Qt5.12实战之QByteArray与字符指针及字符串转换

示例源码:

#include <QCoreApplication>
#include <QDebug>
#include <QTextStream>
static QTextStream cout (stdout,QIODevice::WriteOnly);
#include <iostream>
#include <QtGlobal>
#include <QByteArray>void test()
{qDebug() << "HelloWorld-qdebug";cout << "Helloword-QTextStream" <<endl;std::cout<<"Helloword-std::cout"<<std::endl;
}void test_types()
{qint8 signed_char_type;//signed char 有符号8bitqint16 signed_short_type;//signed short 有符号16bitqint32 signed_int_type;//signed int 有符号32bitqint64 signed_long_long_int_type;//signed long long int 有符号64bitqDebug() <<"sizeof(qint8)="  <<sizeof (signed_char_type)<<"sizeof(qint16)=" <<sizeof (signed_short_type)<<"sizeof(qint32)=" <<sizeof(signed_int_type)<<"sizeof(qint64)=" <<sizeof (signed_long_long_int_type)<<endl;;qptrdiff qint32_or_qint64_type;//32位系统 qint32 64位系统 qint64qreal double_or_float_type;//默认是double，如果加上-qreal float选项，那么是floatqintptr same_as_qptrdiff;//32位系统 qint32 64位系统 qint64quintptr quint32_or_quint64_type;//32位系统 quint32 64位系统 quint64qDebug() <<"sizeof(qptrdiff)="  <<sizeof (qint32_or_qint64_type)<<"sizeof(qreal)=" <<sizeof (double_or_float_type)<<"sizeof(qintptr)=" <<sizeof(same_as_qptrdiff)<<"sizeof(quintptr)=" <<sizeof (quint32_or_quint64_type)<<endl;quint8 unsigned_char_type;//unsigned char 无符号8bitquint16 unsigned_short_type;//unsigned short 无符号16bitquint32 unsigned_int_type;//unsigned int 无符号32bitquint64 unsigned_long_long_int_type;//unsigned long long int 无符号64bitqDebug() <<"sizeof(quint8)="  <<sizeof (unsigned_char_type)<<"sizeof(quint16)=" <<sizeof (unsigned_short_type)<<"sizeof(quint32)=" <<sizeof(unsigned_int_type)<<"sizeof(quint64)=" <<sizeof (unsigned_long_long_int_type)<<endl;qlonglong same_as_qint64_type;//相当于qint64qulonglong same_as_quint64_type;//相当于quint64qDebug() <<"sizeof(qlonglong)="  <<sizeof (same_as_qint64_type)<<"sizeof(qulonglong)=" <<sizeof (same_as_quint64_type)<<endl;uchar unsigned_char_type_same_quint8;//unsigned char 无符号8bitushort unsigned_short_type_same_quint16;//unsigned short 无符号16bituint unsigned_int_type_same_quint32;//unsigned int 无符号32bitulong unsigned_long_type;//unsigned long 无符号32bitqDebug() <<"sizeof(uchar)="  <<sizeof (unsigned_char_type_same_quint8)<<"sizeof(ushort)=" <<sizeof (unsigned_short_type_same_quint16)<<"sizeof(uint)=" <<sizeof(unsigned_int_type_same_quint32)<<"sizeof(ulong)=" <<sizeof (unsigned_long_type)<<endl;}void test_qbytearray()
{QByteArray bArray("Hello QByteArray"); // '\0'int len = bArray.length();char cLast = bArray[17];qDebug()<<"string len:"<<len<<"last char:"<<cLast<<endl;
}void test_qbytearray_resize()
{QByteArray ba;ba.resize(3);ba[0]=0x3c;ba[1]=0xb8;ba[2]=0x64;qDebug()<<endl<<"ba length:"<<ba.length()<<endl;
}void test_qbytearray_fill()
{QByteArray ba("hello");qDebug()<<"ba before fill:"<<ba<<endl;ba.fill('K');qDebug()<<"ba after fill:"<<ba<<endl;ba.fill('K',2);qDebug()<<"ba after fill two char:"<<ba<<endl;ba.fill('Q',10);qDebug()<<"ba after fill ten char Q:"<<ba<<"qbytearray length:"<<ba.length()<<"sizeof(ba)="<<sizeof (ba)<<endl //ba is a point of QByteArray<<"sizeof(QByteArray[])="<<sizeof ( (char)ba[1])<<endl;ba.data()[7]='A';qDebug()<<ba.at(4)<<ba.data()[5]<<ba.constData()[7]<<endl;
}void test_qbytearray_right_left_mid()
{QByteArray ba("HelloWorld2023");qDebug()<<ba.left(5);qDebug()<<ba.right(4);qDebug()<<ba.mid(5,5);
}void test_qbytearray_size()
{QByteArray ba("HelloWorld");qDebug()<<ba.length();qDebug()<<ba.size();qDebug()<<ba.count();QByteArray ba1("He\0llo");qDebug()<<ba1.length();
}void test_datatype_convert()
{QByteArray ba("HelloWorld");QByteArray ba_hex =  ba.toHex();qDebug() << "HelloWorld to Hex: "<<ba_hex<<endl; //48656c6c6f576f726c64QByteArray ba_fromhex = QByteArray::fromHex("48656c6c6f576f726c64");qDebug() << "QByteArray from Hex: "<<ba_fromhex<<endl;int digit = 255;uint u_digit = 255u;qlonglong qll_digit = 255ll;qulonglong qull_digit = 255ull;qDebug()<<"number base 10 on int :"<< QByteArray::number(digit);qDebug()<<"number base 10 on uint :"<<QByteArray::number(u_digit);qDebug()<<"number base 10 on qlonglong :"<<QByteArray::number(qll_digit);qDebug()<<"number base 10 on qulonglong :"<<QByteArray::number(qull_digit);qDebug()<<"number base 10 on int :"<< QByteArray::number(78);qDebug()<<"number base 10 on uint :"<<QByteArray::number(78u);qDebug()<<"number base 10 on qlonglong :"<<QByteArray::number(78ll);qDebug()<<"number base 10 on qulonglong :"<<QByteArray::number(78ull);qDebug()<<"number base 10 on int :"<< QByteArray::number(digit,16);qDebug()<<"number base 10 on uint :"<<QByteArray::number(u_digit,16);qDebug()<<"number base 10 on qlonglong :"<<QByteArray::number(qll_digit,16);qDebug()<<"number base 10 on qulonglong :"<<QByteArray::number(qull_digit,16);qDebug()<<"number base 10 on int :"<< QByteArray::number(digit,8);qDebug()<<"number base 10 on uint :"<<QByteArray::number(u_digit,8);qDebug()<<"number base 10 on qlonglong :"<<QByteArray::number(qll_digit,8);qDebug()<<"number base 10 on qulonglong :"<<QByteArray::number(qull_digit,8);qDebug()<<"number base 10 on int :"<< QByteArray::number(digit,2);qDebug()<<"number base 10 on uint :"<<QByteArray::number(u_digit,2);qDebug()<<"number base 10 on qlonglong :"<<QByteArray::number(qll_digit,2);qDebug()<<"number base 10 on qulonglong :"<<QByteArray::number(qull_digit,2);QByteArray num;qDebug()<<"QByteArray::setNum base 10 on int :"<< num.setNum(digit);qDebug()<<"QByteArray::setNum base 10 on uint :"<<num.setNum(u_digit);qDebug()<<"QByteArray::setNum base 10 on qlonglong :"<<num.setNum(qll_digit);qDebug()<<"QByteArray::setNum base 10 on qulonglong :"<<num.setNum(qull_digit);qDebug()<<"QByteArray::setNum base 10 on int :"<< num.setNum(digit,16);qDebug()<<"QByteArray::setNum base 10 on uint :"<<num.setNum(u_digit,16);qDebug()<<"QByteArray::setNum base 10 on qlonglong :"<<num.setNum(qll_digit,16);qDebug()<<"QByteArray::setNum base 10 on qulonglong :"<<num.setNum(qull_digit,16);qDebug()<<"QByteArray::setNum base 10 on int :"<< num.setNum(digit,8);qDebug()<<"QByteArray::setNum base 10 on uint :"<<num.setNum(u_digit,8);qDebug()<<"QByteArray::setNum base 10 on qlonglong :"<<num.setNum(qll_digit,8);qDebug()<<"QByteArray::setNum base 10 on qulonglong :"<<num.setNum(qull_digit,8);qDebug()<<"QByteArray::setNum base 10 on int :"<< num.setNum(digit,2);qDebug()<<"QByteArray::setNum base 10 on uint :"<<num.setNum(u_digit,2);qDebug()<<"QByteArray::setNum base 10 on qlonglong :"<<num.setNum(qll_digit,2);qDebug()<<"QByteArray::setNum base 10 on qulonglong :"<<num.setNum(qull_digit,2);double dbNum=12345.66;qDebug()<<"number base 10 on double of e format(prec=6) :"<< QByteArray::number(dbNum,'e');qDebug()<<"number base 10 on double of e format(prec=3) :"<< QByteArray::number(dbNum,'e',3);qDebug()<<"number base 10 on double of E format(prec=6) :"<< QByteArray::number(dbNum,'E');qDebug()<<"number base 10 on double of e format(prec=3) :"<< QByteArray::number(dbNum,'E',3);qDebug()<<"number base 10 on double of f format(prec=6) :"<< QByteArray::number(dbNum,'f');qDebug()<<"number base 10 on double of f format(prec=3) :"<< QByteArray::number(dbNum,'f',3);qDebug()<<"number base 10 on double of f format(prec=3) :"<< QByteArray::number(dbNum,'f',1);qDebug()<<"number base 10 on double of g format(prec=6) :"<< QByteArray::number(dbNum,'g');qDebug()<<"number base 10 on double of g format(prec=3) :"<< QByteArray::number(dbNum,'g',3);qDebug()<<"number base 10 on double of G format(prec=6) :"<< QByteArray::number(dbNum,'G');qDebug()<<"number base 10 on double of G format(prec=3) :"<< QByteArray::number(dbNum,'G',3);QByteArray abc="HelloWorld";qDebug()<<"HelloWorld ->toLower() : "<<abc.toLower();qDebug()<<"HelloWorld ->toUpper() : "<<abc.toUpper();QByteArray strNum="-123456";QByteArray strNumU="123456";qDebug()<<"strNum ->toInt() : "<<strNum.toInt();qDebug()<<"strNum ->toUInt() : "<<strNumU.toUInt();bool isBase=false;QByteArray strDigit="255";QByteArray strBin="11111111";qDebug()<<"digit ->toInt() base on 10 : "<<strDigit.toInt(&isBase)<<",isBase:"<<isBase;qDebug()<<"digit ->toInt() base on 16 : "<<strDigit.toInt(&isBase,16)<<",isBase:"<<isBase;qDebug()<<"digit ->toInt() base on 8 : "<<strDigit.toInt(&isBase,8)<<",isBase:"<<isBase;qDebug()<<"digit ->toInt() base on 2 : "<<strBin.toInt(&isBase,2)<<",isBase:"<<isBase;QByteArray strDouble="3.14159";qDebug()<<"strDouble ->toDouble() : "<<strDouble.toDouble(&isBase)<<",isBase:"<<isBase;qDebug()<<"strDouble ->toFloat() : "<<strDouble.toFloat(&isBase)<<",isBase:"<<isBase;qDebug()<<QByteArray::number(strDouble.toDouble());qDebug()<<QByteArray::number(strDouble.toDouble(),'g');qDebug()<<QByteArray::number(strDouble.toDouble(),'g',3);qDebug()<<QByteArray::number(strDouble.toDouble(),'G');qDebug()<<QByteArray::number(strDouble.toDouble(),'G',3);qDebug()<<QByteArray::number(strDouble.toDouble(),'f');qDebug()<<QByteArray::number(strDouble.toDouble(),'f',3);qDebug()<<QByteArray::number(strDouble.toDouble(),'e');qDebug()<<QByteArray::number(strDouble.toDouble(),'e',3);qDebug()<<QByteArray::number(strDouble.toDouble(),'E');qDebug()<<QByteArray::number(strDouble.toDouble(),'E',3);
}typedef struct User{int id;std::string name;
}USER;void test_qbytearray_charpoint_std_string_qstring()
{USER u;u.id=1001;u.name="hello";QByteArray arr;arr.append((char*)&u,sizeof (u));USER *pUser = (USER*)arr.data();qDebug() <<pUser->id<<pUser->name.c_str();QByteArray ba("HelloWorld");char *pBa = ba.data();qDebug() << pBa;qDebug() << *pBa;while (*pBa) {qDebug()<< "item of Array : " << *pBa;++pBa;}char *p = &ba.data()[5];qDebug() <<p;std::string str = ba.toStdString();qDebug()<<"std::string ->"<<str.c_str();QByteArray baStd = QByteArray::fromStdString(std::string("this is a std string"));qDebug()<<"fromStdString ->"<<baStd;QString qstr = QString("HelloWorld");qDebug()<<"QString to QByteArray ->"<<qstr.toLatin1();QByteArray tmpBa = "flkdsjlkfjkdsjfldsjkfjk";qstr=tmpBa;qDebug()<<qstr;if(tmpBa.isEmpty()){qDebug()<<"";}if(QByteArray("").isEmpty()){qDebug()<<"";}if(QByteArray().isEmpty()){qDebug()<<"";}}int main(int argc, char *argv[])
{QCoreApplication a(argc, argv);test();test_types();test_qbytearray();test_qbytearray_resize();test_qbytearray_fill();test_qbytearray_right_left_mid();test_qbytearray_size();test_datatype_convert();test_qbytearray_charpoint_std_string_qstring();return a.exec();
}