import string import types ## json.py implements a JSON (http://json.org) reader and writer. ## Copyright (C) 2005 Patrick D. Logan ## Contact mailto:patrickdlogan@stardecisions.com ## ## This library is free software; you can redistribute it and/or ## modify it under the terms of the GNU Lesser General Public ## License as published by the Free Software Foundation; either ## version 2.1 of the License, or (at your option) any later version. ## ## This library is distributed in the hope that it will be useful, ## but WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## Lesser General Public License for more details. ## ## You should have received a copy of the GNU Lesser General Public ## License along with this library; if not, write to the Free Software ## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA class _StringGenerator(object): def __init__(self, string): self.string = string self.index = -1 def peek(self): i = self.index + 1 if i < len(self.string): return self.string[i] else: return None def next(self): self.index += 1 if self.index < len(self.string): return self.string[self.index] else: raise StopIteration def all(self): return self.string class WriteException(Exception): pass class ReadException(Exception): pass class JsonReader(object): hex_digits = {'A': 10,'B': 11,'C': 12,'D': 13,'E': 14,'F':15} escapes = {'t':'\t','n':'\n','f':'\f','r':'\r','b':'\b'} def read(self, s): self._generator = _StringGenerator(s) result = self._read() return result def _read(self): self._eatWhitespace() peek = self._peek() if peek is None: raise ReadException, "Nothing to read: '%s'" % self._generator.all() if peek == '{': return self._readObject() elif peek == '[': return self._readArray() elif peek == '"': return self._readString() elif peek == '-' or peek.isdigit(): return self._readNumber() elif peek == 't': return self._readTrue() elif peek == 'f': return self._readFalse() elif peek == 'n': return self._readNull() elif peek == '/': self._readComment() return self._read() else: raise ReadException, "Input is not valid JSON: '%s'" % self._generator.all() def _readTrue(self): self._assertNext('t', "true") self._assertNext('r', "true") self._assertNext('u', "true") self._assertNext('e', "true") return True def _readFalse(self): self._assertNext('f', "false") self._assertNext('a', "false") self._assertNext('l', "false") self._assertNext('s', "false") self._assertNext('e', "false") return False def _readNull(self): self._assertNext('n', "null") self._assertNext('u', "null") self._assertNext('l', "null") self._assertNext('l', "null") return None def _assertNext(self, ch, target): if self._next() != ch: raise ReadException, "Trying to read %s: '%s'" % (target, self._generator.all()) def _readNumber(self): isfloat = False result = self._next() peek = self._peek() while peek is not None and (peek.isdigit() or peek == "."): isfloat = isfloat or peek == "." result = result + self._next() peek = self._peek() try: if isfloat: return float(result) else: return int(result) except ValueError: raise ReadException, "Not a valid JSON number: '%s'" % result def _readString(self): result = "" assert self._next() == '"' try: while self._peek() != '"': ch = self._next() if ch == "\\": ch = self._next() if ch in 'brnft': ch = self.escapes[ch] elif ch == "u": ch4096 = self._next() ch256 = self._next() ch16 = self._next() ch1 = self._next() n = 4096 * self._hexDigitToInt(ch4096) n += 256 * self._hexDigitToInt(ch256) n += 16 * self._hexDigitToInt(ch16) n += self._hexDigitToInt(ch1) ch = unichr(n) elif ch not in '"/\\': raise ReadException, "Not a valid escaped JSON character: '%s' in %s" % (ch, self._generator.all()) result = result + ch except StopIteration: raise ReadException, "Not a valid JSON string: '%s'" % self._generator.all() assert self._next() == '"' return result def _hexDigitToInt(self, ch): try: result = self.hex_digits[ch.upper()] except KeyError: try: result = int(ch) except ValueError: raise ReadException, "The character %s is not a hex digit." % ch return result def _readComment(self): assert self._next() == "/" second = self._next() if second == "/": self._readDoubleSolidusComment() elif second == '*': self._readCStyleComment() else: raise ReadException, "Not a valid JSON comment: %s" % self._generator.all() def _readCStyleComment(self): try: done = False while not done: ch = self._next() done = (ch == "*" and self._peek() == "/") if not done and ch == "/" and self._peek() == "*": raise ReadException, "Not a valid JSON comment: %s, '/*' cannot be embedded in the comment." % self._generator.all() self._next() except StopIteration: raise ReadException, "Not a valid JSON comment: %s, expected */" % self._generator.all() def _readDoubleSolidusComment(self): try: ch = self._next() while ch != "\r" and ch != "\n": ch = self._next() except StopIteration: pass def _readArray(self): result = [] assert self._next() == '[' done = self._peek() == ']' while not done: item = self._read() result.append(item) self._eatWhitespace() done = self._peek() == ']' if not done: ch = self._next() if ch != ",": raise ReadException, "Not a valid JSON array: '%s' due to: '%s'" % (self._generator.all(), ch) assert ']' == self._next() return result def _readObject(self): result = {} assert self._next() == '{' done = self._peek() == '}' while not done: key = self._read() if type(key) is not types.StringType: raise ReadException, "Not a valid JSON object key (should be a string): %s" % key self._eatWhitespace() ch = self._next() if ch != ":": raise ReadException, "Not a valid JSON object: '%s' due to: '%s'" % (self._generator.all(), ch) self._eatWhitespace() val = self._read() result[key] = val self._eatWhitespace() done = self._peek() == '}' if not done: ch = self._next() if ch != ",": raise ReadException, "Not a valid JSON array: '%s' due to: '%s'" % (self._generator.all(), ch) assert self._next() == "}" return result def _eatWhitespace(self): p = self._peek() while p is not None and p in string.whitespace or p == '/': if p == '/': self._readComment() else: self._next() p = self._peek() def _peek(self): return self._generator.peek() def _next(self): return self._generator.next() class JsonWriter(object): def _append(self, s): self._results.append(s) def write(self, obj, escaped_forward_slash=False): self._escaped_forward_slash = escaped_forward_slash self._results = [] self._write(obj) return "".join(self._results) def _write(self, obj): ty = type(obj) if ty is types.DictType: n = len(obj) self._append("{") for k, v in obj.items(): self._write(k) self._append(":") self._write(v) n = n - 1 if n > 0: self._append(",") self._append("}") elif ty is types.ListType or ty is types.TupleType: n = len(obj) self._append("[") for item in obj: self._write(item) n = n - 1 if n > 0: self._append(",") self._append("]") elif ty is types.StringType or ty is types.UnicodeType: self._append('"') obj = obj.replace('\\', r'\\') if self._escaped_forward_slash: obj = obj.replace('/', r'\/') obj = obj.replace('"', r'\"') obj = obj.replace('\b', r'\b') obj = obj.replace('\f', r'\f') obj = obj.replace('\n', r'\n') obj = obj.replace('\r', r'\r') obj = obj.replace('\t', r'\t') self._append(obj) self._append('"') elif ty is types.IntType or ty is types.LongType: self._append(str(obj)) elif ty is types.FloatType: self._append("%f" % obj) elif obj is True: self._append("true") elif obj is False: self._append("false") elif obj is None: self._append("null") else: raise WriteException, "Cannot write in JSON: %s" % repr(obj) def write(obj, escaped_forward_slash=False): return JsonWriter().write(obj, escaped_forward_slash) def read(s): return JsonReader().read(s) def fread(f): return read(f.read())