motiejus/zig
1
Fork 0
Code Releases Activity

json.stringify: properly implement RFC8259 recommendation

Browse Source 
The previous magic numbers used `1 << 52`, which did not account for the
implicit leading one in the floating point format.  The RFC is correct
when it uses an exponent of 53.  Technically these exclusive endpoints
are also representable, but everyone including the RFC seems to use them
exclusively.

Also, delete special case optimizations related to the type which have
already been implemented in the zig compiler to produce comptime values
for tautological runtime comparisons.
This commit is contained in:
Jacob Young
2023-08-06 00:17:37 -04:00
parent 7dacf77745
commit 1cce539ddc
1 changed files with 6 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
lib/std/json/stringify.zig
View File

@@ -34,7 +34,7 @@ pub const StringifyOptions = struct {
/// Should unicode characters be escaped in strings?
escape_unicode: bool = false,
/// When true, renders numbers outside the range `±1<<53` (the precise integer range of f64) as JSON strings in base 10.
/// When true, renders numbers outside the range `+-1<<53` (the precise integer range of f64) as JSON strings in base 10.
emit_big_numbers_quoted: bool = false,
};
@@ -164,7 +164,7 @@ pub fn writeStreamArbitraryDepth(
/// * Zig `bool` -> JSON `true` or `false`.
/// * Zig `?T` -> `null` or the rendering of `T`.
/// * Zig `i32`, `u64`, etc. -> JSON number or string.
/// * If the value is outside the range `±1<<53` (the precise integer range of f64), it is rendered as a JSON string in base 10. Otherwise, it is rendered as JSON number.
/// * If the value is outside the range `+-1<<53` (the precise integer range of f64), it is rendered as a JSON string in base 10. Otherwise, it is rendered as JSON number.
/// * Zig floats -> JSON number or string.
/// * If the value cannot be precisely represented by an f64, it is rendered as a JSON string. Otherwise, it is rendered as JSON number.
/// * TODO: Float rendering will likely change in the future, e.g. to remove the unnecessary "e+00".
@@ -402,13 +402,11 @@ pub fn WriteStream(
pub fn write(self: *Self, value: anytype) Error!void {
const T = @TypeOf(value);
switch (@typeInfo(T)) {
.Int => |info| {
const emit_unquoted =
if (!self.options.emit_big_numbers_quoted) true
else if (info.bits < 53) true
else (value < 4503599627370496 and (info.signedness == .unsigned or value > -4503599627370496));
.Int => {
try self.valueStart();
if (emit_unquoted) {
if (!self.options.emit_big_numbers_quoted or
(value > -(1 << 53) and value < (1 << 53)))
{
try self.stream.print("{}", .{value});
} else {
try self.stream.print("\"{}\"", .{value});