;;; json/read.clj: JavaScript Object Notation (JSON) parser ;; by Stuart Sierra, http://stuartsierra.com/ ;; February 13, 2009 ;; Copyright (c) Stuart Sierra, 2009. All rights reserved. The use ;; and distribution terms for this software are covered by the Eclipse ;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) ;; which can be found in the file epl-v10.html at the root of this ;; distribution. By using this software in any fashion, you are ;; agreeing to be bound by the terms of this license. You must not ;; remove this notice, or any other, from this software. ;; Change Log ;; ;; February 13, 2009: added custom handler for quoted strings, to ;; allow escaped forward backslash characters ("\/") in strings. ;; ;; January 26, 2009: initial version ;; For more information on JSON, see http://www.json.org/ ;; ;; This library parses data in JSON format. This is a fairly strict ;; implementation of JSON as described at json.org, not a full-fledged ;; JavaScript parser. JavaScript functions and object constructors ;; are not supported. Object field names must be quoted strings; they ;; may not be bare symbols. (ns #^{:author "Stuart Sierra", :doc "JavaScript Object Notation (JSON) parser For more information on JSON, see http://www.json.org/ This library parses data in JSON format. This is a fairly strict implementation of JSON as described at json.org, not a full-fledged JavaScript parser. JavaScript functions and object constructors are not supported. Object field names must be quoted strings; they may not be bare symbols.", :see-also [["http://www.json.org", "JSON Home Page"]]} clojure.contrib.json.read (:import (java.io PushbackReader StringReader EOFException)) (:use [clojure.contrib.test-is :only (deftest- is)])) (declare read-json) (defn- read-json-array [#^PushbackReader stream] ;; Expects to be called with the head of the stream AFTER the ;; opening bracket. (loop [i (.read stream), result []] (let [c (char i)] (cond (= i -1) (throw (EOFException. "JSON error (end-of-file inside array)")) (Character/isWhitespace c) (recur (.read stream) result) (= c \,) (recur (.read stream) result) (= c \]) result :else (do (.unread stream (int c)) (let [element (read-json stream)] (recur (.read stream) (conj result element)))))))) (defn- read-json-object [#^PushbackReader stream] ;; Expects to be called with the head of the stream AFTER the ;; opening bracket. (loop [i (.read stream), key nil, result {}] (let [c (char i)] (cond (= i -1) (throw (EOFException. "JSON error (end-of-file inside object)")) (Character/isWhitespace c) (recur (.read stream) key result) (= c \,) (recur (.read stream) nil result) (= c \:) (recur (.read stream) key result) (= c \}) (if (nil? key) result (throw (Exception. "JSON error (key missing value in object)"))) :else (do (.unread stream i) (let [element (read-json stream)] (if (nil? key) (if (string? element) (recur (.read stream) element result) (throw (Exception. "JSON error (non-string key in object)"))) (recur (.read stream) nil (assoc result key element))))))))) (defn- read-json-hex-character [stream] ;; Expects to be called with the head of the stream AFTER the ;; initial "\u". Reads the next four characters from the stream. (let [digits [(.read stream) (.read stream) (.read stream) (.read stream)]] (when (some neg? digits) (throw (EOFException. "JSON error (end-of-file inside Unicode character escape)"))) (let [chars (map char digits)] (when-not (every? #{\0 \1 \2 \3 \4 \5 \6 \7 \8 \9 \a \b \c \d \e \f \A \B \C \D \E \F} chars) (throw (Exception. "JSON error (invalid hex character in Unicode character escape)"))) (char (Integer/parseInt (apply str chars) 16))))) (defn- read-json-escaped-character [stream] ;; Expects to be called with the head of the stream AFTER the ;; initial backslash. (let [c (char (.read stream))] (cond (#{\" \\ \/} c) c (= c \b) \backspace (= c \f) \formfeed (= c \n) \newline (= c \r) \return (= c \t) \tab (= c \u) (read-json-hex-character stream)))) (defn- read-json-quoted-string [#^PushbackReader stream] ;; Expects to be called with the head of the stream AFTER the ;; opening quotation mark. (let [buffer (StringBuilder.)] (loop [i (.read stream)] (let [c (char i)] (cond (= i -1) (throw (EOFException. "JSON error (end-of-file inside string)")) (= c \") (str buffer) (= c \\) (do (.append buffer (read-json-escaped-character stream)) (recur (.read stream))) :else (do (.append buffer c) (recur (.read stream)))))))) (defn read-json "Read the next JSON record from stream, which must be an instance of java.io.PushbackReader." ([] (read-json *in* true nil)) ([stream] (read-json stream true nil)) ([#^PushbackReader stream eof-error? eof-value] (loop [i (.read stream)] (let [c (char i)] (cond ;; Handle end-of-stream (= i -1) (if eof-error? (throw (EOFException. "JSON error (end-of-file)")) eof-value) ;; Ignore whitespace (Character/isWhitespace c) (recur (.read stream)) ;; Read numbers, true, and false with Clojure reader (#{\- \0 \1 \2 \3 \4 \5 \6 \7 \8 \9} c) (do (.unread stream i) (read stream true nil)) ;; Read strings (= c \") (read-json-quoted-string stream) ;; Read null as nil (= c \n) (let [ull [(char (.read stream)) (char (.read stream)) (char (.read stream))]] (if (= ull [\u \l \l]) nil (throw (Exception. (str "JSON error (expected null): " c ull))))) ;; Read true (= c \t) (let [rue [(char (.read stream)) (char (.read stream)) (char (.read stream))]] (if (= rue [\r \u \e]) true (throw (Exception. (str "JSON error (expected true): " c rue))))) ;; Read false (= c \f) (let [alse [(char (.read stream)) (char (.read stream)) (char (.read stream)) (char (.read stream))]] (if (= alse [\a \l \s \e]) false (throw (Exception. (str "JSON error (expected false): " c alse))))) ;; Read JSON objects (= c \{) (read-json-object stream) ;; Read JSON arrays (= c \[) (read-json-array stream) :else (throw (Exception. (str "JSON error (unexpected character): " c)))))))) (defn read-json-string [string] (read-json (PushbackReader. (StringReader. string)))) ;;; TESTS (deftest- can-read-numbers (is (= 42 (read-json-string "42"))) (is (= -3 (read-json-string "-3"))) (is (= 3.14159 (read-json-string "3.14159"))) (is (= 6.022e23 (read-json-string "6.022e23")))) (deftest- can-read-null (is (= nil (read-json-string "null")))) (deftest- can-read-strings (is (= "Hello, World!" (read-json-string "\"Hello, World!\"")))) (deftest- handles-escaped-slashes-in-strings (is (= "/foo/bar" (read-json-string "\"\\/foo\\/bar\"")))) (deftest- handles-unicode-escapes (is (= " \u0beb " (read-json-string "\" \\u0bEb \"")))) (deftest- handles-escaped-whitespace (is (= "foo\nbar" (read-json-string "\"foo\\nbar\""))) (is (= "foo\rbar" (read-json-string "\"foo\\rbar\""))) (is (= "foo\tbar" (read-json-string "\"foo\\tbar\"")))) (deftest- can-read-booleans (is (= true (read-json-string "true"))) (is (= false (read-json-string "false")))) (deftest- can-ignore-whitespace (is (= nil (read-json-string "\r\n null")))) (deftest- can-read-arrays (is (= [1 2 3] (read-json-string "[1,2,3]"))) (is (= ["Ole" "Lena"] (read-json-string "[\"Ole\", \r\n \"Lena\"]")))) (deftest- can-read-objects (is (= {"a" 1, "b" 2} (read-json-string "{\"a\": 1, \"b\": 2}")))) (deftest- can-read-nested-structures (is (= {"a" [1 2 {"b" [3 "four"]} 5.5]} (read-json-string "{\"a\":[1,2,{\"b\":[3,\"four\"]},5.5]}")))) (deftest- disallows-non-string-keys (is (thrown? Exception (read-json-string "{26:\"z\"")))) (deftest- disallows-barewords (is (thrown? Exception (read-json-string " foo ")))) (deftest- disallows-unclosed-arrays (is (thrown? Exception (read-json-string "[1, 2, ")))) (deftest- disallows-unclosed-objects (is (thrown? Exception (read-json-string "{\"a\":1, "))))