I'm trying to read the first line of an MP3 file (I edited this mp3 file to contain the text "I'm an MP3" right at the beginning of the file).
This is what I'm trying to do:
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main()
{
fstream mp3;
mp3.open("05 Imagine.mp3", ios::binary | ios::in | ios::out);
/*mp3.seekg(0, ios::end);
int lof = mp3.tellg();
cout << "Length of file: " << lof << endl;
mp3.seekg(0, ios::beg);*/
//char ch;
//cout << mp3.get(ch) << endl;
char* somebuf;
while(mp3.read(somebuf, 10)) //Read the first 10 chars which are "I'm an MP3 file".
{
//cout << somebuf;
}
return 0;
}
For some reason, that is crashing. At some point it didn't crash, but it didn't print anything when I did cout << somebuf. Can someone help me with this?
You never allocated anything for somebuf:
char* somebuf;
therefore, it doesn't point anywhere.
char* somebuf = new char[11];
somebuf[10] = '\0'; // Not sure if it is necessary to null-terminate...
while(mp3.read(somebuf, 10)) // Read the first 10 chars which are "I'm an MP3 file".
{
//cout << somebuf;
}
// and free it later
delete [] somebuf;
Alternatively:
char somebuf[11];
somebuf[10] = '\0'; // Not sure if it is necessary to null-terminate...
while(mp3.read(somebuf, 10)) // Read the first 10 chars which are "I'm an MP3 file".
{
//cout << somebuf;
}
Initialize the buffer:
char somebuf[10];
while(mp3.read(somebuf, 10)) //Read the first 10 chars which are "I'm an MP3 file".
{
//cout << somebuf;
}
Related
I am a new programmer working in C++, I am trying to make a program that will import information from a file to an output file and then I'm going to do a search algorithm on the data. I am trying to use a structure of data and import that into an array and then call it in the main program.
For some reason I can't, for the life of me, get my function call to work; I keep getting an undeclared identifier error on inputFile in my function call in the main program. I realize I'm probably doing something fundamentally wrong, so I would really appreciate any help that can be given.
#include <iostream>
#include <iomanip>
#include <string>
#include <cstdlib>
#include <fstream>
using namespace std;
const int MAX_LOG_SIZE = 7584;
const string LOGFILE ="crimes.dat";
const string OUTPUT_FILE ="crimesorted.log";
// Structure of strings based on info from crimes.dat
struct CrimeInfo
{
string Crimedescr;
string Date;
string Time;
string Address;
string Grid;
string Latitude;
string Longitude;
};
CrimeInfo crimeList [MAX_LOG_SIZE];
void openInputFile(ifstream& inputFile, string inputFilename)
// here we open the input file crimes.dat
{
inputFile.open(inputFilename.c_str());
while (inputFile.fail())
{
cout << "Failed to open input file: " << inputFilename << ".\n";
exit(1);
}
};
void getLogEntry(ifstream &LOGFILE, CrimeInfo &entry)
{
getline(LOGFILE, entry.Date);
getline(LOGFILE, entry.Time);
getline(LOGFILE, entry.Address);
getline(LOGFILE, entry.Grid);
getline(LOGFILE, entry.Crimedescr);
getline(LOGFILE, entry.Latitude);
getline(LOGFILE, entry.Longitude);
}
/* opens an output file */
void openOutputFile(ofstream& outputFile, string outputFilename)
{
outputFile.open(outputFilename.c_str());
if (outputFile.fail())
{
cout << "Failed to open output file: " << outputFilename << ".\n";
exit(2);
}
}
void outputLogFile(string outputFilename, CrimeInfo arr[], int size)
{
// open output files
ofstream outputLogFile;
openOutputFile(outputLogFile, outputFilename);
// output the crime file
outputLogFile << "\nCrime log sort ^^:\n\n";
for (int i = 0; i < size; i++)
{
outputLogFile << arr[i].Date << " ";
outputLogFile << arr[i].Address << " (";
outputLogFile << arr[i].Longitude << " ";
outputLogFile << arr[i].Latitude << " ";
outputLogFile << arr[i].Time << " ";
outputLogFile << arr[i].Grid << " ";
outputLogFile << arr[i].Crimedescr << "";
outputLogFile << endl;
}
outputLogFile.close();
}
int main()
{
outputLogFile(OUTPUT_FILE, crimeList, MAX_LOG_SIZE);
for (int i =0; i < MAX_LOG_SIZE; i++)
getLogEntry(inputFile, crimeList[i].Date);
}
There are a lot of problems with your code. To help you out, I went through your code and left a lot of my own comments to tell you some suggestions I had; to make it easy, I deleted your comments so there's no confusion on what was yours and what I put there.
Here are some things I noticed in your code:
using namespace std is generally considered a very bad practice. Instead, just specify the namespace (e.g. std::string instead of just string).
You declared LOGFILE as a string at the top of your program, but then tried to use it as an ifstream& in the function getLogEntry.
Your main method is out of order. I'm assuming you want to load some data into the program from a file and then output that data to another file. The way you have it in your main method is, first, you output information you don't have yet and, second, import information but don't do anything with it.
You have a LOT of functions. As a general rule of thumb, don't make a whole function for opening a file, then a separate one for using it, then a separate one for closing it. There are a lot of big reasons why not to do this. The biggest reasons are that your program becomes very difficult to follow, and no one else will be able to use your code. In real-world applications, your code is only 20% for the computer and 80% for other programmers.
There are various formatting errors and such.
So, here is your original code with my comments...
#include <iostream>
#include <iomanip>
#include <string>
#include <cstdlib> // Unneeded since other headers here already include this
#include <fstream>
using namespace std; // NEVER globally use the entire standard namespace!
const int MAX_LOG_SIZE = 7584; // Can be declared 'constexpr'
const string LOGFILE ="crimes.dat";
const string OUTPUT_FILE ="crimesorted.log";
/*
NOTE:
> It often looks a lot cleaner to have a header part of your code
and then define your functions seperately. This is good practice
for when you need to start using header files with big projects
*/
struct CrimeInfo
{ // Can declare all variables by only listing type once if they're all the same type
string Crimedescr;
string Date;
string Time;
string Address;
string Grid;
string Latitude;
string Longitude;
};
CrimeInfo crimeList [MAX_LOG_SIZE]; // This should be in 'main()'
/*
This should not be its own function.
Making too many function can make things look a bit confusing.
Here, this is only 4 lines of code, so you shouldn't be making
an entire function for it.
*/
void openInputFile(ifstream& inputFile, string inputFilename)
{
inputFile.open(inputFilename.c_str());
while (inputFile.fail())
{
cout << "Failed to open input file: " << inputFilename << ".\n";
exit(1);
}
};
/*
This should also just be written out where its used. There's
no need to make a whole function for a task like this.
ERROR HERE:
> LOGFILE is NOT an std::ifstream! It is a std::string!
*/
void getLogEntry(ifstream &LOGFILE, CrimeInfo &entry)
{
getline(LOGFILE, entry.Date);
getline(LOGFILE, entry.Time);
getline(LOGFILE, entry.Address);
getline(LOGFILE, entry.Grid);
getline(LOGFILE, entry.Crimedescr);
getline(LOGFILE, entry.Latitude);
getline(LOGFILE, entry.Longitude);
}
/*
This should not be its own function.
Making too many function can make things look a bit confusing.
Here, this is only 4 lines of code, so you shouldn't be making
an entire function for it.
*/
void openOutputFile(ofstream& outputFile, string outputFilename)
{
outputFile.open(outputFilename.c_str());
if (outputFile.fail())
{
cout << "Failed to open output file: " << outputFilename << ".\n";
exit(2);
}
}
// It's a good idea to use some sort of documentation style for functions
void outputLogFile(
// Declare variables const when they aren't modified
/* (const) */ string outputFilename,
/* (const) */ CrimeInfo arr[],
/* (const) */ int size)
{
ofstream outputLogFile;
openOutputFile(outputLogFile, outputFilename); // Just write out the code
outputLogFile << "\nCrime log sort ^^:\n\n";
for (int i = 0; i < size; i++)
{
/*
You only need to declare the name of the stream one time
e.g.
outputLogFile << thing1 << thing2
<< thing3 << thing4 << thing5
<< thing6
<< endl;
*/
outputLogFile << arr[i].Date << " ";
outputLogFile << arr[i].Address << " (";
outputLogFile << arr[i].Longitude << " ";
outputLogFile << arr[i].Latitude << " ";
outputLogFile << arr[i].Time << " ";
outputLogFile << arr[i].Grid << " ";
outputLogFile << arr[i].Crimedescr << ""; // Empty quotes not needed here
outputLogFile << endl;
}
outputLogFile.close();
}
int main()
{
// What data are you outputting?
outputLogFile(OUTPUT_FILE, crimeList, MAX_LOG_SIZE);
// Are you trying to load the data you just outputted?
for (int i =0; i < MAX_LOG_SIZE; i++)
{ // I added these braces, but it's a good idea to always have braces
// You have not declared 'inputFile' anywhere
getLogEntry(inputFile, crimeList[i].Date);
}
}
Instead of leaving you to have to figure all that out on your own (I know how frustrating that can be), I went ahead and wrote your program how I'd do it. I tried to put comments in a lot of places to make it easy to follow along with. If you have any questions about it, feel free to ask me.
#include <fstream>
#include <iomanip>
#include <iostream>
#include <string>
/*
If you're using C++17, the lines below can just become one line:
using std::cin, std::cout, std::endl, std::ifstream,
std::ofstream, std::string, std::getline;
*/
using std::cin;
using std::cout;
using std::endl;
using std::ifstream;
using std::ofstream;
using std::string;
constexpr int MAX_LOG_SIZE = 7584;
const string LOGFILE_NAME = "crimes.dat";
// I'm assuming: inputFile ^^^
// outputFile vvv
const string OUTPUT_FILE_NAME = "crimesorted.log";
/*
NOTE: If you're trying to export data to "crimesorted.log"
and then load it back into the program through "crimes.dat",
that will be a problem. I say this because the main method
in your original code, this is the order you had it in.
*/
// [BEGIN] Function Prototypes
// Structure of strings based on info from crimes.dat
struct CrimeInfo
{
string Crimedescr, Date, Time, Address,
Grid, Latitude, Longitude;
};
/** (This is JavaDoc-style documentation)
[Purpose of function here]
#param outputFile [Describe paramater here]
#param arr[] [Describe parameter here]
#param size_of_arr Size of 'arr[]'
*/
void outputLogFile(
ofstream& outputFile, // Changed to 'std::ofstream&' because I declare this in 'main()'
const CrimeInfo arr[],
const int size_of_arr);
// [END] Function Prototypes
int main()
{
// Create std::ifstream and open a file
ifstream file_to_load;
file_to_load.open(LOGFILE_NAME);
// Constructing and using 'crimeList' here allows the size to be known in
// this scope. However, if it's passed to a function, it's passed as a pointer
CrimeInfo crimeList[MAX_LOG_SIZE];
// Check if file was open and do stuff with it
if (file_to_load.is_open())
{ // File was opened
for (int i = 0; i < MAX_LOG_SIZE; i++)
{
getline(file_to_load, crimeList[i].Date);
getline(file_to_load, crimeList[i].Time);
getline(file_to_load, crimeList[i].Address);
getline(file_to_load, crimeList[i].Grid);
getline(file_to_load, crimeList[i].Crimedescr);
getline(file_to_load, crimeList[i].Latitude);
getline(file_to_load, crimeList[i].Longitude);
}
file_to_load.close(); // Close file
}
else
{ // File could not be
cout << "Could not open file: " << LOGFILE_NAME << endl;
return 1;
}
// Create std::ofstream and output the log
ofstream outputFile;
outputFile.open(OUTPUT_FILE_NAME);
// Check if 'outputFile' opened OUTPUT_FILE_NAME successfully
if(outputFile.is_open())
{ // File was opened
outputLogFile(outputFile, crimeList, MAX_LOG_SIZE);
outputFile.close();
}
else
{ // File could not be opened
cout << "Could not open file: " << OUTPUT_FILE_NAME << endl;
return 1;
}
}
// Function definition for outputLogFile()
void outputLogFile(
ofstream &outputFile,
const CrimeInfo arr[],
const int size_of_arr)
{
outputFile << "\nCrime log sort ^^:\n\n";
for (int i = 0; i < size_of_arr; i++)
{
outputFile
<< arr[i].Date << '\n' // Newlines may look better than spaces here
<< arr[i].Address << " ("
<< arr[i].Longitude << ", "
<< arr[i].Latitude << ")\n"
<< arr[i].Time << '\n'
<< arr[i].Grid << '\n'
<< arr[i].Crimedescr
<< endl;
}
}
The output of the code show gibberish values for all the variables of the Student struct. When the display function is ran.
I've include the relevant code in each of the add and display function for the binary file.
For the second function, does the seekg pointer automatically move to read the the next record each time the for loop runs?
//Student struct
struct Student
{
char name [30];
float labTest;
float assignments;
float exam;
};
//Writing function
afile.open(fileName,ios::out|ios::binary);
Student S;
strcpy(S.name,"test");
S.labTest = rand()%100+1;
S.assignments = rand()%100+1;
S.exam = rand()%100+1;
afile.write(reinterpret_cast<char*>(&S),sizeof(S));
afile.close();
//Reading function
afile.open(fileName,ios::in|ios::binary);
afile.seekg(0,ios::end);
int nobyte = afile.tellg();
int recno = nobyte / sizeof(Student);
Student S;
//Loop and read every record
for(int i = 0;i<recno;i++)
{
afile.read(reinterpret_cast<char*>(&S),sizeof(S));
cout << "Name of Student: " << S.name << endl
<< "Lab mark: " << S.labTest << endl
<< "Assignment mark: " << S.assignments << endl
<< "Exam mark: " << S.exam << endl << endl;
}
afile.close();
There are a lot of problems with your code:
Calling your write function will permanently overwrite the last written data set. You have to add: ios::append, so that new data will be written behind the last data you wrote before.
After you move with afile.seekg(0,ios::end); to get with tellg the file size, you have to go back to the start of the file before reading with afile.seekg(0,ios::beg)
It looks that you use a char array to store a string. This is not c++ style! And it is dangerous how you use it. If you use strcpy, you can copy a string which is longer than the space you reserved for it. So you should prefer std::string for that. But you can't simply write a struct which constains std::string as binary! To get checked copy you can use strncpy, but that is still not c++ ;)
For the second function, does the seekg pointer automatically move to read the the next record each time the for loop runs?
Yes, the file position moves which each successful read and write.
A general remark writing binary data by simply dumping memory content:
That is not a good idea, because you can only read that data back, if you use the same machine type and the same compiler options. That means: A machine with different endianness will read data totally corrupted. Also a different integer type ( 32 bit vs 64 bit ) will break that code!
So you should invest some time how to serialize data in a portable way. There are a lot of libraries around which can be used to read/write also complex data types like std::string or container types.
A hint using SO:
Please provide code which everybody can simply cut and paste and compiled. I did not know what your Student struct is. So I take a lot of assumptions! Is your struct really using char[]? We don't know!
#include <iostream>
#include <fstream>
#include <cstring>
const char* fileName="x.bin";
struct Student
{
char name[100]; // not c++ style!
int labTest;
int assignments;
int exam;
};
// Writing function
void Write()
{
std::ofstream afile;
afile.open(fileName,std::ios::out|std::ios::binary|std::ios::app);
Student S;
strcpy(S.name,"test"); // should not be done this way!
S.labTest = rand()%100+1;
S.assignments = rand()%100+1;
S.exam = rand()%100+1;
afile.write(reinterpret_cast<char*>(&S),sizeof(S));
afile.close();
}
void Read()
{
//Reading function
std::ifstream afile;
afile.open(fileName,std::ios::in|std::ios::binary);
afile.seekg(0,std::ios::end);
int nobyte = afile.tellg();
int recno = nobyte / sizeof(Student);
afile.seekg(0, std::ios::beg);
Student S;
//Loop and read every record
for(int i = 0;i<recno;i++)
{
afile.read(reinterpret_cast<char*>(&S),sizeof(S));
std::cout << "Name of Student: " << S.name << std::endl
<< "Lab mark: " << S.labTest << std::endl
<< "Assignment mark: " << S.assignments << std::endl
<< "Exam mark: " << S.exam << std::endl << std::endl;
}
afile.close();
}
int main()
{
for ( int ii= 0; ii<10; ii++) Write();
Read();
}
EDIT. Apparently, I was a bit too late in responding. Klaus has compiled a better, more comprehensive response dwelling into other problems regarding C-style char [], std::string and the endianness of the platform.
You should append to the file opened for every record. In your code you don't have this, at all. Please write the code in a way we can copy and paste, and test. As a working example, you should write some code that can be compiled and run as below:
#include <algorithm>
#include <cstring>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>
// Student struct
struct Student {
char name[30];
float labTest;
float assignments;
float exam;
};
// Serializer
void serialize_student(const Student &s, const std::string &filename) {
// Append to the file, do not overwrite it
std::ofstream outfile(filename, std::ios::binary | std::ios::app);
if (outfile)
outfile.write(reinterpret_cast<const char *>(&s), sizeof(Student));
}
// Deserializer
std::vector<Student> deserialize_students(const std::string &filename) {
std::ifstream infile(filename, std::ios::binary);
std::vector<Student> students;
Student s;
while (infile.read(reinterpret_cast<char *>(&s), sizeof(Student)))
students.push_back(std::move(s));
return std::move(students);
}
int main(int argc, char *argv[]) {
// Generate records
std::vector<Student> mystudents;
std::generate_n(std::back_inserter(mystudents), 10, []() {
Student s;
std::strcpy(s.name, "test");
s.labTest = rand() % 100 + 1;
s.assignments = rand() % 100 + 1;
s.exam = rand() % 100 + 1;
return s;
});
// Print and write the records
for (const auto &student : mystudents) {
std::cout << student.name << ": [" << student.labTest << ','
<< student.assignments << ',' << student.exam << "].\n";
serialize_student(student, "students.bin");
}
// Read and print the records
auto records = deserialize_students("students.bin");
std::cout << "===\n";
for (const auto &student : records)
std::cout << student.name << ": [" << student.labTest << ','
<< student.assignments << ',' << student.exam << "].\n";
return 0;
}
I am trying to parse Json files using JsonCpp library. but I am facing a problem Which I can not fix it. the code shown below is working perfectly when I am parsing one file but when I added the part which iterates over files in directory the program crashes.
The first function is used to search in a certain directory for Json files and save their names in vector of string (results).
In main function, the program starts by defining the extension required (.json) then calling search function. after that I tried to open each file to parse it.
Finally, Thanks and I really appreciate any kind of help.
#include "jsoncpp.cpp"
#include <stdio.h>
#include "json.h"
#include <iostream>
#include <fstream>
#include <string>
#include <cstdio>
#include <cstring>
#include <unistd.h>
#include <dirent.h>
#include <vector>
using namespace std;
vector<string> results; // holds search results
// recursive search algorithm
void search(string curr_directory, string extension){
DIR* dir_point = opendir(curr_directory.c_str());
dirent* entry = readdir(dir_point);
while (entry){ // if !entry then end of directory
if (entry->d_type == DT_DIR){ // if entry is a directory
string fname = entry->d_name;
if (fname != "." && fname != "..")
search(entry->d_name, extension); // search through it
}
else if (entry->d_type == DT_REG){ // if entry is a regular file
string fname = entry->d_name; // filename
// if filename's last characters are extension
if (fname.find(extension, (fname.length() - extension.length())) != string::npos)
results.push_back(fname); // add filename to results vector
}
entry = readdir(dir_point);
}
return;
}
//
//
//
//
int main(int argc, char *argv[])
{
// read Files list
string extension; // type of file to search for
extension = "json";
// setup search parameters
string curr_directory = "/Users/ITSGC_Ready2Go/3dMap";
search(curr_directory, extension);
// loop over files
//if (results.size()){
//std::cout << results.size() << " files were found:" << std::endl;
for (unsigned int z = 0; z < results.size(); ++z){ // used unsigned to appease compiler warnings
// Opening the file using ifstream function from fstream library
cout <<results[z].c_str()<<endl;
Json::Value obj;
Json::Reader reader;
ifstream test(results[z].c_str());
//test.open (results[z].c_str(), std::fstream::in );
// Selection objects inside the file
reader.parse(test,obj);
//test >> obj;
// Parsing ID object and returning its value as integer
// cout << "id :" << stoi(obj["id"].asString()) <<endl;
// Parsing Line object with its internal objects
const Json::Value& lines = obj["lines"];
for (int i=0; i<lines.size();i++){
cout << "index : " << i << endl;
cout << "id:" << lines[i]["id"].asString() <<endl;
cout << "type:" << lines[i]["type"].asString() <<endl;
cout << "function:" << lines[i]["function"].asString() <<endl;
cout << "color:" << lines[i]["color"].asString() <<endl;
const Json::Value& poly = lines[i]["polyPoints"];
for (int j=0; j<poly.size();j++){
cout << "batch#"<<j<<endl;
cout << "latitude" << poly[j]["latitude"].asFloat()<<endl;
cout << "longitude" << poly[j]["longitude"].asFloat()<<endl;
cout << "altitude" << poly[j]["altitude"].asFloat()<<endl;
}
}
// Reading the OccupancyGrid object
// OccupancyGrid object is copied into constant to parse the arrays inside
const Json::Value& occupancyGrid = obj["occupancyGrid"];
cout << occupancyGrid.size() <<endl;
// The size of occupancyGrid is the used as number of iterations (#of rows)
for (int l=0; l<occupancyGrid.size();l++){
// Arrays inside occupancyGrid are copied into constant to parse the elements inside each array
const Json::Value& element = occupancyGrid[l];
// iterations over the size of the array in order to parse every element
cout << "row" << l << "--> ";
for (int k=0;k<element.size();k++){
cout << element[k].asFloat();
if(k<element.size()-1){ cout<< ",";}
}
cout << endl;
}
// Parsing roadSigns object as found in the file
// Need to understand the difference between format in the mail and the 1456 file
const Json::Value& roadsigns = obj["roadSigns"];
cout << "ArrayType: " << roadsigns["_ArrayType_"].asString()<<endl;
const Json::Value& ArraySize = roadsigns["_ArraySize_"];
for(int t=0;t<ArraySize.size();t++){
cout << ArraySize[t].asInt();
if (t<ArraySize.size()-1){ cout << " , ";}
}
cout<< endl;
if (roadsigns["_ArrayData_"].asString().empty()) {
cout << "ArrayData: "<<roadsigns["_ArrayData_"].asFloat(); }
else { cout << "ArrayData: empty "; }
cout <<endl;
test.close();
test.clear();
cout << "Done" << endl;
cout << "...." << endl;
cout << "...." << endl;
}
//else{
// std::cout << "No files ending in '" << extension << "' were found." << std::endl;
//}
}
Without access to the JSON library I can't help you too much, but the first obvious place for potential crashes would be if (fname.find(extension, (fname.length() - extension.length())) != string::npos). You need to make sure that your file name is longer than the size of your extension before making that call.
Also, for extremely deep directory trees you should put a limit on recursion, and all OSes I know of have some sort of character limit on directory and file names.
I have a code that i want it to get input file from command line and create output file with XXX at the end - meanning if intput= "blabla.txt" or "/johny/first/blabla.txt" i till get "blablaXXX.txt" or "/johny/first/blablaXXX.txt"
The second question is that when i find a line i was looking for i want to copy only the numbers (keep in date mode) and the len
Line will be "IT IS HERE time 12:04:56.186, len 000120"
And i want to get in the new file line: 12:04:56.186 120
#include <iostream>
#include <fstream>
using namespace std;
int main( int argc, char* args[] )
{
string inputName=args[1];
ifstream inputName(inputFileName);
////// here i will need to get the output string name some thing like
// string outputFileName=EDITED_INPUT_NAME+"XXX"+".txt";
ofstream outpuName(outputFileName);
while( std::getline( inputName, line ) )
{
if(line.find("IT IS HERE") != string::npos)
// how to make it take only the parts i need??????
outpuName << line << endl;
cout << line << endl;
}
inputName.close();
outpuName.close();
return 0;
}
Does this solve your problem:
#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;
int main(int argc, char* args[]) {
ifstream inputFile(args[1]);
// Your first problem
string outputFileName(args[1]);
outputFileName.insert(outputFileName.find("."), "XXX");
cout << "Writing to " << outputFileName << endl;
// End of first problem
ofstream outputFile(outputFileName.c_str());
string line;
while (getline(inputFile, line)) {
if (line.find("IT IS HERE") != string::npos) {
// Your second problem
string::size_type time_start = line.find("time ") + 5;
string::size_type time_end = line.find(",", time_start);
cout << time_start << " " << time_end << endl;
string time = line.substr(time_start, time_end - time_start);
string::size_type len_start = line.find("len ") + 4;
string::size_type len_end = line.find(" ", len_start);
if (len_end != string::npos)
len_end += 4;
int len = atoi(line.substr(len_start, len_end - len_start).c_str());
// End of second problem
outputFile << time << " " << len << endl;
cout << time << " " << len << endl;
}
}
inputFile.close();
outputFile.close();
return 0;
}
Example input:
sdfghjk sdfghjk fghjkl
IT IS HERE time 12:04:56.186, len 000120
usjvowv weovnwoivjw wvijwvjwv
IT IS HERE time 12:05:42.937, len 000140
Example output:
12:04:56.186 120
12:05:42.937 140
The code could look nicer with std::regex and auto, but as this wasn't tagged with C++11, I held back.
This question already has answers here:
Question about seekg() function of ifstream in C++?
(3 answers)
Closed 8 years ago.
In the process of writing a lz4 csv to compressed binary file converter (high volume forex tick data csv) in the hope of reducing the storage/disk bandwidth requirements on my tiny vps.
self contained code to illustrate
#include <string>
#include <fstream>
#include <iostream>
#include "lz4.h"
using namespace std;
int main()
{
char szString[] = "2013-01-07 00:00:04,0.98644,0.98676 2013-01-07 00:01:19,0.98654,0.98676 2013-01-07 00:01:38,0.98644,0.98696";
const char* pchSource = szString;
int nInputSize = sizeof(szString);
cout <<"- pchSource -" << endl << pchSource << endl;
cout <<"nbytes = "<< nInputSize << endl << endl;
ofstream source("pchSource.txt");
source << pchSource;
int nbytesPassed = 0;
int nMaxCompressedSize = LZ4_compressBound(nInputSize);
char *pszDest = new char[nMaxCompressedSize];
nbytesPassed = LZ4_compress(pchSource, pszDest, nInputSize);
cout <<"- pszDest Compressed-" << endl;
cout <<"nbytesPassed = "<< nbytesPassed << endl;
cout << pszDest << endl << endl;
// pszDest garbage ?
char *pszDestUnCompressed = new char[nInputSize];
LZ4_uncompress(pszDest, pszDestUnCompressed, nInputSize);
cout <<"- pszDestUnCompressed -" << endl;
cout <<"nbytesPassed = "<< nbytesPassed << endl;
cout << pszDestUnCompressed << endl << endl;
//pszDestUnCompressed is correct ?
delete[] pszDestUnCompressed;
pszDestUnCompressed = 0;
// ok lets write compressed pszDest to pszDest.dat
ofstream outCompressedFile("pszDest.dat",std::ofstream::binary);
outCompressedFile.write (pszDest,nMaxCompressedSize);
delete[] pszDest;
pszDest = 0;
//read it back in and try to uncompress it
ifstream infile("pszDest.dat",std::ifstream::binary);
infile.seekg (0,infile.end);
int nCompressedInputSize = infile.tellg();
infile.seekg (0);
char* buffer = new char[nCompressedInputSize];
infile.read (buffer,nCompressedInputSize);
const char* pchbuffer = buffer;
char* pszUnCompressedFile = new char[nInputSize];
nbytesPassed = LZ4_uncompress(pchbuffer, pszUnCompressedFile, nInputSize);
cout <<"- pszUnCompressedFile -" << endl;
cout <<"nbytesPassed = "<< nbytesPassed << endl;
cout << pszUnCompressedFile << endl;
//write uncompressed pszDest.dat to pszUnCompressedFile.txt
ofstream outUncompressedSource("pszUnCompressedFile.txt");
outUncompressedSource << pszUnCompressedFile;
// On my system 32bit ArchLinux 3.7.10-1 - gcc 4.7.2-4
// file contains random Garbage
delete[] buffer;
buffer = 0;
delete[] pszUnCompressedFile;
pszUnCompressedFile = 0;
return 0;
}
CONSOLE OUTPUT :
- pchSource -
2013-01-07 00:00:04,0.98644 .....
nbytes = 108
- pszDest Compressed-
nbytesPassed = 63
�2013-01-07 00:
- pszDestUnCompressed -
nbytesPassed = 63
2013-01-07 00:00:04,0.98644 .....
- pszUnCompressedFile -
nbytesPassed = -17
�W��W�-07 q
Process returned 0 (0x0) execution time : 0.010 s
Press ENTER to continue.
I'm obviously missing something, apart form the samples included in the source are there any-other usage examples ?
All working now thanks, here is the code for anyone that is interested
#include <fstream>
#include <iostream>
#include "lz4.h"
using namespace std;
int main()
{
char szSource[] = "2013-01-07 00:00:04,0.98644,0.98676 2013-01-07 00:01:19,0.98654,0.98676 2013-01-07 00:01:38,0.98644,0.98696";
int nInputSize = sizeof(szSource);
// compress szSource into pchCompressed
char* pchCompressed = new char[nInputSize];
int nCompressedSize = LZ4_compress((const char *)(&szSource), pchCompressed, nInputSize);
// write pachCompressed to binary lz4.dat
ofstream outBinaryFile("lz4.dat",ofstream::binary);
outBinaryFile.write(pchCompressed, nCompressedSize);
outBinaryFile.close();
delete[] pchCompressed;
pchCompressed = 0;
//read compressed binary file (assume we pass/encode nInputSize but don't know nCompressedSize)
ifstream infCompressedBinaryFile( "lz4.dat", ifstream::binary );
//Get compressed file size for buffer
infCompressedBinaryFile.seekg (0,infCompressedBinaryFile.end);
int nCompressedInputSize = infCompressedBinaryFile.tellg();
infCompressedBinaryFile.clear();
infCompressedBinaryFile.seekg(0,ios::beg);
//Read file into buffer
char* pchCompressedInput = new char[nCompressedInputSize];
infCompressedBinaryFile.read(pchCompressedInput,nCompressedSize);
infCompressedBinaryFile.close();
// Decompress buffer
char* pchDeCompressed = new char[nInputSize]; //(nCompressedInputSize *2) +8
LZ4_uncompress(pchCompressedInput, pchDeCompressed, nInputSize);
delete[] pchCompressedInput;
pchCompressedInput = 0;
// write decompressed pachUnCompressed to
ofstream outFile("lz4.txt");
outFile.write(pchDeCompressed, nInputSize);
outFile.close();
delete[] pchDeCompressed;
pchDeCompressed = 0;
return 0;
}
I am also working on a a simple CLI csv to binary I/O example here