I am using CEdit with the property of Multiline.My objective is to retrieve the individual line and place it in my CStringArray.
While retrieving the line using GetLine , I have to know the string length of that line.
How to get this?
I tried the function GetLineLength() but that will return the size of the entire line rather than the specified text.
I pasted the code that i have implemented so far:
CEdit m_strMnemonicCode;
CStringArray strMnemonicArray;
LPTSTR temp = new TCHAR[50];;
int nLineCount = m_strMnemonicCode.GetLineCount();
for(int ni = 0 ; ni < nLineCount ; ni++)
{
int len = m_strMnemonicCode.LineLength(m_strMnemonicCode.LineIndex(ni));
//m_strMnemonicCode.GetLine(ni, strText.GetBuffer(len), len);
m_strMnemonicCode.GetLine( ni , temp );
strMnemonicArray.Add(strText);
}
But you need to know the length of the whole line, don't you?
I would not define the buffer as an array of TCHARs, but as a CString, then do GetBuffer() on it.
Check the example in CEdit::GetLineCount
It seems to do more or less what you need.
Edit
I've just written the following test, and it works perfectly for me:
int lc = m_Edit.GetLineCount();
CString strLine;
CStringArray arr;
for (int i = 0; i < lc ; i++)
{
int len = m_Edit.LineLength(m_Edit.LineIndex(i));
m_Edit.GetLine(i, strLine.GetBuffer(len), len);
strLine.ReleaseBuffer(len);
arr.Add(strLine);
}
Maybe you are forgetting to add the buffer length to ReleaseBuffer()?
Related
I'm writing a dialog based MFC application in Visual Studio 2017 in C++. In the dialog I added a list control where the user can change the values of the cells as shown in the picture below:
after he changes the values, I want to check if those values are valid (so if he accidentally pressed the wrong button he will be notified). For this purpose I'm iterating over the different cells of the list and from each cell I extract the text which is written in it into a CString type variable. I want to check that this variable has only 8 characters which are '1' or '0'. The problem with the code I've written is that I get weird values when I try to print the different characters of the CString variable.
The Code for checking the validity of the CString:
void CEditableListControlDlg::OnBnClickedButton4()
{
// TODO: Add your control notification handler code here
// Iterate over the different cells
int bit7Col = 2;
int bit6Col = 3;
int bit5Col = 4;
int bit4Col = 5;
int bit3Col = 6;
int bit2Col = 7;
int bit1Col = 8;
int bit0Col = 9;
for (int i = 0; i < m_EditableList.GetItemCount(); ++i) {
CString bit7 = m_EditableList.GetItemText(i, bit7Col);
CString bit6 = m_EditableList.GetItemText(i, bit6Col);
CString bit5 = m_EditableList.GetItemText(i, bit5Col);
CString bit4 = m_EditableList.GetItemText(i, bit4Col);
CString bit3 = m_EditableList.GetItemText(i, bit3Col);
CString bit2 = m_EditableList.GetItemText(i, bit2Col);
CString bit1 = m_EditableList.GetItemText(i, bit1Col);
CString bit0 = m_EditableList.GetItemText(i, bit0Col);
CString cvalue = bit7 + bit6 + bit5 + bit4 + bit3 + bit1 + bit0;
std::string value((LPCSTR)cvalue);
int length = value.length();
if (length != 7) {
MessageBox("Register Value Is Too Long", "Error");
return;
}
for (int i = 0; i < length; i++) {
if (value[i] != static_cast<char>(0) || value[i] != static_cast<char>(1)) {
char c = value[i];
MessageBox(&c, "value"); // this is where I try to print the value
return;
}
}
}
}
Picture of what get's printed in the message box when I try to print one character of the variable value. I expect to see '1' but instead I see in the message box '1iiiiii`:
I've tried extracting the characters directly from the variable cvalue of type CString like this:
cvalue[i]
and it's length I got by using
strlen(cvalue[i])
but I've got the same result. I've also tried accessing the characters in the variable cvalue of type CString as follows:
cvalue.GetAt(i)
and to get it's length by using:
cvalue.GetLength()
But again, I've got the same results.
Perhaps anyone could advice me how can I check that the characters in the variable cvalue of type CString are '0' or '1'?
Thank you.
You don't need to use std::string to process your strings in this case: CString works fine.
Assuming that your CString cvalue is the string you want to check, you can write a simple loop like this:
// Check cvalue for characters different than '0' and '1'
for (int i = 0; i < cvalue.GetLength(); i++)
{
TCHAR currChar = cvalue.GetAt(i);
if ((currChar != _T('0')) && (currChar != _T('1')))
{
CString message;
message.Format(_T("Invalid character at position %d : %c"), i, currChar);
MessageBox(message, _T("Error"));
}
}
The reason for the apparently weird output in your case is that you are passing a pointer to a character that is not followed by a null-terminator:
// Wrong code
char c = value[i];
MessageBox(&c, "value");
If you don't want to build a CString with a formatted message containing the offending character, like I did in the previous sample code, an alternative could be creating a simple raw char array storing the character you want to output followed by the null-terminator:
// This is an array storing two chars: value[i] followed by '\0' (null)
char s[2] = {value[i], '\0'};
MessageBox(s, "value");
P.S.
I used TCHAR in my code sample instead of char, to make the code more easily portable to Unicode builds. Think of TCHAR as a preprocessor macro that maps to char for ANSI/MBCS builds (which seems your current case), and to wchar_t for Unicode builds.
A Brief Note on Validating User Input
With the above answer, I tried to strictly address your specific problem with CString character validation. But, if you can take a look from a broader perspective, I would definitely consider validating the user input before storing it in the list-view control. For example, you could handle the LVN_ENDLABELEDIT notification from the list-view control, and reject invalid input values.
Or, considering that the only valid values for each bit are 0 and 1, you could let the user select them from a combo-box.
Doing that starting from the MFC's CListCtrl is non-trivial work; so, you may also consider using other open-source controls, like this CGridListCtrlEx control available from CodeProject.
As you write in your last paragraph, "check that the characters in the variable cvalue of type CString are '0' or '1'?".
That's exactly how. '0' is the character 0. But you check for the integer 0, which is equal to the character '\0'. That's the end-of-string character.
I have to read a text file into a array of structures.I have already written a program but it is taking too much time as there are about 13 lac structures in the file.
Please suggest me the best possible and fastest way to do this in C++.
here is my code:
std::ifstream input_counter("D:\\cont.txt");
/**********************************************************/
int counter = 0;
while( getline(input_counter,line) )
{
ReadCont( line,&contract[counter]); // function to read data to structure
counter++;
line.clear();
}
input_counter.close();
keep your 'parsing' as simple as possible: where you know the field' format apply the knowledge, for instance
ReadCont("|PE|1|0|0|0|0|1|1||2|0||2|0||3|0|....", ...)
should apply fast char to integer conversion, something like
ReadCont(const char *line, Contract &c) {
if (line[1] == 'P' && line[2] == 'E' && line[3] == '|') {
line += 4;
for (int field = 0; field < K_FIELDS_PE; ++field) {
c.int_field[field] = *line++ - '0';
assert(*line == '|');
++line;
}
}
well, beware to details, but you got the idea...
I would use Qt entirely in this case.
struct MyStruct {
int Col1;
int Col2;
int Col3;
int Col4;
// blabla ...
};
QByteArray Data;
QFile f("D:\\cont.txt");
if (f.open(QIODevice::ReadOnly)) {
Data = f.readAll();
f.close();
}
MyStruct* DataPointer = reinterpret_cast<MyStruct*>(Data.data());
// Accessing data
DataPointer[0] = ...
DataPointer[1] = ...
Now you have your data and you can access it as array.
In case your data is not binary and you have to parse it first you will need a conversion routine. For example if you read csv file with 4 columns:
QVector<MyStruct> MyArray;
QString StringData(Data);
QStringList Lines = StringData.split("\n"); // or whatever new line character is
for (int i = 0; i < Lines.count(); i++) {
String Line = Lines.at(i);
QStringList Parts = Line.split("\t"); // or whatever separator character is
if (Parts.count() >= 4) {
MyStruct t;
t.Col1 = Parts.at(0).toInt();
t.Col2 = Parts.at(1).toInt();
t.Col3 = Parts.at(2).toInt();
t.Col4 = Parts.at(3).toInt();
MyArray.append(t);
} else {
// Malformed input, do something
}
}
Now your data is parsed and in MyArray vector.
As user2617519 says, this can be made faster by multithreading. I see that you are reading each line and parsing it. Put these lines in a queue. Then let different threads pop them off the queue and parse the data into structures.
An easier way to do this (without the complication of multithreading) is to split the input data file into multiple files and run an equal number of processes to parse them. The data can then be merged later.
QFile::readAll() may cause a memory problem and std::getline() is slow (as is ::fgets()).
I faced a similar problem where I needed to parse very large delimited text files in a QTableView. Using a custom model, I parsed the file to find the offsets to the start of a each line. Then when data is needed to display in the table I read the line and parse it on demand. This results in a lot of parsing, but that is actually fast enough to not notice any lag in scrolling or update speed.
It also has the added benefit of low memory usage as I do not read the file contents into memory. With this strategy nearly any size file is possible.
Parsing code:
m_fp = ::fopen(path.c_str(), "rb"); // open in binary mode for faster parsing
if (m_fp != NULL)
{
// read the file to get the row pointers
char buf[BUF_SIZE+1];
long pos = 0;
m_data.push_back(RowData(pos));
int nr = 0;
while ((nr = ::fread(buf, 1, BUF_SIZE, m_fp)))
{
buf[nr] = 0; // null-terminate the last line of data
// find new lines in the buffer
char *c = buf;
while ((c = ::strchr(c, '\n')) != NULL)
{
m_data.push_back(RowData(pos + c-buf+1));
c++;
}
pos += nr;
}
// squeeze any extra memory not needed in the collection
m_data.squeeze();
}
RowData and m_data are specific to my implementation, but they are simply used to cache information about a row in the file (such as the file position and number of columns).
The other performance strategy I employed was to use QByteArray to parse each line, instead of QString. Unless you need unicode data, this will save time and memory:
// optimized line reading procedure
QByteArray str;
char buf[BUF_SIZE+1];
::fseek(m_fp, rd.offset, SEEK_SET);
int nr = 0;
while ((nr = ::fread(buf, 1, BUF_SIZE, m_fp)))
{
buf[nr] = 0; // null-terminate the string
// find new lines in the buffer
char *c = ::strchr(buf, '\n');
if (c != NULL)
{
*c = 0;
str += buf;
break;
}
str += buf;
}
return str.split(',');
If you need to split each line with a string, rather than a single character, use ::strtok().
I have a method that that creates a MatLab array name from a file path and returns it as a std::string. the resulting string is passed into another method that writes the name to the file. When I try to get the length of the passed in string, it displays 0 when the length of the string is 12 or 13 chars.
My code:
bool MyClass::masterMethod(std::string fileURI){
FILE* dataStream;
// Assume dataStream is set up correctly
// Get arrayName from File URI
std::string arrayName = this->makeArrayNameFromPath( fileURI);
//Write array name to file
this->writeArrayName(arrayName , dataStream)
}
std::string MyClass::makeArrayNameFromPath(std::string filePathURI){
std::string tempString = filePathURI.substr(filePathURI.find_last_of('/')+1);
std::string returnString = "";
long index = 0;
for(long i = 0; i < tempString.length(); i++){
if((tempString[i] != ' ') && (tempString[i] != '.')){
returnString[index++] = tempString[i];
}
}
return returnString;
}
void MyClass::writeArrayName(std::string name , FILE *nameStream){
// long testLength = name.length();
// long testLength2 = name.size();
// const char* testChar = nam.c_str();
// long testCharLen = strlen(testChar);
// The size of the name is the number of Chars * sizeof(int8_t)
int32_t sizeOfName = (int32_t)(name.length() * sizeof(int8_t));
int32_t nameType = miINT8;
fwrite(&nameType , sizeof(int32_t) , 1 , nameStream);
fwrite(&sizeOfName, sizeof(sizeOfName), 1, nameStream);
fwrite(&name , sizeof(name[0]), sizeOfName , nameStream);
}
So I'm not sure why string::length is not working. If a create a std::string test = name, and print it , I can get the value of the string but can not get its length or size.
If I use const char* testName = name.c_str(); long test = strlen(testName), I get a the
correct value, but thought that wasn't necessary.
So any advice or suggestion is appreciated.
returnString[index++] = tempString[i]; doesn't do what you think it does. It's not adding additional space or length to the string, only overwriting memory at a location that the string doesn't actually own. I think returnString.append(1, tempString[i]) or similar should do it.
You never give the string a size, just trying to assign positions that isn't there.
Try this instead to add characters to the return value
returnString += tempString[i];
I am working on an assignment for my GUI programming class, in which we are to make a windows program that displays the contents of a file in hexadecimal. I have a class that holds the text and creates the hex in string format.
I'm attempting to create an array of character arrays to store each line for output. However, when I use new to create the array of character pointers, I get an access violation error.
I've done some searching, but haven't had any luck finding the answer.
The class has these member variables:
char* fileText;
char** Lines;
int numChars;
int numLines;
bool fileCopied;
My constructor:
Text::Text(char* fileName){ //load and copy file.
fileText = NULL;
Lines = NULL;
fileCopied = ExtractText(fileName);
if ( fileCopied ) {
CreateHex();
}//endif
}//end constructor
ExtractText loads the file given to the constructor, and copies it into a large string.
bool Text::ExtractText(char fileName[]){
char buffer = '/0'; //buffer for text transfer
numChars = 0; //initialize numLines
ifstream fin( fileName, ios::in|ios::out ); //load file stream
if ( !fin ) { //return false if the file fails to load
return false;
}//endif
while ( !fin.eof() ) { //count the lines in the file
fin.get(buffer);
numChars++;
}//endwh
fileText = new char[numLines]; //create an array of strings, one for each line in the file.
fin.clear(); //clear the eof flag
fin.seekg(0, ios::beg); //move the get pointer back to the start of the file.
for ( int i = 0; i < numChars; i++ ) { //copy the text from the file into the string array.
fin.get(fileText[i]);
}//endfr
fileText[numChars-1] = '\0';
fin.close();
numLines = (numChars % 16 == 0) ? (numChars/16) : (numChars/16 + 1);
return true;
}//end fun ExtractText
Then comes the problem code. In the CreateHex function, the first line is where try to create the array of character pointers.
void Text::CreateHex(){
Lines = new char*[numLines];
As soon as the program runs that line of code, that's when I get the access violation. I'm not really sure what the problem is, because I've used that exact same method before in a previous program. The only difference was the name of pointer. I'm using Borland C++ 5.02 if that makes any difference. It's not my first choice in compilers, but its what our teacher wants us to use.
When you execute the line
fileText = new char[numLines]
The variable numLines has not yet been initialized. As a member variable, it's initialized to 0, so you are allocating an empty array for fileText.
So, thanks for all the help guys, I am just have one last problem, I am putting the website source in a char var, and then reading the product title (I have gotten that), however it only works if I take part of the source, or only the html from one of the featured products on neweggs page. I think the program is crashing, because it doesnt know which title to pick when I need to get all three titles and put them into an array. Any ideas? Thanks. Here is the parser code:
http://paste2.org/p/809045
Any solution is greatly appreciated.
/**
* num_to_next -
* takes in a pointer to a string and then counts how many
* characters are until the next occurance of the specified character
* #ptr: the pointer to a string in which to search
* #c: char delimiter to search until
**/
int num_to_next(char *ptr, char c)
{
unsigned int i = 0;
for (i = 0; i < strlen(ptr); i++) {
if (ptr[i] == c) {
return i;
}
}
return -1;
}
/**
* space_to_underscore -
* this should help to alleviate some problems when dealing with
* filepaths that have spaces in them (basically just changes all
* spaces in a string to underscores)
* #string: the string to convert, yo
**/
int space_to_underscore(char *string)
{
for (unsigned int i = 0; i < strlen(string); i++) {
if (string[i] == ' ') {
string[i] = '_';
}
}
return 0;
}
char *file_name = (char *)malloc(sizeof(char *)); // allocate memory for where the app name will be stored
memset(file_name, 0, sizeof(file_name)); // zero the memory
char td_one[] = "<ul class="featureCells"><li id="ItemCell" class="cell">";
char *pstr = strstr(buffer, td_one) + strlen(td_one) + 6; // buffer is the source
char *poop = pstr + num_to_next(pstr, '>') + 1;
int blah = num_to_next(poop, '<');
strncpy(file_name, poop, blah);
// null terminate the string //
file_name[blah] = '\0';
space_to_underscore(file_name);
MessageBox(NULL, file_name, "Product Name", MB_OK);
free(file_name);
I'm not sure if these are your only problems, but...
First, you can't do char* filename = (char*)malloc(sizeof(char*)) (well, you can, but that's not what you actually want from your app).
What you want to have is char* filename = (char*)malloc(SIZE_OF_YOUR_STRING * sizeof(char));, so you can't allocate just an abstract buffer for your string and you have to know the expected size of it. Actually, here you don't have to write sizeof(char) because it always equals 1, but this sometimes this way of writing the code can help you(or somebody else) to understand that this block would store a string as array of chars).
Another example on the same problem: char* filename = (char*)malloc(65); - is ok and will allocate a block of memory to store 65 char symbols.
If we go further (where you're doing the memset), char* is a plain pointer and sizeof(filename) in your case would return the size of your pointer, but not your string. What you should write here is strlen(filename).