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Changing the location where the shared strings cache is stored #898

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Merged
michelebastione merged 1 commit into from
Nov 12, 2025
Merged

Changing the location where the shared strings cache is stored #898

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2 changes: 1 addition & 1 deletion src/MiniExcel/OpenXml/ExcelOpenXmlSheetReader.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -449,7 +449,7 @@ private void SetSharedStrings()
var idx = 0;
if (_config.EnableSharedStringCache && sharedStringsEntry.Length >= _config.SharedStringCacheSize)
{
_sharedStrings = new SharedStringsDiskCache();
_sharedStrings = new SharedStringsDiskCache(_config.SharedStringCachePath);
foreach (var sharedString in XmlReaderHelper.GetSharedStrings(stream, _ns))
_sharedStrings[idx++] = sharedString;
}
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8 changes: 8 additions & 0 deletions src/MiniExcel/OpenXml/OpenXmlConfiguration.cs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
using System.IO;
using MiniExcelLibs.Attributes;

namespace MiniExcelLibs.OpenXml
Expand All @@ -18,6 +19,13 @@ public class OpenXmlConfiguration : Configuration
public bool IgnoreEmptyRows { get; set; } = false;
public bool EnableSharedStringCache { get; set; } = true;
public long SharedStringCacheSize { get; set; } = 5 * 1024 * 1024;

/// <summary>
/// The directory where the shared strings cache files are stored.
/// It defaults to the system's temporary folder.
/// </summary>
public string SharedStringCachePath { get; set; } = Path.GetTempPath();

public OpenXmlStyleOptions StyleOptions { get; set; } = new OpenXmlStyleOptions();
public DynamicExcelSheet[] DynamicSheets { get; set; }
public bool EnableWriteFilePath{ get; set; } = true;
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17 changes: 10 additions & 7 deletions src/MiniExcel/OpenXml/SharedStringsDiskCache.cs
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Expand Up @@ -23,12 +23,15 @@ public bool ContainsKey(int key)
return key <= _maxIndx;
}

public SharedStringsDiskCache()
public SharedStringsDiskCache(string sharedStringsCacheDir)
{
var path = $"{Guid.NewGuid().ToString()}_miniexcelcache";
_positionFs = new FileStream($"{path}_position", FileMode.OpenOrCreate);
_lengthFs = new FileStream($"{path}_length", FileMode.OpenOrCreate);
_valueFs = new FileStream($"{path}_data", FileMode.OpenOrCreate);
if (string.IsNullOrWhiteSpace(sharedStringsCacheDir) || !Directory.Exists(sharedStringsCacheDir))
throw new DirectoryNotFoundException($"\"{sharedStringsCacheDir}\" is not a valid directory for the shared strings cache.");

var prefix = $"{Path.GetRandomFileName()}_miniexcel";
_positionFs = new FileStream(Path.Combine(sharedStringsCacheDir, $"{prefix}_position"), FileMode.OpenOrCreate);
_lengthFs = new FileStream(Path.Combine(sharedStringsCacheDir, $"{prefix}_length"), FileMode.OpenOrCreate);
_valueFs = new FileStream(Path.Combine(sharedStringsCacheDir, $"{prefix}_data"), FileMode.OpenOrCreate);
Comment on lines +32 to +34
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@gemini-code-assist gemini-code-assist bot Nov 12, 2025

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medium

Using FileMode.OpenOrCreate with a randomly generated file name could potentially lead to issues if a file with the same name already exists from a previous unclean shutdown. This might cause the cache to be created with incorrect data. To ensure that a new, empty file is always created, it would be safer to use FileMode.CreateNew. This mode throws an IOException if the file already exists, which would prevent accidental data corruption. Given the low probability of a name collision, this change would make the cache creation more robust.

            _positionFs = new FileStream(Path.Combine(sharedStringsCacheDir, $"{prefix}_position"), FileMode.CreateNew);
            _lengthFs = new FileStream(Path.Combine(sharedStringsCacheDir, $"{prefix}_length"), FileMode.CreateNew);
            _valueFs = new FileStream(Path.Combine(sharedStringsCacheDir, $"{prefix}_data"), FileMode.CreateNew);

}

// index must start with 0-N
Expand Down Expand Up @@ -140,13 +143,13 @@ public bool Remove(KeyValuePair<int, string> item)

public IEnumerator<KeyValuePair<int, string>> GetEnumerator()
{
for (int i = 0; i < _maxIndx; i++)
for (int i = 0; i <= _maxIndx; i++)
yield return new KeyValuePair<int, string>(i, this[i]);
}

IEnumerator IEnumerable.GetEnumerator()
{
for (int i = 0; i < _maxIndx; i++)
for (int i = 0; i <= _maxIndx; i++)
yield return this[i];
}

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4 changes: 2 additions & 2 deletions tests/MiniExcelTests/MiniExcelIssueTests.cs
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Expand Up @@ -413,7 +413,7 @@ public void TestIssue360()
public void TestIssue117()
{
{
var cache = new SharedStringsDiskCache();
var cache = new SharedStringsDiskCache(Path.GetTempPath());
for (int i = 0; i < 100; i++)
{
cache[i] = i.ToString();
Expand All @@ -425,7 +425,7 @@ public void TestIssue117()
Assert.Equal(100, cache.Count);
}
{
var cache = new SharedStringsDiskCache();
var cache = new SharedStringsDiskCache(Path.GetTempPath());
Assert.Empty(cache);
}
}
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