QBitArray to QByteArray

Question

当我们用这个文本"ali ata bak"创建一个文本文件时，我们使用这个文件作为程序的输入。代码运行正常。但是当我们在文本文件中输入"111111111111111111"这个文本时，代码并没有按预期运行。那么问题出在哪里呢？

#include <QtCore/QCoreApplication>
#include <QBitArray>
#include <QByteRef>
#include <QFile>
#include <iostream>
#include <stdlib.h>
#include <QTextStream>
// Buffer Size #num of KB's
#define BUFFER_SIZE_KB 1
// Do not change !!
#define BUFFER_SIZE_BYTE BUFFER_SIZE_KB*1024
#define BUFFER_SIZE_BIT  BUFFER_SIZE_BYTE*8
using namespace std;

QBitArray bytesToBits(QByteArray bytes) {
    QBitArray bits(bytes.count()*8);
    // Convert from QByteArray to QBitArray
    for(int i=0; i<bytes.count(); ++i)
        for(int b=0; b<8; ++b)
            bits.setBit(i*8+b, bytes.at(i)&(1<<b));
    return bits;
}

QByteArray bitsToBytes(QBitArray bits) {
    QByteArray bytes;
    bytes.resize(bits.count()/8);
    // Convert from QBitArray to QByteArray
    for(int b=0; b<bits.count(); ++b)
        bytes[b/8] = ( bytes.at(b/8) | ((bits[b]?1:0)<<(b%8)));
    return bytes;
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QString inFilename;
    QString outFilename;
    QTextStream qtin(stdin);

    cout << "Filename : ";
    qtin >> inFilename;
    outFilename.append("_");
    outFilename.append(inFilename);
    QFile infile(inFilename);
    if (!infile.open(QIODevice::ReadOnly)) {
        cout << "nFile cant openedn";
        system("pause");
        return 1;
    }
    QFile outfile(outFilename);
    if (!outfile.open(QIODevice::WriteOnly)) {
        cout << "nFile cant openedn";
        system("pause");
        return 2;
    }
    QByteArray bytes, bytes2;
    QBitArray bits;

    while ((bytes = infile.read(BUFFER_SIZE_BYTE)) >0 ) {
        bits = bytesToBits(bytes);
        bytes2 = bitsToBytes(bits);// PROBLEM IS HERE
        outfile.write(bytes2);
    }
    outfile.close();
    infile.close();
    cout << "Finishedn";
    return a.exec();
}

Answer 1

初始化问题。

QByteArray bitsToBytes(QBitArray bits) {
    QByteArray bytes;
    bytes.resize(bits.count()/8+1);
    bytes.fill(0);
    // Convert from QBitArray to QByteArray
    for(int b=0; b<bits.count(); ++b)
        bytes[b/8] = ( bytes.at(b/8) | ((bits[b]?1:0)<<(b%8)));
    return bytes;
}

这会产生正确的答案

Answer 2

QByteArray bitsToBytes(const QBitArray& bits)
{
    QByteArray bytes;
    QDataStream stream(&bytes, QIODevice::WriteOnly);
    stream << bits;
    return bytes;
}

Answer 3

QBitArray bits(8);
// The deep copy of bits
QByteArray bytes(bits.bits(), bits.count() / 8); 
--------------------------------------------------------------------------
// The bits are not copied
QByteArray bytes = QByteArray::fromRawData(bits.bits(), bits.count() / 8); 

Answer 4

您可能还想从维基百科上了解endiannesshttp://en.wikipedia.org/wiki/Endianness

Answer 5

根据iloahz的回答，解决输出文件大小增加1字节的问题。

QByteArray bitsToBytes(QBitArray bits) {
    QByteArray bytes;
    bytes.resize(bits.count() / 8 + ((bits.count() % 8)? 1: 0));
    bytes.fill(0x00);
    // Convert from QBitArray to QByteArray
    for(int b = 0; b < bits.count(); ++b)
        bytes[b / 8] = (bytes.at(b / 8) | ((bits[b]? 1: 0) << (b % 8)));
    return bytes;
}