[Support] Add LEB128 support to BinaryStreamReader/Writer.

Summary:
This patch adds support for ULEB128 and SLEB128 encoding and decoding to
BinaryStreamWriter and BinaryStreamReader respectively.

Support for ULEB128/SLEB128 will be used for eh-frame parsing in the JITLink
library currently under development (see https://reviews.llvm.org/D58704).

Reviewers: zturner, dblaikie

Subscribers: kristina, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60810

llvm-svn: 358584

1 files changed, 71 insertions, 0 deletions

diff --git a/llvm/unittests/Support/BinaryStreamTest.cpp b/llvm/unittests/Support/BinaryStreamTest.cpp
index fe574072a11..5291a31013c 100644
--- a/llvm/unittests/Support/BinaryStreamTest.cpp
+++ b/llvm/unittests/Support/BinaryStreamTest.cpp
@@ -610,6 +610,77 @@ TEST_F(BinaryStreamTest, StreamReaderEnum) {
   }
 }
 
+TEST_F(BinaryStreamTest, StreamReaderULEB128) {
+  std::vector<uint64_t> TestValues = {
+      0,                  // Zero
+      0x7F,               // One byte
+      0xFF,               // One byte, all-ones
+      0xAAAA,             // Two bytes
+      0xAAAAAAAA,         // Four bytes
+      0xAAAAAAAAAAAAAAAA, // Eight bytes
+      0xffffffffffffffff  // Eight bytess, all-ones
+  };
+
+  // Conservatively assume a 10-byte encoding for each of our LEB128s, with no
+  // alignment requirement.
+  initializeOutput(10 * TestValues.size(), 1);
+  initializeInputFromOutput(1);
+
+  for (auto &Stream : Streams) {
+    // Write fields.
+    BinaryStreamWriter Writer(*Stream.Output);
+    for (const auto &Value : TestValues)
+      ASSERT_THAT_ERROR(Writer.writeULEB128(Value), Succeeded());
+
+    // Read fields.
+    BinaryStreamReader Reader(*Stream.Input);
+    std::vector<uint64_t> Results;
+    Results.resize(TestValues.size());
+    for (unsigned I = 0; I != TestValues.size(); ++I)
+      ASSERT_THAT_ERROR(Reader.readULEB128(Results[I]), Succeeded());
+
+    for (unsigned I = 0; I != TestValues.size(); ++I)
+      EXPECT_EQ(TestValues[I], Results[I]);
+  }
+}
+
+TEST_F(BinaryStreamTest, StreamReaderSLEB128) {
+  std::vector<int64_t> TestValues = {
+      0,                  // Zero
+      0x7F,               // One byte
+      -0x7F,              // One byte, negative
+      0xFF,               // One byte, all-ones
+      0xAAAA,             // Two bytes
+      -0xAAAA,            // Two bytes, negative
+      0xAAAAAAAA,         // Four bytes
+      -0xAAAAAAAA,        // Four bytes, negative
+      0x2AAAAAAAAAAAAAAA, // Eight bytes
+      -0x7ffffffffffffff  // Eight bytess, negative
+  };
+
+  // Conservatively assume a 10-byte encoding for each of our LEB128s, with no
+  // alignment requirement.
+  initializeOutput(10 * TestValues.size(), 1);
+  initializeInputFromOutput(1);
+
+  for (auto &Stream : Streams) {
+    // Write fields.
+    BinaryStreamWriter Writer(*Stream.Output);
+    for (const auto &Value : TestValues)
+      ASSERT_THAT_ERROR(Writer.writeSLEB128(Value), Succeeded());
+
+    // Read fields.
+    BinaryStreamReader Reader(*Stream.Input);
+    std::vector<int64_t> Results;
+    Results.resize(TestValues.size());
+    for (unsigned I = 0; I != TestValues.size(); ++I)
+      ASSERT_THAT_ERROR(Reader.readSLEB128(Results[I]), Succeeded());
+
+    for (unsigned I = 0; I != TestValues.size(); ++I)
+      EXPECT_EQ(TestValues[I], Results[I]);
+  }
+}
+
 TEST_F(BinaryStreamTest, StreamReaderObject) {
   struct Foo {
     int X;