昨天看到博客园有个面试者笔试出现此题，昨天大概给出思路，今天经过思考将实现，并做出优化改进
，逻辑易懂，基本都可以看懂，经过初步测试正确。代码如下：
1 // MindryBuffer.cpp : 定义控制台应用程序的入口点。
2 //
3
4 #include "stdafx.h"
5 #include <iostream>
6 #include <string.h>
7 using namespace std;
8
9 class CMindryBuffer
10 {
11 public:
12 CMindryBuffer(int iBufLenth = MindryBufferLenth);
13 ~CMindryBuffer(void);
14
15 int ReSize(int iBufLenth); //重置缓冲区大小
16 int Read(char * pData,int iReadDataLength); //读取指定数据
17 int Write(char * pData,int iWriteDataLength); //写入指定数据
18
19 void Clear(); //清空缓冲区
20 int GetCapicity(); //获取缓冲区容量
21 int GetWriteAvailable(); //缓冲区可写数据 可通过此函数判断缓冲区是否已满
22 int GetReadAvailable(); //缓冲区可读数据 可通过此函数判断缓冲区是否为空
23
24 private:
25 const static int MindryBufferLenth = 10; //默认缓冲区长度
26 int m_iBufLenth; //缓冲区
27 int m_iWritePos; //写入起始位置
28 int m_iReadPos; //读取起始位置
29 int m_iDataLenth; //缓冲区存放数据长度
30 char *m_PData; //缓冲区数据指针
31 };
32
33 CMindryBuffer::CMindryBuffer(int iBufLenth)
34 {
35 m_PData = NULL;
36 m_iWritePos = 0;
37 m_iReadPos = 0;
38 m_iDataLenth = 0;
39 m_iBufLenth = iBufLenth;
40 if (m_iBufLenth > 0)
41 {
42 m_PData = new char[m_iBufLenth];
43 }
44 }
45
46 CMindryBuffer::~CMindryBuffer(void)
47 {
48 if (m_PData)
49 {
50 delete [] m_PData;
51 }
52 }
53
54
55 int CMindryBuffer::Write(char * pData,int iWriteDataLength)
56 {
57 if (m_iBufLenth - m_iDataLenth == 0 || !m_PData )
58 {
59 return 0;
60 }
61
62 int iCanWriteDataLength = iWriteDataLength> GetWriteAvailable()? GetWriteAvailable():iWriteDataLength;
63
64 int iNowWriteToEndLength = m_iBufLenth - m_iWritePos;
65 if (iNowWriteToEndLength >= iCanWriteDataLength)
66 {
67 memcpy(&m_PData[m_iWritePos],pData,iCanWriteDataLength);
68 m_iWritePos += iCanWriteDataLength;
69 }
70 else
71 {
72 memcpy(&m_PData[m_iWritePos],pData,iNowWriteToEndLength);
73 memcpy(m_PData,&pData[iNowWriteToEndLength],iCanWriteDataLength - iNowWriteToEndLength);
74 m_iWritePos = iCanWriteDataLength - iCanWriteDataLength;
75 }
76 m_iDataLenth += iCanWriteDataLength;
77 return iCanWriteDataLength;
78 }
79
80 int CMindryBuffer::Read(char * pData,int iReadDataLength)
81 {
82 if (m_iDataLenth == 0)
83 {
84 return 0;
85 }
86 int iCanReadDataLength = iReadDataLength>m_iDataLenth? m_iDataLenth:iReadDataLength;
87 int iNowReadToEndLength = m_iBufLenth - m_iReadPos;
88
89 if (iNowReadToEndLength >= iCanReadDataLength)
90 {
91 memcpy(pData,&m_PData[m_iReadPos],iCanReadDataLength);
92 m_iReadPos += iCanReadDataLength;
93 }
94 else
95 {
96 memcpy(pData,&m_PData[m_iReadPos],iNowReadToEndLength);
97 memcpy(&pData[iNowReadToEndLength],m_PData,iCanReadDataLength - iNowReadToEndLength);
98
99 m_iReadPos = iCanReadDataLength - iNowReadToEndLength;
100 }
101 m_iDataLenth -= iCanReadDataLength;
102 return iCanReadDataLength;
103 }
104
105 int CMindryBuffer::ReSize(int iBufLenth)
106 {
107 if (iBufLenth > m_iBufLenth )
108 {
109 char * pData = new char[iBufLenth];
110 Read(pData ,m_iDataLenth);
111
112 delete []m_PData;
113 m_PData = pData;
114 m_iReadPos = 0;
115 m_iWritePos = m_iDataLenth;
116 m_iBufLenth = iBufLenth;
117 }
118 return m_iDataLenth;
119 }
120
121 void CMindryBuffer::Clear()
122 {
123 m_iReadPos = 0;
124 m_iWritePos = 0;
125 m_iDataLenth = 0;
126 }
127
128 int CMindryBuffer::GetCapicity()
129 {
130 return m_iBufLenth;
131 }
132
133 int CMindryBuffer::GetWriteAvailable()
134 {
135 return m_iBufLenth -m_iDataLenth;
136
137 }
138 int CMindryBuffer::GetReadAvailable()
139 {
140 return m_iDataLenth;
141 }
142
143 int _tmain(int argc, _TCHAR* argv[])
144 {
145
146 CMindryBuffer mindBuf;
147
148 int iReadLenth;
149 char buf[100];
150 mindBuf.Write("abcd",4);
151
152 iReadLenth = mindBuf.Read(buf,1);
153 buf[iReadLenth] = 0;
154 cout<<buf<<endl;
155
156 mindBuf.Write("efghi",5);
157 iReadLenth = mindBuf.Read(buf,5);
158 buf[iReadLenth] = 0;
159 cout<<buf<<endl;
160
161 mindBuf.Write("gklmn",5);
162 iReadLenth = mindBuf.Read(buf,8);
163 buf[iReadLenth] = 0;
164 cout<<buf<<endl;
165
166
167 return 0;
168 }
时间： 2024-08-30 12:03:27