emkornfield commented on a change in pull request #6985:
URL: https://github.com/apache/arrow/pull/6985#discussion_r419855100
##########
File path: cpp/src/arrow/util/bit_util_test.cc
##########
@@ -315,6 +318,115 @@ TEST(FirstTimeBitmapWriter, NormalOperation) {
}
}
+std::string BitmapToString(const uint8_t* bitmap, int64_t bit_count) {
+ return arrow::internal::Bitmap(bitmap, /*offset*/ 0,
/*length=*/bit_count).ToString();
+}
+
+std::string BitmapToString(const std::vector<uint8_t>& bitmap, int64_t
bit_count) {
+ return BitmapToString(bitmap.data(), bit_count);
+}
+
+TEST(FirstTimeBitmapWriter,
AppendWordOffsetOverwritesCorrectBitsOnExistingByte) {
+ auto check_append = [](const std::string& expected_bits, int64_t offset) {
+ std::vector<uint8_t> valid_bits = {0x00};
+ constexpr int64_t kBitsAfterAppend = 8;
+ internal::FirstTimeBitmapWriter writer(valid_bits.data(), offset,
+ /*length=*/(8 * valid_bits.size())
- offset);
+ writer.AppendWord(/*word=*/0xFF, /*number_of_bits=*/kBitsAfterAppend -
offset);
+ writer.Finish();
+ EXPECT_EQ(BitmapToString(valid_bits, kBitsAfterAppend), expected_bits);
+ };
+ check_append("11111111", 0);
+ check_append("01111111", 1);
+ check_append("00111111", 2);
+ check_append("00011111", 3);
+ check_append("00001111", 4);
+ check_append("00000111", 5);
+ check_append("00000011", 6);
+ check_append("00000001", 7);
+}
+
+TEST(FirstTimeBitmapWriter, AppendZeroBitsHasNoImpact) {
+ std::vector<uint8_t> valid_bits(/*count=*/1, 0);
+ internal::FirstTimeBitmapWriter writer(valid_bits.data(), /*start_offset=*/1,
+ /*length=*/valid_bits.size() * 8);
+ writer.AppendWord(/*word=*/0xFF, /*number_of_bits=*/0);
+ writer.AppendWord(/*word=*/0xFF, /*number_of_bits=*/0);
+ writer.AppendWord(/*word=*/0x01, /*number_of_bits=*/1);
+ writer.Finish();
+ EXPECT_EQ(valid_bits[0], 0x2);
+}
+
+TEST(FirstTimeBitmapWriter, AppendLessThenByte) {
Review comment:
fixed.
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