Can anyone help converting the Int to char array
as i have buffer as
char *buffer = NULL;
int lengthOfComponent = -1;
char *obj;
buffer[index]= (char *)&lengthOfComponent;
if i do this it is thorwing EXCESS BAD ACCESS after the execution how to store the value of the obj to buffer using memcpy
Of course you cannot write in buffer[index], it is not allocated!
buffer = malloc(sizeof(char) * lengthOfBuffer);
should do it. After that you can write the buffer with memcpy or with an assignation, like you are doing.
buffer[index] = (char *)&lengthOfComponent;
buffer[index] is like dereferencing the pointer. But buffer is not pointing to any valid location. Hence the runtime error.
The C solution is using snprintf. Try -
int i = 11;
char buffer[10];
snprintf(buffer, sizeof(buffer), "%d", i);
Related
I am facing an error whenever I call a recvfrom() function for UDP in server side:
buffer overflow detected ***: terminated Aborted
What is the meaning of this error? I am not able to understand.
unsigned int len;
int rv,i;
int tmp;
//char msg[200],command=0;
unsigned short *Fptr;
float Float_Temp;
//make socket blocking
FD_ZERO(&readnbs);
FD_SET(g_iUDP_datalogger_soc, &readnbs);
g_UDP_Blocktimervalue.tv_sec = 0;
g_UDP_Blocktimervalue.tv_usec = UDP_REC_BLOCKTIME;
rv = select(g_iUDP_datalogger_soc + 1, &readnbs, NULL, NULL, &g_UDP_Blocktimervalue);
len = sizeof(g_UDP_ClientAddr);
if (rv == 1) {
printf(" \n\n\n\n\n rv=%d\n\n\n\n",rv);
tmp = recvfrom(g_iUDP_datalogger_soc, &tmp, SIZE_UDP_MSG, 0,(struct sockaddr *) &g_UDP_ClientAddr, &len);
tmp = recvfrom(g_iUDP_datalogger_soc, [YOUR BUFFER ?] , SIZE_UDP_MSG, 0,(struct sockaddr *)...
You're trying to buffer the received data into a single int (tmp) object, which you are also using as the return value from the recvfrom(), and even not checking in any way - either for error, nor for received data.
You are asking recvfrom() to read SIZE_UDP_MSG number of bytes into tmp, which is an int. You did not show what SIZE_UDP_MSG is defined as, but if SIZE_UDP_MSG > sizeof(int), you are going to be writing bytes past the bounds of tmp into surrounding memory, corrupting the memory. That is a buffer overflow.
Perhaps you meant to receive the bytes into your (commented out) msg buffer instead?
char msg[SIZE_UDP_MSG];
tmp = recvfrom(..., msg, SIZE_UDP_MSG, ...);
Considering having, for example, this type of hex string:
char hex_str[100] = "0x01 0x03 0x04 0x0A";
How to get out of this string the byte array representation in CAPL, like:
byte hex_str_as_byte_arr[4] = {0x01, 0x03, 0x04, 0x0A};
EDIT: Only Vector CANoe supported data types/functions are allowed!
Use strtok to split the character array into separate hex strings, then use long strtol( const char *restrict str, char **restrict str_end, int base ) to convert each hex string to an integral value.
Thanks to all...
Actually I've found a solution myself:
char hex_str[100] = "0x01 0x03 0x04 0x0A";
long data[4];
dword pos = 0;
pos = strtol(hex_str, pos, data[0]);
pos = strtol(hex_str, pos, data[1]);
pos = strtol(hex_str, pos, data[2]);
pos = strtol(hex_str, pos, data[3]);
write("0x%02x,0x%02x,0x%02x, 0x%02x", data[0], data[1], data[2], data[3]);
Now it's a simple cast: (byte) data[0]
We can use sscanf() to convert the numbers to unsigned char. In a loop, we'll need to also use a %n conversion to determine the reading position for the next iteration.
Here's a simple example (in real life, you'll need some range checking to make sure you don't overrun the output buffer):
#include <stdio.h>
int main(void)
{
const char hex_str[100] = "0x01, 0x03, 0x04, 0x0A";
unsigned char bytes[4];
{
int position;
unsigned char *b = bytes;
for (const char *input = hex_str; sscanf(input, "%hhi, %n", b, &position) == 1; ++b) {
input += position;
}
}
/* prove we did it */
for (size_t i = 0; i < sizeof bytes; ++i) {
printf("%hhu ", bytes[i]);
}
puts("");
}
int main()
{
unsigned short crc = 0x00;
unsigned char buffer[4] = {0x01,0x02,0x72,0xAE};
memcpy((void *)&crc, (void *)&buffer[2],2);
printf("crc = 0x%x \n",crc);
return 0;
}
for above program i was expecting crc value to be : 0x72AE but it comes out to be:
crc = 0xAE72
I am not able to understand why the bytes are shuffled, even though i am doing a memcpy?
Any kind of help will be appreciated. Thanks in advance.
I have this method to make a xor between 2 NSStrings, i´m printing the result on NSLog but it isn´t the expect.
Can´t figure out what i´m doing wrong.
(void)XorSecretKeyDeviceId
{
NSString* secretKey = #"123";//
NSString* deviceId = #"abcdef";//
NSData* stringKey = [secretKey dataUsingEncoding:NSUTF8StringEncoding];
NSData* stringDeviceId = [deviceId dataUsingEncoding:NSUTF8StringEncoding];
unsigned char* pBytesInput = (unsigned char*)[stringKey bytes]; //Bytes
unsigned char* pBytesKey = (unsigned char*)[stringDeviceId bytes];
unsigned int vlen = [secretKey length]; //Keys Length
unsigned int klen = [deviceId length];
unsigned int v;
unsigned int k = vlen % klen;
unsigned char c;
for(v = 0; v < vlen; v++)
{
c = pBytesInput[v] ^ pBytesKey[k];
pBytesInput[v] = c;
NSLog(#"%c", c);
k = (++k < klen ? k : 0);
}
}
Are you setting your pBytesInput and pBytesKey variables correctly? At the moment, you have unsigned char* pBytesInput = (unsigned char*)[stringKey bytes]; (i.e. the input is the "key"), and pBytesKey is the device ID. This seems odd.
Also, be careful using UTF-8 encoding. UTF-8 uses the high bit on any byte in the string to indicate a "continuation" of a multi-byte character into the next byte. Your encoding could plausibly generate invalid UTF-8 by giving the setting the high bit of the final byte in the encryption.
For more than that, you'll have to say what the "wrong result" is.
I have three CGLayers who's data I'd like to compare.
void *a = CGBitmapContextGetData(CGLayerGetContext(layerA));
void *b = CGBitmapContextGetData(CGLayerGetContext(layerB));
void *c = CGBitmapContextGetData(CGLayerGetContext(layerC));
I'd like to get a result like ((a OR b) AND c) where only bits that are on in layerA or layerB and also on in layerC end up in the result. These layers are kCGImageAlphaOnly so they are only 8 bits "deep", and I've only drawn into them with 1.0 alpha. I also don't need to know where the overlap lies, I just need to know whether there are any bits on in the result.
I'm really missing QuickDraw today, it had plenty of bit-oriented operations that were very speedy. Any thoughts on how to accomplish something like this?
Here's a naive implementation, assuming all three are the same size:
unsigned char *a = CGBitmapContextGetData(CGLayerGetContext(layerA));
unsigned char *b = CGBitmapContextGetData(CGLayerGetContext(layerB));
CGContextRef context = CGLayerGetContext(layerC);
unsigned char *c = CGBitmapContextGetData(context);
size_t bytesPerRow = CGBitmapContextGetBytesPerRow(context);
size_t height = CGBitmapContextGetHeight(context);
size_t len = bytesPerRow * height;
BOOL bitsFound = NO;
for (int i = 0; i < len; i++) {
if ((a[i] | b[i]) & c[i]) { bitsFound = YES; break; }
}
Since you're hankering for QuickDraw, I assume you could have written that yourself, and you know that will probably be slow.
If you can guarantee the bitmap sizes, you could use int instead of char and operate on four bytes at a time.
For more serious optimization, you should check out the Accelerate framework.
What about the CGBlendModes? kCGBlendModeDestinationOver acts as OR for A and B, and then you can use kCGBlendModeDestinationIn to AND that result with C.