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view src/goodjava/json/JsonParser.java @ 1826:3cd1d267508c default tip
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author | Franklin Schmidt <fschmidt@gmail.com> |
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date | Sat, 24 Aug 2024 21:36:47 -0600 |
parents | 27efb1fcbcb5 |
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package goodjava.json; import java.util.List; import java.util.ArrayList; import java.util.Map; import java.util.LinkedHashMap; import java.util.Collections; import goodjava.parser.Parser; import goodjava.parser.ParseException; public final class JsonParser { public static Object parse(String text) throws ParseException { return new JsonParser(text).parse(); } private final Parser parser; private JsonParser(String text) { this.parser = new Parser(text); } private ParseException exception(String msg) { return new ParseException(parser,msg); } private Object parse() throws ParseException { spaces(); Object value = value(); spaces(); if( !parser.endOfInput() ) throw exception("unexpected text"); return value; } private Object value() throws ParseException { if( parser.match("null") ) return null; if( parser.match("true") ) return Boolean.TRUE; if( parser.match("false") ) return Boolean.FALSE; String s = string(); if( s != null ) return s; Number n = number(); if( n != null ) return n; List a = array(); if( a != null ) return a; Map o = object(); if( o != null ) return o; throw exception("invalid value"); } private String string() throws ParseException { parser.begin(); if( !parser.match('"') ) return parser.failure(null); StringBuilder sb = new StringBuilder(); while( parser.anyChar() ) { char c = parser.lastChar(); switch(c) { case '"': return parser.success(sb.toString()); case '\\': if( parser.anyChar() ) { c = parser.lastChar(); switch(c) { case '"': case '\'': // not in spec case '\\': case '/': sb.append(c); continue; case 'b': sb.append('\b'); continue; case 'f': sb.append('\f'); continue; case 'n': sb.append('\n'); continue; case 'r': sb.append('\r'); continue; case 't': sb.append('\t'); continue; case 'u': int n = 0; for( int i=0; i<4; i++ ) { int d; if( parser.inCharRange('0','9') ) { d = parser.lastChar() - '0'; } else if( parser.inCharRange('a','f') ) { d = parser.lastChar() - 'a' + 10; } else if( parser.inCharRange('A','F') ) { d = parser.lastChar() - 'A' + 10; } else { throw exception("invalid hex digit"); } n = 16*n + d; } sb.append((char)n); continue; } } throw exception("invalid escape char"); default: sb.append(c); } } parser.failure(); throw exception("unclosed string"); } private Number number() { int start = parser.begin(); boolean isFloat = false; parser.match('-'); if( !parser.match('0') ) { if( !parser.inCharRange('1','9') ) return parser.failure(null); while( parser.inCharRange('0','9') ); } if( parser.match('.') ) { if( !parser.inCharRange('0','9') ) return parser.failure(null); while( parser.inCharRange('0','9') ); isFloat = true; } if( parser.anyOf("eE") ) { parser.anyOf("+-"); if( !parser.inCharRange('0','9') ) return parser.failure(null); while( parser.inCharRange('0','9') ); isFloat = true; } String s = parser.textFrom(start); Number n; if(isFloat) n = Double.valueOf(s); else n = Long.valueOf(s); return parser.success(n); } private List array() throws ParseException { parser.begin(); if( !parser.match('[') ) return parser.failure(null); spaces(); if( parser.match(']') ) return parser.success(Collections.emptyList()); List list = new ArrayList(); list.add( value() ); spaces(); while( parser.match(',') ) { spaces(); list.add( value() ); spaces(); } if( parser.match(']') ) return parser.success(list); if( parser.endOfInput() ) { parser.failure(); throw exception("unclosed array"); } throw exception("unexpected text in array"); } private Map object() throws ParseException { parser.begin(); if( !parser.match('{') ) return parser.failure(null); spaces(); if( parser.match('}') ) return parser.success(Collections.emptyMap()); Map map = new LinkedHashMap(); addEntry(map); while( parser.match(',') ) { spaces(); addEntry(map); } if( parser.match('}') ) return parser.success(map); if( parser.endOfInput() ) { parser.failure(); throw exception("unclosed object"); } throw exception("unexpected text in object"); } private void addEntry(Map map) throws ParseException { String key = string(); if( key==null ) throw exception("invalid object key"); spaces(); if( !parser.match(':') ) throw exception("':' expected"); spaces(); Object value = value(); spaces(); map.put(key,value); } private void spaces() { while( parser.anyOf(" \t\r\n") ); } }