首页 > 代码库 > [源码]DataIOStream 数据流 处理基本数据类型的流
[源码]DataIOStream 数据流 处理基本数据类型的流
纵骑横飞 章仕烜
首先我们来看一下 DataOutputStream
/**
* A data output stream lets an application write primitive Java data
* types to an output stream in a portable way. An application can
* then use a data input stream to read the data back in.
*
* @author unascribed
* @version 1.44, 11/17/05
* @see java.io.DataInputStream
* @since JDK1.0
*/
public
class DataOutputStream extends FilterOutputStream implements DataOutput {
/**
* The number of bytes written to the data output stream so far.
* If this counter overflows, it will be wrapped to Integer.MAX_VALUE.
*/
protected int written;
/**
* bytearr is initialized on demand by writeUTF
*/
private byte[] bytearr = null;
public DataOutputStream(OutputStream out) {
super(out);
}
/**
* Increases the written counter by the specified value
* until it reaches Integer.MAX_VALUE.
*如果说缓冲区溢出就
*/
private void incCount(int value) {
int temp = written + value;
if (temp < 0) {
temp = Integer.MAX_VALUE;
}
written = temp;
}
/**
* 这两个方法 和OutputStream一样的效果
*/
public synchronized void write(int b) throws IOException {
out.write(b);
incCount(1);
}
public synchronized void write(byte b[], int off, int len)
throws IOException {
out.write(b, off, len);
incCount(len);
}
/**
* 刷新 和OutputStream一样的效果
*/
public void flush() throws IOException {
out.flush();
}
/**
* 这是 标志数据流的特性的部分
*/
public final void writeBoolean(boolean v) throws IOException {
out.write(v ? 1 : 0); //true写的是1 底层保存的是01
incCount(1);
}
/**
* 对于整型,除去long类型肯定传的是long类型的,其他传入的都是int类型的
*/
public final void writeByte(int v) throws IOException {
out.write(v);
incCount(1);
}
/**
* 0xFF 十六进制 15*16+15=255 补码 0000 0000 1111 1111
* v>>>8也就是 除以2^8
* 如果你真传一个short值 那么
* 第一个数 往后挪动8位 肯定是 0000 0000 0000 0000 所以结果是写进去个空格
* 第二个数 原封不动 &255 拿到的还是原来的数 所以写进去的是对应的字符
* 所以说 这两句话就是 让写入的东西占两个位置 一个空格 一个对应的字符
*/
public final void writeShort(int v) throws IOException {
out out
incCount(2);
}
public final void writeChar(int v) throws IOException {
out.write((v >>> 8) & 0xFF);
out.write((v >>> 0) & 0xFF);
incCount(2);
}
public final void writeInt(int v) throws IOException {
out.incCount(4);
}
private byte writeBuffer[] = new byte[8];
/**
*这边 代码的解读 让我茅塞顿开
* 让我搞明白了 write某种类型 绝对不是简单的把那个数字扔进输出流
* 实际上是 某种类型有几位 就拆成几位 分别用ascii方式扔进输出流
*/
public final void writeLong(long v) throws IOException {
writeBuffer[0] = (byte)(v >>> 56);
writeBuffer[1] = (byte)(v >>> 48);
writeBuffer[2] = (byte)(v >>> 40);
writeBuffer[3] = (byte)(v >>> 32);
writeBuffer[4] = (byte)(v >>> 24);
writeBuffer[5] = (byte)(v >>> 16);
writeBuffer[6] = (byte)(v >>> 8);
writeBuffer[7] = (byte)(v >>> 0);
out.write(writeBuffer, 0, 8);
incCount(8);
}
/**
*
*
*/
public final void writeFloat(float v) throws IOException {
writeInt(Float.floatToIntBits(v));
}
public final void writeDouble(double v) throws IOException {
writeLong(Double.doubleToLongBits(v));
}
public final void writeBytes(String s) throws IOException {
int len = s.length();
for (int i = 0 ; i < len ; i++) {
out.write((byte)s.charAt(i));
}
incCount(len);
}
/**
*
*/
public final void writeChars(String s) throws IOException {
int len = s.length();
for (int i = 0 ; i < len ; i++) {
int v = s.charAt(i);
out.write((v >>> 8) & 0xFF);
out.write((v >>> 0) & 0xFF);
}
incCount(len * 2);
}
/**
* 心得: 如果说以后要写两个 工具方法 先写功能更完善的工具方法,然后就可以调用它完成
*若干简单的工具方法
*/
public final void writeUTF(String str) throws IOException {
writeUTF(str, this);
}
static int writeUTF(String str, DataOutput out) throws IOException {
int strlen = str.length();
int utflen = 0;
int c, count = 0;
/* use charAt instead of copying String to char array */
for (int i = 0; i < strlen; i++) {
c = str.charAt(i);
if ((c >= 0x0001) && (c <= 0x007F)) {
utflen++;
} else if (c > 0x07FF) {
utflen += 3;
} else {
utflen += 2;
}
}
if (utflen > 65535)
throw new UTFDataFormatException(
"encoded string too long: " + utflen + " bytes");
byte[] bytearr = null;
if (out instanceof DataOutputStream) {
DataOutputStream dos = (DataOutputStream)out;
if(dos.bytearr == null || (dos.bytearr.length < (utflen+2)))
dos.bytearr = new byte[(utflen*2) + 2];
bytearr = dos.bytearr;
} else {
bytearr = new byte[utflen+2];
}
bytearr[count++] = (byte) ((utflen >>> 8) & 0xFF);
bytearr[count++] = (byte) ((utflen >>> 0) & 0xFF);
int i=0;
for (i=0; i<strlen; i++) {
c = str.charAt(i);
if (!((c >= 0x0001) && (c <= 0x007F))) break;
bytearr[count++] = (byte) c;
}
for (;i < strlen; i++){
c = str.charAt(i);
if ((c >= 0x0001) && (c <= 0x007F)) {
bytearr[count++] = (byte) c;
} else if (c > 0x07FF) {
bytearr[count++] = (byte) (0xE0 | ((c >> 12) & 0x0F));
bytearr[count++] = (byte) (0x80 | ((c >> 6) & 0x3F));
bytearr[count++] = (byte) (0x80 | ((c >> 0) & 0x3F));
} else {
bytearr[count++] = (byte) (0xC0 | ((c >> 6) & 0x1F));
bytearr[count++] = (byte) (0x80 | ((c >> 0) & 0x3F));
}
}
out.write(bytearr, 0, utflen+2);
return utflen + 2;
}
public final int size() {
return written;
}
}
1.在上面的 write某种类型或者说write的过程中是把多种类型都统一拆分成多个byte,如果这么存,数据会不会流失?
如果说存到一个文本文件里边会不会丢失? -----会 文本文件是ASCII码存 超出范围就用同一个?字符代替 这样这个byte就不知道是多少了
所以要 配合 内存流使用 :相当于 把这些字节扔进 byte[]里边 ,这样就会保证这个数据无偏差。
2.那么假如说我要混存 int short byte boolean char float double 怎么办?
那就要记住 存放的顺序 不然就 张冠李戴了。
2.再来看一下 这个 DataInputStream.class
public
class DataInputStream extends FilterInputStream implements DataInput {
public DataInputStream(InputStream in) {
super(in);
}
/**
* working arrays initialized on demand by readUTF
*/
private byte new byte[80];
private char chararr[] = new char[80];
public final int read(byte b[]) throws IOException {
return in.read(b, 0, b.length);
}
public final int read(byte b[], int off, int len) throws IOException {
return in.read(b, off, len);
}
public final void readFully(byte b[]) throws IOException {
readFully(b, 0, b.length);
}
public final void readFully(byte b[], int off, int len) throws IOException {
if (len < 0)
throw new IndexOutOfBoundsException();
int n = 0;
while (n < len) {
int count = in.read(b, off + n, len - n);
if (count < 0)
throw new EOFException();
n += count;
}
}
public final int skipBytes(int n) throws IOException {
int total = 0;
int cur = 0;
while ((total<n) && ((cur = (int) in.skip(n-total)) > 0)) {
total += cur;
}
return total;
}
/**
* 这下边的read某种类型的方法就是制定把读进去多少个byte然后转成
*
* 由此可见 DataIOStream的好处 : 制定读取协议
* 我可以 指定 读多少个byte 作为int 读多少个byte作为short
*/
public final boolean readBoolean() throws IOException {
int ch = in.read();
if (ch < 0)
throw new EOFException();
return (ch != 0);
}
public final byte readByte() throws IOException {
int ch = in.read();
if (ch < 0)
throw new EOFException();
return (byte)(ch);
}
public final int readUnsignedByte() throws IOException {
int ch = in.read();
if (ch < 0)
throw new EOFException();
return ch;
}
public final short readShort() throws IOException {
int ch1 = in.read();
int ch2 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (short)((ch1 << 8) + (ch2 << 0));
}
public final int readUnsignedShort() throws IOException {
int ch1 = in.read();
int ch2 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (ch1 << 8) + (ch2 << 0);
}
public final char readChar() throws IOException {
int ch1 = in.read();
int ch2 = in.read();
if ((ch1 | ch2) < 0)
throw new EOFException();
return (char)((ch1 << 8) + (ch2 << 0));
}
public final int readInt() throws IOException {
int ch1 = in.read();
int ch2 = in.read();
int ch3 = in.read();
int ch4 = in.read();
if ((ch1 | ch2 | ch3 | ch4) < 0)
throw new EOFException();
return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
}
private byte readBuffer[] = new byte[8];
public final long readLong() throws IOException {
readFully(readBuffer, 0, 8);
return (((long)readBuffer[0] << 56) +
((long)(readBuffer[1] & 255) << 48) +
((long)(readBuffer[2] & 255) << 40) +
((long)(readBuffer[3] & 255) << 32) +
((long)(readBuffer[4] & 255) << 24) +
((readBuffer[5] & 255) << 16) +
((readBuffer[6] & 255) << 8) +
((readBuffer[7] & 255) << 0));
}
/**
*
*/
public final float readFloat() throws IOException {
return Float.intBitsToFloat(readInt());
}
/**
*
*/
public final double readDouble() throws IOException {
return Double.longBitsToDouble(readLong());
}
private char lineBuffer[];
/**
*
*/
@Deprecated
public final String readLine() throws IOException {
char buf[] = lineBuffer;
if (buf == null) {
buf = lineBuffer = new char[128];
}
int room = buf.length;
int offset = 0;
int c;
loop: while (true) {
switch (c = in.read()) {
case -1:
case ‘\n‘:
break loop;
case ‘\r‘:
int c2 = in.read();
if ((c2 != ‘\n‘) && (c2 != -1)) {
if (!(in instanceof PushbackInputStream)) {
this.in = new PushbackInputStream(in);
}
((PushbackInputStream)in).unread(c2);
}
break loop;
default:
if (--room < 0) {
buf = new char[offset + 128];
room = buf.length - offset - 1;
System.arraycopy(lineBuffer, 0, buf, 0, offset);
lineBuffer = buf;
}
buf[offset++] = (char) c;
break;
}
}
if ((c == -1) && (offset == 0)) {
return null;
}
return String.copyValueOf(buf, 0, offset);
}
public final String readUTF() throws IOException {
return readUTF(this);
}
public final static String readUTF(DataInput in) throws IOException {
int utflen = in.readUnsignedShort();
byte[] bytearr = null;
char[] chararr = null;
if (in instanceof DataInputStream) {
DataInputStream dis = (DataInputStream)in;
if (dis.length < utflen){
dis.new byte[utflen*2];
dis.chararr = new char[utflen*2];
}
chararr = dis.chararr;
bytearr = dis. } else {
bytearr = new byte[utflen];
chararr = new char[utflen];
}
int c, char2, char3;
int count = 0;
int chararr_count=0;
in.readFully(bytearr, 0, utflen);
while (count < utflen) {
c = (int) bytearr[count] & 0xff;
if (c > 127) break;
count++;
chararr[chararr_count++]=(char)c;
}
while (count < utflen) {
c = (int) bytearr[count] & 0xff;
switch (c >> 4) {
case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
/* 0xxxxxxx*/
count++;
chararr[chararr_count++]=(char)c;
break;
case 12: case 13:
/* 110x xxxx 10xx xxxx*/
count += 2;
if (count > utflen)
throw new UTFDataFormatException(
"malformed input: partial character at end");
char2 = (int) bytearr[count-1];
if ((char2 & 0xC0) != 0x80)
throw new UTFDataFormatException(
"malformed input around byte " + count);
chararr[chararr_count++]=(char)(((c & 0x1F) << 6) |
(char2 & 0x3F));
break;
case 14:
/* 1110 xxxx 10xx xxxx 10xx xxxx */
count += 3;
if (count > utflen)
throw new UTFDataFormatException(
"malformed input: partial character at end");
char2 = (int) bytearr[count-2];
char3 = (int) bytearr[count-1];
if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))
throw new UTFDataFormatException(
"malformed input around byte " + (count-1));
chararr[chararr_count++]=(char)(((c & 0x0F) << 12) |
((char2 & 0x3F) << 6) |
((char3 & 0x3F) << 0));
break;
default:
/* 10xx xxxx, 1111 xxxx */
throw new UTFDataFormatException(
"malformed input around byte " + count);
}
}
// The number of chars produced may be less than utflen
return new String(chararr, 0, chararr_count);
}
}
作业:
1.把 一个数 用write某种类型的方法写进一个文本文件 再读取出来看看是什么效果
2.制定一套协议 完成信息 的传输
[源码]DataIOStream 数据流 处理基本数据类型的流
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