AntoinePrv commented on code in PR #47294:
URL: https://github.com/apache/arrow/pull/47294#discussion_r2354994158
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cpp/src/arrow/util/bit_util_test.cc:
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@@ -1997,11 +1997,191 @@ TEST(BitUtil, RoundUpToPowerOf2) {
#undef U64
#undef S64
+/// Test the maximum number of bytes needed to write a LEB128 of a give size.
+TEST(LEB128, MaxLEB128ByteLenFor) {
+ EXPECT_EQ(bit_util::kMaxLEB128ByteLenFor<int16_t>, 3);
+ EXPECT_EQ(bit_util::kMaxLEB128ByteLenFor<int32_t>, 5);
+ EXPECT_EQ(bit_util::kMaxLEB128ByteLenFor<int64_t>, 10);
+}
+
+/// Utility function to test LEB128 encoding with known input value and
expected byte
+/// array
+template <typename Int>
+void TestLEB128Encode(Int input_value, const std::vector<uint8_t>&
expected_data,
+ std::size_t buffer_size) {
+ std::vector<uint8_t> buffer(buffer_size);
+ auto bytes_written = bit_util::WriteLEB128(input_value, buffer.data(),
+
static_cast<int32_t>(buffer.size()));
+
+ EXPECT_EQ(bytes_written, expected_data.size());
+ // Encoded data
+ for (std::size_t i = 0; i < expected_data.size(); ++i) {
+ EXPECT_EQ(buffer.at(i), expected_data.at(i));
+ }
+
+ // When the value is successfully encoded, the remaining of the buffer is
untouched
+ if (bytes_written > 0) {
+ for (std::size_t i = bytes_written; i < buffer.size(); ++i) {
+ EXPECT_EQ(buffer.at(i), 0);
+ }
+ }
+}
+
+/// Test encoding to known LEB128 byte sequences with edge cases parameters.
+/// \see LEB128.KnownSuccessfulValues for other known values tested.
+TEST(LEB128, WriteEdgeCases) {
+ // Single byte value 0
+ TestLEB128Encode(0U, {0x00}, 1);
+ // Single byte value 127
+ TestLEB128Encode(127U, {0x7F}, 1);
+ // Three byte value 16384, encoded in larger buffer
+ TestLEB128Encode(16384U, {0x80, 0x80, 0x01}, 10);
+ // Two byte boundary values
+ TestLEB128Encode(129U, {0x81, 0x01}, 2);
+ TestLEB128Encode(16383U, {0xFF, 0x7F}, 2);
+ // Error case: Buffer too small for value 128 (needs 2 bytes but only 1
provided)
+ TestLEB128Encode(128U, {}, 1);
+ // Error case: Buffer too small for uint32_t max (needs 5 bytes but only 4
provided)
+ TestLEB128Encode(4294967295U, {}, 4);
Review Comment:
We have them in `LEB128.KnownSuccessfulValues`.
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