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var at, // The index of the current character
ch, // The current character
escapee = {
'"': '"',
'\\': '\\',
'/': '/',
b: '\b',
f: '\f',
n: '\n',
r: '\r',
t: '\t'
},
text,
error = function (m) {
// Call error when something is wrong.
throw {
name: 'SyntaxError',
message: m,
at: at,
text: text
};
},
next = function (c) {
// If a c parameter is provided, verify that it matches the current character.
if (c && c !== ch) {
error("Expected '" + c + "' instead of '" + ch + "'");
}
// Get the next character. When there are no more characters,
// return the empty string.
ch = text.charAt(at);
at += 1;
return ch;
},
number = function () {
// Parse a number value.
var number,
string = '';
if (ch === '-') {
string = '-';
next('-');
}
while (ch >= '0' && ch <= '9') {
string += ch;
next();
}
if (ch === '.') {
string += '.';
while (next() && ch >= '0' && ch <= '9') {
string += ch;
}
}
if (ch === 'e' || ch === 'E') {
string += ch;
next();
if (ch === '-' || ch === '+') {
string += ch;
next();
}
while (ch >= '0' && ch <= '9') {
string += ch;
next();
}
}
number = +string;
if (!isFinite(number)) {
error("Bad number");
} else {
return number;
}
},
string = function () {
// Parse a string value.
var hex,
i,
string = '',
uffff;
// When parsing for string values, we must look for " and \ characters.
if (ch === '"') {
while (next()) {
if (ch === '"') {
next();
return string;
} else if (ch === '\\') {
next();
if (ch === 'u') {
uffff = 0;
for (i = 0; i < 4; i += 1) {
hex = parseInt(next(), 16);
if (!isFinite(hex)) {
break;
}
uffff = uffff * 16 + hex;
}
string += String.fromCharCode(uffff);
} else if (typeof escapee[ch] === 'string') {
string += escapee[ch];
} else {
break;
}
} else {
string += ch;
}
}
}
error("Bad string");
},
white = function () {
// Skip whitespace.
while (ch && ch <= ' ') {
next();
}
},
word = function () {
// true, false, or null.
switch (ch) {
case 't':
next('t');
next('r');
next('u');
next('e');
return true;
case 'f':
next('f');
next('a');
next('l');
next('s');
next('e');
return false;
case 'n':
next('n');
next('u');
next('l');
next('l');
return null;
}
error("Unexpected '" + ch + "'");
},
value, // Place holder for the value function.
array = function () {
// Parse an array value.
var array = [];
if (ch === '[') {
next('[');
white();
if (ch === ']') {
next(']');
return array; // empty array
}
while (ch) {
array.push(value());
white();
if (ch === ']') {
next(']');
return array;
}
next(',');
white();
}
}
error("Bad array");
},
object = function () {
// Parse an object value.
var key,
object = {};
if (ch === '{') {
next('{');
white();
if (ch === '}') {
next('}');
return object; // empty object
}
while (ch) {
key = string();
white();
next(':');
if (Object.hasOwnProperty.call(object, key)) {
error('Duplicate key "' + key + '"');
}
object[key] = value();
white();
if (ch === '}') {
next('}');
return object;
}
next(',');
white();
}
}
error("Bad object");
};
value = function () {
// Parse a JSON value. It could be an object, an array, a string, a number,
// or a word.
white();
switch (ch) {
case '{':
return object();
case '[':
return array();
case '"':
return string();
case '-':
return number();
default:
return ch >= '0' && ch <= '9' ? number() : word();
}
};
// Return the json_parse function. It will have access to all of the above
// functions and variables.
module.exports = function (source, reviver) {
var result;
text = source;
at = 0;
ch = ' ';
result = value();
white();
if (ch) {
error("Syntax error");
}
// If there is a reviver function, we recursively walk the new structure,
// passing each name/value pair to the reviver function for possible
// transformation, starting with a temporary root object that holds the result
// in an empty key. If there is not a reviver function, we simply return the
// result.
return typeof reviver === 'function' ? (function walk(holder, key) {
var k, v, value = holder[key];
if (value && typeof value === 'object') {
for (k in value) {
if (Object.prototype.hasOwnProperty.call(value, k)) {
v = walk(value, k);
if (v !== undefined) {
value[k] = v;
} else {
delete value[k];
}
}
}
}
return reviver.call(holder, key, value);
}({'': result}, '')) : result;
};
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