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Fix #1579: no false "changed on disk" warning on a network share

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On a CIFS/SMB share every save asked "Someone else changed the file on
disk", because the size and modification time read straight after
saving can be the client's cached values, not the server's final ones,
and the next save demanded an exact match.

The size and time are still the quick check. When they differ, the file
now counts as changed only if its content differs from what this QET
last read or wrote (a SHA-1 kept at open and after each save). A real
change by someone else still asks; the same bytes with a new time do
not.

tst_changedondisk: sameContentNewTimeSaves fails before and passes
after; the two conflict cases now move a symbol so the content really
changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
ispyisail
2026-10-22 21:36:24 +13:00
parent 149d92545d
commit 3da3a78850
3 changed files with 50 additions and 7 deletions
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sources/qetproject.cpp
+32 -5
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@@ -504,7 +504,7 @@ QETProject::ProjectState QETProject::openFile(QFile *file)
//Extract the content of the xml. The raw bytes are kept : a project
//file without a persisted uuid derives its uuid from them.
const QByteArray content = file->readAll();
rememberDiskState();
rememberDiskState(&content);
//Each folio's text is kept while it is not built (readDiagramsXml()):
//from a .qet only, a .qetz is a zip of parts
if (!content.startsWith("PK\x03\x04"))
@@ -2803,16 +2803,37 @@ QETResult QETProject::writeCopyForOlderVersions(const QString &path)
}
/**
@brief QETProject::rememberDiskState
Remember the size and modification time of the project file, as this QET
has just read or written it. changedOnDisk() compares against them.
@brief diskHash
@return the SHA-1 of @p content, or of the file at @p path when
@p content is null; empty if the file cannot be read
*/
void QETProject::rememberDiskState()
static QByteArray diskHash(const QString &path, const QByteArray *content = nullptr)
{
QCryptographicHash hash(QCryptographicHash::Sha1);
if (content) {
hash.addData(*content);
return hash.result();
}
QFile file(path);
if (!file.open(QIODevice::ReadOnly) || !hash.addData(&file))
return QByteArray();
return hash.result();
}
/**
@brief QETProject::rememberDiskState
Remember the size, modification time and content hash of the project
file, as this QET has just read or written it. changedOnDisk() compares
against them.
@param content the bytes just read from the file, if they are at hand
*/
void QETProject::rememberDiskState(const QByteArray *content)
{
const QFileInfo info(m_file_path);
m_disk_path = m_file_path;
m_disk_size = info.exists() ? info.size() : -1;
m_disk_mtime = info.exists() ? info.lastModified() : QDateTime();
m_disk_hash = info.exists() ? diskHash(m_file_path, content) : QByteArray();
}
/**
@@ -2822,6 +2843,10 @@ void QETProject::rememberDiskState()
last read or wrote: another user, another program or another QET saved
it since. A file that does not exist yet, or one this QET never read
or wrote (Save As to another name), is not a change.
A different size or time alone is not enough: right after a save, a
network share (CIFS with its attribute cache, #1579) can report the size
and time from before the server settled them. The file is a change only
if its content differs from what this QET read or wrote.
*/
bool QETProject::changedOnDisk(QDateTime *when) const
{
@@ -2833,6 +2858,8 @@ bool QETProject::changedOnDisk(QDateTime *when) const
return false;
if (info.size() == m_disk_size && info.lastModified() == m_disk_mtime)
return false;
if (!m_disk_hash.isEmpty() && diskHash(target) == m_disk_hash)
return false;
if (when)
*when = info.lastModified();
return true;