Java IO - Data
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Java IO - Data
目录
- Java IO - Data
- 目录
- DataInputStream
- DataOutputStream
DataInputStream 和 DataOutputStream.
DataInputStream
package java.io;/** * data input stream 允许 应用读取 Java 基本数据类型。应用程序使用 data output stream 写入的数据 * 可以在后面使用 data input stream 来读取。 * 线程不安全，需要用户自己保证多线程的安全使用。 */publicclass DataInputStream extends FilterInputStream implements DataInput { public DataInputStream(InputStream in) { super(in); } /** * working arrays initialized on demand by readUTF */ private byte bytearr[] = new byte[80]; private char chararr[] = new char[80]; /** * 从输入流中读取一些字节到字节数组中。返回读取的字节数。 * 阻塞方法。 */ public final int read(byte b[]) throws IOException { return in.read(b, 0, b.length); } /** * 读取最多 len 长度字节的数据到数组。 * 阻塞方法。 */ 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); } /** * 一定要读到 len 长度的数据，不然会抛异常 */ 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; } // 下面这些方法在 RandomAccessFile中已经介绍过了。 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.bytearr.length < utflen){ dis.bytearr = new byte[utflen*2]; dis.chararr = new char[utflen*2]; } chararr = dis.chararr; bytearr = dis.bytearr; } 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); }}DataOutputStream
package java.io;/** * data output stream 允许应用往 output stream 中写入原始类型的数据。 * 应用程序使用 data output stream 写入的数据可以被 data input stream 读取。 */publicclass DataOutputStream extends FilterOutputStream implements DataOutput { /** * 已经写入到 data output stream 的字节数。 */ protected int written; private byte[] bytearr = null; public DataOutputStream(OutputStream out) { super(out); } private void incCount(int value) { int temp = written + value; if (temp < 0) { temp = Integer.MAX_VALUE; } written = temp; } /** * 写入一个字节(只写 低 8 位，高 24 位忽略) */ 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); } public void flush() throws IOException { out.flush(); } public final void writeBoolean(boolean v) throws IOException { out.write(v ? 1 : 0); // 把 boolean 换成了 1 和 0 incCount(1); } public final void writeByte(int v) throws IOException { out.write(v); incCount(1); } // 大端？ public final void writeShort(int v) throws IOException { out.write((v >>> 8) & 0xFF); out.write((v >>> 0) & 0xFF); incCount(2); } // Java 中的 char 是 16 bit 的 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.write((v >>> 24) & 0xFF); out.write((v >>> 16) & 0xFF); out.write((v >>> 8) & 0xFF); out.write((v >>> 0) & 0xFF); incCount(4); } private byte writeBuffer[] = new byte[8]; 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); } 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; }} 0 0
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