From 787b4fe586456565c2dda457ad81f1dd420e9249 Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@wolfbeast.com>
Date: Thu, 14 Nov 2019 09:51:07 +0100
Subject: Issue #1288 - Part 2: Add a partial LZ4 decompression routine.

This function never writes beyond `aDest` + `aMaxOutputSize`, and is
therefore protexted against malicious datapackets.
It also ignores unconsumed input upon reaching `aMaxOutputSize` and can
therefore be used for parial decompression of LZ4 input up to a desired
resulting size of decompressed data.
---
 mfbt/Compression.cpp | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

(limited to 'mfbt/Compression.cpp')

diff --git a/mfbt/Compression.cpp b/mfbt/Compression.cpp
index 6be8020a9..5646b56b2 100644
--- a/mfbt/Compression.cpp
+++ b/mfbt/Compression.cpp
@@ -76,3 +76,24 @@ LZ4::decompress(const char* aSource, size_t aInputSize, char* aDest,
   return false;
 }
 
+bool
+LZ4::decompressPartial(const char* aSource, size_t aInputSize, char* aDest,
+                       size_t aMaxOutputSize, size_t* aOutputSize)
+{
+  CheckedInt<int> maxOutputSizeChecked = aMaxOutputSize;
+  MOZ_ASSERT(maxOutputSizeChecked.isValid());
+  CheckedInt<int> inputSizeChecked = aInputSize;
+  MOZ_ASSERT(inputSizeChecked.isValid());
+
+  int ret = LZ4_decompress_safe_partial(aSource, aDest,
+                                        inputSizeChecked.value(),
+                                        maxOutputSizeChecked.value(),
+                                        maxOutputSizeChecked.value());
+  if (ret >= 0) {
+    *aOutputSize = ret;
+    return true;
+  }
+
+  *aOutputSize = 0;
+  return false;
+}
-- 
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