Tres
    When I retrieve a record from the database which has a column of type "uniqueidentifier", Doctrine fills it with "null" rather than the unique id from the database. Some research and testing has brought this down to a PDO/dblib driver issue. When directly querying via PDO, null is returned in place of the unique id. For reference, http://trac.doctrine-project.org/ticket/1096, has a bit on this, however, it was updated 11 months ago with no comment for resolution. A way around this, as mentioned at http://bugs.php.net/bug.php?id=24752&edit=1, is to cast the column as a char. However, it doesn't seem Doctrine exposes the native field type outside of generating models which makes it a bit hard to detect uniqueidentifier types and cast them internally when building the sql query. Has anyone found a workaround for this?

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  • I need a simple Example of JNA which can map char * of c dll.

    - by Vikas Sharma
    I have one dll of cpp and i need to call its function which returns char*. Im using String in native Declaration but getting out put like ???? or some crap thing. I just want to knw that do i have to decode the String.i have already set my system property like System.setProperty("jna.encoding","UTF-8"); Im in big mess. Hope to get Some Positive replies from u guys. Thanks in Advance.. Cheers...!

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  • Why does C's "fopen" take a "const char *" as its second argument?

    - by Chris Cooper
    It has always struck me as strange that the C function "fopen" takes a "const char *" as the second argument. I would think it would be easier to both read your code and implement the library's code if there were bit masks defined in stdio.h, like "IO_READ" and such, so you could do things like: FILE* myFile = fopen("file.txt", IO_READ & IO_WRITE); Is there a programmatic reason for the way it actually is, or is it just historic? (i.e. "That's just the way it is.")

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  • casting BSTR as char* in a dll; different results depnding on VB/C# caller.

    - by Toby Wilson
    I have a dll function that takes BSTR parameters. These are casted as char* before being used for other things. When the dll is called from VB code this works fine. However, when it is called from C# code, only the first character is pointed to. Both of these are excel addIns for Pre-2007 and 2007+ versions of Office, which call into a faster C++ AddIn. They actually call it directly, not through Excel. The VB function declaration looks like this: Private Declare Function Test Lib "ExcelAddIn.xll" (ByVal param As String) As String The C# function declaration looks like this: [DllImport("ExcelAddIn.xll", CharSet=CharSet.Ansi)] [return:MarshalAs(UnmanagedType.BStr)] private static extern string Test([MarshalAs(UnmanagedType.BStr)] string param); When debugging the dll and watching the input BSTR values, they appear to be correct from both; just the C# one only casts the first character. Charset=CharSet.Unicode makes no difference. Any ideas anyone?

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  • is there a way to use cin.getline() without having to define a char array size before hand?

    - by zebraman
    Basically my task is having to sort a bunch of strings of variable length ignoring case. I understand there is a function strcasecmp() that compares cstrings, but doesn't work on strings. Right now I'm using getline() for strings so I can just read in the strings one line at a time. I add these to a vector of strings, then convert to cstrings for each call of strcasecmp(). Instead of having to convert each string to a cstring before comparing with strcasecmp(), I was wondering if there was a way I could use cin.getline() for cstrings without having a predefined char array size. Or, would the best solution be to just read in string, convert to cstring, store in vector, then sort?

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  • Any way to find out which line break char(s) to use in Javascript?

    - by Irro
    I'm trying to parse some text into a textarea control and at the same time replace all with ordinary line break chars. I have been able to do it in windows by replacing with CR (it didn't work with CRLF strangely enough, it gave me linebreak + empty space) but I'm afraid that this code won't work in Unix/Mac because they use LF for line break. Is there any way to use the system default line break char in javascript? Something similar to Environment.NewLine in .Net (I wasn't able to write backslash in this editor but I use /r for CR and /n for LF, replace / with backslash)

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  • Setting an empty default value for a char-column in MySQL?

    - by user281434
    Hi In phpMyAdmin I have a char(32) column that has no default value(ie. Default: None). When I try to insert data through a SQL query, it throws out an error saying that the column "doesn't have a default value". I need it to be empty, so instead I've just set it's default value as "As defined: " and then nothing in the value field. Is this a bad idea? And is it any better than simply throwing in an empty value for the column in the SQL query? Thanks for your time.

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  • Haskell: Left-biased/short-circuiting function

    - by user2967411
    Two classes ago, our professor presented to us a Parser module. Here is the code: module Parser (Parser,parser,runParser,satisfy,char,string,many,many1,(+++)) where import Data.Char import Control.Monad import Control.Monad.State type Parser = StateT String [] runParser :: Parser a -> String -> [(a,String)] runParser = runStateT parser :: (String -> [(a,String)]) -> Parser a parser = StateT satisfy :: (Char -> Bool) -> Parser Char satisfy f = parser $ \s -> case s of [] -> [] a:as -> [(a,as) | f a] char :: Char -> Parser Char char = satisfy . (==) alpha,digit :: Parser Char alpha = satisfy isAlpha digit = satisfy isDigit string :: String -> Parser String string = mapM char infixr 5 +++ (+++) :: Parser a -> Parser a -> Parser a (+++) = mplus many, many1 :: Parser a -> Parser [a] many p = return [] +++ many1 p many1 p = liftM2 (:) p (many p) Today he gave us an assignment to introduce "a left-biased, or short-circuiting version of (+++)", called (<++). His hint was for us to consider the original implementation of (+++). When he first introduced +++ to us, this was the code he wrote, which I am going to call the original implementation: infixr 5 +++ (+++) :: Parser a -> Parser a -> Parser a p +++ q = Parser $ \s -> runParser p s ++ runParser q s I have been having tons of trouble since we were introduced to parsing and so it continues. I have tried/am considering two approaches. 1) Use the "original" implementation, as in p +++ q = Parser $ \s - runParser p s ++ runParser q s 2) Use the final implementation, as in (+++) = mplus Here are my questions: 1) The module will not compile if I use the original implementation. The error: Not in scope: data constructor 'Parser'. It compiles fine using (+++) = mplus. What is wrong with using the original implementation that is avoided by using the final implementation? 2) How do I check if the first Parser returns anything? Is something like (not (isNothing (Parser $ \s - runParser p s) on the right track? It seems like it should be easy but I have no idea. 3) Once I figure out how to check if the first Parser returns anything, if I am to base my code on the final implementation, would it be as easy as this?: -- if p returns something then p <++ q = mplus (Parser $ \s -> runParser p s) mzero -- else (<++) = mplus Best, Jeff

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  • Wrapping a pure virtual method with multiple arguments with Boost.Python

    - by fallino
    Hello, I followed the "official" tutorial and others but still don't manage to expose this pure virtual method (getPeptide) : ms_mascotresults.hpp class ms_mascotresults { public: ms_mascotresults(ms_mascotresfile &resfile, const unsigned int flags, double minProbability, int maxHitsToReport, const char * unigeneIndexFile, const char * singleHit = 0); ... virtual ms_peptide getPeptide(const int q, const int p) const = 0; } ms_mascotresults.cpp #include <boost/python.hpp> using namespace boost::python; #include "msparser.hpp" // which includes "ms_mascotresults.hpp" using namespace matrix_science; #include <iostream> #include <sstream> struct ms_mascotresults_wrapper : ms_mascotresults, wrapper<ms_mascotresults> { ms_peptide getPeptide(const int q, const int p) { this->get_override("getPeptide")(q); this->get_override("getPeptide")(p); } }; BOOST_PYTHON_MODULE(ms_mascotresults) { class_<ms_mascotresults_wrapper, boost::noncopyable>("ms_mascotresults") .def("getPeptide", pure_virtual(&ms_mascotresults::getPeptide) ) ; } Here are the bjam's errors : /usr/local/boost_1_42_0/boost/python/object/value_holder.hpp:66: error: cannot declare field ‘boost::python::objects::value_holder<ms_mascotresults_wrapper>::m_held’ to be of abstract type ‘ms_mascotresults_wrapper’ ms_mascotresults.cpp:12: note: because the following virtual functions are pure within ‘ms_mascotresults_wrapper’: ... include/ms_mascotresults.hpp:334: note: virtual matrix_science::ms_peptide matrix_science::ms_mascotresults::getPeptide(int, int) const ms_mascotresults.cpp: In constructor ‘ms_mascotresults_wrapper::ms_mascotresults_wrapper()’: ms_mascotresults.cpp:12: error: no matching function for call to ‘matrix_science::ms_mascotresults::ms_mascotresults()’ include/ms_mascotresults.hpp:284: note: candidates are: matrix_science::ms_mascotresults::ms_mascotresults(matrix_science::ms_mascotresfile&, unsigned int, double, int, const char*, const char*) include/ms_mascotresults.hpp:109: note: matrix_science::ms_mascotresults::ms_mascotresults(const matrix_science::ms_mascotresults&) ... /usr/local/boost_1_42_0/boost/python/object/value_holder.hpp: In constructor ‘boost::python::objects::value_holder<Value>::value_holder(PyObject*) [with Value = ms_mascotresults_wrapper]’: /usr/local/boost_1_42_0/boost/python/object/value_holder.hpp:137: note: synthesized method ‘ms_mascotresults_wrapper::ms_mascotresults_wrapper()’ first required here /usr/local/boost_1_42_0/boost/python/object/value_holder.hpp:137: error: cannot allocate an object of abstract type ‘ms_mascotresults_wrapper’ ms_mascotresults.cpp:12: note: since type ‘ms_mascotresults_wrapper’ has pure virtual functions So I tried to change the constructor's signature by : BOOST_PYTHON_MODULE(ms_mascotresults) { //class_<ms_mascotresults_wrapper, boost::noncopyable>("ms_mascotresults") class_<ms_mascotresults_wrapper, boost::noncopyable>("ms_mascotresults", init<ms_mascotresfile &, const unsigned int, double, int, const char *,const char *>()) .def("getPeptide", pure_virtual(&ms_mascotresults::getPeptide) ) Giving these errors : /usr/local/boost_1_42_0/boost/python/object/value_holder.hpp:66: error: cannot declare field ‘boost::python::objects::value_holder<ms_mascotresults_wrapper>::m_held’ to be of abstract type ‘ms_mascotresults_wrapper’ ms_mascotresults.cpp:12: note: because the following virtual functions are pure within ‘ms_mascotresults_wrapper’: include/ms_mascotresults.hpp:334: note: virtual matrix_science::ms_peptide matrix_science::ms_mascotresults::getPeptide(int, int) const ... ms_mascotresults.cpp:24: instantiated from here /usr/local/boost_1_42_0/boost/python/object/value_holder.hpp:137: error: no matching function for call to ‘ms_mascotresults_wrapper::ms_mascotresults_wrapper(matrix_science::ms_mascotresfile&, const unsigned int&, const double&, const int&, const char* const&, const char* const&)’ ms_mascotresults.cpp:12: note: candidates are: ms_mascotresults_wrapper::ms_mascotresults_wrapper(const ms_mascotresults_wrapper&) ms_mascotresults.cpp:12: note: ms_mascotresults_wrapper::ms_mascotresults_wrapper() If I comment the virtual function getPeptide in the .hpp, it builds perfectly with this constructor : class_<ms_mascotresults>("ms_mascotresults", init<ms_mascotresfile &, const unsigned int, double, int, const char *,const char *>() ) So I'm a bit lost...

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  • Suggestions for duplicate file finder algorithm (using C)

    - by Andrei Ciobanu
    Hello, I wanted to write a program that test if two files are duplicates (have exactly the same content). First I test if the files have the same sizes, and if they have i start to compare their contents. My first idea, was to "split" the files into fixed size blocks, then start a thread for every block, fseek to startup character of every block and continue the comparisons in parallel. When a comparison from a thread fails, the other working threads are canceled, and the program exits out of the thread spawning loop. The code looks like this: dupf.h #ifndef __NM__DUPF__H__ #define __NM__DUPF__H__ #define NUM_THREADS 15 #define BLOCK_SIZE 8192 /* Thread argument structure */ struct thread_arg_s { const char *name_f1; /* First file name */ const char *name_f2; /* Second file name */ int cursor; /* Where to seek in the file */ }; typedef struct thread_arg_s thread_arg; /** * 'arg' is of type thread_arg. * Checks if the specified file blocks are * duplicates. */ void *check_block_dup(void *arg); /** * Checks if two files are duplicates */ int check_dup(const char *name_f1, const char *name_f2); /** * Returns a valid pointer to a file. * If the file (given by the path/name 'fname') cannot be opened * in 'mode', the program is interrupted an error message is shown. **/ FILE *safe_fopen(const char *name, const char *mode); #endif dupf.c #include <errno.h> #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <unistd.h> #include "dupf.h" FILE *safe_fopen(const char *fname, const char *mode) { FILE *f = NULL; f = fopen(fname, mode); if (f == NULL) { char emsg[255]; sprintf(emsg, "FOPEN() %s\t", fname); perror(emsg); exit(-1); } return (f); } void *check_block_dup(void *arg) { const char *name_f1 = NULL, *name_f2 = NULL; /* File names */ FILE *f1 = NULL, *f2 = NULL; /* Streams */ int cursor = 0; /* Reading cursor */ char buff_f1[BLOCK_SIZE], buff_f2[BLOCK_SIZE]; /* Character buffers */ int rchars_1, rchars_2; /* Readed characters */ /* Initializing variables from 'arg' */ name_f1 = ((thread_arg*)arg)->name_f1; name_f2 = ((thread_arg*)arg)->name_f2; cursor = ((thread_arg*)arg)->cursor; /* Opening files */ f1 = safe_fopen(name_f1, "r"); f2 = safe_fopen(name_f2, "r"); /* Setup cursor in files */ fseek(f1, cursor, SEEK_SET); fseek(f2, cursor, SEEK_SET); /* Initialize buffers */ rchars_1 = fread(buff_f1, 1, BLOCK_SIZE, f1); rchars_2 = fread(buff_f2, 1, BLOCK_SIZE, f2); if (rchars_1 != rchars_2) { /* fread failed to read the same portion. * program cannot continue */ perror("ERROR WHEN READING BLOCK"); exit(-1); } while (rchars_1-->0) { if (buff_f1[rchars_1] != buff_f2[rchars_1]) { /* Different characters */ fclose(f1); fclose(f2); pthread_exit("notdup"); } } /* Close streams */ fclose(f1); fclose(f2); pthread_exit("dup"); } int check_dup(const char *name_f1, const char *name_f2) { int num_blocks = 0; /* Number of 'blocks' to check */ int num_tsp = 0; /* Number of threads spawns */ int tsp_iter = 0; /* Iterator for threads spawns */ pthread_t *tsp_threads = NULL; thread_arg *tsp_threads_args = NULL; int tsp_threads_iter = 0; int thread_c_res = 0; /* Thread creation result */ int thread_j_res = 0; /* Thread join res */ int loop_res = 0; /* Function result */ int cursor; struct stat buf_f1; struct stat buf_f2; if (name_f1 == NULL || name_f2 == NULL) { /* Invalid input parameters */ perror("INVALID FNAMES\t"); return (-1); } if (stat(name_f1, &buf_f1) != 0 || stat(name_f2, &buf_f2) != 0) { /* Stat fails */ char emsg[255]; sprintf(emsg, "STAT() ERROR: %s %s\t", name_f1, name_f2); perror(emsg); return (-1); } if (buf_f1.st_size != buf_f2.st_size) { /* File have different sizes */ return (1); } /* Files have the same size, function exec. is continued */ num_blocks = (buf_f1.st_size / BLOCK_SIZE) + 1; num_tsp = (num_blocks / NUM_THREADS) + 1; cursor = 0; for (tsp_iter = 0; tsp_iter < num_tsp; tsp_iter++) { loop_res = 0; /* Create threads array for this spawn */ tsp_threads = malloc(NUM_THREADS * sizeof(*tsp_threads)); if (tsp_threads == NULL) { perror("TSP_THREADS ALLOC FAILURE\t"); return (-1); } /* Create arguments for every thread in the current spawn */ tsp_threads_args = malloc(NUM_THREADS * sizeof(*tsp_threads_args)); if (tsp_threads_args == NULL) { perror("TSP THREADS ARGS ALLOCA FAILURE\t"); return (-1); } /* Initialize arguments and create threads */ for (tsp_threads_iter = 0; tsp_threads_iter < NUM_THREADS; tsp_threads_iter++) { if (cursor >= buf_f1.st_size) { break; } tsp_threads_args[tsp_threads_iter].name_f1 = name_f1; tsp_threads_args[tsp_threads_iter].name_f2 = name_f2; tsp_threads_args[tsp_threads_iter].cursor = cursor; thread_c_res = pthread_create( &tsp_threads[tsp_threads_iter], NULL, check_block_dup, (void*)&tsp_threads_args[tsp_threads_iter]); if (thread_c_res != 0) { perror("THREAD CREATION FAILURE"); return (-1); } cursor+=BLOCK_SIZE; } /* Join last threads and get their status */ while (tsp_threads_iter-->0) { void *thread_res = NULL; thread_j_res = pthread_join(tsp_threads[tsp_threads_iter], &thread_res); if (thread_j_res != 0) { perror("THREAD JOIN FAILURE"); return (-1); } if (strcmp((char*)thread_res, "notdup")==0) { loop_res++; /* Closing other threads and exiting by condition * from loop. */ while (tsp_threads_iter-->0) { pthread_cancel(tsp_threads[tsp_threads_iter]); } } } free(tsp_threads); free(tsp_threads_args); if (loop_res > 0) { break; } } return (loop_res > 0) ? 1 : 0; } The function works fine (at least for what I've tested). Still, some guys from #C (freenode) suggested that the solution is overly complicated, and it may perform poorly because of parallel reading on hddisk. What I want to know: Is the threaded approach flawed by default ? Is fseek() so slow ? Is there a way to somehow map the files to memory and then compare them ?

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  • Variable declared with variable keyword in sql plus(oracle 9i)?

    - by Vineet
    I am trying to declare g_num ,number data type with size it gives an error but in case of varchar2,char it does not. variable g_name varchar2(5);//correct accept size for varchar 2 variable g_num number(23);//Gives an error " VAR[IABLE] [ <variable> [ NUMBER | CHAR | CHAR (n [CHAR|BYTE]) | VARCHAR2 (n [CHAR|BYTE]) | NCHAR | NCHAR (n) | NVARCHAR2 (n) | CLOB | NCLOB | REFCURSOR ] ]" Please suggest!

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  • Implement python replace() function without using regexp

    - by jwesonga
    I'm trying to rewrite the equivalent of the python replace() function without using regexp. Using this code, i've managed to get it to work with single chars, but not with more than one character: def Replacer(self, find_char, replace_char): s = [] for char in self.base_string: if char == find_char: char = replace_char #print char s.append(char) s = ''.join(s) my_string.Replacer('a','E') Anybody have any pointers how to make this work with more than one character? example: my_string.Replacer('kl', 'lll')

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  • zlib gzgets extremely slow?

    - by monkeyking
    I'm doing stuff related to parsing huge globs of textfiles, and was testing what input method to use. There is not much of a difference using c++ std::ifstreams vs c FILE, According to the documentation of zlib, it supports uncompressed files, and will read the file without decompression. I'm seeing a difference from 12 seconds using non zlib to more than 4 minutes using zlib.h This I've tested doing multiple runs, so its not a disk cache issue. Am I using zlib in some wrong way? thanks #include <zlib.h> #include <cstdio> #include <cstdlib> #include <fstream> #define LENS 1000000 size_t fg(const char *fname){ fprintf(stderr,"\t-> using fgets\n"); FILE *fp =fopen(fname,"r"); size_t nLines =0; char *buffer = new char[LENS]; while(NULL!=fgets(buffer,LENS,fp)) nLines++; fprintf(stderr,"%lu\n",nLines); return nLines; } size_t is(const char *fname){ fprintf(stderr,"\t-> using ifstream\n"); std::ifstream is(fname,std::ios::in); size_t nLines =0; char *buffer = new char[LENS]; while(is. getline(buffer,LENS)) nLines++; fprintf(stderr,"%lu\n",nLines); return nLines; } size_t iz(const char *fname){ fprintf(stderr,"\t-> using zlib\n"); gzFile fp =gzopen(fname,"r"); size_t nLines =0; char *buffer = new char[LENS]; while(0!=gzgets(fp,buffer,LENS)) nLines++; fprintf(stderr,"%lu\n",nLines); return nLines; } int main(int argc,char**argv){ if(atoi(argv[2])==0) fg(argv[1]); if(atoi(argv[2])==1) is(argv[1]); if(atoi(argv[2])==2) iz(argv[1]); }

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  • Why do we have reinterpret_cast in C++ when two chained static_cast can do it's job?

    - by Nawaz
    Say I want to cast A* to char* and vice-versa, we have two choices (I mean, many of us think we've two choices, because both seems to work! Hence the confusion!): struct A { int age; char name[128]; }; A a; char *buffer = static_cast<char*>(static_cast<void*>(&a)); //choice 1 char *buffer = reinterpret_cast<char*>(&a); //choice 2 Both work fine. //convert back A *pA = static_cast<A*>(static_cast<void*>(buffer)); //choice 1 A *pA = reinterpret_cast<A*>(buffer); //choice 2 Even this works fine! So why do we have reinterpret_cast in C++ when two chained static_cast can do it's job? Some of you might think this topic is a duplicate of the previous topics such as listed at the bottom of this post, but it's not. Those topics discuss only theoretically, but none of them gives even a single example demonstrating why reintepret_cast is really needed, and two static_cast would surely fail. I agree, one static_cast would fail. But how about two? If the syntax of two chained static_cast looks cumbersome, then we can write a function template to make it more programmer-friendly: template<class To, class From> To any_cast(From v) { return static_cast<To>(static_cast<void*>(v)); } And then we can use this, as: char *buffer = any_cast<char*>(&a); //choice 1 char *buffer = reinterpret_cast<char*>(&a); //choice 2 //convert back A *pA = any_cast<A*>(buffer); //choice 1 A *pA = reinterpret_cast<A*>(buffer); //choice 2 Also, see this situation where any_cast can be useful: Proper casting for fstream read and write member functions. So my question basically is, Why do we have reinterpret_cast in C++? Please show me even a single example where two chained static_cast would surely fail to do the same job? Which cast to use; static_cast or reinterpret_cast? Cast from Void* to TYPE* : static_cast or reinterpret_cast

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  • Split string in C every white space

    - by redsolja
    I want to write a program in C that displays each word of a whole sentence (taken as input) at a seperate line. This is what i have done so far: void manipulate(char *buffer); int get_words(char *buffer); int main(){ char buff[100]; printf("sizeof %d\nstrlen %d\n", sizeof(buff), strlen(buff)); // Debugging reasons bzero(buff, sizeof(buff)); printf("Give me the text:\n"); fgets(buff, sizeof(buff), stdin); manipulate(buff); return 0; } int get_words(char *buffer){ // Function that gets the word count, by counting the spaces. int count; int wordcount = 0; char ch; for (count = 0; count < strlen(buffer); count ++){ ch = buffer[count]; if((isblank(ch)) || (buffer[count] == '\0')){ // if the character is blank, or null byte add 1 to the wordcounter wordcount += 1; } } printf("%d\n\n", wordcount); return wordcount; } void manipulate(char *buffer){ int words = get_words(buffer); char *newbuff[words]; char *ptr; int count = 0; int count2 = 0; char ch = '\n'; ptr = buffer; bzero(newbuff, sizeof(newbuff)); for (count = 0; count < 100; count ++){ ch = buffer[count]; if (isblank(ch) || buffer[count] == '\0'){ buffer[count] = '\0'; if((newbuff[count2] = (char *)malloc(strlen(buffer))) == NULL) { printf("MALLOC ERROR!\n"); exit(-1); } strcpy(newbuff[count2], ptr); printf("\n%s\n",newbuff[count2]); ptr = &buffer[count + 1]; count2 ++; } } } Although the output is what i want, i have really many black spaces after the final word displayed, and the malloc() returns NULL so the MALLOC ERROR! is displayed in the end. I can understand that there is a mistake at my malloc() implementation but i do not know what it is. Is there another more elegant - generally better way to do it? Thanks in advance.

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  • mysql timeout - c/C++

    - by user1262876
    Guys i'm facing a problem with this code, the problem is the timeout by timeout i mean the time it takes the program to tell me if the server is connected or not. If i use my localhost i get the answer fast, but when i connect to outside my localhost it takes 50sc - 1.5 min to response and the program frezz until it done. HOw can i fix the frezzing, or make my own timeout, like if still waiting after 50sc, tell me connection failed and stop? please use codes as help, becouse i would understand it better, thanks for any help i get PS: USING MAC #include "mysql.h" #include <stdio.h> #include <stdlib.h> // Other Linker Flags: -lmysqlclient -lm -lz // just going to input the general details and not the port numbers struct connection_details { char *server; char *user; char *password; char *database; }; MYSQL* mysql_connection_setup(struct connection_details mysql_details) { // first of all create a mysql instance and initialize the variables within MYSQL *connection = mysql_init(NULL); // connect to the database with the details attached. if (!mysql_real_connect(connection,mysql_details.server, mysql_details.user, mysql_details.password, mysql_details.database, 0, NULL, 0)) { printf("Conection error : %s\n", mysql_error(connection)); exit(1); } return connection; } MYSQL_RES* mysql_perform_query(MYSQL *connection, char *sql_query) { // send the query to the database if (mysql_query(connection, sql_query)) { printf("MySQL query error : %s\n", mysql_error(connection)); exit(1); } return mysql_use_result(connection); } int main() { MYSQL *conn; // the connection MYSQL_RES *res; // the results MYSQL_ROW row; // the results row (line by line) struct connection_details mysqlD; mysqlD.server = (char*)"Localhost"; // where the mysql database is mysqlD.user = (char*)"root"; // the root user of mysql mysqlD.password = (char*)"123456"; // the password of the root user in mysql mysqlD.database = (char*)"test"; // the databse to pick // connect to the mysql database conn = mysql_connection_setup(mysqlD); // assign the results return to the MYSQL_RES pointer res = mysql_perform_query(conn, (char*) "SELECT * FROM me"); printf("MySQL Tables in mysql database:\n"); while ((row = mysql_fetch_row(res)) !=NULL) printf("%s - %s\n", row[0], row[1], row[2]); // <-- Rows /* clean up the database result set */ mysql_free_result(res); /* clean up the database link */ mysql_close(conn); return 0; }

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