I am trying to create a formatted string , however I do not know why I cannot print global array which I have modified inside the function.Also the strange behavior is that I cannot access only a specific global array (rand_session_key) rest of the other global arrays are behaving as normal(similar operations are being done on them except their size varies) and I can access their value properly. This code is run on an esp32 (DOIT Dev Kit V1) (with Arduino-Core) , when I run this program on my computer (modifying a few functions etc.) the result is what I expect , I think I am overlapping the characters in the memory or accessing it the wrong way , but had it been the case I would not have yielded the expected output on my computer.
I tried to modify my program and made it more verbose. Also I ran the same code (with some obvious modifications to make it run on my computer) , and the result is good as expected.
char persistent_peripheral_id[] = "FRUCTOSE96";
char rand_session_iden[7] = {'\0'};
char rand_session_key[17] = {'\0'};
char rand_session_channel[3] = {'\0'};
char *generate_random_session_identifier(char *rand_session_iden_local)
{
srand(time(NULL));
int counter = 0;
for (counter = 0; counter < 6; counter++)
*(rand_session_iden_local + counter) = (random(10) % ('~' - ' ')) + 'k';
rand_session_iden_local[counter] = '\0';
printf("Identifier : %s\n", rand_session_iden); //acessing global defintion of array everything is good until here
return &rand_session_iden_local[0];
}
char *generate_random_session_key(char *rand_session_key_local)
{
srand(time(NULL));
int counter = 0;
for (counter = 0; counter < 16; counter++)
*(rand_session_key_local + counter) = (random(10) % ('~' - ' ')) + 'b';
rand_session_key_local[counter] = '\0';
printf("Key : %s\n", rand_session_key);//acessing global defintion of array everything is good until here
return &rand_session_key_local[0];
}
char *generate_random_session_channel(char *rand_session_channel_local)
{
srand(time(NULL));
int channel_value = random(100);
sprintf(rand_session_channel_local, "%03ld", channel_value);
printf("Channel : %s\n", rand_session_channel);//acessing global defintion of array everything is good until here
return &rand_session_channel_local[0];
}
void begin_exchange_package()
{
//If this does not works here (observe rand_session_key) , it will not work for sprintf also ??
printf("\n %s-%s-%s-%s \n", (char *)persistent_peripheral_id,
generate_random_session_identifier(rand_session_iden),
generate_random_session_key(rand_session_key),
generate_random_session_channel(rand_session_channel));
//Notice it prints here ????
printf("\n %s \n",generate_random_session_key(rand_session_key));
Serial.println("Done");
//sprintf((char *)plain_text_package, "{\"p\":\"%s\",\"r\":\"%s\",\"k\":\"%s\",\"c\":\"%s\"}", (char *)persistent_peripheral_id,(char *)rand_session_iden, (char *)rand_session_key , (char *)rand_session_channel);
}
void setup()
{
Serial.begin(115200);
begin_exchange_package();
}
void loop()
{
}
The Output is
FRUCTOSE96-tnltkp--094
Where I expected all the 4 arrays to be printed ?? but it does print separately , is my array being terminated in the wrong way ?? also the logic to assign a random character will always yield a printable ASCII Character (I learned this from a forum on esp32's website)
This code ...
sprintf(rand_session_channel_local, "%03ld", channel_value);
... requires rand_session_channel_local to point to an array of at least four characters, because at will print at least three digits plus a string terminator. The array into which it points, rand_session_channel, is only three characters long. The resulting behavior is undefined.
The observed manifestation of the UB is consistent with the global arrays being laid out in memory such that rand_session_key immediately follows rand_session_channel, such that overflowing the latter means that the string terminator is written to position 0 of the former, making it an empty string. Note, however, that you cannot rely on predicting manifestations of UB, nor is it generally of much use to analyze them. Instead, avoid exercising UB.
It's unclear what random function you are using, since the C standard library's does not take an argument, but if the argument to yours specifies an exclusive upper bound then you could just change the sprintf format to "%02ld". Alternatively, increase the size of rand_session_channel to at least 4.
I have one long array, and I'm trying to figure out how to split it up into two separate arrays, the second array has the right contents but the first is empty, I'm also getting an Abort Trap:6 and I'm not sure what that means.
I have an array called entireA, which looks something like this:
HELLO:WORLD, I want to put HELLO in a separate array (firstA) and WORLD in secondA. When I print first and second array at the end, secondA has the right contents but firstA doesn't event though I'm printing to check if the right characters are being passed over and they are -- but the firstA is still empty and I'm getting and abort trap i don't understand.
I've just started learning C, why is the first array empty and what does the error mean?
#define ARRSIZE 10000
char entireA[ARRSIZE] = "";
char firstA[ARRSIZE] = "";
char secondA[ARRSIZE] = "";
strcpy(entireA,"HELLO:WORLD\n");
int firstVar = 0;
int entireVar = 0;
while(entireA[entireVar] != ':') {
if(entireA[entireVar] == ';') {
break;
}
printf("%c \n",entireA[entireVar]);
firstA[firstVar] = entireA[entireVar];
firstVar++;
entireVar++;
}
firstA[firstVar] = '\0';
int secondVar = 0;
entireVar++; //skip ':'
while(entireA[entireVar] != '\n') {
secondA[secondVar] = entireA[entireVar];
secondVar++;
entireVar++;
}
secondA[secondVar] = '\0';
printf("%s", firstA);
printf("%s", secondA);
There is nothing wrong with the code you posted.
After execution, the variables have the following values:
entireA 0x02efcdb4 "HELLO:WORLD\n" char[0x00002710]
entireVar 0x0000000b int
firstA 0x02efa69c "HELLO" char[0x00002710]
firstVar 0x00000005 int
secondA 0x02ef7f84 "WORLD" char[0x00002710]
secondVar 0x00000005 int
Whatever your problem is, it's most likely something to do with your environment. I would suggest reducing the value of ARRSIZE to, say 80 characters, and seeing if that changes your results.
I want my program to extract the first two characters of the given hash hash. These first two characters represent a nonce/salt that the password was encrypted with (DES-based, crypt() function). The first two characters of hash are stored in the array nonceAsArray[], which is being passed down to the function concatenateCharacters(), whose job is to turn these characters into a nonce of type string and save it in the variable nonce so that it can be used later on in order to encrypt a password.
The function seems to concatenate the two characters perfectly fine. However, when nonce is given to the crypt() function as an argument, it returns null but only, if I calculate both, generatedHash1 and generatedHash2:
Output:
generatedHash1: 14dJperBYV6zU
generatedHash2: (null)
However, when I exclude the calculation of the first hash string generatedHash1 = crypt("myPassword", "14");, my program outputs the following:
generatedHash2: dJperBYV6zU
The crypt() function now seems to have accepted the value that is being stored in nonce. Another odd thing is that crypt() returns a hash without the nonce being represented in the first two characters of generatedHash2. The encrypted password however should be 13 characters long in total.
Fired up the debugger and checked the values that are being stored in nonce. I stumbled upon this:
nonce: 0x7fffffffdd40 "14"
and
*nonce: 49 '1'
I assume that the first part that starts with 0x7f... is the memmory address and next to it the value that stored at this address.
Can anyone help me understand as to why the crypt() function doesn't seem to accept the value in nonce? I would greatly appreciate if anyone could give me a hint where to look or an explenation as to why it fails.
(...)
#include <cs50.h>
#include <string.h>
(...)
// extract the first two characters of 'hash' (== nonce/salt)
string hash = "14dJperBYV6zU";
char nonceAsArray[2];
for (int i = 0; i < 2; i++)
{
nonceAsArray[i] = hash[i];
}
string nonce = concatenateCharacters(nonceAsArray, 2);
printf("first hash: %s\n", crypt("myPassword", "14"));
printf("second hash: %s\n", crypt("myPassword", nonce));
// connects characters to strings
string concatenateCharacters(char characters[], int arraySize)
{
char terminator[1] = {'\0'};
// create array that can store the password and to which the terminator can be appended (hence +1)
char bigEnoughArray[arraySize + 1];
for (int i = 0; i < arraySize; i++)
{
bigEnoughArray[i] = characters[i];
}
return strcat(bigEnoughArray, terminator);
}
I "guess" it helps to replace this
string hash = "14dJperBYV6zU";
char nonceAsArray[2];
for (int i = 0; i < 2; i++)
{
nonceAsArray[i] = hash[i];
}
string nonce = concatenateCharacters(nonceAsArray, 2);
by
#define NONCE_MAX (2);
string hash = "14dJperBYV6zU";
char nonceAsArray[NONCE_MAX + 1] = ""; /* zeros out all nonceAsArray */
strncpy(nonceAsArray, hash, NONCE_MAX);
string nonce = nonceAsArray;
I've searched around for a quiet some time but surprisingly I couldn't find an answer to it:
I want to rewrite a char array starting from [0], but all what's happening is: it's always appending. Here's my code:
The algorithm is: I have a very long string which I like to break into several lines (wherever there is a blank space at the end of a line). Each line shall be saved in an array Index (lineContent);
void print_text(char* content, int menu_width, int which_selected, int menu_height, int scroll_pos)
{
int posCounter = 0;
int charCounter = menu_width-10;
int printOutCounter;
char* lineContent[400]; // 400 lines max
short spaceFound;
while (strlen(content) > menu_width) // If string is longer than 1 line
{
//Interesting Part ---------- START
char changeString [strlen(content)];
char printString [menu_width-10];
spaceFound = 0;
charCounter = menu_width-10;
lineContent[posCounter] = malloc(MAXITEMSTR);
while (spaceFound == 0)
{
if (content[charCounter] == ' ')
{
// I guess the error goes between here ...
strncpy(changeString,content,strlen(content));
strncpy(printString,content,menu_width-10);
// ...and here
memmove(&changeString[0], &changeString[charCounter], strlen(content));
content=changeString;
lineContent[posCounter]=printString;
strcat(lineContent[posCounter],"\0");
posCounter++;
spaceFound = 1;
//Interesting Part ---------- END
}
charCounter--;
if (charCounter <= 0)
spaceFound = 1;
}
}
}
As I said, in the end, when checking the content of lineContent, every entry is the same (the one from the last line).
I think this is because, strcpy just appends to the end, therefor I have to clear the array, to erase the former line. So it will start from [0] and not from the last printed letter.
Has anybody an idea how to do this? Is there a function that overwrites a char array instead of appending it?
Kind Regards
Strcat appends to the end, strcpy overwrites the value stored in the string.
Arduino (C language) parsing string with delimiter (input through serial interface)
Didn't find the answer here :/
I want to send to my arduino through a serial interface (Serial.read()) a simple string of three numbers delimited with comma. Those three numbers could be of range 0-255.
Eg.
255,255,255
0,0,0
1,20,100
90,200,3
What I need to do is to parse this string sent to arduino to three integers (let's say r, g and b).
So when I send
100,50,30
arduino will translate it to
int r = 100
int g = 50
int b = 30
I tried lots of codes, but none of them worked. The main problem is to translate string (bunch of chars) to integer. I figured out that there will probably be strtok_r for delimiter purpose, but that's about it.
Thanks for any suggestions :)
To answer the question you actually asked, String objects are very powerful and they can do exactly what you ask. If you limit your parsing rules directly from the input, your code becomes less flexible, less reusable, and slightly convoluted.
Strings have a method called indexOf() which allows you to search for the index in the String's character array of a particular character. If the character is not found, the method should return -1. A second parameter can be added to the function call to indicate a starting point for the search. In your case, since your delimiters are commas, you would call:
int commaIndex = myString.indexOf(',');
// Search for the next comma just after the first
int secondCommaIndex = myString.indexOf(',', commaIndex + 1);
Then you could use that index to create a substring using the String class's substring() method. This returns a new String beginning at a particular starting index, and ending just before a second index (Or the end of a file if none is given). So you would type something akin to:
String firstValue = myString.substring(0, commaIndex);
String secondValue = myString.substring(commaIndex + 1, secondCommaIndex);
String thirdValue = myString.substring(secondCommaIndex + 1); // To the end of the string
Finally, the integer values can be retrieved using the String class's undocumented method, toInt():
int r = firstValue.toInt();
int g = secondValue.toInt();
int b = thirdValue.toInt();
More information on the String object and its various methods can be found int the Arduino documentation.
Use sscanf;
const char *str = "1,20,100"; // assume this string is result read from serial
int r, g, b;
if (sscanf(str, "%d,%d,%d", &r, &g, &b) == 3) {
// do something with r, g, b
}
Use my code here if you want to parse a stream of string ex: 255,255,255 0,0,0 1,20,100 90,200,3Parsing function for comma-delimited string
Simplest, I think, is using parseInt() to do this task:
void loop(){
if (Serial.available() > 0){
int r = Serial.parseInt();
int g = Serial.parseInt();
int b = Serial.parseInt();
}
}
does the trick.
I think you want to do something like this to read in the data:
String serialDataIn;
String data[3];
int counter;
int inbyte;
void setup(){
Serial.begin(9600);
counter = 0;
serialDataIn = String("");
}
void loop()
{
if(serial.available){
inbyte = Serial.read();
if(inbyte >= '0' & inbyte <= '9')
serialDataIn += inbyte;
if (inbyte == ','){ // Handle delimiter
data[counter] = String(serialDataIn);
serialDataIn = String("");
counter = counter + 1;
}
if(inbyte == '\r'){ // end of line
handle end of line a do something with data
}
}
}
Then use atoi() to convert the data to integers and use them.
This is great!
The last comment about "thirdvalue = 0" is true from the code given in the most upvoted response by #dsnettleton. However, instead of using "lastIndexOf(',');" , the code should just add a "+1" to "secondCommaIndex" like #dsnettleton correctly did for commaIndex+1 (missing +1 is probably just a typo from the guy).
Here is the updated piece of code
int commaIndex = myString.indexOf(',');
int secondCommaIndex = myString.indexOf(',', commaIndex+1);
String firstValue = myString.substring(0, commaIndex);
String secondValue = myString.substring(commaIndex+1, secondCommaIndex);
String thirdValue = myString.substring(secondCommaIndex+1); //To the end of the string
Example)
For a myString = "1,2,3"
commaIndex = 1 (Searches from index 0, the spot taken by the character 1, to the location of the first comma)
secondCommaIndex = 3 (Searches from index 2, the spot taken by the character 2, to the location of the next comma)
firstValue reads from index 0-1 = "1"
secondValue reads from index 2-3 = "2"
thirdvalue reads from index 4-4(the last index spot of the string) = "3"
Note: Don't confuse INDEX with the LENGTH of the string. The length of the string is 5. Since the String indexOf counts starting from 0, the last index is 4.
The reason why just
String thirdValue = myString.substring(secondCommaIndex);
returns 0 when using .toInt() is because thirdValue = ",3" and not "3" which screws up toInt().
ps. sorry to write all the instructions out but as a mech eng, even I sometimes would like someone to dumb down code for me especially having been in consulting for the past 7 years. Keep up the awesome posting! Helps people like me out a lot!
For n number delimited in string
int end;
while((end=str.indexOf(","))!=-1){
String num = str.substring(0,end);
str= asc.substring(end+1,str.length());
Serial.println(num);
}
The new SafeString Arduino library (available via the library manager) provides an stoken() method and a toLong() method which handles this case and avoids the heap fragmenation problems of the String class.
see https://www.forward.com.au/pfod/ArduinoProgramming/SafeString/index.html
for a detailed tutorial
#include "SafeString.h"
void setup() {
Serial.begin(9600);
createSafeString(appCmd, 50); // large enough for the largest cmd
createSafeString(token1, 10);
createSafeString(token2, 10);
createSafeString(token3, 10);
long r;
long g;
long b;
appCmd = "1,20a,100";
token1.clear();token2.clear();token3.clear(); // clear any old data
size_t nextIdx = 0;
nextIdx = appCmd.stoken(token1, nextIdx, ",");
nextIdx++; //step over delimiter
nextIdx = appCmd.stoken(token2, nextIdx, ",");
nextIdx++; //step over delimiter
nextIdx = appCmd.stoken(token3, nextIdx, ",");
nextIdx++; //step over delimiter
// now parse the numbers
bool have3ValidNumbers = true;
if (!token1.toLong(r)) {
have3ValidNumbers = false;
Serial.print("Red number invalid:");Serial.println(token1);
}
if (!token2.toLong(g)) {
have3ValidNumbers = false;
Serial.print("Green number invalid:");Serial.println(token2);
}
if (!token3.toLong(b)) {
have3ValidNumbers = false;
Serial.print("Blue number invalid:");Serial.println(token3);
}
if (have3ValidNumbers) {
Serial.print("The values are ");
Serial.print(" r:");Serial.print(r);
Serial.print(" g:");Serial.print(g);
Serial.print(" b:");Serial.print(b);
Serial.println();
}
}
void loop() {
}
The output for this input "1,20a,100" is
Green number invalid:20a
The 'standard' toInt() method would have returned 1 20 100 as the result.
For an input like "1,a,50" the 'standard' toInt() method would return 1 0 100
The SafeString toLong() method does more error checking when attempting to convert a string to an integer.
You should also add checks for <0 and >255 to ensure the input is valid range
#cstrutton -Excellent suggestion on using 'indexOf' . it saved me a ton of time for my project. One minor pointer though,
I noticed the thirdvalue did not get displayed (was coming back as ZERO). Upon playing with it little-bit and going through the doc at http://arduino.cc/en/Tutorial/StringIndexOf
I realized, I can use lastIndexOf for the last value.
Here are two lines of modifications that provided correct third value.
int lastCommaIndex = myString.lastIndexOf(',');
String thirdValue = myString.substring(lastCommaIndex+1); // To the end of the string
String myString = "dfsdfgsafhffgsdvbsdvdsvsdvsdsdfdfsdsff|date|recipt|weight|time|date|";
// the setup routine runs once when you press reset:
void setup() {
Serial.begin(9600);
}
// the loop routine runs over and over again forever:
void loop() {
int Index1 = myString.indexOf('|');
int Index2 = myString.indexOf('|', Index1+1);
int Index3 = myString.indexOf('|', Index2+1);
int Index4 = myString.indexOf('|', Index3+1);
int Index5 = myString.indexOf('|', Index4+1);
int Index6 = myString.indexOf('|', Index5+1);
String secondValue = myString.substring(Index1+1, Index2);
String thirdValue = myString.substring(Index2+1, Index3);
String fourthValue = myString.substring(Index3+1, Index4);
String fifthValue = myString.substring(Index4+1, Index5);
String firstValue = myString.substring(Index5+1, Index6);
//Serial.println(Index1);
//
Serial.println(secondValue);
Serial.println(thirdValue);
Serial.println(fourthValue);
Serial.println(fifthValue);
Serial.println(firstValue);
delay(14000);
}