The main goal here is to make the function pointers comptime, so that we don't have to do the crazy stuff with async function frames. Since InStream, OutStream, and SeekableStream are already generic across error sets, it's not really worse to make them generic across the vtable as well. See #764 for the open issue acknowledging that using generics for these abstractions is a design flaw. See #130 for the efforts to make these abstractions non-generic. This commit also changes the OutStream API so that `write` returns number of bytes written, and `writeAll` is the one that loops until the whole buffer is written.
309 lines
11 KiB
Zig
309 lines
11 KiB
Zig
const std = @import("../std.zig");
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const assert = std.debug.assert;
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const maxInt = std.math.maxInt;
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const State = enum {
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Complete,
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Value,
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ArrayStart,
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Array,
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ObjectStart,
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Object,
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};
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/// Writes JSON ([RFC8259](https://tools.ietf.org/html/rfc8259)) formatted data
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/// to a stream. `max_depth` is a comptime-known upper bound on the nesting depth.
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/// TODO A future iteration of this API will allow passing `null` for this value,
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/// and disable safety checks in release builds.
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pub fn WriteStream(comptime OutStream: type, comptime max_depth: usize) type {
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return struct {
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const Self = @This();
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pub const Stream = OutStream;
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/// The string used for indenting.
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one_indent: []const u8 = " ",
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/// The string used as a newline character.
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newline: []const u8 = "\n",
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/// The string used as spacing.
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space: []const u8 = " ",
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stream: OutStream,
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state_index: usize,
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state: [max_depth]State,
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pub fn init(stream: OutStream) Self {
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var self = Self{
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.stream = stream,
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.state_index = 1,
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.state = undefined,
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};
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self.state[0] = .Complete;
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self.state[1] = .Value;
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return self;
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}
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pub fn beginArray(self: *Self) !void {
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assert(self.state[self.state_index] == State.Value); // need to call arrayElem or objectField
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try self.stream.writeByte('[');
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self.state[self.state_index] = State.ArrayStart;
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}
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pub fn beginObject(self: *Self) !void {
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assert(self.state[self.state_index] == State.Value); // need to call arrayElem or objectField
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try self.stream.writeByte('{');
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self.state[self.state_index] = State.ObjectStart;
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}
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pub fn arrayElem(self: *Self) !void {
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const state = self.state[self.state_index];
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switch (state) {
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.Complete => unreachable,
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.Value => unreachable,
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.ObjectStart => unreachable,
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.Object => unreachable,
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.Array, .ArrayStart => {
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if (state == .Array) {
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try self.stream.writeByte(',');
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}
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self.state[self.state_index] = .Array;
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self.pushState(.Value);
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try self.indent();
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},
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}
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}
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pub fn objectField(self: *Self, name: []const u8) !void {
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const state = self.state[self.state_index];
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switch (state) {
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.Complete => unreachable,
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.Value => unreachable,
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.ArrayStart => unreachable,
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.Array => unreachable,
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.Object, .ObjectStart => {
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if (state == .Object) {
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try self.stream.writeByte(',');
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}
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self.state[self.state_index] = .Object;
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self.pushState(.Value);
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try self.indent();
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try self.writeEscapedString(name);
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try self.stream.writeAll(":");
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try self.stream.writeAll(self.space);
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},
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}
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}
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pub fn endArray(self: *Self) !void {
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switch (self.state[self.state_index]) {
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.Complete => unreachable,
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.Value => unreachable,
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.ObjectStart => unreachable,
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.Object => unreachable,
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.ArrayStart => {
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try self.stream.writeByte(']');
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self.popState();
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},
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.Array => {
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try self.indent();
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self.popState();
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try self.stream.writeByte(']');
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},
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}
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}
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pub fn endObject(self: *Self) !void {
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switch (self.state[self.state_index]) {
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.Complete => unreachable,
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.Value => unreachable,
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.ArrayStart => unreachable,
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.Array => unreachable,
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.ObjectStart => {
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try self.stream.writeByte('}');
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self.popState();
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},
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.Object => {
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try self.indent();
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self.popState();
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try self.stream.writeByte('}');
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},
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}
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}
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pub fn emitNull(self: *Self) !void {
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assert(self.state[self.state_index] == State.Value);
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try self.stream.writeAll("null");
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self.popState();
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}
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pub fn emitBool(self: *Self, value: bool) !void {
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assert(self.state[self.state_index] == State.Value);
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if (value) {
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try self.stream.writeAll("true");
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} else {
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try self.stream.writeAll("false");
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}
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self.popState();
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}
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pub fn emitNumber(
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self: *Self,
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/// An integer, float, or `std.math.BigInt`. Emitted as a bare number if it fits losslessly
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/// in a IEEE 754 double float, otherwise emitted as a string to the full precision.
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value: var,
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) !void {
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assert(self.state[self.state_index] == State.Value);
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switch (@typeInfo(@TypeOf(value))) {
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.Int => |info| {
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if (info.bits < 53) {
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try self.stream.print("{}", .{value});
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self.popState();
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return;
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}
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if (value < 4503599627370496 and (!info.is_signed or value > -4503599627370496)) {
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try self.stream.print("{}", .{value});
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self.popState();
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return;
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}
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},
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.Float => if (@floatCast(f64, value) == value) {
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try self.stream.print("{}", .{value});
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self.popState();
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return;
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},
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else => {},
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}
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try self.stream.print("\"{}\"", .{value});
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self.popState();
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}
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pub fn emitString(self: *Self, string: []const u8) !void {
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try self.writeEscapedString(string);
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self.popState();
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}
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fn writeEscapedString(self: *Self, string: []const u8) !void {
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try self.stream.writeByte('"');
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for (string) |s| {
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switch (s) {
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'"' => try self.stream.writeAll("\\\""),
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'\t' => try self.stream.writeAll("\\t"),
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'\r' => try self.stream.writeAll("\\r"),
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'\n' => try self.stream.writeAll("\\n"),
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8 => try self.stream.writeAll("\\b"),
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12 => try self.stream.writeAll("\\f"),
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'\\' => try self.stream.writeAll("\\\\"),
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else => try self.stream.writeByte(s),
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}
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}
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try self.stream.writeByte('"');
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}
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/// Writes the complete json into the output stream
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pub fn emitJson(self: *Self, json: std.json.Value) Stream.Error!void {
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switch (json) {
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.Null => try self.emitNull(),
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.Bool => |inner| try self.emitBool(inner),
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.Integer => |inner| try self.emitNumber(inner),
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.Float => |inner| try self.emitNumber(inner),
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.String => |inner| try self.emitString(inner),
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.Array => |inner| {
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try self.beginArray();
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for (inner.toSliceConst()) |elem| {
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try self.arrayElem();
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try self.emitJson(elem);
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}
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try self.endArray();
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},
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.Object => |inner| {
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try self.beginObject();
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var it = inner.iterator();
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while (it.next()) |entry| {
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try self.objectField(entry.key);
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try self.emitJson(entry.value);
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}
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try self.endObject();
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},
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}
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}
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fn indent(self: *Self) !void {
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assert(self.state_index >= 1);
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try self.stream.writeAll(self.newline);
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var i: usize = 0;
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while (i < self.state_index - 1) : (i += 1) {
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try self.stream.writeAll(self.one_indent);
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}
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}
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fn pushState(self: *Self, state: State) void {
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self.state_index += 1;
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self.state[self.state_index] = state;
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}
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fn popState(self: *Self) void {
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self.state_index -= 1;
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}
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};
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}
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test "json write stream" {
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var out_buf: [1024]u8 = undefined;
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var slice_stream = std.io.SliceOutStream.init(&out_buf);
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const out = &slice_stream.stream;
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var arena_allocator = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena_allocator.deinit();
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var w = std.json.WriteStream(@TypeOf(out).Child, 10).init(out);
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try w.emitJson(try getJson(&arena_allocator.allocator));
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const result = slice_stream.getWritten();
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const expected =
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\\{
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\\ "object": {
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\\ "one": 1,
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\\ "two": 2.0e+00
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\\ },
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\\ "string": "This is a string",
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\\ "array": [
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\\ "Another string",
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\\ 1,
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\\ 3.14e+00
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\\ ],
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\\ "int": 10,
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\\ "float": 3.14e+00
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\\}
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;
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std.testing.expect(std.mem.eql(u8, expected, result));
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}
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fn getJson(allocator: *std.mem.Allocator) !std.json.Value {
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var value = std.json.Value{ .Object = std.json.ObjectMap.init(allocator) };
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_ = try value.Object.put("string", std.json.Value{ .String = "This is a string" });
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_ = try value.Object.put("int", std.json.Value{ .Integer = @intCast(i64, 10) });
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_ = try value.Object.put("float", std.json.Value{ .Float = 3.14 });
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_ = try value.Object.put("array", try getJsonArray(allocator));
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_ = try value.Object.put("object", try getJsonObject(allocator));
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return value;
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}
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fn getJsonObject(allocator: *std.mem.Allocator) !std.json.Value {
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var value = std.json.Value{ .Object = std.json.ObjectMap.init(allocator) };
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_ = try value.Object.put("one", std.json.Value{ .Integer = @intCast(i64, 1) });
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_ = try value.Object.put("two", std.json.Value{ .Float = 2.0 });
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return value;
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}
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fn getJsonArray(allocator: *std.mem.Allocator) !std.json.Value {
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var value = std.json.Value{ .Array = std.json.Array.init(allocator) };
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var array = &value.Array;
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_ = try array.append(std.json.Value{ .String = "Another string" });
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_ = try array.append(std.json.Value{ .Integer = @intCast(i64, 1) });
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_ = try array.append(std.json.Value{ .Float = 3.14 });
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return value;
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}
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