Document how source ranges work
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@117450 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/InternalsManual.html b/docs/InternalsManual.html
index 2eee5c2..cf89c19 100644
--- a/docs/InternalsManual.html
+++ b/docs/InternalsManual.html
@@ -25,6 +25,7 @@
<li><a href="#Diagnostics">The Diagnostics Subsystem</a></li>
<li><a href="#SourceLocation">The SourceLocation and SourceManager
classes</a></li>
+ <li><a href="#SourceRange">SourceRange and CharSourceRange</a></li>
</ul>
</li>
<li><a href="#libdriver">The Driver Library</a>
@@ -545,6 +546,30 @@
Clang depends on being able to find the original input characters for the token.
This concept maps directly to the "spelling location" for the token.</p>
+
+<!-- ======================================================================= -->
+<h3 id="SourceRange">SourceRange and CharSourceRange</h3>
+<!-- ======================================================================= -->
+<!-- mostly taken from
+ http://lists.cs.uiuc.edu/pipermail/cfe-dev/2010-August/010595.html -->
+
+<p>Clang represents most source ranges by [first, last], where first and last
+each point to the beginning of their respective tokens. For example
+consider the SourceRange of the following statement:</p>
+<pre>
+x = foo + bar;
+^first ^last
+</pre>
+
+<p>To map from this representation to a character-based
+representation, the 'last' location needs to be adjusted to point to
+(or past) the end of that token with either
+<code>Lexer::MeasureTokenLength()</code> or
+<code>Preprocessor::getLocForEndOfToken()</code>. For the rare cases
+where character-level source ranges information is needed we use
+the <code>CharSourceRange</code> class.</p>
+
+
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<h2 id="libdriver">The Driver Library</h2>
<!-- ======================================================================= -->