Source Code for Apache Log4j API

Apache Log4j API provides the interface that applications should code to and provides the adapter components required for implementers to create a logging implementation. Apache Log4j API is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j API is provided in a separate JAR file like log4j-api-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like apache-log4j-2.14.1-bin.zip and source package like apache-log4j-2.14.1-src.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j API 2.14.1 below.

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org/apache/logging/log4j/message/ParameterFormatter.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache license, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the license for the specific language governing permissions and
 * limitations under the license.
 */
package org.apache.logging.log4j.message;

import org.apache.logging.log4j.util.StringBuilders;

import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.IdentityHashMap;
import java.util.Map;
import java.util.Set;

/**
 * Supports parameter formatting as used in ParameterizedMessage and ReusableParameterizedMessage.
 */
final class ParameterFormatter {
    /**
     * Prefix for recursion.
     */
    static final String RECURSION_PREFIX = "[...";
    /**
     * Suffix for recursion.
     */
    static final String RECURSION_SUFFIX = "...]";

    /**
     * Prefix for errors.
     */
    static final String ERROR_PREFIX = "[!!!";
    /**
     * Separator for errors.
     */
    static final String ERROR_SEPARATOR = "=>";
    /**
     * Separator for error messages.
     */
    static final String ERROR_MSG_SEPARATOR = ":";
    /**
     * Suffix for errors.
     */
    static final String ERROR_SUFFIX = "!!!]";

    private static final char DELIM_START = '{';
    private static final char DELIM_STOP = '}';
    private static final char ESCAPE_CHAR = '\\';

    private static final ThreadLocal<SimpleDateFormat> SIMPLE_DATE_FORMAT_REF =
            ThreadLocal.withInitial(() -> new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ"));

    private ParameterFormatter() {
    }

    /**
     * Counts the number of unescaped placeholders in the given messagePattern.
     *
     * @param messagePattern the message pattern to be analyzed.
     * @return the number of unescaped placeholders.
     */
    static int countArgumentPlaceholders(final String messagePattern) {
        if (messagePattern == null) {
            return 0;
        }
        final int length = messagePattern.length();
        int result = 0;
        boolean isEscaped = false;
        for (int i = 0; i < length - 1; i++) {
            final char curChar = messagePattern.charAt(i);
            if (curChar == ESCAPE_CHAR) {
                isEscaped = !isEscaped;
            } else if (curChar == DELIM_START) {
                if (!isEscaped && messagePattern.charAt(i + 1) == DELIM_STOP) {
                    result++;
                    i++;
                }
                isEscaped = false;
            } else {
                isEscaped = false;
            }
        }
        return result;
    }

    /**
     * Counts the number of unescaped placeholders in the given messagePattern.
     *
     * @param messagePattern the message pattern to be analyzed.
     * @return the number of unescaped placeholders.
     */
    static int countArgumentPlaceholders2(final String messagePattern, final int[] indices) {
        if (messagePattern == null) {
            return 0;
        }
        final int length = messagePattern.length();
        int result = 0;
        boolean isEscaped = false;
        for (int i = 0; i < length - 1; i++) {
            final char curChar = messagePattern.charAt(i);
            if (curChar == ESCAPE_CHAR) {
                isEscaped = !isEscaped;
                indices[0] = -1; // escaping means fast path is not available...
                result++;
            } else if (curChar == DELIM_START) {
                if (!isEscaped && messagePattern.charAt(i + 1) == DELIM_STOP) {
                    indices[result] = i;
                    result++;
                    i++;
                }
                isEscaped = false;
            } else {
                isEscaped = false;
            }
        }
        return result;
    }

    /**
     * Counts the number of unescaped placeholders in the given messagePattern.
     *
     * @param messagePattern the message pattern to be analyzed.
     * @return the number of unescaped placeholders.
     */
    static int countArgumentPlaceholders3(final char[] messagePattern, final int length, final int[] indices) {
        int result = 0;
        boolean isEscaped = false;
        for (int i = 0; i < length - 1; i++) {
            final char curChar = messagePattern[i];
            if (curChar == ESCAPE_CHAR) {
                isEscaped = !isEscaped;
            } else if (curChar == DELIM_START) {
                if (!isEscaped && messagePattern[i + 1] == DELIM_STOP) {
                    indices[result] = i;
                    result++;
                    i++;
                }
                isEscaped = false;
            } else {
                isEscaped = false;
            }
        }
        return result;
    }

    /**
     * Replace placeholders in the given messagePattern with arguments.
     *
     * @param messagePattern the message pattern containing placeholders.
     * @param arguments      the arguments to be used to replace placeholders.
     * @return the formatted message.
     */
    static String format(final String messagePattern, final Object[] arguments) {
        final StringBuilder result = new StringBuilder();
        final int argCount = arguments == null ? 0 : arguments.length;
        formatMessage(result, messagePattern, arguments, argCount);
        return result.toString();
    }

    /**
     * Replace placeholders in the given messagePattern with arguments.
     *
     * @param buffer the buffer to write the formatted message into
     * @param messagePattern the message pattern containing placeholders.
     * @param arguments      the arguments to be used to replace placeholders.
     */
    static void formatMessage2(final StringBuilder buffer, final String messagePattern,
            final Object[] arguments, final int argCount, final int[] indices) {
        if (messagePattern == null || arguments == null || argCount == 0) {
            buffer.append(messagePattern);
            return;
        }
        int previous = 0;
        for (int i = 0; i < argCount; i++) {
            buffer.append(messagePattern, previous, indices[i]);
            previous = indices[i] + 2;
            recursiveDeepToString(arguments[i], buffer);
        }
        buffer.append(messagePattern, previous, messagePattern.length());
    }

    /**
     * Replace placeholders in the given messagePattern with arguments.
     *
     * @param buffer the buffer to write the formatted message into
     * @param messagePattern the message pattern containing placeholders.
     * @param arguments      the arguments to be used to replace placeholders.
     */
    static void formatMessage3(final StringBuilder buffer, final char[] messagePattern, final int patternLength,
            final Object[] arguments, final int argCount, final int[] indices) {
        if (messagePattern == null) {
            return;
        }
        if (arguments == null || argCount == 0) {
            buffer.append(messagePattern);
            return;
        }
        int previous = 0;
        for (int i = 0; i < argCount; i++) {
            buffer.append(messagePattern, previous, indices[i]);
            previous = indices[i] + 2;
            recursiveDeepToString(arguments[i], buffer);
        }
        buffer.append(messagePattern, previous, patternLength);
    }

    /**
     * Replace placeholders in the given messagePattern with arguments.
     *
     * @param buffer the buffer to write the formatted message into
     * @param messagePattern the message pattern containing placeholders.
     * @param arguments      the arguments to be used to replace placeholders.
     */
    static void formatMessage(final StringBuilder buffer, final String messagePattern,
            final Object[] arguments, final int argCount) {
        if (messagePattern == null || arguments == null || argCount == 0) {
            buffer.append(messagePattern);
            return;
        }
        int escapeCounter = 0;
        int currentArgument = 0;
        int i = 0;
        final int len = messagePattern.length();
        for (; i < len - 1; i++) { // last char is excluded from the loop
            final char curChar = messagePattern.charAt(i);
            if (curChar == ESCAPE_CHAR) {
                escapeCounter++;
            } else {
                if (isDelimPair(curChar, messagePattern, i)) { // looks ahead one char
                    i++;

                    // write escaped escape chars
                    writeEscapedEscapeChars(escapeCounter, buffer);

                    if (isOdd(escapeCounter)) {
                        // i.e. escaped: write escaped escape chars
                        writeDelimPair(buffer);
                    } else {
                        // unescaped
                        writeArgOrDelimPair(arguments, argCount, currentArgument, buffer);
                        currentArgument++;
                    }
                } else {
                    handleLiteralChar(buffer, escapeCounter, curChar);
                }
                escapeCounter = 0;
            }
        }
        handleRemainingCharIfAny(messagePattern, len, buffer, escapeCounter, i);
    }

    /**
     * Returns {@code true} if the specified char and the char at {@code curCharIndex + 1} in the specified message
     * pattern together form a "{}" delimiter pair, returns {@code false} otherwise.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 22 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static boolean isDelimPair(final char curChar, final String messagePattern, final int curCharIndex) {
        return curChar == DELIM_START && messagePattern.charAt(curCharIndex + 1) == DELIM_STOP;
    }

    /**
     * Detects whether the message pattern has been fully processed or if an unprocessed character remains and processes
     * it if necessary, returning the resulting position in the result char array.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 28 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static void handleRemainingCharIfAny(final String messagePattern, final int len,
            final StringBuilder buffer, final int escapeCounter, final int i) {
        if (i == len - 1) {
            final char curChar = messagePattern.charAt(i);
            handleLastChar(buffer, escapeCounter, curChar);
        }
    }

    /**
     * Processes the last unprocessed character and returns the resulting position in the result char array.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 28 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static void handleLastChar(final StringBuilder buffer, final int escapeCounter, final char curChar) {
        if (curChar == ESCAPE_CHAR) {
            writeUnescapedEscapeChars(escapeCounter + 1, buffer);
        } else {
            handleLiteralChar(buffer, escapeCounter, curChar);
        }
    }

    /**
     * Processes a literal char (neither an '\' escape char nor a "{}" delimiter pair) and returns the resulting
     * position.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 16 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static void handleLiteralChar(final StringBuilder buffer, final int escapeCounter, final char curChar) {
        // any other char beside ESCAPE or DELIM_START/STOP-combo
        // write unescaped escape chars
        writeUnescapedEscapeChars(escapeCounter, buffer);
        buffer.append(curChar);
    }

    /**
     * Writes "{}" to the specified result array at the specified position and returns the resulting position.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 18 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static void writeDelimPair(final StringBuilder buffer) {
        buffer.append(DELIM_START);
        buffer.append(DELIM_STOP);
    }

    /**
     * Returns {@code true} if the specified parameter is odd.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 11 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static boolean isOdd(final int number) {
        return (number & 1) == 1;
    }

    /**
     * Writes a '\' char to the specified result array (starting at the specified position) for each <em>pair</em> of
     * '\' escape chars encountered in the message format and returns the resulting position.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 11 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static void writeEscapedEscapeChars(final int escapeCounter, final StringBuilder buffer) {
        final int escapedEscapes = escapeCounter >> 1; // divide by two
        writeUnescapedEscapeChars(escapedEscapes, buffer);
    }

    /**
     * Writes the specified number of '\' chars to the specified result array (starting at the specified position) and
     * returns the resulting position.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 20 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static void writeUnescapedEscapeChars(int escapeCounter, final StringBuilder buffer) {
        while (escapeCounter > 0) {
            buffer.append(ESCAPE_CHAR);
            escapeCounter--;
        }
    }

    /**
     * Appends the argument at the specified argument index (or, if no such argument exists, the "{}" delimiter pair) to
     * the specified result char array at the specified position and returns the resulting position.
     */
    // Profiling showed this method is important to log4j performance. Modify with care!
    // 25 bytes (allows immediate JVM inlining: < 35 bytes) LOG4J2-1096
    private static void writeArgOrDelimPair(final Object[] arguments, final int argCount, final int currentArgument,
            final StringBuilder buffer) {
        if (currentArgument < argCount) {
            recursiveDeepToString(arguments[currentArgument], buffer);
        } else {
            writeDelimPair(buffer);
        }
    }

    /**
     * This method performs a deep toString of the given Object.
     * Primitive arrays are converted using their respective Arrays.toString methods while
     * special handling is implemented for "container types", i.e. Object[], Map and Collection because those could
     * contain themselves.
     * <p>
     * It should be noted that neither AbstractMap.toString() nor AbstractCollection.toString() implement such a
     * behavior. They only check if the container is directly contained in itself, but not if a contained container
     * contains the original one. Because of that, Arrays.toString(Object[]) isn't safe either.
     * Confusing? Just read the last paragraph again and check the respective toString() implementation.
     * </p>
     * <p>
     * This means, in effect, that logging would produce a usable output even if an ordinary System.out.println(o)
     * would produce a relatively hard-to-debug StackOverflowError.
     * </p>
     * @param o The object.
     * @return The String representation.
     */
    static String deepToString(final Object o) {
        if (o == null) {
            return null;
        }
        // Check special types to avoid unnecessary StringBuilder usage
        if (o instanceof String) {
            return (String) o;
        }
        if (o instanceof Integer) {
            return Integer.toString((Integer) o);
        }
        if (o instanceof Long) {
            return Long.toString((Long) o);
        }
        if (o instanceof Double) {
            return Double.toString((Double) o);
        }
        if (o instanceof Boolean) {
            return Boolean.toString((Boolean) o);
        }
        if (o instanceof Character) {
            return Character.toString((Character) o);
        }
        if (o instanceof Short) {
            return Short.toString((Short) o);
        }
        if (o instanceof Float) {
            return Float.toString((Float) o);
        }
        if (o instanceof Byte) {
            return Byte.toString((Byte) o);
        }
        final StringBuilder str = new StringBuilder();
        recursiveDeepToString(o, str);
        return str.toString();
    }

    /**
     * This method performs a deep {@code toString()} of the given {@code Object}.
     * <p>
     * Primitive arrays are converted using their respective {@code Arrays.toString()} methods, while
     * special handling is implemented for <i>container types</i>, i.e. {@code Object[]}, {@code Map} and {@code Collection},
     * because those could contain themselves.
     * <p>
     * It should be noted that neither {@code AbstractMap.toString()} nor {@code AbstractCollection.toString()} implement such a behavior.
     * They only check if the container is directly contained in itself, but not if a contained container contains the original one.
     * Because of that, {@code Arrays.toString(Object[])} isn't safe either.
     * Confusing? Just read the last paragraph again and check the respective {@code toString()} implementation.
     * <p>
     * This means, in effect, that logging would produce a usable output even if an ordinary {@code System.out.println(o)}
     * would produce a relatively hard-to-debug {@code StackOverflowError}.
     *
     * @param o      the {@code Object} to convert into a {@code String}
     * @param str    the {@code StringBuilder} that {@code o} will be appended to
     */
    static void recursiveDeepToString(final Object o, final StringBuilder str) {
        recursiveDeepToString(o, str, null);
    }

    /**
     * This method performs a deep {@code toString()} of the given {@code Object}.
     * <p>
     * Primitive arrays are converted using their respective {@code Arrays.toString()} methods, while
     * special handling is implemented for <i>container types</i>, i.e. {@code Object[]}, {@code Map} and {@code Collection},
     * because those could contain themselves.
     * <p>
     * {@code dejaVu} is used in case of those container types to prevent an endless recursion.
     * <p>
     * It should be noted that neither {@code AbstractMap.toString()} nor {@code AbstractCollection.toString()} implement such a behavior.
     * They only check if the container is directly contained in itself, but not if a contained container contains the original one.
     * Because of that, {@code Arrays.toString(Object[])} isn't safe either.
     * Confusing? Just read the last paragraph again and check the respective {@code toString()} implementation.
     * <p>
     * This means, in effect, that logging would produce a usable output even if an ordinary {@code System.out.println(o)}
     * would produce a relatively hard-to-debug {@code StackOverflowError}.
     *
     * @param o      the {@code Object} to convert into a {@code String}
     * @param str    the {@code StringBuilder} that {@code o} will be appended to
     * @param dejaVu a set of container objects directly or transitively containing {@code o}
     */
    private static void recursiveDeepToString(final Object o, final StringBuilder str, final Set<Object> dejaVu) {
        if (appendSpecialTypes(o, str)) {
            return;
        }
        if (isMaybeRecursive(o)) {
            appendPotentiallyRecursiveValue(o, str, dejaVu);
        } else {
            tryObjectToString(o, str);
        }
    }

    private static boolean appendSpecialTypes(final Object o, final StringBuilder str) {
        return StringBuilders.appendSpecificTypes(str, o) || appendDate(o, str);
    }

    private static boolean appendDate(final Object o, final StringBuilder str) {
        if (!(o instanceof Date)) {
            return false;
        }
        final Date date = (Date) o;
        final SimpleDateFormat format = SIMPLE_DATE_FORMAT_REF.get();
        str.append(format.format(date));
        return true;
    }

    /**
     * Returns {@code true} if the specified object is an array, a Map or a Collection.
     */
    private static boolean isMaybeRecursive(final Object o) {
        return o.getClass().isArray() || o instanceof Map || o instanceof Collection;
    }

    private static void appendPotentiallyRecursiveValue(
            final Object o,
            final StringBuilder str,
            final Set<Object> dejaVu) {
        final Class<?> oClass = o.getClass();
        if (oClass.isArray()) {
            appendArray(o, str, dejaVu, oClass);
        } else if (o instanceof Map) {
            appendMap(o, str, dejaVu);
        } else if (o instanceof Collection) {
            appendCollection(o, str, dejaVu);
        } else {
            throw new IllegalArgumentException("was expecting a container, found " + oClass);
        }
    }

    private static void appendArray(
            final Object o,
            final StringBuilder str,
            final Set<Object> dejaVu,
            final Class<?> oClass) {
        if (oClass == byte[].class) {
            str.append(Arrays.toString((byte[]) o));
        } else if (oClass == short[].class) {
            str.append(Arrays.toString((short[]) o));
        } else if (oClass == int[].class) {
            str.append(Arrays.toString((int[]) o));
        } else if (oClass == long[].class) {
            str.append(Arrays.toString((long[]) o));
        } else if (oClass == float[].class) {
            str.append(Arrays.toString((float[]) o));
        } else if (oClass == double[].class) {
            str.append(Arrays.toString((double[]) o));
        } else if (oClass == boolean[].class) {
            str.append(Arrays.toString((boolean[]) o));
        } else if (oClass == char[].class) {
            str.append(Arrays.toString((char[]) o));
        } else {
            // special handling of container Object[]
            final Set<Object> effectiveDejaVu = getOrCreateDejaVu(dejaVu);
            final boolean seen = !effectiveDejaVu.add(o);
            if (seen) {
                final String id = identityToString(o);
                str.append(RECURSION_PREFIX).append(id).append(RECURSION_SUFFIX);
            } else {
                final Object[] oArray = (Object[]) o;
                str.append('[');
                boolean first = true;
                for (final Object current : oArray) {
                    if (first) {
                        first = false;
                    } else {
                        str.append(", ");
                    }
                    recursiveDeepToString(current, str, cloneDejaVu(effectiveDejaVu));
                }
                str.append(']');
            }
        }
    }

    /**
     * Specialized handler for {@link Map}s.
     */
    private static void appendMap(
            final Object o,
            final StringBuilder str,
            final Set<Object> dejaVu) {
        final Set<Object> effectiveDejaVu = getOrCreateDejaVu(dejaVu);
        final boolean seen = !effectiveDejaVu.add(o);
        if (seen) {
            final String id = identityToString(o);
            str.append(RECURSION_PREFIX).append(id).append(RECURSION_SUFFIX);
        } else {
            final Map<?, ?> oMap = (Map<?, ?>) o;
            str.append('{');
            boolean isFirst = true;
            for (final Object o1 : oMap.entrySet()) {
                final Map.Entry<?, ?> current = (Map.Entry<?, ?>) o1;
                if (isFirst) {
                    isFirst = false;
                } else {
                    str.append(", ");
                }
                final Object key = current.getKey();
                final Object value = current.getValue();
                recursiveDeepToString(key, str, cloneDejaVu(effectiveDejaVu));
                str.append('=');
                recursiveDeepToString(value, str, cloneDejaVu(effectiveDejaVu));
            }
            str.append('}');
        }
    }

    /**
     * Specialized handler for {@link Collection}s.
     */
    private static void appendCollection(
            final Object o,
            final StringBuilder str,
            final Set<Object> dejaVu) {
        final Set<Object> effectiveDejaVu = getOrCreateDejaVu(dejaVu);
        final boolean seen = !effectiveDejaVu.add(o);
        if (seen) {
            final String id = identityToString(o);
            str.append(RECURSION_PREFIX).append(id).append(RECURSION_SUFFIX);
        } else {
            final Collection<?> oCol = (Collection<?>) o;
            str.append('[');
            boolean isFirst = true;
            for (final Object anOCol : oCol) {
                if (isFirst) {
                    isFirst = false;
                } else {
                    str.append(", ");
                }
                recursiveDeepToString(anOCol, str, cloneDejaVu(effectiveDejaVu));
            }
            str.append(']');
        }
    }

    private static Set<Object> getOrCreateDejaVu(Set<Object> dejaVu) {
        return dejaVu == null
                ? createDejaVu()
                : dejaVu;
    }

    private static Set<Object> createDejaVu() {
        return Collections.newSetFromMap(new IdentityHashMap<>());
    }

    private static Set<Object> cloneDejaVu(Set<Object> dejaVu) {
        Set<Object> clonedDejaVu = createDejaVu();
        clonedDejaVu.addAll(dejaVu);
        return clonedDejaVu;
    }

    private static void tryObjectToString(final Object o, final StringBuilder str) {
        // it's just some other Object, we can only use toString().
        try {
            str.append(o.toString());
        } catch (final Throwable t) {
            handleErrorInObjectToString(o, str, t);
        }
    }

    private static void handleErrorInObjectToString(final Object o, final StringBuilder str, final Throwable t) {
        str.append(ERROR_PREFIX);
        str.append(identityToString(o));
        str.append(ERROR_SEPARATOR);
        final String msg = t.getMessage();
        final String className = t.getClass().getName();
        str.append(className);
        if (!className.equals(msg)) {
            str.append(ERROR_MSG_SEPARATOR);
            str.append(msg);
        }
        str.append(ERROR_SUFFIX);
    }

    /**
     * This method returns the same as if Object.toString() would not have been
     * overridden in obj.
     * <p>
     * Note that this isn't 100% secure as collisions can always happen with hash codes.
     * </p>
     * <p>
     * Copied from Object.hashCode():
     * </p>
     * <blockquote>
     * As much as is reasonably practical, the hashCode method defined by
     * class {@code Object} does return distinct integers for distinct
     * objects. (This is typically implemented by converting the internal
     * address of the object into an integer, but this implementation
     * technique is not required by the Java&#8482; programming language.)
     * </blockquote>
     *
     * @param obj the Object that is to be converted into an identity string.
     * @return the identity string as also defined in Object.toString()
     */
    static String identityToString(final Object obj) {
        if (obj == null) {
            return null;
        }
        return obj.getClass().getName() + '@' + Integer.toHexString(System.identityHashCode(obj));
    }

}

org/apache/logging/log4j/message/ParameterFormatter.java

 

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