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fix: parquet pre-1970 DATE/TIMESTAMP panic (Issue #235) #246

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Merged
vmvarela merged 1 commit into from
Sep 12, 2026
Merged

fix: parquet pre-1970 DATE/TIMESTAMP panic (Issue #235) #246

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25 changes: 22 additions & 3 deletions src/parquet.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -16,10 +16,15 @@ fn isLeapYear(year: i32) bool {
return @rem(year, 4) == 0 and (@rem(year, 100) != 0 or @rem(year, 400) == 0);
}

// ponytail: Gregorian calendar only, no Julian/Gregorian switch. Non-negative epoch days only.
// ponytail: Gregorian calendar only, no Julian/Gregorian switch. Years < 0 or > 9999 unsupported.
fn epochDaysToIso(days: i32, buf: *[10]u8) []const u8 {
var y: i32 = 1970;
var d = days;
// ponytail: walk backwards for pre-1970 dates (Issue #235)
while (d < 0) {
y -= 1;
d += if (isLeapYear(y)) 366 else 365;
}
while (true) {
const days_in_year: i32 = if (isLeapYear(y)) 366 else 365;
if (d < days_in_year) break;
Expand Down Expand Up @@ -50,8 +55,10 @@ fn epochDaysToIso(days: i32, buf: *[10]u8) []const u8 {
}

fn epochSecondsToIso(secs: i64, buf: *[20]u8) []const u8 {
const days = @divTrunc(secs, 86400);
const time_secs = @rem(secs, 86400);
// ponytail: floor decomposition (Issue #235) — trunc gives negative
// time-of-day for pre-1970 secs; @mod keeps it in 0..86399
const days = @divFloor(secs, 86400);
const time_secs = @mod(secs, 86400);
const hours = @divTrunc(time_secs, 3600);
const minutes = @divTrunc(@rem(time_secs, 3600), 60);
const seconds = @rem(time_secs, 60);
Expand Down Expand Up @@ -143,6 +150,18 @@ fn intToBuf(value: i64, buf: []u8) []const u8 {
return buf[0..end];
}

test "epochDaysToIso / epochSecondsToIso: pre-1970 dates (Issue #235)" {
var db: [10]u8 = undefined;
try std.testing.expectEqualStrings("1969-12-31", epochDaysToIso(-1, &db));
try std.testing.expectEqualStrings("1969-01-01", epochDaysToIso(-365, &db));
try std.testing.expectEqualStrings("1968-12-31", epochDaysToIso(-366, &db));
try std.testing.expectEqualStrings("1970-01-01", epochDaysToIso(0, &db));
var sb: [20]u8 = undefined;
try std.testing.expectEqualStrings("1969-12-31 23:59:59", epochSecondsToIso(-1, &sb));
try std.testing.expectEqualStrings("1969-12-31 00:00:00", epochSecondsToIso(-86400, &sb));
try std.testing.expectEqualStrings("1970-01-01 00:00:00", epochSecondsToIso(0, &sb));
}

test "decimalToText: negative sub-unit value keeps its sign (Issue #234)" {
var buf: [64]u8 = undefined;
try std.testing.expectEqualStrings("-0.01", decimalToText(-1, 2, &buf));
Expand Down
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