[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
This commit is contained in:
Lang Hames 2019-04-17 15:38:27 +00:00
parent 258a425c69
commit c1106c9b11
5 changed files with 142 additions and 1 deletions

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@ -96,6 +96,18 @@ public:
return Error::success();
}
/// Read an unsigned LEB128 encoded value.
///
/// \returns a success error code if the data was successfully read, otherwise
/// returns an appropriate error code.
Error readULEB128(uint64_t &Dest);
/// Read a signed LEB128 encoded value.
///
/// \returns a success error code if the data was successfully read, otherwise
/// returns an appropriate error code.
Error readSLEB128(int64_t &Dest);
/// Read a null terminated string from \p Dest. Whether a copy occurs depends
/// on the implementation of the underlying stream. Updates the stream's
/// offset to point after the newly read data.

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@ -79,6 +79,20 @@ public:
return writeInteger<U>(static_cast<U>(Num));
}
/// Write the unsigned integer Value to the underlying stream using ULEB128
/// encoding.
///
/// \returns a success error code if the data was successfully written,
/// otherwise returns an appropriate error code.
Error writeULEB128(uint64_t Value);
/// Write the unsigned integer Value to the underlying stream using ULEB128
/// encoding.
///
/// \returns a success error code if the data was successfully written,
/// otherwise returns an appropriate error code.
Error writeSLEB128(int64_t Value);
/// Write the string \p Str to the underlying stream followed by a null
/// terminator. On success, updates the offset so that subsequent writes
/// occur at the next unwritten position. \p Str need not be null terminated

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@ -10,6 +10,7 @@
#include "llvm/Support/BinaryStreamError.h"
#include "llvm/Support/BinaryStreamRef.h"
#include "llvm/Support/LEB128.h"
using namespace llvm;
using endianness = llvm::support::endianness;
@ -40,6 +41,36 @@ Error BinaryStreamReader::readBytes(ArrayRef<uint8_t> &Buffer, uint32_t Size) {
return Error::success();
}
Error BinaryStreamReader::readULEB128(uint64_t &Dest) {
SmallVector<uint8_t, 10> EncodedBytes;
ArrayRef<uint8_t> NextByte;
// Copy the encoded ULEB into the buffer.
do {
if (auto Err = readBytes(NextByte, 1))
return Err;
EncodedBytes.push_back(NextByte[0]);
} while (NextByte[0] & 0x80);
Dest = decodeULEB128(EncodedBytes.begin(), nullptr, EncodedBytes.end());
return Error::success();
}
Error BinaryStreamReader::readSLEB128(int64_t &Dest) {
SmallVector<uint8_t, 10> EncodedBytes;
ArrayRef<uint8_t> NextByte;
// Copy the encoded ULEB into the buffer.
do {
if (auto Err = readBytes(NextByte, 1))
return Err;
EncodedBytes.push_back(NextByte[0]);
} while (NextByte[0] & 0x80);
Dest = decodeSLEB128(EncodedBytes.begin(), nullptr, EncodedBytes.end());
return Error::success();
}
Error BinaryStreamReader::readCString(StringRef &Dest) {
uint32_t OriginalOffset = getOffset();
uint32_t FoundOffset = 0;
@ -145,4 +176,4 @@ BinaryStreamReader::split(uint32_t Off) const {
BinaryStreamReader W1{First};
BinaryStreamReader W2{Second};
return std::make_pair(W1, W2);
}
}

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@ -11,6 +11,7 @@
#include "llvm/Support/BinaryStreamError.h"
#include "llvm/Support/BinaryStreamReader.h"
#include "llvm/Support/BinaryStreamRef.h"
#include "llvm/Support/LEB128.h"
using namespace llvm;
@ -31,6 +32,18 @@ Error BinaryStreamWriter::writeBytes(ArrayRef<uint8_t> Buffer) {
return Error::success();
}
Error BinaryStreamWriter::writeULEB128(uint64_t Value) {
uint8_t EncodedBytes[10] = {0};
unsigned Size = encodeULEB128(Value, &EncodedBytes[0]);
return writeBytes({EncodedBytes, Size});
}
Error BinaryStreamWriter::writeSLEB128(int64_t Value) {
uint8_t EncodedBytes[10] = {0};
unsigned Size = encodeSLEB128(Value, &EncodedBytes[0]);
return writeBytes({EncodedBytes, Size});
}
Error BinaryStreamWriter::writeCString(StringRef Str) {
if (auto EC = writeFixedString(Str))
return EC;

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@ -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;