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Extend ExtractUVarInt to support customizable kMaxVarintLen64 #1757

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Extend ExtractUVarInt to support customizable kMaxVarintLen64 #1757

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5 changes: 2 additions & 3 deletions src/stirling/utils/binary_decoder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,6 @@
namespace px {
namespace stirling {

constexpr int kMaxVarintLen64 = 10;

/**
* Provides functions to extract bytes from a bytes buffer.
Expand Down Expand Up @@ -75,7 +74,7 @@ class BinaryDecoder {
// Extract UVarInt encoded value and return result as uint64_t. The details of this encoding's
// specification can be see in the following link:
// https://cs.opensource.google/go/go/+/refs/tags/go1.20.5:src/encoding/binary/varint.go;l=7-25
StatusOr<uint64_t> ExtractUVarInt() {
StatusOr<uint64_t> ExtractUVarInt(int kMaxVarintLen64 = 10, bool cap_final_byte_val = true) {
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k prefixed variables with camelCase are constants. Since this is a function parameter, it should be snake case and not have a prefix.

We largely follow Google's C++ style guide as mentioned here.

uint64_t x = 0;
uint bits = 0;
int i = 0;
Expand All @@ -85,7 +84,7 @@ class BinaryDecoder {
buf_.remove_prefix(1);

if (b < 0x80) {
if (i == kMaxVarintLen64 - 1 && b > 1) {
if (cap_final_byte_val && i == kMaxVarintLen64 - 1 && b > 1) {
return error::ResourceUnavailable("Insufficient number of bytes.");
}
return x | uint64_t(b) << bits;
Expand Down
37 changes: 37 additions & 0 deletions src/stirling/utils/binary_decoder_test.cc
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Expand Up @@ -92,6 +92,43 @@ TEST(BinaryDecoderTest, ExtractUVarInt) {
}
}

TEST(BinaryDecoderTest, ExtractUVarIntLimit) {
std::vector<std::tuple<std::vector<uint8_t>, uint64_t, uint64_t>> uVarIntsWithLimits = {
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uVarIntsWithLimits should be snake case according to our style guide.

{{0x80, 0x01, 0x00}, 2, 128},
{{0xff, 0x7f, 0x00}, 2, 16383},
{{0xff, 0xff, 0x7f, 0xff}, 3, 2097151},
{{0xC0, 0xC0, 0x04}, 3, 73792},
{{0x80, 0x80, 0x80, 0x01, 0x00}, 4, 2097152},
{{0xff, 0xff, 0xff, 0x7f}, 4, 268435455},
{{0xff, 0xff, 0xff, 0x7f, 0xff}, 4, 268435455},
};

for (auto& p : uVarIntsWithLimits) {
auto data = std::get<0>(p);
auto limit = std::get<1>(p);
auto expected_val = std::get<2>(p);
std::string_view s(reinterpret_cast<char*>(data.data()), data.size());
BinaryDecoder bin_decoder(s);
ASSERT_OK_AND_EQ(bin_decoder.ExtractUVarInt(limit, false), expected_val);
}

std::vector<std::tuple<std::vector<uint8_t>, uint64_t>> uVarIntsWithLimitsOverflow = {
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Same casing change as the earlier comment.

{{0x80}, 1},
{{0x80, 0x80, 0x80, 0x02}, 3},
{{0x80, 0x80, 0x80, 0x80, 0x80}, 4},
{{0x80, 0x80, 0x80, 0x80, 0x02}, 4},
{{0x81, 0x82, 0x83, 0x84, 0x05}, 4}
};

for (auto& p : uVarIntsWithLimitsOverflow) {
auto data = std::get<0>(p);
auto limit = std::get<1>(p);
std::string_view s(reinterpret_cast<char*>(data.data()), data.size());
BinaryDecoder bin_decoder(s);
ASSERT_NOT_OK(bin_decoder.ExtractUVarInt(limit, false));
}
}

TEST(BinaryDecoderTest, ExtractUVarIntOverflow) {
std::vector<std::vector<uint8_t>> uVarInts = {
{0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x02},
Expand Down
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