从数组捕获字符串

Question

我想弄清楚如何从一个给定的位置开始从数组中获取字符串。假设我们有一个任意长的数组，并且我的字符串从1000开始。如果我想从文件中获取字符串，我只需使用getc或scanf之类的东西。我如何在数组而不是文件上执行这些相同的功能？

*哦，请记住，该数组的类型为int，并且充满了ASCII字符的数字表示形式。

Answer 1

假设字符串为null结束的元素（不指定你怎么知道的字符串的结尾），那么一点点LINQ的应该做的伎俩：

var chars = ints.Skip(1000).TakeWhile(i => i != 0).Select(i => (char)i); 
var str = new string(chars.ToArray()); 

第一像跳过1000个整数，需要他们，而他们不是空终止，然后将它们转换成字符作为适合表示ASCII码整数。第二行简单地将它们变成一个字符串。

如果字符串没有空终止符，并且刚刚在数组结束时结束，那么只需删除对TakeWhile的调用。

Answer 2

如果你用byte[]处理数组，那么你可能只是这样做：

string yourString = Encoding.ASCII.GetString(yourArray, startIndex, length); 

因为你的阵列是int[]类型，那么的 - 假设每个元素代表一个ASCII字符 - 你会需要首先将这些int s转换为byte。如果数组是“任意长”，那么你可能不希望整个事情转换为byte[]阵列，在这种情况下，只是转换您需要的部分：

byte[] temp = 
    yourArray.Skip(startIndex).Take(length).Select(i => (byte)i).ToArray(); 
string yourString = Encoding.ASCII.GetString(temp); 

如果您int[]阵列中的每个元素没有按” t实际上代表一个ASCII字符，那么你需要给我们更多关于它使用的精确格式的信息。

Answer 3

你能切从阵列和呼叫ASCIIEncoding.GetString（）就可以了

Answer 4

LINQ有时可以是相当的手...

var ints = Enumerable.Range(0, 255).ToArray(); 
var start = 65; 
var length = 26; 
var value = new string(ints.Select(i => (char)i) 
          .Skip(start) 
          .Take(length) 
          .ToArray()); 
Console.WriteLine(value); //ABCDEFGHIJKLMNOPQRSTUVWXYZ 

Answer 5

这里是一个替代（类似于solution provided by LukeH），可能会更快（因为它使用内置的阵列方法，而不是LINQ）：

public static string GetString(int[] array, int startIndex, int length) 
{ 
    var subarray = new int[length]; 
    Array.Copy(array, startIndex, subarray, 0, length); 
    return Encoding.ASCII.GetString(Array.ConvertAll(subarray, i => (byte)i)); 
} 

Answer 6

这是我的代码仅供参考。如果你转到“SYSCALL”部分，你会发现有关“open 4”的if语句，这是我卡住的地方。哦，顺便说一下，我没有使用visual studio，我正在使用一个名为“Verilator”的程序，它允许我将Verilog代码与C++代码进行交互。

#include "VMIPS.h" 
#include "VMIPS_MIPS.h"//required to explicitly access signals from submodules 
#include <verilated.h> 

#include <cstdio> 
#include <cmath> 
#include <iostream> 
#include <fstream> 
#include <iomanip> 
#include <string> 
#include <cstdlib> 
#include <vector> 
using namespace std; 

unsigned int main_time = 0; 

static inline int hexCharValue(char ch) 
{ 
    if (ch>='0' && ch<='9')return ch-'0'; 
    if (ch>='a' && ch<='f')return ch-'a'+10; 
    return 0; 
} 

int main(int argc, char **argv) 
{ 
///////////////////////////////////////// Instruction Capture ///////////////////////////////////////////// 
    ifstream inClientFile("TEXT.txt",ios::in); //stream object 

    //test if instruction file can be opened 
    if (!inClientFile) 
    { 
     cerr << "File couldn't be opened" << endl; 
     return 1; //no point using exit inside main 
    } 

    //fill string array with all file values and determines length of program 
    vector<string> words; 
    words.reserve(274815); 
    string word; 
    while (inClientFile >> word)words.push_back(word); //helper function is unnecessary 

    cout << "Number of words:" << words.size() << endl; 

    const int wordCount=words.size(); 
    vector<int> InstructionMemory; 
    vector<string> tempInstructionMemory; 
    tempInstructionMemory.reserve(wordCount); 

    //cut out undesired strings from vector 
    for(int i=0; i<wordCount; i++) 
    { 
     if (words[i].length()==8 && words[i].find("fs24")==string::npos) //f0 can exist at pos 1 in a valid hex string 
     { 
      tempInstructionMemory.push_back(words[i]); 
     } 
    } 

    //convert string hex to numerical decimal 
    InstructionMemory.resize(tempInstructionMemory.size()); 
    for(int j=0; j<tempInstructionMemory.size(); j++) 
    { 
     for(int y=0; y<8; y++) 
     { 
      InstructionMemory[j]+=hexCharValue(tempInstructionMemory[j][y])<<(4*(7-y));//4194608+4* 
     } 
    } 
    //printf("Amortized Instruction Vector Size:%d\n",InstructionMemory.size());  
////////////////////////////////////// Data Capture //////////////////////////////////////////////// 
    ifstream inClientDataFile("DATA.txt",ios::in); //stream object 

    //test if instruction file can be opened 
    if (!inClientDataFile) 
    { 
     cerr << "File couldn't be opened" << endl; 
     return 1; //no point using exit inside main 
    } 

    //fill string array with all file values and determines length of program 
    vector<string> datas; 
    datas.reserve(274815); 
    string data; 
    while (inClientDataFile >> data)datas.push_back(data); //helper function is unnecessary 

    cout << "Number of data packets:" << datas.size() << endl; 

    const int dataCount=datas.size(); 
    vector<int> DataMemory; 
    vector<string> tempDataMemory; 
    tempDataMemory.reserve(dataCount); 

    //cut out undesired strings from vector 
    for(int i=0; i<dataCount; i++) 
    { 
     if (datas[i].length()==8 && datas[i].find("fs24")==string::npos) //f0 can exist at pos 1 in a valid hex string 
     { 
      tempDataMemory.push_back(datas[i]); 
     } 
    } 

    //convert string hex to numerical decimal 
    DataMemory.resize(tempDataMemory.size()); 
    for(int j=0; j<tempDataMemory.size(); j++) 
    { 
     for(int y=0; y<8; y++) 
     { 
      DataMemory[j]+=hexCharValue(tempDataMemory[j][y])<<(4*(7-y)); 
     } 
    } 
    //printf("Amortized Data Vector Size:%d\n",DataMemory.size()); 
/////////////////////////////////////////// MIPS I processor interface /////////////////////////////////////////////  
    Verilated::commandArgs(argc, argv); 
    VMIPS *top = new VMIPS; 
    top->CLK = 0; 
    vector<int> HS0,HS1,HS2; 

    vector<string> FDT_filename; 
    vector<int> FDT_state;//1 = open, 0 = closed 
    int FileDescriptorIndex = 3;//start of non-reserved indecies 
    FILE *f; 

    //first 3 positions reserved for stdin, stdout, and stderr  
    FDT_filename.push_back("stdin"); 
    FDT_filename.push_back("stdout"); 
    FDT_filename.push_back("stderr"); 
    FDT_state.push_back(0); 
    FDT_state.push_back(0); 
    FDT_state.push_back(0); 


    //int FDT[100]; 

    printf("IMAddr:%d IM:%d \n***************\n",top->Iaddr,InstructionMemory[(top->Iaddr)/4]); 

    while (!Verilated::gotFinish()) 
    { 
     //clock generation 
     top->CLK=!(top->CLK); 

     //vector mapping 
     if ((top->Daddr >= 0) && (top->Daddr <= 419604)) 
     { 
      if(top->MemRead) 
       top->Din = HS0[(top->Daddr)/4]; 
      if(top->MemWrite) 
       HS0[(top->Daddr)/4] = top->Dout; 
     } 
     else if ((top->Daddr >= (419608+InstructionMemory.size()+4)) && (top->Daddr <= 268435452)) 
     { 
      if(top->MemRead) 
       top->Din = HS1[(top->Daddr-419608)/4]; 
      if(top->MemWrite) 
       HS1[(top->Daddr-419608)/4] = top->Dout; 
     } 
     else if ((top->Daddr >= 268435456) && (top->Daddr <= (268435456+DataMemory.size()))) 
     { 
      if(top->MemRead) 
       top->Din = DataMemory[(top->Daddr-2668435456)/4]; 
      if(top->MemWrite) 
       DataMemory[(top->Daddr-2668435456)/4] = top->Dout; 
     } 
     else if (top->Daddr >=(268435456+DataMemory.size()+4)) 
     { 
      if(top->MemRead) 
       top->Din = HS2[(top->Daddr-(268435456+DataMemory.size()+4))/4]; 
      if(top->MemWrite) 
       HS2[(top->Daddr-(268435456+DataMemory.size()+4))/4] = top->Dout; 
     } 

     //instruction supply mapping 
     if (top->Iaddr < 4194608) 
     { 
      top->Iin = InstructionMemory[(top->Iaddr)/4]; 

     } 
     else 
     { 
      top->Iin = InstructionMemory[(top->Iaddr-4194608)/4]; 

     } 

     //instruction split 
     if(main_time%2) 
      printf("IMAddr:%d IM:%d \n***************\n",top->Iaddr,InstructionMemory[(top->Iaddr)/4]);//-4194608)/4]); 

     //evaluate instruction call and increment time counter 
     top->eval(); 
     main_time++; 

     //exit loop 
     if(main_time>=2) 
     { 
      return 0; 
     } 

     top->Iin = 3690987776; 

     //SYSCALL 
     if (top->Iin == 3690987584)//exit 1 
     { 
      cout << "Exit" << endl; 
      return 0; 
     } 
     else if (top->Iin == 3690987776)//open 4 
     { 
      cout << endl << endl << "Open File" << endl << endl; 
      string filename; 

      filename = "DATA.txt"; 


      //fill filename with characters from memory 
       //FDT_filename(top->a0) is the string start pointer 

      FDT_filename.push_back(filename);//add new filename to newest location 
      FDT_state.push_back(1);//add new open indicator to newest location 
      top->v0 = FileDescriptorIndex;//place file descriptor into register 
      FileDescriptorIndex++;//ready the next file descriptor 

      //printf("Filename:%d FileDescriptorIndex:%d",FDT_filename.at3(FileDescriptorIndex),FileDescriptorIndex); 
     } 
     else if (top->Iin == 3690987648)//read 2 
     { 
      cout << "Read" << endl; 
      int max_char_count = top->a2; 
      int char_CTR = 0; 

      //create file object and open filename 
       //read chars from file 
       //place in 

      //FILE *f = fopen(filename,"rb"); 
      //scanf("%s %top->a2",&FDT_filename(top->a0) >> top->a1; 
      //top->v0 = char_CTR; 

     } 
     else if (top->Iin == 3690987712)//write 3 
     { 
      cout << "Write" << endl; 
      int max_char_count = top->a2; 
      int char_CTR = 0; 
      //f fopen(FDT_filename(top->a0)); 

     } 
     else if (top->Iin == 3690987840)//close 5 
     { 
      cout << "Close File" << endl; 
      //FDT_state(top->v0)=0; 
     } 
     else if (top->Iin == 3690987904)//time 6 
     { 
      cout << "Time:" << main_time << endl; 
      top->a0 = main_time; 
      top->a1 = main_time; 
     } 
    } 
}