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Stop using member variables T, N & S in ext2 class (!119) 

FileSystem member variables T, N & S are being used like local variables
in many of the file system specific set_used_sectors() methods.  They
are only used within each set_used_sectors() call and not used to
represent persistent information of a FileSystem interface class or to
pass information between separate methods.  Therefore stop using them
and replace them with local variables instead.

This block of code finds a field in the output and scans the number:
    Glib::ustring::size_type index = output.find("Block count:");
    if (index >= output.length() ||
        sscanf(output.substr(index).c_str(), "Block count: %lld", &T) != 1)
            T = -1;
The if statement says "if leading text is not found or scanning the
number fails then assign -1".  A sequence of two negatives leading to
assigning an error value is hard to understand.  Instead this an
equivalent block from btrfs::set_used_sectors():
    long long total_bytes = -1;
    Glib::ustring::size_type index = output.find("\ntotal_bytes");
    if (index < output.length())
            sscanf(output.substr(index).c_str(), "\ntotal_bytes %lld", &total_bytes);
This assigns a default error value and the if statement says "if leading
text found then scan the number".  Much simpler to understand.
Therefore change the code around to use this same pattern.

Anchor the leading text matches to the start of a new line in the
output where possible.  Just because it's what some of the other file
system's set_used_sectors() methods do (btrfs, reiser4 and xfs) and it
seems like more robust text matching.

Closes !119 -  Tidy-ups for file system interface classes
This commit is contained in:
Mike Fleetwood 2023-10-09 19:33:38 +01:00 committed by Curtis Gedak
parent 92dfbac0d1
commit ef3e1d1cce
1 changed files with 26 additions and 25 deletions
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51
src/ext2.cc
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@ -158,28 +158,28 @@ void ext2::set_used_sectors( Partition & partition )
if ( ! Utils::execute_command( "dumpe2fs -h " + Glib::shell_quote( partition.get_path() ),
output, error, true ) )
{
Glib::ustring::size_type index = output.find( "Block count:" );
if ( index >= output .length() ||
sscanf( output.substr( index ).c_str(), "Block count: %lld", &T ) != 1 )
T = -1 ;
long long block_count = -1;
Glib::ustring::size_type index = output.find("\nBlock count:");
if (index < output.length())
sscanf(output.substr(index).c_str(), "\nBlock count: %lld", &block_count);
index = output .find( "Block size:" ) ;
if ( index >= output.length() ||
sscanf( output.substr( index ).c_str(), "Block size: %lld", &S ) != 1 )
S = -1 ;
long long block_size = -1;
index = output.find("\nBlock size:");
if (index < output.length())
sscanf(output.substr(index).c_str(), "\nBlock size: %lld", &block_size);
long long free_blocks = -1;
if ( partition .busy )
{
Byte_Value ignored ;
Byte_Value fs_free ;
if ( Utils::get_mounted_filesystem_usage( partition .get_mountpoint(),
ignored, fs_free, error ) == 0 )
Byte_Value fs_free_bytes;
if (Utils::get_mounted_filesystem_usage(partition.get_mountpoint(),
ignored, fs_free_bytes, error) == 0)
{
N = fs_free / S;
free_blocks = fs_free_bytes / block_size;
}
else
{
N = -1 ;
partition.push_back_message( error );
}
}
@ -187,35 +187,36 @@ void ext2::set_used_sectors( Partition & partition )
{
// Resize2fs won't shrink a file system smaller than it's own
// estimated minimum size, so use that to derive the free space.
N = -1;
Glib::ustring output2;
Glib::ustring error2;
if ( ! Utils::execute_command( "resize2fs -P " + Glib::shell_quote( partition.get_path() ),
output2, error2, true ) )
{
if ( sscanf( output2.c_str(), "Estimated minimum size of the filesystem: %lld", &N ) == 1 )
N = T - N;
long long minimum_blocks = -1;
sscanf(output2.c_str(), "Estimated minimum size of the filesystem: %lld", &minimum_blocks);
if (minimum_blocks > -1)
free_blocks = block_count - minimum_blocks;
}
// Resize2fs can fail reporting please run fsck first. Fall back
// to reading dumpe2fs output for free space.
if ( N == -1 )
if (free_blocks == -1)
{
index = output.find( "Free blocks:" );
index = output.find("\nFree blocks:");
if ( index < output.length() )
sscanf( output.substr( index ).c_str(), "Free blocks: %lld", &N );
sscanf( output.substr(index).c_str(), "\nFree blocks: %lld", &free_blocks);
}
if ( N == -1 && ! error2.empty() )
partition.push_back_message( error );
if (free_blocks == -1 && error2.empty())
partition.push_back_message( error2 );
}
if ( T > -1 && N > -1 && S > -1 )
if (block_count > -1 && block_size > -1 && free_blocks > -1)
{
Sector fs_size = T * S / partition.sector_size;
Sector fs_free = N * S / partition.sector_size;
Sector fs_size = block_count * block_size / partition.sector_size;
Sector fs_free = free_blocks * block_size / partition.sector_size;
partition.set_sector_usage(fs_size, fs_free);
partition.fs_block_size = S;
partition.fs_block_size = block_size;
}
}
else