Hi I tried to write my own version of memmove and I find the following code resulting in a segmentation fault. It would be great if someone could help me figure out why this behavior would occur!
However, when I use something like:
char source[20] = "Hello, this is Piranava", the code works fine!
void *memmoveLocal(void *dest, const void *src, unsigned int n)
{
char *destL = dest;
const char *srcL = src;
int i = 0;
if(dest == NULL || src == NULL)
{
return NULL;
}
else
{
// if dest comes before source, even if there's an overlap, we should move forward
// because if there's an overlap (when dest < src) and we move backward, we'd overwrite the overlapping bytes in src
if(destL < srcL)
{
printf("Forward\n");
while(i < n)
{
destL[i] = srcL[i];
i++;
}
}
else // in all other cases (even if there's overlap or no overlap, we can move backward)
{
printf("Backward\n");
i = n - 1;
while(i >= 0)
{
destL[i] = srcL[i];
i--;
}
}
}
return dest;
}
void main()
{
char *source = "Hello, this is ABC";
char *destination = malloc(strlen(source)+1);
memmoveLocal(source+5, source, 5);
printf("Source: %s \nDestination: %s, size: %d\n", source, destination, strlen(destination));
}
However, if I replace
char *source = "Hello, this is ABC";
with
char source[20] = "Hello, this is ABC";
, it works fine!
memmoveLocal(source+5, source, 5);
You are trying to overwrite a string literal, which is not writable.
Did you intend to memmoveLocal(destination, source+5, 5) instead?
char source[20] = "Hello, this is ABC";
That turns source from a string literal into a char[] array initialized with a string literal. The array is writable, so your program no longer crashes.
Related
I'm struggling with an issue where an ESP32 is running as a AP with AsyncTCP connecting multiple ESP32 clients. The AP receives some JSON data and replies with some JSON data. Without the handleData() function, the code runs 100% fine with no issues. Heap is static when no clients connect and issues only occur when clients start connecting.
Can anyone see anything with my code that could be causing heap corruption or other memory weirdness?
static void handleData(void* arg, AsyncClient* client, void *data, size_t len) {
int i = 0, j = 0;
char clientData[CLIENT_DATA_MAX];
char packetData[len];
char *packetBuf;
packetBuf = (char *)data;
clientData[0] = '\0';
for (i=0;i <= len;i++) {
packetData[j] = packetBuf[i]; //packetBuf[i];
if ((packetData[j] == '\n') || (i == len)) {
packetData[j] = '\0';
if ((j > 0) && (packetData[0] != '\n') && (packetData[0] != '\r')) {
// See sensorData() below...
parseData.function(packetData, clientData);
if (clientData != NULL) {
// TCP reply to client
if (client->space() > 32 && client->canSend()) {
client->write(clientData);
}
}
}
j = 0;
} else
j++;
}
}
void sensorData(void *data, void *retData) {
StaticJsonDocument<CLIENT_DATA_MAX> fields;
StaticJsonDocument<CLIENT_DATA_MAX> output;
char sensor[15] = "\0";
char MAC[18] = "\0";
char value[20] = "\0";
bool sendOK = false;
memcpy((char *)retData, "\0", 1);
DeserializationError error = deserializeJson(fields, (char *)data, CLIENT_DATA_MAX);
if (error) {
DEBUG_PRINTLN(F("deserializeJson() failed"));
return;
}
if (fields["type"])
strcpy(sensor, fields["type"]);
switch (sensor[0]) {
case 'C':
if (fields["value"])
strcpy(value, fields["value"]);
sendOK = true;
break;
case 'T': //DEBUG_PRINT(F("Temp "));
setExtTempSensor(fields["value"]);
sendOK = true;
break;
case 'N':
output["IT"] = intTempC; //Internal temp
output["B1"] = battLevels[0];
serializeJson(output, (char *)retData, CLIENT_DATA_MAX-1);
break;
}
if (sendOK) {
output["Resp"] = "Ok";
serializeJson(output, (char *)retData, CLIENT_DATA_MAX-1);
}
strcat((char *)retData, "\n");
}
static void handleNewClient(void* arg, AsyncClient* client) {
client->setRxTimeout(1000);
client->setAckTimeout(500);
client->onData(&handleData, NULL);
client->onError(&handleError, NULL);
client->onDisconnect(&handleDisconnect, NULL);
client->onTimeout(&handleTimeOut, NULL);
}
void startServer() {
server = new AsyncServer(WIFI_SERVER_PORT);
server->onClient(&handleNewClient, &server)
}
Using AsyncTCP on the ESP32 was having multiple issues. Heap issues, socket issues, assert issues, ACK timeouts, connection timeouts, etc. Swapping to AsyncUDP using the exact same code as shown above with romkey's changes, resolved all of my issues. (Just using romkey's fixes did not fix the errors I was having with AsyncTCP.) I don't believe the issue is with AsyncTCP but with ESP32 libraries.
Either you should declare packetData to be of length len + 1 or your for loop should iterate until i < len. Because the index starts at 0, packetData[len] is actually byte len + 1, so you'll overwrite something random when you store something in packetData[len] if the array is only len chars long.That something random may be the pointer stored in packetBuf, which could easily cause heap corruption.
You should always use strncpy() and never strcpy(). Likewise use strncat() rather than strcat(). Don't depend on having done the math correctly or on sizes not changing as your code evolves. strncpy() and strncat() will guard against overflows. You'll need to pass a length into sensorData() to do that, but sensorData() shouldn't be making assumptions about the available length of retData.
Your test
if (clientData != NULL) {
will never fail because clientData is the address of array and cannot change. I'm not sure what you're trying to test for here but this if will always succeed.
You can just write:
char sensor[15] = "";
you don't need to explicitly assign a string with a null byte in it.
And
memcpy((char *)retData, "\0", 1);
is equivalent to
((char *)retData)[0] = '\0';
What's the point of declaring retData to be void * in the arguments to sensorData()? Your code starts out with it being a char* before calling sensorData() and uses it as a char* inside sensorData(). void * is meant to be an escape hatch for passing around pointers without worrying about their type. You don't need that here and end up needing to extra casts back to char* because of it. Just declare the argument to be char* and don't worry about casting it again.
You didn't share the code that calls handleData() so there may well be issues outside of these functions.
After creating a hash table and assigning each letter to a value for the table, i am noticing the first word output by the table for the beginning of every linked list is the same word. Somehow it seems I am transferring the entire dictionary to each array in the table even though I have attempted to separate them. Any assistance would be awesome! Thanks in advance
// Implements a dictionary's functionality
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include "dictionary.h"
// Represents a node in a hash table
typedef struct node
{
char *word;
struct node *next;
}
node;
// Number of buckets in hash table
const unsigned int N = 25;
// Hash table
node *table[N];
char lowerword[LENGTH+1];
// Returns true if word is in dictionary else false
bool check(const char *word)
{
int bucketfind = 0;
int x = 0;
for (int b = word[x]; b != '\0';b = word[x], x++)
{
int lowertemp = tolower(word[x]);
if (x == 0)
{
bucketfind = lowertemp - 97;
}
char lowerfinal = lowertemp;
lowerword[x] = lowerfinal;
//printf("%c", lowerword[x]);
}
int wordlen = x + 1;
int pr = 0;
while (table[bucketfind] -> next != NULL)
{
int dwlen = strlen(table[bucketfind]-> word);
pr++;
//printf("%i, %i, %s, %i\n", pr, dwlen, table[bucketfind] -> word, bucketfind);
}
//TODO
return false;
}
// Hashes word to a number
unsigned int hash(const char *word)
{
int asciifirst = word[0];
int lowerfirst = tolower(asciifirst);
int bucketnum = lowerfirst - 97;
return bucketnum;
}
// Loads dictionary into memory, returning true if successful else false
int dictwords = 0;
//char *cword = (char*)malloc(sizeof(char)*46);
bool load(const char *dictionary)
{
char *cword = malloc(sizeof(char)*46);
FILE *dict = fopen(dictionary, "r");
if (dictionary == NULL)
{
return false;
}
int x = 0;
while ((fscanf(dict, "%s", cword) != EOF))
{
node *nword = malloc(sizeof(node));
nword -> word = cword;
nword -> next = NULL;
int bucket = hash(cword);
//printf("%i\n", bucket);
if (table[bucket] != NULL)
{
nword -> next = table[bucket];
table[bucket] = nword;
}
else
{
table[bucket]= nword;
}
dictwords++;
}
fclose(dict);
return true;
}
// Returns number of words in dictionary if loaded else 0 if not yet loaded
unsigned int size(void)
{
return dictwords;
}
// Unloads dictionary from memory, returning true if successful else false
bool unload(void)
{
// TODO
return false;
}
It's not just the first word; every word in the linked list is the same word (the last one read). cword gets 46 bytes of memory at a specific address here char *cword = malloc(sizeof(char)*46);. Every word from dictionary is read into that same address.
My chip just stop doing anything. sometimes it prints good results, sometimes its not, i just cant understand whats wrong with this code( and generally any time you using Strings it happens )
void ParseGetRequest(char* data)
{
String parseGET=data;
String from="GET /";
String to="HTTP";
int ind1 = parseGET.indexOf(from);
int ind2 = parseGET.indexOf(to);
parseGET=parseGET.substring(ind1+from.length(), ind2-1);
strcpy(data, parseGET.c_str () );
}
And calling it with :
void readWifDataAsSever(char* reqData)
{
uint8_t buffer[128] = {0};
uint8_t mux_id;
uint32_t len = wifi.recv(&mux_id, buffer, sizeof(buffer), 100);
char serverData[100]={0};
if (len > 0)
{
for(uint32_t i = 0; i < len; i++)
serverData[i]=(char)buffer[i];
ParseGetRequest( serverData ); ///****** the call
Serial.println(serverData); // prints only part of the values
//here the chip just freeze and stop the main loop
NULL termination !!!!
serverData[len ] = '\0';
I have a String variable and I want to extract the three substrings separeted by ; to three string variables.
String application_command = "{10,12; 4,5; 2}";
I cannot use substring method because this string can be like any of the following or similar patterns also.
String application_command = "{10,12,13,9,1; 4,5; 2}"
String application_command = "{7; 1,2,14; 1}"
The only thing that is common in these patterns is there are three sections separated by ;.
Any insight is much appreciated.
Thank you
I think you need a split-string-into-string-array function with a custom separator character.
There are already several sources on the web and at stackoverflow (e.g. Split String into String array).
// https://stackoverflow.com/questions/9072320/split-string-into-string-array
String getValue(String data, char separator, int index)
{
int found = 0;
int strIndex[] = {0, -1};
int maxIndex = data.length()-1;
for(int i=0; i<=maxIndex && found<=index; i++){
if(data.charAt(i)==separator || i==maxIndex){
found++;
strIndex[0] = strIndex[1]+1;
strIndex[1] = (i == maxIndex) ? i+1 : i;
}
}
return found>index ? data.substring(strIndex[0], strIndex[1]) : "";
}
You can use this function as follows (with ";" as separator):
String part01 = getValue(application_command,';',0);
String part02 = getValue(application_command,';',1);
String part03 = getValue(application_command,';',2);
EDIT: correct single quotes and add semicolons in the example.
The new SafeString Arduino library (available from the library manager) provides a number of tokenizing/substring methods without the heap fragmentation of the String class
See https://www.forward.com.au/pfod/ArduinoProgramming/SafeString/index.html
for a detailed tutorial
In this case your can use
#include "SafeString.h"
void setup() {
Serial.begin(9600);
createSafeString(appCmd, 50); // large enought for the largest cmd
createSafeString(token1, 20);
createSafeString(token2, 20);
createSafeString(token3, 20);
appCmd = "{10,12,13,9,1; 4,5; 2}";
size_t nextIdx = 1; //step over leading {
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
// can trim tokens if needed e.g. token1.trim()
Serial.println(token1);
Serial.println(token2);
Serial.println(token3);
}
void loop() {
}
Also look at pfodParser which parses these types of messages { } for use by pfodApp.
Do not forget to call delete[] to free the memory after the use of the array, that said here is my solution:
String* split(String& v, char delimiter, int& length) {
length = 1;
bool found = false;
// Figure out how many itens the array should have
for (int i = 0; i < v.length(); i++) {
if (v[i] == delimiter) {
length++;
found = true;
}
}
// If the delimiter is found than create the array
// and split the String
if (found) {
// Create array
String* valores = new String[length];
// Split the string into array
int i = 0;
for (int itemIndex = 0; itemIndex < length; itemIndex++) {
for (; i < v.length(); i++) {
if (v[i] == delimiter) {
i++;
break;
}
valores[itemIndex] += v[i];
}
}
// Done, return the values
return valores;
}
// No delimiter found
return nullptr;
}
Here is an example of how to use:
void loop() {
String test = "1,2,3,4,5";
int qtde;
String* t = split(test, ',', qtde);
for (int i = 0; i < qtde; i++) {
Serial.println(t[i]);
delay(1000);
}
delete[] t;
}
I am currently making a simple client and server but I have run into an issue. Part of the system is for the client to query about a local file on the server. The contents of that file must be then sent to the client. I am able to send all the text within a file to the client however it seems to be stuck in the read loop on the client. Below are the code spits for both the client and server that are meant to deal with this:
Client Code That Reads The Loop
else if(strcmp(commandCopy, get) == 0)
{
char *ptr;
int total = 0;
char *arguments[1024];
char copy[2000];
char * temp;
int rc;
strcpy(copy, command);
ptr = strtok(copy," ");
while (ptr != NULL)
{
temp = (char *)malloc(sizeof(ptr));
temp = ptr;
arguments[total] = temp;
total++;
ptr = strtok (NULL, " ");
}
if(total == 4)
{
if (strcmp(arguments[2], "-f") == 0)
{
printf("1111111111111");
send(sockfd, command, sizeof(command), 0 );
printf("sent %s\n", command);
memset(&command, '\0', sizeof(command));
cc = recv(sockfd, command, 2000, 0);
if (cc == 0)
{
exit(0);
}
}
else
{
printf("Here");
strcpy(command, "a");
send(sockfd, command, sizeof(command), 0 );
printf("sent %s\n", command);
memset(&command, '\0', sizeof(command));
cc = recv(sockfd, command, 2000, 0);
}
}
else
{
send(sockfd, command, sizeof(command), 0 );
printf("sent %s\n", command);
memset(&command, '\0', sizeof(command));
while ((rc = read(sockfd, command, 1000)) > 0)
{
printf("%s", command);
}
if (rc)
perror("read");
}
}
Server Code That Reads the File
char* getRequest(char buf[], int fd)
{
char * ptr;
char results[1000];
int total = 0;
char *arguments[1024];
char data[100];
FILE * pFile;
pFile = fopen("test.txt", "r");
ptr = strtok(buf," ");
while (ptr != NULL)
{
char * temp;
temp = (char *)malloc(sizeof(ptr));
temp = ptr;
arguments[total] = temp;
total++;
ptr = strtok (NULL, " ");
}
if(total < 2)
{
strcpy(results, "Invaild Arguments \n");
return results;
}
if(pFile != NULL)
{
while(fgets(results, sizeof(results), pFile) != NULL)
{
//fputs(mystring, fd);
write(fd,results,strlen(results));
}
}
else
{
printf("Invalid File or Address \n");
}
fclose(pFile);
return "End of File \0";
}
Server Code to execute the command
else if(strcmp(command, "get") == 0)
{
int pid = fork();
if (pid ==-1)
{
printf("Failed To Fork...\n");
return-1;
}
if (pid !=0)
{
wait(NULL);
}
else
{
char* temp;
temp = getRequest(buf, newsockfd);
strcpy(buf, temp);
send(newsockfd, buf, sizeof(buf), 0 );
exit(1);
}
}
The whole else if clause in the client code is a bit large for a function, let alone a part of a function as it presumably is. The logic in the code is ... interesting. Let us dissect the first section:
else if (strcmp(commandCopy, get) == 0)
{
char *ptr;
int total = 0;
char *arguments[1024];
char *temp;
ptr = strtok(copy, " ");
while (ptr != NULL)
{
temp = (char *)malloc(sizeof(ptr));
temp = ptr;
arguments[total] = temp;
total++;
ptr = strtok(NULL, " ");
}
I've removed immaterial declarations and some code. The use of strtok() is fine in context, but the memory allocation is leaky. You allocate enough space for a character pointer, and then copy the pointer from strtok() over the only pointer to the allocated space (thus leaking it). Then the pointer is copied to arguments[total]. The code could, therefore, be simplified to:
else if (strcmp(commandCopy, get) == 0)
{
char *ptr;
int total = 0;
char *arguments[1024];
ptr = strtok(copy, " ");
while (ptr != NULL)
{
arguments[total++] = ptr;
ptr = strtok(NULL, " ");
}
Nominally, there should be a check that you don't overflow the arguments list, but since the original limits the string to 2000 characters, you can't have more than 1000 arguments (all single characters separated by single spaces).
What you have works - it achieves the same assignment the long way around, but it leaks memory prodigiously.
The main problem seems to be that the server sends all the contents, but it doesn't close the socket, so the client has no way of knowing the server's done. If you close the socket after you finish sending the data (or just call shutdown()), then the client's read() will return 0 when it finishes reading the data.
FWIW, there are lots of other problems with this code:
getRequest: you call malloc but never free. In fact, the return value is thrown away.
Why bother forking if you're just going to wait() on the child?
You probably want to use strlcpy instead of strpcy to avoid buffer overruns.