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GH-41044: [C++] formatting.h: Make sure space is allocated for the 'Z' when formatting timestamps #41045

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Merged
felipecrv merged 3 commits into from
Apr 6, 2024
Merged

GH-41044: [C++] formatting.h: Make sure space is allocated for the 'Z' when formatting timestamps #41045

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e9b04fe
formatting.h: Clarify meaning of cursor in FormatOneChar
felipecrv Apr 5, 2024
87c2d49
formatting_util_test.cc: Add a test case that uses all the bytes in f…
felipecrv Apr 5, 2024
d3afed7
formatting.h: Make sure space is allocated for the 'Z' in formatted t…
felipecrv Apr 5, 2024
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11 changes: 8 additions & 3 deletions cpp/src/arrow/util/formatting.h
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Original file line number Diff line number Diff line change
Expand Up @@ -126,8 +126,10 @@ namespace detail {
ARROW_EXPORT extern const char digit_pairs[];

// Based on fmtlib's format_int class:
// Write digits from right to left into a stack allocated buffer
inline void FormatOneChar(char c, char** cursor) { *--*cursor = c; }
// Write digits from right to left into a stack allocated buffer.
// \pre *cursor points to the byte after the one that will be written.
// \post *cursor points to the byte that was written.
inline void FormatOneChar(char c, char** cursor) { *(--(*cursor)) = c; }

template <typename Int>
void FormatOneDigit(Int value, char** cursor) {
Expand Down Expand Up @@ -326,6 +328,7 @@ class StringFormatter<DoubleType> : public FloatToStringFormatterMixin<DoubleTyp
namespace detail {

constexpr size_t BufferSizeYYYY_MM_DD() {
// "-"? "99999-12-31"
return 1 + detail::Digits10(99999) + 1 + detail::Digits10(12) + 1 +
detail::Digits10(31);
}
Expand All @@ -352,6 +355,7 @@ inline void FormatYYYY_MM_DD(arrow_vendored::date::year_month_day ymd, char** cu

template <typename Duration>
constexpr size_t BufferSizeHH_MM_SS() {
// "23:59:59" ("." "9"+)?
return detail::Digits10(23) + 1 + detail::Digits10(59) + 1 + detail::Digits10(59) + 1 +
detail::Digits10(Duration::period::den) - 1;
}
Expand Down Expand Up @@ -505,8 +509,9 @@ class StringFormatter<TimestampType> {
timepoint_days -= days(1);
}

// YYYY_MM_DD " " HH_MM_SS "Z"?
constexpr size_t buffer_size =
detail::BufferSizeYYYY_MM_DD() + 1 + detail::BufferSizeHH_MM_SS<Duration>();
detail::BufferSizeYYYY_MM_DD() + 1 + detail::BufferSizeHH_MM_SS<Duration>() + 1;

std::array<char, buffer_size> buffer;
char* cursor = buffer.data() + buffer_size;
Expand Down
8 changes: 8 additions & 0 deletions cpp/src/arrow/util/formatting_util_test.cc
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Expand Up @@ -533,6 +533,14 @@ TEST(Formatting, Timestamp) {
}
}

{
constexpr int64_t kMillisInDay = 24 * 60 * 60 * 1000;
auto ty = timestamp(TimeUnit::MILLI, "+01:00");
StringFormatter<TimestampType> formatter(ty.get());
AssertFormatting(formatter, -15000 * 365 * kMillisInDay + 1,
"-13021-12-17 00:00:00.001Z");
}

{
auto ty = timestamp(TimeUnit::MILLI, "Pacific/Maruesas");
StringFormatter<TimestampType> formatter(ty.get());
Expand Down