Hello fellow Programmers,
int main()
int n;
scanf("%d", &n ,);
printf("nibble = %d%d%d%d", (n/8)%2, (n/4)%2, (n/2)%2 , n%2 );
return 0;}
I´ve build this code so far, the code converts a decimal value into a nibble.
It works but i have questions regarding on how to restrict the input to 0-9,
without using if statemens. Is there any possiblty to do that and if how ?
At the moment the code uses 0 - 15 decimals.And can you please give me an example or explain to me so i can understand it .
Thank you!
that is not possible without using conditions
but tell us what your program should do if a decimal >9 is putted in?
scanf("%d", &n ,);
if ((n>=0) && (n<10))
printf("nibble = %d%d%d%d", (n/8)%2, (n/4)%2, (n/2)%2 , n%2 );
else
printf("err: input out of range");
Related
I'm learning at GCC and while I was trying various solutions to verify the entry of a certain word, IF Word = Word {do something;}
It seems that in C it cannot be done directly and so I tried this solution that seems to work:
#include <stdio.h>
#include <string.h>
int main(){
int CClose = 0;
int VerifyS = 0;
char PWord[30] ={'\0'};
do {
printf("\n Type a word: ");
scanf(" %s", &PWord);
VerifyS = strncmp(PWord, "exit", 4);
if (!VerifyS){ CClose = 1;}else{ printf("\n The Word is:%s", PWord);}
}while (CClose != 1);
return 0;
}
I wanted to know if there is another way to do the same thing.
Thank you.
What you've written is essentially the most common way to do this. There is indeed no way in C to compare two strings in a single expression without calling a function.
You can cut out the temporary variable VerifyS if you like, by writing
if (!strncmp(pWord, "exit", 4)) { /...
or, perhaps slightly clearer
if (strncmp(pWord, "exit", 4) == 0) { /...
This is my first question on stackoverflow and my englsich is unfortunately poor. But I want to try it.
A customized routine of twotonetest of kissfft brings on two different systems very different results.
The under ubuntu translated with gcc on x86 program brings the correct values. That with the openWRT SDK translated for the Arduino YUN (Atheros AR9331) program displays incorrect values. It seems as if since the definition of FIXED_POINT is ignored.
Defined is:
#define FIXED_POINT 32
the function:
double GetFreqBuf( tBuf * io_pBuf, int nfft)
{
kiss_fftr_cfg cfg = NULL;
kiss_fft_cpx *kout = NULL;
kiss_fft_scalar *tbuf = NULL;
uint32_t ptr;
int i;
double sigpow=0;
double noisepow=0;
long maxrange = SHRT_MAX;
cfg = kiss_fftr_alloc(nfft , 0, NULL, NULL);
tbuf = KISS_FFT_MALLOC(nfft * sizeof(kiss_fft_scalar));
kout = KISS_FFT_MALLOC(nfft * sizeof(kiss_fft_cpx));
/* generate the array from samples*/
for (i = 0; i < nfft; i++) {
//nur einen Kanal, eine Krücke, würde nun auch mit 2 kanälen gehen, aber so ist schneller
if (io_pBuf->IndexNextValue >= (i*2))
ptr = io_pBuf->IndexNextValue - (i*2);
else
ptr = io_pBuf->bufSize - ((i*2) - io_pBuf->IndexNextValue);
tbuf[i] = io_pBuf->aData[ptr] ;
}
kiss_fftr(cfg, tbuf, kout);
for (i=0;i < (nfft/2+1);++i) {
double tmpr = (double)kout[i].r / (double)maxrange;
double tmpi = (double)kout[i].i / (double)maxrange;
double mag2 = tmpr*tmpr + tmpi*tmpi;
if (i!=0 && i!= nfft/2)
mag2 *= 2; /* all bins except DC and Nyquist have symmetric counterparts implied*/
/* if there is power between the frq's, it is signal, otherwise noise*/
if ( i > nfft/96 && i < nfft/32 )
noisepow += mag2;
else
sigpow += mag2;
}
kiss_fft_cleanup();
//printf("TEST %d Werte, noisepow: %f sigpow: %f noise # %fdB\n",nfft,noisepow,sigpow,10*log10(noisepow/sigpow +1e-30) );
free(cfg);
free(tbuf);
free(kout);
return 10*log10(noisepow/sigpow +1e-30);
}
As input samples of 16-bit sound from the same file be used. Results differ for example from-3dB to-15dB. AWhere could you start troubleshooting?
Possibility #1 (most likely)
You are compiling kissfft.c or kiss_fftr.c differently than the calling code. This happens to a lot of people.
An easy way to force the same FIXED_POINT is to edit the kiss_fft.h directly. Another option: verify with some printf debugging. i.e. place the following in various places:
printf( __FILE__ " sees sizeof(kiss_fft_scalar)=%d\n" , sizeof(kiss_fft_scalar) )
Possibility #2
Perhaps the FIXED_POINT=16 code works but the FIXED_POINT=32 code does not because something is being handled incorrectly either inside kissfft or on the platform. The 32 bit fixed code relies on int64_t being implemented correctly.
Is that Atheros a 16 bit processor? I know kissfft has been used successfully on 16 bit platforms, but I'm not sure if FIXED_POINT=32 real FFTs on a 16 bit fixed point has been used.
viel Glück,
Mark
So, here is a countdown.
My aim is the next: if you don't do anything for the given time (ent_sec) the countdown will reach 0 after a time and return with 0, BUT if you press down the letter c (code: 99) the countdown stops and you can enter your PIN code and return with it.
I have already solved the problem with Windows.h in the next way:
if (GetAsyncKeyState(VK_SPACE))
This solves the problem is through WIN32 API (in this case you have to press SPACE, not letter 'c'), but it revealed that I can't use any WinAPI function (school project). So I rewrite this line to the following:
if (getchar() == 99)
But unfortunately it doesn't work in the proper way, cause my countdown stops in almost every second until I dont't press some "wrong" key (for example I press 'x', then the countdown goes forward, but in the next sec it stops again)... In the first solution (win func) this problem doesn't exist... So how can I fix that? Thanks. Here is the whole code of my function:
unsigned Timer::DownCount
{
int ent_sec = this.time;
cout << "The counter has started (" << this.time << "sec), press 'C' to enter your PIN code: " << endl;
while (ent_sec >= 0)
{
if (getchar() == 99) // c letter's code is 99 in ANSI (or ASCII dunno)
{
unsigned code;
cout << "PIN code: ";
cin >> code;
return code;
}
else
{
SecCounter(1); // this function counts 1 secundum
cout << ent_sec << endl;
ent_sec--;
}
}
return 0;
}
I don't believe there's a standard way to do this that will work across all platforms, but here's one way of doing it that will work on Windows without actually using Windows API functions.
int getch_nowait()
{
if (!kbhit()) return -1;
return getch();
}
Then your check just becomes if (getch_nowait() == 99) ...
This code may be compiler specific. If it doesn't work for you, it'll help if you tell us what compiler and operating system you are using.
I have the following method as part of a password generating program to generate a random password which is then validated.
My problem is that the srand function never meets the validation requirements and keeps looping back to create a new password.
Im posting the code below to ask if anyone has a more efficient way to create the random password so that it will meet validation requirements instead of looping back continously.Thanks.
static bool verifyThat(bool condition, const char* error) {
if(!condition) printf("%s", error);
return !condition;
}
//method to generate a random password for user following password guidelines.
void generatePass()
{
FILE *fptr;//file pointer
int iChar,iUpper,iLower,iSymbol,iNumber,iTotal;
printf("\n\n\t\tGenerate Password selected ");
get_user_password:
printf("\n\n\t\tPassword creation in progress... ");
int i,iResult,iCount;
char password[10 + 1];
char strLower[59+1] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRTUVWXYZ!£$%^&*";
srand(time (0));
for(i = 0; i < 10;i++)
{
password[i] = strLower[(rand() % 52)];
}
password[i] = '\0';
iChar = countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);
//folowing statements used to validate password
iChar = countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);
iUpper = countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);
iLower =countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);
iSymbol =countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);
iNumber = countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);
iTotal = countLetters(password,&iUpper,&iLower,&iSymbol,&iNumber,&iTotal);
if(verifyThat(iUpper >= 2, "Not enough uppercase letters!!!\n")
|| verifyThat(iLower >= 2, "Not enough lowercase letters!!!\n")
|| verifyThat(iSymbol >= 1, "Not enough symbols!!!\n")
|| verifyThat(iNumber >= 2, "Not enough numbers!!!\n")
|| verifyThat(iTotal >= 9, "Not enough characters!!!\n")
|| verifyThat(iTotal <= 15, "Too many characters!!!\n"))
goto get_user_password;
iResult = checkWordInFile("dictionary.txt", password);
if(verifyThat(iResult != gC_FOUND, "Password contains small common 3 letter word/s."))
goto get_user_password;
iResult = checkWordInFile("passHistory.txt",password);
if(verifyThat(iResult != gC_FOUND, "Password contains previously used password."))
goto get_user_password;
printf("\n\n\n Your new password is verified ");
printf(password);
//writing password to passHistroy file.
fptr = fopen("passHistory.txt", "w"); // create or open the file
for( iCount = 0; iCount < 8; iCount++)
{
fprintf(fptr, "%s\n", password[iCount]);
}
fclose(fptr);
printf("\n\n\n");
system("pause");
}//end of generatePass method.
I looked at your code at glance and I think I have found the reasons inspite of which validation requirements aren`t meet.
I suggest you to pay attention to the following parts of your code:
1) char strLower[59+1] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRTUVWXYZ!£$%^&*";
here you should add numbers 0..9, this is one of the reasons why requirements could not be met, because how number can be picked if it isn`t in the set of numbers from which you pick?!
replace it for ex. with:
char strLower[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRTUVWXYZ!£$%^&*0123456789";
2) password[i] = strLower[(rand() % 52)]; - and in this part of the code, replace 52 with total number of symbols in string from which you randomly pick numbers.
I recommend you to replace it with the following code:
password[i] = strLower[(rand() % (sizeof(strLower) / sizeof(char) - 1))];
you could alter your algorithm.
choose at random a number of Upper characeters that is above 2.
choose at random a number of Lower character that is above 2.
choose at random a number of Sybmol character that is above 1.
choose at random a number of Number characters that is above 2.
and then recompose your password with the random items, re-ordered at random. Fill with whatever character you want to pas the verifyThat predicates: >=9 and <= 15.
And please: don't use goto. Make function calls instead.
I am using a toolkit to do some Elliptical Curve Cryptography on an ATMega2560. When trying to use the print functions in the toolkit I am getting an empty string. I know the print functions work because the x86 version prints the variables without a problem. I am not experienced with ATMega and would love any help on this matter. The print code is included below.
Code to print a big number (it itself calls a util_print)
void bn_print(bn_t a) {
int i;
if (a->sign == BN_NEG) {
util_print("-");
}
if (a->used == 0) {
util_print("0\n");
} else {
#if WORD == 64
util_print("%lX", (unsigned long int)a->dp[a->used - 1]);
for (i = a->used - 2; i >= 0; i--) {
util_print("%.*lX", (int)(2 * (BN_DIGIT / 8)),
(unsigned long int)a->dp[i]);
}
#else
util_print("%llX", (unsigned long long int)a->dp[a->used - 1]);
for (i = a->used - 2; i >= 0; i--) {
util_print("%.*llX", (int)(2 * (BN_DIGIT / 8)),
(unsigned long long int)a->dp[i]);
}
#endif
util_print("\n");
}
}
The code to actually print a big number variable:
static char buffer[64 + 1];
void util_printf(char *format, ...) {
#ifndef QUIET
#if ARCH == AVR
char *pointer = &buffer[1];
va_list list;
va_start(list, format);
vsnprintf(pointer, 128, format, list);
buffer[0] = (unsigned char)2;
va_end(list);
#elif ARCH == MSP
va_list list;
va_start(list, format);
vprintf(format, list);
va_end(list);
#else
va_list list;
va_start(list, format);
vprintf(format, list);
fflush(stdout);
va_end(list);
#endif
#endif
}
edit: I do have UART initialized and can output printf statments to a console.
I'm one of the authors of the RELIC toolkit. The current util_printf() function is used to print inside the Avrora simulator, for debugging purposes. I'm glad that you could adapt the code to your purposes. As a side note, the buffer size problem was already fixed in more recent releases of the toolkit.
Let me know you have further problems with the library. You can either contact me personally or write directly to the discussion group.
Thank you!
vsnprintf store it's output on the given buffer (which in this case is the address point by pointer variable), in order for it to show on the console (through UART) you must send your buffer using printf (try to add printf("%s", pointer) after vsnprintf), if you're using avr-libc don't forget to initialized std stream first before making any call to printf function
oh btw your code is vulnerable to buffer overflow attack, buffer[64 + 1] means your buffer size is only 65 bytes, vsnprintf(pointer, 128, format, list); means that the maximum buffer defined by your application is 128 bytes, try to change it below 65 bytes in order to avoid overflow
Alright so I found a workaround to print the bn numbers to a stdout on an ATMega2560. The toolkit comes with a function that writes a variable to a string (bn_write_str). So I implemented my own print function as such:
void print_bn(bn_t a)
{
char print[BN_SIZE]; // max precision of a bn number
int bi = bn_bits(a); // get the number of bits of the number
bn_write_str(print, bi, a, 16) // 16 indicates the radix (hexadecimal)
printf("%s\n"), print);
}
This function will print a bn number in hexadecimal format.
Hope this helps anyone using the RELIC toolkit with an AVR.
This skips the util_print calls.