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Catch both old uppercase 5-char hash and newer lowercase 5-char hash when migrating to new hash (#1552)

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Co-authored-by: Oleksii Holub <1935960+Tyrrrz@users.noreply.github.com>
This commit is contained in:
Nick
2026-06-20 20:16:48 +09:00
committed by GitHub
parent 97485c280b
commit 8bc9fe7c72
1 changed files with 33 additions and 22 deletions
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55
DiscordChatExporter.Core/Exporting/ExportAssetDownloader.cs
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@@ -38,23 +38,28 @@ internal partial class ExportAssetDownloader(string workingDirPath, bool reuse)
return _previousPathsByUrl[url] = filePath;
// Check for a file cached by the legacy naming scheme (5-char hash) and rename it
// to the new naming scheme to preserve backwards compatibility with existing exports
// to the new naming scheme to preserve backwards compatibility with existing exports.
// This will catch both the 5-char lowercase hash and the 5-char uppercase hash variants.
if (reuse)
{
var legacyFilePath = Path.Combine(workingDirPath, GetLegacyFileNameFromUrl(url));
if (File.Exists(legacyFilePath))
var legacyFileNames = GetLegacyFileNamesFromUrl(url);
foreach (var legacyFileName in legacyFileNames)
{
// Overwrite in case the destination file was created concurrently between our
// earlier existence check and this move operation
try
var legacyFilePath = Path.Combine(workingDirPath, legacyFileName);
if (File.Exists(legacyFilePath))
{
File.Move(legacyFilePath, filePath, overwrite: true);
return _previousPathsByUrl[url] = filePath;
}
catch (IOException)
{
// The legacy file was moved or deleted concurrently or something else happened.
// Upgrading old files is not crucial, so we can just move on.
// Overwrite in case the destination file was created concurrently between our
// earlier existence check and this move operation
try
{
File.Move(legacyFilePath, filePath, true);
return _previousPathsByUrl[url] = filePath;
}
catch (IOException)
{
// The legacy file was moved or deleted concurrently or something else happened.
// Upgrading old files is not crucial, so we can just move on.
}
}
}
}
@@ -137,13 +142,19 @@ internal partial class ExportAssetDownloader
);
// Legacy naming used a 5-char hash, kept for backwards compatibility with existing exports
private static string GetLegacyFileNameFromUrl(string url) =>
GetFileNameFromUrl(
url,
SHA256
.HashData(Encoding.UTF8.GetBytes(NormalizeUrl(url)))
.Pipe(Convert.ToHexStringLower)
// 5 chars = 20 bits, reaches 1% collision probability at ~145 files
.Truncate(5)
);
private static IReadOnlyList<string> GetLegacyFileNamesFromUrl(string url)
{
var hashData = SHA256.HashData(Encoding.UTF8.GetBytes(NormalizeUrl(url)));
return
[
// Lowercase variant (introduced in 2.46.1)
GetFileNameFromUrl(url, Convert.ToHexStringLower(hashData).Truncate(5)),
// Uppercase variant (original)
GetFileNameFromUrl(
url,
Convert.ToHexString(hashData).Truncate(5)
)
];
}
}