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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,38 +1,53 @@ | ||
| <h2>Why is this an issue?</h2> | ||
| <p>You cannot assume that any given stream reading call will fill the <code>byte[]</code> passed in to the method with the number of bytes requested. | ||
| Instead, you must check the value returned by the read method to see how many bytes were read. Fail to do so, and you introduce a bug that is both | ||
| harmful and difficult to reproduce.</p> | ||
| <p>This rule raises an issue when a <code>Stream.Read</code> or a <code>Stream.ReadAsync</code> method is called, but the return value is not | ||
| checked.</p> | ||
| <h3>Noncompliant code example</h3> | ||
| <pre> | ||
| public void DoSomething(string fileName) | ||
| <p>Invoking a stream reading method without verifying the number of bytes read can lead to erroneous assumptions. A Stream can represent any I/O | ||
| operation, such as reading a file, network communication, or inter-process communication. As such, it is not guaranteed that the <code>byte[]</code> | ||
| passed into the method will be filled with the requested number of bytes. Therefore, inspecting the value returned by the reading method is important | ||
| to ensure the number of bytes read.</p> | ||
| <p>Neglecting the returned length read can result in a bug that is difficult to reproduce.</p> | ||
| <p>This rule raises an issue when the returned value is ignored for the following methods:</p> | ||
| <ul> | ||
| <li> <a href="https://learn.microsoft.com/en-us/dotnet/api/system.io.stream.read">Stream.Read</a> </li> | ||
| <li> <a href="https://learn.microsoft.com/en-us/dotnet/api/system.io.stream.readasync">Stream.ReadAsync</a> </li> | ||
| <li> <a href="https://learn.microsoft.com/en-us/dotnet/api/system.io.stream.readatleast">Stream.ReadAtLeast</a> </li> | ||
| <li> <a href="https://learn.microsoft.com/en-us/dotnet/api/system.io.stream.readatleastasync">Stream.ReadAtLeastAsync</a> </li> | ||
| </ul> | ||
| <h2>How to fix it</h2> | ||
| <p>Check the return value of stream reading methods to verify the actual number of bytes read, and use this value when processing the data to avoid | ||
| potential bugs.</p> | ||
| <h3>Code examples</h3> | ||
| <h4>Noncompliant code example</h4> | ||
| <pre data-diff-id="1" data-diff-type="noncompliant"> | ||
| public byte[] ReadFile(string fileName) | ||
| { | ||
| using (var stream = File.Open(fileName, FileMode.Open)) | ||
| { | ||
| using var stream = File.Open(fileName, FileMode.Open); | ||
| var result = new byte[stream.Length]; | ||
|
|
||
| stream.Read(result, 0, (int)stream.Length); // Noncompliant | ||
| // ... do something with result | ||
| } | ||
|
|
||
| return result; | ||
| } | ||
| </pre> | ||
| <h3>Compliant solution</h3> | ||
| <pre> | ||
| public void DoSomething(string fileName) | ||
| <h4>Compliant solution</h4> | ||
| <pre data-diff-id="1" data-diff-type="compliant"> | ||
| public byte[] ReadFile(string fileName) | ||
| { | ||
| using (var stream = File.Open(fileName, FileMode.Open)) | ||
| { | ||
| using var stream = File.Open(fileName, FileMode.Open); | ||
| using var ms = new MemoryStream(); | ||
| var buffer = new byte[1024]; | ||
| using (var ms = new MemoryStream()) | ||
| int read; | ||
|
|
||
| while ((read = stream.Read(buffer, 0, buffer.Length)) > 0) | ||
| { | ||
| int read; | ||
| while ((read = stream.Read(buffer, 0, buffer.Length)) > 0) | ||
| { | ||
| ms.Write(buffer, 0, read); | ||
| } | ||
| // ... do something with ms | ||
| ms.Write(buffer, 0, read); | ||
| } | ||
| } | ||
|
|
||
| return ms.ToArray(); | ||
| } | ||
| </pre> | ||
| <h2>Resources</h2> | ||
| <h3>Documentation</h3> | ||
| <ul> | ||
| <li> Microsoft Learn - <a href="https://learn.microsoft.com/en-us/dotnet/api/system.io.stream.read">Stream.Read Method</a> </li> | ||
| <li> Microsoft Learn - <a href="https://learn.microsoft.com/en-us/dotnet/api/system.io.stream.readasync">Stream.ReadAsync Method</a> </li> | ||
| </ul> | ||
|
|
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