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refactor(file_scanner): improve comments and error checking

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This commit is contained in:
Marcus Holland-Moritz 2024-04-29 09:17:32 +02:00
parent 8c3334cdc8
commit 2c5ef8ff23
1 changed files with 15 additions and 9 deletions
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24
src/dwarfs/file_scanner.cpp
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@ -288,6 +288,9 @@ void file_scanner_<LoggerPolicy>::scan_dedupe(file* p) {
uint64_t size = p->size(); uint64_t size = p->size();
uint64_t start_hash{0}; uint64_t start_hash{0};
LOG_TRACE << "scanning file " << p->path_as_string() << " [size=" << size
<< "]";
if (size >= kLargeFileThreshold) { if (size >= kLargeFileThreshold) {
if (!p->is_invalid()) { if (!p->is_invalid()) {
try { try {
@ -311,7 +314,7 @@ void file_scanner_<LoggerPolicy>::scan_dedupe(file* p) {
inode::files_vector()); inode::files_vector());
if (is_new) { if (is_new) {
// A file size that has never been seen before. We can safely // A file (size, start_hash) that has never been seen before. We can safely
// create a new inode and we'll keep track of the file. // create a new inode and we'll keep track of the file.
it->second.push_back(p); it->second.push_back(p);
@ -320,13 +323,13 @@ void file_scanner_<LoggerPolicy>::scan_dedupe(file* p) {
add_inode(p, __LINE__); add_inode(p, __LINE__);
} }
} else { } else {
// This file size has been seen before, so this is potentially // This file (size, start_hash) has been seen before, so this is potentially
// a duplicate. // a duplicate.
std::shared_ptr<condition_barrier> cv; std::shared_ptr<condition_barrier> cv;
if (it->second.empty()) { if (it->second.empty()) {
// This is any file of this size after the second file // This is any file of this (size, start_hash) after the second file
std::lock_guard lock(mx_); std::lock_guard lock(mx_);
if (auto ffi = first_file_hashed_.find(size); if (auto ffi = first_file_hashed_.find(size);
@ -334,16 +337,18 @@ void file_scanner_<LoggerPolicy>::scan_dedupe(file* p) {
cv = ffi->second; cv = ffi->second;
} }
} else { } else {
// This is the second file of this size. We now need to hash // This is the second file of this (size, start_hash). We now need to
// both the first and second file and ensure that the first // hash both the first and second file and ensure that the first file's
// file's hash is stored to `by_hash_` first. We set up a // hash is stored to `by_hash_` first. We set up a condition variable
// condition variable to synchronize insertion into `by_hash_`. // to synchronize insertion into `by_hash_`.
cv = std::make_shared<condition_barrier>(); cv = std::make_shared<condition_barrier>();
{ {
std::lock_guard lock(mx_); std::lock_guard lock(mx_);
first_file_hashed_.emplace(size, cv); DWARFS_CHECK(
first_file_hashed_.emplace(size, cv).second,
"internal error: first file condition barrier already exists");
} }
// Add a job for the first file // Add a job for the first file
@ -359,7 +364,8 @@ void file_scanner_<LoggerPolicy>::scan_dedupe(file* p) {
by_raw_inode_[p->raw_inode_num()].push_back(p); by_raw_inode_[p->raw_inode_num()].push_back(p);
} else { } else {
auto& ref = by_hash_[p->hash()]; auto& ref = by_hash_[p->hash()];
assert(ref.empty()); DWARFS_CHECK(ref.empty(),
"internal error: unexpected existing hash");
ref.push_back(p); ref.push_back(p);
} }