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Library of functions for use in JSON parsing and formatting
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/*
* @(#) JSONFunctions.java
*
* json-functions Functions for use in JSON parsing and formatting
* Copyright (c) 2021, 2022, 2023 Peter Wall
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package net.pwall.json;
import java.io.IOException;
import java.util.function.IntConsumer;
import net.pwall.text.TextMatcher;
import net.pwall.util.IntOutput;
/**
* A set of static functions used in conversion to and from JSON string representations.
*
* @author Peter Wall
*/
public class JSONFunctions {
public static final String UNTERMINATED_STRING = "Unterminated JSON string";
public static final String ILLEGAL_CHAR = "Illegal character in JSON string";
public static final String ILLEGAL_UNICODE_SEQUENCE = "Illegal Unicode sequence in JSON string";
public static final String ILLEGAL_ESCAPE_SEQUENCE = "Illegal escape sequence in JSON string";
/**
* Append a {@link CharSequence} to an {@link Appendable} in JSON quoted string form (applying JSON escaping rules).
* The characters above the ASCII range ({@code 0x20} to {@code 0x7E}) are output as Unicode escape sequences unless
* the {@code includeNonASCII} flag is set to {@code true}.
*
* @param a the {@link Appendable}
* @param cs the {@link CharSequence}
* @param includeNonASCII if {@code true}, output the characters above the ASCII range without escaping
* @throws IOException if thrown by the {@link Appendable}
*/
public static void appendString(Appendable a, CharSequence cs, boolean includeNonASCII) throws IOException {
a.append('"');
for (int i = 0, n = cs.length(); i < n; i++)
appendChar(a, cs.charAt(i), includeNonASCII);
a.append('"');
}
/**
* Output a {@link CharSequence} using an {@link IntConsumer} in JSON quoted string form (applying JSON escaping
* rules). The characters above the ASCII range ({@code 0x20} to {@code 0x7E}) are output as Unicode escape
* sequences unless the {@code includeNonASCII} flag is set to {@code true}.
*
* @param cs the {@link CharSequence}
* @param includeNonASCII if {@code true}, output the characters above the ASCII range without escaping
* @param consumer the {@link IntConsumer}
*/
public static void outputString(CharSequence cs, boolean includeNonASCII, IntConsumer consumer) {
consumer.accept('"');
for (int i = 0, n = cs.length(); i < n; i++)
outputChar(cs.charAt(i), includeNonASCII, consumer);
consumer.accept('"');
}
/**
* Convert a {@link CharSequence} to a {@link String} in JSON quoted string form (applying JSON escaping rules).
* The characters above the ASCII range ({@code 0x20} to {@code 0x7E}) are output as Unicode escape sequences unless
* the {@code includeNonASCII} flag is set to {@code true}.
*
* @param cs the {@link CharSequence}
* @param includeNonASCII if {@code true}, output the characters above the ASCII range without escaping
* @return the converted string
*/
public static String escapeString(CharSequence cs, boolean includeNonASCII) {
StringBuilder sb = new StringBuilder();
try {
appendString(sb, cs, includeNonASCII);
}
catch (IOException ignore) {
// Can't happen - StringBuilder doesn't throw exception
}
return sb.toString();
}
/**
* Convert a {@link CharSequence} to a {@link String}, applying JSON escaping rules without enclosing quotes. The
* characters above the ASCII range ({@code 0x20} to {@code 0x7E}) are output as Unicode escape sequences unless the
* {@code includeNonASCII} flag is set to {@code true}. If there are no characters requiring conversion, the
* original string is returned unmodified.
*
* @param cs the {@link CharSequence}
* @param includeNonASCII if {@code true}, output the characters above the ASCII range without escaping
* @return the converted string
*/
public static String escapeStringUnquoted(CharSequence cs, boolean includeNonASCII) {
for (int i = 0, n = cs.length(); i < n; i++) {
char ch = cs.charAt(i);
if (ch < ' ' || ch >= '\u007F' || ch == '"' || ch == '\\') {
try {
StringBuilder sb = new StringBuilder();
if (i > 0)
sb.append(cs, 0, i);
while (true) {
appendChar(sb, ch, includeNonASCII);
if (++i >= n)
break;
ch = cs.charAt(i);
}
return sb.toString();
}
catch (IOException e) {
// Can't happen - StringBuilder doesn't throw exception
}
}
}
return cs.toString();
}
/**
* Convert a {@link CharSequence} to a {@link String}, applying JSON escaping rules without enclosing quotes. If
* there are no characters requiring conversion, the original string is returned unmodified.
*
* @param cs the {@link CharSequence}
* @return the converted string
*/
public static String escapeStringUnquoted(CharSequence cs) {
return escapeStringUnquoted(cs, false);
}
/**
* Append a single character to an {@link Appendable} applying JSON escaping rules. The characters above the ASCII
* range ({@code 0x20} to {@code 0x7E}) are output as Unicode escape sequences unless the {@code includeNonASCII}
* flag is set to {@code true}.
*
* @param a the {@link Appendable}
* @param ch the character
* @param includeNonASCII if {@code true}, output the characters above the ASCII range without escaping
* @throws IOException if thrown by the {@link Appendable}
*/
public static void appendChar(Appendable a, char ch, boolean includeNonASCII) throws IOException {
if (ch == '"' || ch == '\\') {
a.append('\\');
a.append(ch);
}
else if (ch == '\b')
a.append("\\b");
else if (ch == '\f')
a.append("\\f");
else if (ch == '\n')
a.append("\\n");
else if (ch == '\r')
a.append("\\r");
else if (ch == '\t')
a.append("\\t");
else if (ch < 0x20 || ch >= 0x7F && ch < 0xA0 || ch >= 0xA0 && !includeNonASCII) {
a.append("\\u");
IntOutput.append4HexLC(a, ch);
}
else
a.append(ch);
}
/**
* Output a single character using an {@link IntConsumer} applying JSON escaping rules. The characters above the
* ASCII range ({@code 0x20} to {@code 0x7E}) are output as Unicode escape sequences unless the
* {@code includeNonASCII} flag is set to {@code true}.
*
* @param ch the character
* @param includeNonASCII if {@code true}, output the characters above the ASCII range without escaping
* @param consumer the {@link IntConsumer}
*/
public static void outputChar(char ch, boolean includeNonASCII, IntConsumer consumer) {
if (ch == '"' || ch == '\\') {
consumer.accept('\\');
consumer.accept(ch);
}
else if (ch == '\b') {
consumer.accept('\\');
consumer.accept('b');
}
else if (ch == '\f') {
consumer.accept('\\');
consumer.accept('f');
}
else if (ch == '\n') {
consumer.accept('\\');
consumer.accept('n');
}
else if (ch == '\r') {
consumer.accept('\\');
consumer.accept('r');
}
else if (ch == '\t') {
consumer.accept('\\');
consumer.accept('t');
}
else if (ch < 0x20 || ch >= 0x7F && ch < 0xA0 || ch >= 0xA0 && !includeNonASCII) {
consumer.accept('\\');
consumer.accept('u');
IntOutput.output4HexLC(ch, consumer);
}
else
consumer.accept(ch);
}
/**
* Create a display form of a string, usually for error reporting. The string is constrained to a maximum number of
* characters, and if it exceeds that number the string is split and " ... " is inserted in the middle.
*
* @param str the string
* @param maxChars the maximum number of characters
* @return the display string
*/
public static String displayString(String str, int maxChars) {
StringBuilder sb = new StringBuilder();
sb.append('"');
try {
int i = 0;
int n = str.length();
if (maxChars > 7 && n > maxChars) {
int m = (maxChars - 4) >> 1;
while (i < m)
appendChar(sb, str.charAt(i++), true);
sb.append(" ... ");
i = n - ((maxChars - 5) >> 1);
}
while (i < n)
appendChar(sb, str.charAt(i++), true);
}
catch (IOException ignore) {
// can't happen - StringBuilder doesn't throw exception
}
sb.append('"');
return sb.toString();
}
/**
* Parse a JSON string from the current position of a {@link TextMatcher} (which must be positioned after the
* opening double quote). The index is left positioned after the closing double quote.
*
* @param tm a {@link TextMatcher}
* @return the JSON string
* @throws IllegalArgumentException if there are any errors in the JSON
*/
public static String parseString(TextMatcher tm) {
int start = tm.getIndex();
while (true) {
if (tm.isAtEnd())
throw new IllegalArgumentException(UNTERMINATED_STRING);
char ch = tm.nextChar();
if (ch == '"')
return tm.getString(start, tm.getStart());
if (ch == '\\')
break;
if (ch < 0x20)
throw new IllegalArgumentException(ILLEGAL_CHAR);
}
StringBuilder sb = new StringBuilder(tm.getCharSeq(start, tm.getStart()));
while (true) {
if (tm.isAtEnd())
throw new IllegalArgumentException(UNTERMINATED_STRING);
char ch = tm.nextChar();
if (ch == '"')
sb.append('"');
else if (ch == '\\')
sb.append('\\');
else if (ch == '/')
sb.append('/');
else if (ch == 'b')
sb.append('\b');
else if (ch == 'f')
sb.append('\f');
else if (ch == 'n')
sb.append('\n');
else if (ch == 'r')
sb.append('\r');
else if (ch == 't')
sb.append('\t');
else if (ch == 'u') {
if (!tm.matchHex(4, 4))
throw new IllegalArgumentException(ILLEGAL_UNICODE_SEQUENCE);
sb.append((char)tm.getResultHexInt());
}
else
throw new IllegalArgumentException(ILLEGAL_ESCAPE_SEQUENCE);
while (true) {
if (tm.isAtEnd())
throw new IllegalArgumentException(UNTERMINATED_STRING);
ch = tm.nextChar();
if (ch == '"')
return sb.toString();
if (ch == '\\')
break;
if (ch < 0x20)
throw new IllegalArgumentException(ILLEGAL_CHAR);
sb.append(ch);
}
}
}
/**
* Test whether a given character is a space, according to the JSON specification.
*
* @param ch the character
* @return {@code true} if the character is a space
*/
public static boolean isSpaceCharacter(char ch) {
return ch == ' ' || ch == '\n' || ch == '\t' || ch == '\r';
}
}
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