ASCII图形波形发生器

Question

最近在编写一些文档时，我需要将许多异步串行波形转换为ASCII图形字符。我决定写一个程序来帮我画，而不是用手画。我对代码回顾感兴趣，尤其是如果有更聪明/更短的方法来编写类的话。

#include <iostream>
#include <vector>
#include <string>
#include <bitset>

class waveform
{
public:
    waveform(std::string &s) : data_(s) {}
    std::vector<bool> to_bits() const
    {
        std::vector<bool> bits;
        bits.reserve(data_.size() * 10);
        for (auto &ch : data_) {
            bits.push_back(0); // start bit
            for (int mask=1u; mask != 0x100; mask <<= 1) {
                bits.push_back(ch & mask);
            }
            bits.push_back(1); // stop bit
        }
        return bits;
    }
    friend std::ostream& operator<<(std::ostream& out, const waveform& w) {
        auto bits = w.to_bits();
        bool last = 1;
        for (const auto &b : bits) {
            out << (b ? "+---" : (last ? "+   " : "    "));
            last = b;
        }
        out << '\n';
        last = 1;
        for (const auto &b : bits) {
            out << (b != last ? "|   " : "    ");
            last = b;
        }
        out << '\n';
        last = 1;
        for (const auto &b : bits) {
            out << (b ? (last ? "    " : "+   ") : "+---");
            last = b;
        }
        out << '\n';
        int special = 0x201;
        for (const auto &b : bits) {
            if (special & 1) {
                out << (b ? "  P " : "  S ");
            } else {
                out << (b ? "  1 " : "  0 ");
            }
            special >>= 1;
            if (special == 0)
                special = 0x201;
        }
        out << '\n';
        return out;
    }
private:
    std::string data_;
};

示例驱动程序

int main()
{
    std::string msg{"ST"};
    std::cout << waveform(msg) << std::endl;
}

样本输出

+   +---+---+       +---+   +---+   +---+           +---+   +---+   +---+   +---
|   |       |       |   |   |   |   |   |           |   |   |   |   |   |   |   
+---+       +---+---+   +---+   +---+   +---+---+---+   +---+   +---+   +---+   
  S   1   1   0   0   1   0   1   0   P   S   0   0   1   0   1   0   1   0   P 

注意，在这个图中，S代表一个开始位，P代表一个停止位，而8个数据位首先被发送到最不重要的位。

Answer 1

OOP的设计似乎对你没有多大帮助。感觉就像你只需要一个函数就能得到基本相同的效果。另一方面，operator<<方法基本上是一个状态机，它看起来比需要的要麻烦一些。这里有复制和粘贴代码，各地都有ASCII的一些艺术，还有一台使用神奇数字0x201的迷你图灵机。

假设to_bits()助手函数对您不重要(我假设它并不那么重要，因为您编写了#include <bitset>然后改变了主意)，您可以通过定义一个过滤输出流来做得更好。下面是我试图实现这样一件事的尝试：

#include <climits>
#include <iostream>
#include <sstream>
#include <streambuf>
#include <string>

class waveform_ostream : public std::streambuf
{
public:
    explicit waveform_ostream(std::ostream &sink) : sink(sink) {}

protected:
    // Accept a byte of data
    virtual std::streambuf::int_type overflow(std::streambuf::int_type c) {
        output_bit(0, 'S');             // Start bit
        for (int i = 0; i < CHAR_BIT; ++i) {
            output_bit((c >> i) & 1);   // Data bits, LSB first
        }
        output_bit(1, 'P');             // Stop bit
        return c;
    }

    // Flush
    int sync() {
        for (int row = 0; row < 4; ++row) {
            std::string s = lines[row]->str();
            sink << s << '\n';
            lines[row]->str("");
        }
        sink << std::flush;
        return 0;   // success
    }

private:
    bool state = 1;
    std::ostream &sink;
    std::stringstream level[2], risefall, captions;
    std::stringstream *const lines[4] = {
        &level[1],
        &risefall,
        &level[0],
        &captions
    };

    void output_bit(bool b, char caption='\0') {
        level[!b] << ((b == state) ? "    " : "+   ");
        risefall  << ((b == state) ? "    " : "|   ");
        level[ b] <<                          "+---";
        captions  << "  " << (char)(caption ? caption : b ? '1' : '0') << ' ';
        state = b;
    }
};

int main()
{
    waveform_ostream wout(std::cout);
    std::ostream out(&wout);
    out << std::string("ST") << std::flush;
}

Answer 2

我不太喜欢原来的，所以我改变了一些东西，并制作了这个新版本。它允许可变数量的数据位和停止位，并且结构更好。每一行分别生成，图像使用两位查找表进行选择.

波形h

#ifndef WAVEFORM_H
#define WAVEFORM_H

#include <iostream>
#include <iomanip>
#include <vector>
#include <string>

namespace WAVE {
class Waveform
{
public:
    Waveform(std::string &s, int bits=8, int stopbits=1);
    std::size_t bits_per_char() const { return 1 + bits_ + stop_; }
    std::vector<bool> to_bits() const;
    void graphics_line(std::ostream& out, const std::vector<bool>& bits, int linenum) const;
    void bitlabel_line(std::ostream& out, const std::vector<bool>& bits) const;
    friend std::ostream& operator<<(std::ostream& out, const Waveform& w) {
        auto bits = w.to_bits();
        for (int i=0; i < 3; ++i)
            w.graphics_line(out, bits, i);
        w.bitlabel_line(out, bits);
        for (const auto &ch: w.data_) {
            out 
                << std::setw(2*w.bits_per_char()) << "0x" << std::hex 
                << static_cast<unsigned>(ch & 0xff)
                << std::setw(2*w.bits_per_char()-2) << ' ';
        }
        return out;
    }
private:
    std::string data_;
    int bits_;
    int stop_;
};
}
#endif //WAVEFORM_H

Waveform.cpp

#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include "Waveform.h"

namespace WAVE {
Waveform::Waveform(std::string &s, int bits, int stopbits) 
    : data_(s), bits_(bits), stop_(stopbits) 
{
}

std::vector<bool> Waveform::to_bits() const
{
    std::vector<bool> bits;
    bits.reserve(data_.size() * bits_per_char());
    for (auto &ch : data_) {
        bits.push_back(0); // start bit
        for (int i=bits_, c=ch; i; --i) {
            bits.push_back(c & 1);
            c >>= 1;
        }
        for (int i=stop_; i; --i) {
            bits.push_back(1); // stop bit
        }
    }
    return bits;
}

void Waveform::graphics_line(std::ostream& out, const std::vector<bool>& bits, int linenum) const 
{
    static const char* graphic[3][4]{
        // 00      01      10      11
        {"    ", "+---", "+   ", "+---"}, 
        {"    ", "|   ", "|   ", "    "},
        {"+---", "+   ", "+---", "    "}
    };
    int last = 2;   // assume previous bit was 1
    for (const auto &b : bits) {
        last |= b;
        out << graphic[linenum][last];
        last = (last << 1) & 0x3;
    }
    out << '\n';
}

void Waveform::bitlabel_line(std::ostream& out, const std::vector<bool>& bits) const 
{
    enum states { START, DATA, STOP } state = START;
    int bitcount = bits_;
    for (unsigned i=0; i < bits.size(); ++i) {
        switch (state) {
            case START:
                out << (bits[i] ? " SE " : "  S ");
                state = DATA;
                break;
            case DATA:
                out << (bits[i] ? "  1 " : "  0 ");
                if (--bitcount == 0) {
                    bitcount = stop_;
                    state = STOP;
                }
                break;
            case STOP:
                out << (bits[i] ? "  P " : " EP ");
                if (--bitcount == 0) {
                    bitcount = bits_;
                    state = START;
                }
                break;
        }
    }
    out << '\n';
}
}

test.cpp

#include <iostream>
#include "Waveform.h"
using namespace std;

int main()
{
    string msg{"ST"};
    WAVE::Waveform wave = WAVE::Waveform(msg);
    WAVE::Waveform wave2{wave};
    cout << wave << endl;
    cout << WAVE::Waveform(msg,7,1) << endl;
    cout << WAVE::Waveform(msg,7,2) << endl;
    auto bits = wave2.to_bits();
    for (bool b : bits)
        cout << b;
    cout << endl;
}

输出

+   +---+---+       +---+   +---+   +---+           +---+   +---+   +---+   +---
|   |       |       |   |   |   |   |   |           |   |   |   |   |   |   |   
+---+       +---+---+   +---+   +---+   +---+---+---+   +---+   +---+   +---+   
  S   1   1   0   0   1   0   1   0   P   S   0   0   1   0   1   0   1   0   P 
                  0x53                                      0x54                    
+   +---+---+       +---+   +---+---+           +---+   +---+   +---+---
|   |       |       |   |   |       |           |   |   |   |   |       
+---+       +---+---+   +---+       +---+---+---+   +---+   +---+       
  S   1   1   0   0   1   0   1   P   S   0   0   1   0   1   0   1   P 
                0x53                                  0x54                  
+   +---+---+       +---+   +---+---+---+           +---+   +---+   +---+---+---
|   |       |       |   |   |           |           |   |   |   |   |           
+---+       +---+---+   +---+           +---+---+---+   +---+   +---+           
  S   1   1   0   0   1   0   1   P   P   S   0   0   1   0   1   0   1   P   P 
                  0x53                                      0x54                    
01100101010001010101