ludus/src/json.janet
2024-06-07 13:42:11 -04:00

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# pulled from cfiggers/jayson
(defmacro- letv [bindings & body]
~(do ,;(seq [[k v] :in (partition 2 bindings)] ['var k v]) ,;body))
(defn- read-hex [n]
(scan-number (string "0x" n)))
(defn- check-utf-16 [capture]
(let [u (read-hex capture)]
(if (and (>= u 0xD800)
(<= u 0xDBFF))
capture
false)))
(def- utf-8->bytes
(peg/compile
~{:double-u-esc (/ (* "\\u" (cmt (<- 4) ,|(check-utf-16 $)) "\\u" (<- 4))
,|(+ (blshift (- (read-hex $0) 0xD800) 10)
(- (read-hex $1) 0xDC00) 0x10000))
:single-u-esc (/ (* "\\u" (<- 4)) ,|(read-hex $))
:unicode-esc (/ (+ :double-u-esc :single-u-esc)
,|(string/from-bytes
;(cond
(<= $ 0x7f) [$]
(<= $ 0x7ff)
[(bor (band (brshift $ 6) 0x1F) 0xC0)
(bor (band (brshift $ 0) 0x3F) 0x80)]
(<= $ 0xffff)
[(bor (band (brshift $ 12) 0x0F) 0xE0)
(bor (band (brshift $ 6) 0x3F) 0x80)
(bor (band (brshift $ 0) 0x3F) 0x80)]
# Otherwise
[(bor (band (brshift $ 18) 0x07) 0xF0)
(bor (band (brshift $ 12) 0x3F) 0x80)
(bor (band (brshift $ 6) 0x3F) 0x80)
(bor (band (brshift $ 0) 0x3F) 0x80)])))
:escape (/ (* "\\" (<- (set "avbnfrt\"\\/")))
,|(get {"a" "\a" "v" "\v" "b" "\b"
"n" "\n" "f" "\f" "r" "\r"
"t" "\t"} $ $))
:main (+ (some (+ :unicode-esc :escape (<- 1))) -1)}))
(defn decode
``
Returns a janet object after parsing JSON. If `keywords` is truthy,
string keys will be converted to keywords. If `nils` is truthy, `null`
will become `nil` instead of the keyword `:json/null`.
``
[json-source &opt keywords nils]
(def json-parser
{:null (if nils
~(/ (<- (+ "null" "Null")) nil)
~(/ (<- (+ "null" "Null")) :json/null))
:bool-t ~(/ (<- (+ "true")) true)
:bool-f ~(/ (<- (+ "false")) false)
:number ~(/ (<- (* (? "-") :d+ (? (* "." :d+)))) ,|(scan-number $))
:string ~(/ (* "\"" (<- (to (* (> -1 (not "\\")) "\"")))
(* (> -1 (not "\\")) "\""))
,|(string/join (peg/match utf-8->bytes $)))
:array ~(/ (* "[" :s* (? (* :value (any (* :s* "," :value)))) "]") ,|(array ;$&))
:key-value (if keywords
~(* :s* (/ :string ,|(keyword $)) :s* ":" :value)
~(* :s* :string :s* ":" :value))
:object ~(/ (* "{" :s* (? (* :key-value (any (* :s* "," :key-value)))) "}")
,|(from-pairs (partition 2 $&)))
:value ~(* :s* (+ :null :bool-t :bool-f :number :string :array :object) :s*)
:unmatched ~(/ (<- (to (+ :value -1))) ,|[:unmatched $])
:main ~(some (+ :value "\n" :unmatched))})
(first (peg/match (peg/compile json-parser) json-source)))
(def- bytes->utf-8
(peg/compile
~{:four-byte (/ (* (<- (range "\xf0\xff")) (<- 1) (<- 1) (<- 1))
,|(bor (blshift (band (first $0) 0x07) 18)
(blshift (band (first $1) 0x3F) 12)
(blshift (band (first $2) 0x3F) 6)
(blshift (band (first $3) 0x3F) 0)))
:three-byte (/ (* (<- (range "\xe0\xef")) (<- 1) (<- 1))
,|(bor (blshift (band (first $0) 0x0F) 12)
(blshift (band (first $1) 0x3F) 6)
(blshift (band (first $2) 0x3F) 0)))
:two-byte (/ (* (<- (range "\x80\xdf")) (<- 1))
,|(bor (blshift (band (first $0) 0x1F) 6)
(blshift (band (first $1) 0x3F) 0)))
:multi-byte (/ (+ :two-byte :three-byte :four-byte)
,|(if (< $ 0x10000)
(string/format "\\u%04X" $)
(string/format "\\u%04X\\u%04X"
(+ (brshift (- $ 0x10000) 10) 0xD800)
(+ (band (- $ 0x10000) 0x3FF) 0xDC00))))
:one-byte (<- (range "\x20\x7f"))
:0to31 (/ (<- (range "\0\x1F"))
,|(or ({"\a" "\\u0007" "\b" "\\u0008"
"\t" "\\u0009" "\n" "\\u000A"
"\v" "\\u000B" "\f" "\\u000C"
"\r" "\\u000D"} $)
(string/format "\\u%04X" (first $))))
:backslash (/ (<- "\\") "\\\\")
:quote (/ (<- "\"") "\\\"")
:main (+ (some (+ :0to31 :backslash :quote :one-byte :multi-byte)) -1)}))
(defn- encodeone [x depth]
(if (> depth 1024) (error "recurred too deeply"))
(cond
(= x :json/null) "null"
(= x nil) "null"
(bytes? x) (string "\"" (string/join (peg/match bytes->utf-8 x)) "\"")
(indexed? x) (string "[" (string/join (map |(encodeone $ (inc depth)) x) ",") "]")
(dictionary? x) (string "{" (string/join
(seq [[k v] :in (pairs x)]
(string "\"" (string/join (peg/match bytes->utf-8 k)) "\"" ":" (encodeone v (inc depth)))) ",") "}")
(case (type x)
:nil "null"
:boolean (string x)
:number (string x)
(error "type not supported"))))
(defn encode
``
Encodes a janet value in JSON (utf-8). If `buf` is provided, the formated
JSON is append to `buf` instead of a new buffer. Returns the modifed buffer.
``
[x &opt buf]
(letv [ret (encodeone x 0)]
(if (and buf (buffer? buf))
(buffer/push ret)
(thaw ret))))