github.com/jimmyx0x/go-ethereum@v1.10.28/core/rawdb/freezer_utils.go (about)

     1  // Copyright 2022 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package rawdb
    18  
    19  import (
    20  	"io"
    21  	"os"
    22  	"path/filepath"
    23  )
    24  
    25  // copyFrom copies data from 'srcPath' at offset 'offset' into 'destPath'.
    26  // The 'destPath' is created if it doesn't exist, otherwise it is overwritten.
    27  // Before the copy is executed, there is a callback can be registered to
    28  // manipulate the dest file.
    29  // It is perfectly valid to have destPath == srcPath.
    30  func copyFrom(srcPath, destPath string, offset uint64, before func(f *os.File) error) error {
    31  	// Create a temp file in the same dir where we want it to wind up
    32  	f, err := os.CreateTemp(filepath.Dir(destPath), "*")
    33  	if err != nil {
    34  		return err
    35  	}
    36  	fname := f.Name()
    37  
    38  	// Clean up the leftover file
    39  	defer func() {
    40  		if f != nil {
    41  			f.Close()
    42  		}
    43  		os.Remove(fname)
    44  	}()
    45  	// Apply the given function if it's not nil before we copy
    46  	// the content from the src.
    47  	if before != nil {
    48  		if err := before(f); err != nil {
    49  			return err
    50  		}
    51  	}
    52  	// Open the source file
    53  	src, err := os.Open(srcPath)
    54  	if err != nil {
    55  		return err
    56  	}
    57  	if _, err = src.Seek(int64(offset), 0); err != nil {
    58  		src.Close()
    59  		return err
    60  	}
    61  	// io.Copy uses 32K buffer internally.
    62  	_, err = io.Copy(f, src)
    63  	if err != nil {
    64  		src.Close()
    65  		return err
    66  	}
    67  	// Rename the temporary file to the specified dest name.
    68  	// src may be same as dest, so needs to be closed before
    69  	// we do the final move.
    70  	src.Close()
    71  
    72  	if err := f.Close(); err != nil {
    73  		return err
    74  	}
    75  	f = nil
    76  
    77  	if err := os.Rename(fname, destPath); err != nil {
    78  		return err
    79  	}
    80  	return nil
    81  }
    82  
    83  // openFreezerFileForAppend opens a freezer table file and seeks to the end
    84  func openFreezerFileForAppend(filename string) (*os.File, error) {
    85  	// Open the file without the O_APPEND flag
    86  	// because it has differing behaviour during Truncate operations
    87  	// on different OS's
    88  	file, err := os.OpenFile(filename, os.O_RDWR|os.O_CREATE, 0644)
    89  	if err != nil {
    90  		return nil, err
    91  	}
    92  	// Seek to end for append
    93  	if _, err = file.Seek(0, io.SeekEnd); err != nil {
    94  		return nil, err
    95  	}
    96  	return file, nil
    97  }
    98  
    99  // openFreezerFileForReadOnly opens a freezer table file for read only access
   100  func openFreezerFileForReadOnly(filename string) (*os.File, error) {
   101  	return os.OpenFile(filename, os.O_RDONLY, 0644)
   102  }
   103  
   104  // openFreezerFileTruncated opens a freezer table making sure it is truncated
   105  func openFreezerFileTruncated(filename string) (*os.File, error) {
   106  	return os.OpenFile(filename, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
   107  }
   108  
   109  // truncateFreezerFile resizes a freezer table file and seeks to the end
   110  func truncateFreezerFile(file *os.File, size int64) error {
   111  	if err := file.Truncate(size); err != nil {
   112  		return err
   113  	}
   114  	// Seek to end for append
   115  	if _, err := file.Seek(0, io.SeekEnd); err != nil {
   116  		return err
   117  	}
   118  	return nil
   119  }