com.htyleo.extsort.util.IOUtil Maven / Gradle / Ivy
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package com.htyleo.extsort.util;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.io.Reader;
import java.io.Writer;
import com.htyleo.extsort.GroupSortedFileReader;
/**
* IO util
*
* @author htyleo
*/
public class IOUtil {
/**
* Repeatedly read forward and skip the current line
* Note that the line separator could be "\n", "\r" or "\r\n"
*
* Example: (The parenthesis indicates the position of RandomAccessFile's pointer)
*
* - Before: "ABC(\n)HIJ" after: "ABC\n(H)IJ"
* - Before: "A(B)C\nHIJ" after: "ABC\n(H)IJ"
* - Before: "A(B)C\rHIJ" after: "ABC\r(H)IJ"
* - Before: "A(B)C\r\nHIJ" after: "ABC\r\n(H)IJ"
* - Before: "A(B)C[EOF]" after: "ABC([EOF])"
*
*
* @param raf After this operation, raf's pointer will be on the right of the next line separator or at EOF
* @return true if we encounter a line separator, false otherwise (i.e. we meet EOF)
* @throws IOException If an I/O error occurs
*/
public static boolean skipNextLine(RandomAccessFile raf) throws IOException {
boolean eol = false;
boolean eof = false;
while (!eol && !eof) {
switch (raf.read()) {
case -1:
eof = true;
break;
case '\n':
eol = true;
break;
case '\r':
eol = true;
long curr = raf.getFilePointer();
if ((raf.read()) != '\n') {
raf.seek(curr);
}
break;
}
}
return eol;
}
/**
* If RandomAccessFile's pointer points to a line separator, repeatedly read forward and skip consecutive blank lines.
* Note that the line separator could be "\n", "\r" or "\r\n"
*
* Example: (The parenthesis indicates the position of RandomAccessFile's pointer)
*
* - before: "ABC(\n)HIJ" after: "ABC\n(H)IJ"
* - before: "ABC(\n)\n\nHIJ" after: "ABC\n\n\n(H)IJ"
* - before: "AB(C)\nHIJ" after: "AB(C)\nHIJ"
*
*
* @param raf If raf does not currently point to a line separator, its pointer is unchanged. Otherwise, after this operation, raf's pointer will be on the right of the last consecutive line separator or at EOF
* @return true if we encounter blank lines, false otherwise (i.e. stay still, or we reached EOF)
* @throws IOException If an I/O error occurs
*/
public static boolean skipNextBlankLines(RandomAccessFile raf) throws IOException {
boolean eol = false;
while (true) {
switch (raf.read()) {
case '\n':
case '\r':
eol = true;
break;
case -1:
return eol;
default:
raf.seek(raf.getFilePointer() - 1);
return eol;
}
}
}
/**
* Repeatedly read backward and skip the current line
* Note that the line separator could be "\n", "\r" or "\r\n"
*
* Example: (the parenthesis indicates the position of the pointer)
*
* - before: "ABC(\n)HIJ" after: "AB(C)\nHIJ"
* - before: "ABC\nH(I)J" after: "AB(C)\nHIJ"
* - before: "ABC\rH(I)J" after: "AB(C)\rHIJ"
* - before: "ABC\r\nH(I)J" after: "AB(C)\r\nHIJ"
* - before: "AB(C)\n" after: 0
*
*
* @param raf After this operation, raf's pointer will be on the left of the previous line separator or at 0
* @return true if we meet a line separator, false otherwise (i.e. we reached the beginning of the file)
* @throws IOException If an I/O error occurs
*/
public static boolean skipPrevLine(RandomAccessFile raf) throws IOException {
while (true) {
switch (raf.read()) {
case '\n':
raf.seek(Math.max(0, raf.getFilePointer() - 2));
long curr = raf.getFilePointer();
if (raf.read() == '\r') {
raf.seek(Math.max(0, raf.getFilePointer() - 2));
} else {
raf.seek(curr);
}
return true;
case '\r':
raf.seek(Math.max(0, raf.getFilePointer() - 2));
return true;
default:
if (raf.getFilePointer() == 1) {
raf.seek(Math.max(0, raf.getFilePointer() - 2));
return false;
}
raf.seek(Math.max(0, raf.getFilePointer() - 2));
}
}
}
/**
* If RandomAccessFile's pointer points to a line separator, repeatedly read backward and skip consecutive blank lines.
* Note that the line separator could be "\n", "\r" or "\r\n"
*
* Example: (the parenthesis indicate the position of the pointer)
*
* - before: "ABC(\n)HIJ" after: "AB(C)\nHIJ"
* - before: "ABC\n\n(\n)HIJ" after: "AB(C)\n\n\nHIJ"
* - before: "ABC\n(H)IJ" after: "ABC\n(H)IJ"
*
*
* @param raf If raf does not currently point to a line separator, its pointer is unchanged. Otherwise, after this operation, raf's pointer will be on the left of the last consecutive line separator or at 0
* @return true if we meet blank lines, false otherwise (i.e. stay still, or we reached the beginning of the file)
* @throws IOException If an I/O error occurs
*/
public static boolean skipPrevBlankLines(RandomAccessFile raf) throws IOException {
boolean eol = false;
while (true) {
switch (raf.read()) {
case '\n':
case '\r':
eol = true;
raf.seek(Math.max(0, raf.getFilePointer() - 2));
if (raf.getFilePointer() == 0) {
return true;
}
break;
case -1:
raf.seek(raf.getFilePointer() - 1);
break;
default:
raf.seek(raf.getFilePointer() - 1);
return eol;
}
}
}
/**
* Unconditionally close a Reader.
*
* Equivalent to {@link Reader#close()}, except any exceptions will be ignored.
* This is typically used in finally blocks.
*
* @param reader the Reader to close, may be null or already closed
*/
public static void closeQuietly(Reader reader) {
try {
if (reader != null) {
reader.close();
}
} catch (IOException ioe) {
// ignore
}
}
/**
* Unconditionally close a Writer.
*
* Equivalent to {@link Writer#close()}, except any exceptions will be ignored.
* This is typically used in finally blocks.
*
* @param writer the Writer to close, may be null or already closed
*/
public static void closeQuietly(Writer writer) {
try {
if (writer != null) {
writer.close();
}
} catch (IOException ioe) {
// ignore
}
}
/**
* Unconditionally close a RandomAccessFile.
*
* Equivalent to {@link RandomAccessFile#close()}, except any exceptions will be ignored.
* This is typically used in finally blocks.
*
* @param raf the RandomAccessFile to close, may be null or already closed
*/
public static void closeQuietly(RandomAccessFile raf) {
try {
if (raf != null) {
raf.close();
}
} catch (IOException ioe) {
// ignore
}
}
/**
* Unconditionally close a GroupSortedFileReader.
*
* Equivalent to {@link GroupSortedFileReader#close()}, except any exceptions will be ignored.
* This is typically used in finally blocks.
*
* @param groupReader the GroupSortedFileReader to close, may be null or already closed
*/
public static void closeQuietly(GroupSortedFileReader groupReader) {
if (groupReader != null) {
groupReader.close();
}
}
}