251 lines
4.2 KiB
Plaintext
251 lines
4.2 KiB
Plaintext
#------------------------------------------------------------------------------
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# File: RandomAccess.pod -- Documentation for File::RandomAccess
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#
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# Description: Buffer to support random access reading of sequential file
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#
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# Legal: Copyright (c) 2003-2018 Phil Harvey (phil at owl.phy.queensu.ca)
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# This library is free software; you can redistribute it and/or
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# modify it under the same terms as Perl itself.
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#------------------------------------------------------------------------------
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=head1 NAME
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File::RandomAccess - Random access reads of sequential file or scalar
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=head1 SYNOPSIS
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use File::RandomAccess;
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$raf = new File::RandomAccess(\*FILE, $disableSeekTest);
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$raf = new File::RandomAccess(\$data);
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$err = $raf->Seek($pos);
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$num = $raf->Read($buff, $bytes);
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=head1 DESCRIPTION
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Allows random access to sequential file by buffering the file if necessary.
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Also allows access to data in memory to be accessed as if it were a file.
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=head1 METHODS
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=over 4
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=item B<new>
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Creates a new RandomAccess object given a file reference or
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reference to data in memory.
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# Read from open file or pipe
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$raf = new File::RandomAccess(\*FILE);
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# Read from data in memory
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$raf = new File::RandomAccess(\$data);
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object or RandomAccess class name.
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1) File reference or scalar reference.
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2) Flag set if file is already random access (disables automatic SeekTest).
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=item Returns:
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Reference to RandomAccess object.
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=back
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=item B<SeekTest>
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Performs test seek() on file to determine if buffering is necessary. If
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the seek() fails, then the file is buffered to allow random access.
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B<SeekTest>() is automatically called from B<new> unless specified.
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$result = $raf->SeekTest();
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object.
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=item Returns:
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1 if seek test passed (ie. no buffering required).
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=item Notes:
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Must be called before any other i/o.
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=back
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=item B<Tell>
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Get current position in file
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$pos = $raf->Tell();
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object.
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=item Returns:
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Current position in file
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=back
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=item B<Seek>
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Seek to specified position in file. When buffered, this doesn't quite
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behave like seek() since it returns success even if you seek outside the
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limits of the file.
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$success = $raf->Seek($pos, 0);
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object.
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1) Position.
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2) Whence (0=from start, 1=from cur pos, 2=from end).
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=item Returns:
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1 on success, 0 otherwise
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=back
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=item B<Read>
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Read data from the file.
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$num = $raf->Read($buff, 1024);
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object.
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1) Buffer.
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2) Number of bytes to read.
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=item Returns:
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Number of bytes actually read.
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=back
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=item B<ReadLine>
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Read a line from file (end of line is $/).
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object.
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1) Buffer.
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=item Returns:
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Number of bytes read.
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=back
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=item B<Slurp>
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Read whole file into buffer, without changing read pointer.
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object.
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=item Returns:
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Nothing.
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=back
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=item B<BinMode>
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Set binary mode for file.
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object.
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=item Returns:
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Nothing.
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=back
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=item B<Close>
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Close the file and free the buffer.
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=over 4
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=item Inputs:
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0) Reference to RandomAccess object.
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=item Returns:
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Nothing.
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=back
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=back
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=head1 OPTIONS
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=over 4
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=item B<NoBuffer>
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Avoid buffering sequential files.
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$raf->{NoBuffer} = 1;
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When this option is set, old data is purged from the internal buffer before
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a read operation on a sequential file. In this mode, memory requirements
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may be significantly reduced when reading sequential files, but seeking
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backward is limited to within the size of the internal buffer (which will be
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at least as large as the last returned data block), and seeking relative to
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the end of file is not allowed.
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=back
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=head1 AUTHOR
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Copyright 2003-2018 Phil Harvey (phil at owl.phy.queensu.ca)
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This library is free software; you can redistribute it and/or modify it
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under the same terms as Perl itself.
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=head1 SEE ALSO
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L<Image::ExifTool(3pm)|Image::ExifTool>
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=cut
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# end
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