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// file : libbuild2/file-cache.cxx -*- C++ -*-
// license : MIT; see accompanying LICENSE file
#include <libbuild2/file-cache.hxx>
#include <libbutl/lz4.hxx>
#include <libbuild2/filesystem.hxx> // exists(), try_rmfile()
#include <libbuild2/diagnostics.hxx>
using namespace butl;
namespace build2
{
// file_cache::entry
//
file_cache::write file_cache::entry::
init_new ()
{
assert (state_ == uninit);
// Remove stale compressed file if it exists. While not strictly necessary
// (since the presence of the new uncompressed file will render the
// compressed one invalid), this makes things cleaner in case we don't get
// to compressing the new file (for example, if we fail and leave the
// uncompressed file behind for troubleshooting).
//
if (!comp_path_.empty ())
try_rmfile_ignore_error (comp_path_);
pin ();
return write (*this);
}
void file_cache::entry::
init_existing ()
{
assert (state_ == uninit);
// Determine the cache state from the filesystem state.
//
// First check for the uncompressed file. Its presence means that the
// compressed file, if exists, is invalid and we clean it up, similar to
// init_new().
//
// Note that if compression is disabled, we omit the check assuming the
// the uncompressed file exists.
//
if (!comp_path_.empty ())
{
if (exists (path_))
{
try_rmfile_ignore_error (comp_path_);
state_ = uncomp;
}
else if (exists (comp_path_))
{
state_ = comp;
}
else
fail << comp_path_ << " (or its uncompressed variant) does not exist" <<
info << "consider cleaning the build state";
}
else
state_ = uncomp;
}
void file_cache::entry::
preempt ()
{
// Note that this function is called from destructors so it's best if it
// doesn't throw.
//
switch (state_)
{
case uncomp:
{
if (!compress ())
break;
state_ = decomp; // We now have both.
}
// Fall through.
case decomp:
{
if (try_rmfile_ignore_error (path_))
state_ = comp;
break;
}
default:
assert (false);
}
}
bool file_cache::entry::
compress ()
{
tracer trace ("file_cache::entry::compress");
try
{
ifdstream ifs (path_, fdopen_mode::binary, ifdstream::badbit);
ofdstream ofs (comp_path_, fdopen_mode::binary);
uint64_t n (fdstat (ifs.fd ()).size);
// Experience shows that for the type of content we typically cache
// using 1MB blocks results in almost the same comression as for 4MB.
//
uint64_t cn (lz4::compress (ofs, ifs,
1 /* compression_level (fastest) */,
6 /* block_size_id (1MB) */,
n));
ofs.close ();
l6 ([&]{trace << "compressed " << path_ << " to "
<< (cn * 100 / n) << '%';});
}
catch (const std::exception& e)
{
l5 ([&]{trace << "unable to compress " << path_ << ": " << e;});
try_rmfile_ignore_error (comp_path_);
return false;
}
return true;
}
void file_cache::entry::
decompress ()
{
try
{
ifdstream ifs (comp_path_, fdopen_mode::binary, ifdstream::badbit);
ofdstream ofs (path_, fdopen_mode::binary);
lz4::decompress (ofs, ifs);
ofs.close ();
}
catch (const std::exception& e)
{
fail << "unable to decompress " << comp_path_ << ": " << e <<
info << "consider cleaning the build state";
}
}
void file_cache::entry::
remove ()
{
switch (state_)
{
case uninit:
{
// In this case we are cleaning the filesystem without having any idea
// about its state. As a result, if we couldn't remove the compressed
// file, then we don't attempt to remove the uncompressed file either
// since it could be an indicator that the compressed file is invalid.
//
if (comp_path_.empty () || try_rmfile_ignore_error (comp_path_))
try_rmfile_ignore_error (path_);
break;
}
case uncomp:
{
try_rmfile_ignore_error (path_);
break;
}
case comp:
{
try_rmfile_ignore_error (comp_path_);
break;
}
case decomp:
{
// Both are valid so we are ok with failing to remove either.
//
try_rmfile_ignore_error (comp_path_);
try_rmfile_ignore_error (path_);
break;
}
case null:
assert (false);
}
}
}
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