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const std = @import("../std.zig");
const assert = std.debug.assert;
const maxInt = std.math.maxInt;
const State = enum {
Complete,
Value,
ArrayStart,
Array,
ObjectStart,
Object,
};
/// Writes JSON ([RFC8259](https://tools.ietf.org/html/rfc8259)) formatted data
/// to a stream. `max_depth` is a comptime-known upper bound on the nesting depth.
/// TODO A future iteration of this API will allow passing `null` for this value,
/// and disable safety checks in release builds.
pub fn WriteStream(comptime OutStream: type, comptime max_depth: usize) type {
return struct {
const Self = @This();
pub const Stream = OutStream;
/// The string used for indenting.
one_indent: []const u8 = " ",
/// The string used as a newline character.
newline: []const u8 = "\n",
stream: *OutStream,
state_index: usize,
state: [max_depth]State,
pub fn init(stream: *OutStream) Self {
var self = Self{
.stream = stream,
.state_index = 1,
.state = undefined,
};
self.state[0] = .Complete;
self.state[1] = .Value;
return self;
}
pub fn beginArray(self: *Self) !void {
assert(self.state[self.state_index] == State.Value); // need to call arrayElem or objectField
try self.stream.writeByte('[');
self.state[self.state_index] = State.ArrayStart;
}
pub fn beginObject(self: *Self) !void {
assert(self.state[self.state_index] == State.Value); // need to call arrayElem or objectField
try self.stream.writeByte('{');
self.state[self.state_index] = State.ObjectStart;
}
pub fn arrayElem(self: *Self) !void {
const state = self.state[self.state_index];
switch (state) {
.Complete => unreachable,
.Value => unreachable,
.ObjectStart => unreachable,
.Object => unreachable,
.Array, .ArrayStart => {
if (state == .Array) {
try self.stream.writeByte(',');
}
self.state[self.state_index] = .Array;
self.pushState(.Value);
try self.indent();
},
}
}
pub fn objectField(self: *Self, name: []const u8) !void {
const state = self.state[self.state_index];
switch (state) {
.Complete => unreachable,
.Value => unreachable,
.ArrayStart => unreachable,
.Array => unreachable,
.Object, .ObjectStart => {
if (state == .Object) {
try self.stream.writeByte(',');
}
self.state[self.state_index] = .Object;
self.pushState(.Value);
try self.indent();
try self.writeEscapedString(name);
try self.stream.write(": ");
},
}
}
pub fn endArray(self: *Self) !void {
switch (self.state[self.state_index]) {
.Complete => unreachable,
.Value => unreachable,
.ObjectStart => unreachable,
.Object => unreachable,
.ArrayStart => {
try self.stream.writeByte(']');
self.popState();
},
.Array => {
try self.indent();
self.popState();
try self.stream.writeByte(']');
},
}
}
pub fn endObject(self: *Self) !void {
switch (self.state[self.state_index]) {
.Complete => unreachable,
.Value => unreachable,
.ArrayStart => unreachable,
.Array => unreachable,
.ObjectStart => {
try self.stream.writeByte('}');
self.popState();
},
.Object => {
try self.indent();
self.popState();
try self.stream.writeByte('}');
},
}
}
pub fn emitNull(self: *Self) !void {
assert(self.state[self.state_index] == State.Value);
try self.stream.write("null");
self.popState();
}
pub fn emitBool(self: *Self, value: bool) !void {
assert(self.state[self.state_index] == State.Value);
if (value) {
try self.stream.write("true");
} else {
try self.stream.write("false");
}
self.popState();
}
pub fn emitNumber(
self: *Self,
/// An integer, float, or `std.math.BigInt`. Emitted as a bare number if it fits losslessly
/// in a IEEE 754 double float, otherwise emitted as a string to the full precision.
value: var,
) !void {
assert(self.state[self.state_index] == State.Value);
switch (@typeInfo(@typeOf(value))) {
.Int => |info| {
if (info.bits < 53) {
try self.stream.print("{}", value);
self.popState();
return;
}
if (value < 4503599627370496 and (!info.is_signed or value > -4503599627370496)) {
try self.stream.print("{}", value);
self.popState();
return;
}
},
.Float => if (@floatCast(f64, value) == value) {
try self.stream.print("{}", value);
self.popState();
return;
},
else => {},
}
try self.stream.print("\"{}\"", value);
self.popState();
}
pub fn emitString(self: *Self, string: []const u8) !void {
try self.writeEscapedString(string);
self.popState();
}
fn writeEscapedString(self: *Self, string: []const u8) !void {
try self.stream.writeByte('"');
for (string) |s| {
switch (s) {
'"' => try self.stream.write("\\\""),
'\t' => try self.stream.write("\\t"),
'\r' => try self.stream.write("\\r"),
'\n' => try self.stream.write("\\n"),
8 => try self.stream.write("\\b"),
12 => try self.stream.write("\\f"),
'\\' => try self.stream.write("\\\\"),
else => try self.stream.writeByte(s),
}
}
try self.stream.writeByte('"');
}
fn indent(self: *Self) !void {
assert(self.state_index >= 1);
try self.stream.write(self.newline);
var i: usize = 0;
while (i < self.state_index - 1) : (i += 1) {
try self.stream.write(self.one_indent);
}
}
fn pushState(self: *Self, state: State) void {
self.state_index += 1;
self.state[self.state_index] = state;
}
fn popState(self: *Self) void {
self.state_index -= 1;
}
};
}
|
