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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.import { toTransformStream } from "../streams/to_transform_stream.ts";import type { JsonValue, ParseStreamOptions } from "./common.ts";import { parse } from "./_common.ts";
const blank = new Set(" \t\r\n");function isBlankChar(char: string) { return blank.has(char);}
const primitives = new Map( (["null", "true", "false"] as const).map((v) => [v[0], v]),);
/** * Stream to parse [Concatenated JSON](https://en.wikipedia.org/wiki/JSON_streaming#Concatenated_JSON). * * @example * ```ts * import { ConcatenatedJsonParseStream } from "https://deno.land/std@$STD_VERSION/json/concatenated_json_parse_stream.ts"; * * const url = "https://deno.land/std@$STD_VERSION/json/testdata/test.concatenated-json"; * const { body } = await fetch(url); * * const readable = body! * .pipeThrough(new TextDecoderStream()) // convert Uint8Array to string * .pipeThrough(new ConcatenatedJsonParseStream()); // parse Concatenated JSON * * for await (const data of readable) { * console.log(data); * } * ``` */export class ConcatenatedJsonParseStream implements TransformStream<string, JsonValue> { readonly writable: WritableStream<string>; readonly readable: ReadableStream<JsonValue>; /** * @param options * @param options.writableStrategy Controls the buffer of the TransformStream used internally. Check https://developer.mozilla.org/en-US/docs/Web/API/TransformStream/TransformStream. * @param options.readableStrategy Controls the buffer of the TransformStream used internally. Check https://developer.mozilla.org/en-US/docs/Web/API/TransformStream/TransformStream. */ constructor({ writableStrategy, readableStrategy }: ParseStreamOptions = {}) { const { writable, readable } = toTransformStream( this.#concatenatedJSONIterator, writableStrategy, readableStrategy, ); this.writable = writable; this.readable = readable; }
async *#concatenatedJSONIterator(src: AsyncIterable<string>) { // Counts the number of '{', '}', '[', ']', and when the nesting level reaches 0, concatenates and returns the string. let targetString = ""; let hasValue = false; let nestCount = 0; let readingString = false; let escapeNext = false; let readingPrimitive: false | "null" | "true" | "false" = false; let positionInPrimitive = 0; for await (const string of src) { let sliceStart = 0; for (let i = 0; i < string.length; i++) { const char = string[i];
// We're reading a primitive at the top level if (readingPrimitive) { if (char === readingPrimitive[positionInPrimitive]) { positionInPrimitive++;
// Emit the primitive when done reading if (positionInPrimitive === readingPrimitive.length) { yield parse(targetString + string.slice(sliceStart, i + 1)); hasValue = false; readingPrimitive = false; positionInPrimitive = 0; targetString = ""; sliceStart = i + 1; } } else { // If the primitive is malformed, keep reading, maybe the next characters can be useful in the syntax error. readingPrimitive = false; positionInPrimitive = 0; } continue; }
if (readingString) { if (char === '"' && !escapeNext) { readingString = false;
// When the nesting level is 0, it returns a string when '"' comes. if (nestCount === 0 && hasValue) { yield parse(targetString + string.slice(sliceStart, i + 1)); hasValue = false; targetString = ""; sliceStart = i + 1; } } escapeNext = !escapeNext && char === "\\"; continue; }
// Parses number with a nesting level of 0. // example: '0["foo"]' => 0, ["foo"] // example: '3.14{"foo": "bar"}' => 3.14, {foo: "bar"} if ( hasValue && nestCount === 0 && (char === "{" || char === "[" || char === '"' || char === " " || char === "n" || char === "t" || char === "f") ) { yield parse(targetString + string.slice(sliceStart, i)); hasValue = false; readingString = false; targetString = ""; sliceStart = i; i--; continue; }
switch (char) { case '"': readingString = true; escapeNext = false; break; case "{": case "[": nestCount++; break; case "}": case "]": nestCount--; break; }
if (nestCount === 0 && primitives.has(char)) { // The first letter of a primitive at top level was found readingPrimitive = primitives.get(char)!; positionInPrimitive = 1; }
// parse object or array if ( hasValue && nestCount === 0 && (char === "}" || char === "]") ) { yield parse(targetString + string.slice(sliceStart, i + 1)); hasValue = false; targetString = ""; sliceStart = i + 1; continue; }
if (!hasValue && !isBlankChar(char)) { // We want to ignore the character string with only blank, so if there is a character other than blank, record it. hasValue = true; } } targetString += string.slice(sliceStart); } if (hasValue) { yield parse(targetString); } }}