com.netease.stream.util.json.JSONTokener Maven / Gradle / Ivy
package com.netease.stream.util.json;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
/**
* A JSONTokener takes a source string and extracts characters and tokens from it. It is used by the
* JSONObject and JSONArray constructors to parse JSON source strings.
*
* @version 2010-02-02
*/
public class JSONTokener {
private int character;
private boolean eof;
private int index;
private int line;
private char previous;
private Reader reader;
private boolean usePrevious;
/**
* Construct a JSONTokener from a reader.
*
* @param reader A reader.
*/
public JSONTokener(Reader reader) {
this.reader = reader.markSupported() ? reader : new BufferedReader(reader);
this.eof = false;
this.usePrevious = false;
this.previous = 0;
this.index = 0;
this.character = 1;
this.line = 1;
}
/**
* Construct a JSONTokener from a string.
*
* @param s A source string.
*/
public JSONTokener(String s) {
this(new StringReader(s));
}
/**
* Back up one character. This provides a sort of lookahead capability, so that you can test for
* a digit or letter before attempting to parse the next number or identifier.
*
* @throws JSONException JSONException.
*/
public void back() throws JSONException {
if (usePrevious || index <= 0) {
throw new JSONException("Stepping back two steps is not supported");
}
this.index -= 1;
this.character -= 1;
this.usePrevious = true;
this.eof = false;
}
/**
* Get the hex value of a character (base16).
*
* @param c A character between '0' and '9' or between 'A' and 'F' or between 'a' and 'f'.
* @return An int between 0 and 15, or -1 if c was not a hex digit.
*/
public static int dehexchar(char c) {
if (c >= '0' && c <= '9') {
return c - '0';
}
if (c >= 'A' && c <= 'F') {
return c - ('A' - 10);
}
if (c >= 'a' && c <= 'f') {
return c - ('a' - 10);
}
return -1;
}
public boolean end() {
return eof && !usePrevious;
}
/**
* Determine if the source string still contains characters that next() can consume.
*
* @return true if not yet at the end of the source.
* @throws JSONException JSONException.
*/
public boolean more() throws JSONException {
next();
if (end()) {
return false;
}
back();
return true;
}
/**
* Get the next character in the source string.
*
* @return The next character, or 0 if past the end of the source string.
* @throws JSONException JSONException.
*/
public char next() throws JSONException {
int c;
if (this.usePrevious) {
this.usePrevious = false;
c = this.previous;
} else {
try {
c = this.reader.read();
} catch (IOException exception) {
throw new JSONException(exception);
}
if (c <= 0) { // End of stream
this.eof = true;
c = 0;
}
}
this.index += 1;
if (this.previous == '\r') {
this.line += 1;
this.character = c == '\n' ? 0 : 1;
} else if (c == '\n') {
this.line += 1;
this.character = 0;
} else {
this.character += 1;
}
this.previous = (char) c;
return this.previous;
}
/**
* Consume the next character, and check that it matches a specified character.
*
* @param c The character to match.
* @return The character.
* @throws JSONException if the character does not match.
*/
public char next(char c) throws JSONException {
char n = next();
if (n != c) {
throw syntaxError("Expected '" + c + "' and instead saw '" + n + "'");
}
return n;
}
/**
* Get the next n characters.
*
* @param n The number of characters to take.
* @return A string of n characters.
* @throws JSONException Substring bounds error if there are not n characters remaining in the
* source string.
*/
public String next(int n) throws JSONException {
if (n == 0) {
return "";
}
char[] buffer = new char[n];
int pos = 0;
while (pos < n) {
buffer[pos] = next();
if (end()) {
throw syntaxError("Substring bounds error");
}
pos += 1;
}
return new String(buffer);
}
/**
* Get the next char in the string, skipping whitespace.
*
* @return A character, or 0 if there are no more characters.
* @throws JSONException JSONException.
*/
public char nextClean() throws JSONException {
for (;;) {
char c = next();
if (c == 0 || c > ' ') {
return c;
}
}
}
/**
* Return the characters up to the next close quote character. Backslash processing is done. The
* formal JSON format does not allow strings in single quotes, but an implementation is allowed
* to accept them.
*
* @param quote The quoting character, either " (double quote)
* or ' (single quote).
* @return A String.
* @throws JSONException Unterminated string.
*/
public String nextString(char quote) throws JSONException {
char c;
StringBuffer sb = new StringBuffer();
for (;;) {
c = next();
switch (c) {
case 0:
case '\n':
case '\r':
throw syntaxError("Unterminated string");
case '\\':
c = next();
switch (c) {
case 'b':
sb.append('\b');
break;
case 't':
sb.append('\t');
break;
case 'n':
sb.append('\n');
break;
case 'f':
sb.append('\f');
break;
case 'r':
sb.append('\r');
break;
case 'u':
sb.append((char) Integer.parseInt(next(4), 16));
break;
case '"':
case '\'':
case '\\':
case '/':
sb.append(c);
break;
default:
throw syntaxError("Illegal escape.");
}
break;
default:
if (c == quote) {
return sb.toString();
}
sb.append(c);
}
}
}
/**
* Get the text up but not including the specified character or the end of line, whichever comes
* first.
*
* @param d A delimiter character.
* @return A string.
* @throws JSONException JSONException.
*/
public String nextTo(char d) throws JSONException {
StringBuffer sb = new StringBuffer();
for (;;) {
char c = next();
if (c == d || c == 0 || c == '\n' || c == '\r') {
if (c != 0) {
back();
}
return sb.toString().trim();
}
sb.append(c);
}
}
/**
* Get the text up but not including one of the specified delimiter characters or the end of
* line, whichever comes first.
*
* @param delimiters A set of delimiter characters.
* @return A string, trimmed.
* @throws JSONException JSONException.
*/
public String nextTo(String delimiters) throws JSONException {
char c;
StringBuffer sb = new StringBuffer();
for (;;) {
c = next();
if (delimiters.indexOf(c) >= 0 || c == 0 || c == '\n' || c == '\r') {
if (c != 0) {
back();
}
return sb.toString().trim();
}
sb.append(c);
}
}
/**
* Get the next value. The value can be a Boolean, Double, Integer, JSONArray, JSONObject, Long,
* or String, or the JSONObject.NULL object.
*
* @throws JSONException If syntax error.
*
* @return An object.
*/
public Object nextValue() throws JSONException {
char c = nextClean();
String s;
switch (c) {
case '"':
case '\'':
return nextString(c);
case '{':
back();
return new JSONObject(this);
case '[':
case '(':
back();
return new JSONArray(this);
}
/*
* Handle unquoted text. This could be the values true, false, or null, or it can be a
* number. An implementation (such as this one) is allowed to also accept non-standard
* forms.
*
* Accumulate characters until we reach the end of the text or a formatting character.
*/
StringBuffer sb = new StringBuffer();
while (c >= ' ' && ",:]}/\\\"[{;=#".indexOf(c) < 0) {
sb.append(c);
c = next();
}
back();
s = sb.toString().trim();
if (s.equals("")) {
throw syntaxError("Missing value");
}
return JSONObject.stringToValue(s);
}
/**
* Skip characters until the next character is the requested character. If the requested
* character is not found, no characters are skipped.
*
* @param to A character to skip to.
* @return The requested character, or zero if the requested character is not found.
* @throws JSONException JSONException.
*/
public char skipTo(char to) throws JSONException {
char c;
try {
int startIndex = this.index;
int startCharacter = this.character;
int startLine = this.line;
reader.mark(Integer.MAX_VALUE);
do {
c = next();
if (c == 0) {
reader.reset();
this.index = startIndex;
this.character = startCharacter;
this.line = startLine;
return c;
}
} while (c != to);
} catch (IOException exc) {
throw new JSONException(exc);
}
back();
return c;
}
/**
* Make a JSONException to signal a syntax error.
*
* @param message The error message.
* @return A JSONException object, suitable for throwing
*/
public JSONException syntaxError(String message) {
return new JSONException(message + toString());
}
/**
* Make a printable string of this JSONTokener.
*
* @return " at {index} [character {character} line {line}]"
*/
public String toString() {
return " at " + index + " [character " + this.character + " line " + this.line + "]";
}
}