io.helidon.common.http.Preconditions Maven / Gradle / Ivy
/*
* Copyright (c) 2018 Oracle and/or its affiliates. All rights reserved.
*
* Licensed 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 io.helidon.common.http;
/**
* Copied from Guava.
*
* Static convenience methods that help a method or constructor check whether it was invoked
* correctly (whether its preconditions have been met). These methods generally accept a
* {@code boolean} expression which is expected to be {@code true} (or in the case of {@code
* checkNotNull}, an object reference which is expected to be non-null). When {@code false} (or
* {@code null}) is passed instead, the {@code Preconditions} method throws an unchecked exception,
* which helps the calling method communicate to its caller that that caller has made
* a mistake. Example:
{@code
*
* /**
* * Returns the positive square root of the given value.
* *
* * @throws IllegalArgumentException if the value is negative
* *}{@code /
* public static double sqrt(double value) {
* Preconditions.checkArgument(value >= 0.0, "negative value: %s", value);
* // calculate the square root
* }
*
* void exampleBadCaller() {
* double d = sqrt(-1.0);
* }}
*
* In this example, {@code checkArgument} throws an {@code IllegalArgumentException} to indicate
* that {@code exampleBadCaller} made an error in its call to {@code sqrt}.
*
* Warning about performance
*
* The goal of this class is to improve readability of code, but in some circumstances this may
* come at a significant performance cost. Remember that parameter values for message construction
* must all be computed eagerly, and autoboxing and varargs array creation may happen as well, even
* when the precondition check then succeeds (as it should almost always do in production). In some
* circumstances these wasted CPU cycles and allocations can add up to a real problem.
* Performance-sensitive precondition checks can always be converted to the customary form:
*
{@code
*
* if (value < 0.0) {
* throw new IllegalArgumentException("negative value: " + value);
* }}
*
* Other types of preconditions
*
* Not every type of precondition failure is supported by these methods. Continue to throw
* standard JDK exceptions such as {@link java.util.NoSuchElementException} or
* {@link UnsupportedOperationException} in the situations they are intended for.
*
*
Non-preconditions
*
* It is of course possible to use the methods of this class to check for invalid conditions
* which are not the caller's fault. Doing so is not recommended because it is
* misleading to future readers of the code and of stack traces. See
* Conditional failures
* explained in the Guava User Guide for more advice.
*
*
Only {@code %s} is supported
*
* In {@code Preconditions} error message template strings, only the {@code "%s"} specifier is
* supported, not the full range of {@link java.util.Formatter} specifiers.
*
*
More information
*
* See the Guava User Guide on
* using {@code
* Preconditions}.
*
* @author Kevin Bourrillion
*/
final class Preconditions {
private Preconditions() {
}
/**
* Ensures that {@code index} specifies a valid position in an array, list or string of
* size {@code size}. A position index may range from zero to {@code size}, inclusive.
*
* @param index a user-supplied index identifying a position in an array, list or string
* @param size the size of that array, list or string
* @return the value of {@code index}
* @throws IndexOutOfBoundsException if {@code index} is negative or is greater than {@code size}
* @throws IllegalArgumentException if {@code size} is negative
*/
public static int checkPositionIndex(int index, int size) {
return checkPositionIndex(index, size, "index");
}
/**
* Ensures that {@code index} specifies a valid position in an array, list or string of
* size {@code size}. A position index may range from zero to {@code size}, inclusive.
*
* @param index a user-supplied index identifying a position in an array, list or string
* @param size the size of that array, list or string
* @param desc the text to use to describe this index in an error message
* @return the value of {@code index}
* @throws IndexOutOfBoundsException if {@code index} is negative or is greater than {@code size}
* @throws IllegalArgumentException if {@code size} is negative
*/
public static int checkPositionIndex(int index, int size, String desc) {
// Carefully optimized for execution by hotspot (explanatory comment above)
if (index < 0 || index > size) {
throw new IndexOutOfBoundsException(badPositionIndex(index, size, desc));
}
return index;
}
/**
* Ensures that {@code start} and {@code end} specify a valid positions in an array, list
* or string of size {@code size}, and are in order. A position index may range from zero to
* {@code size}, inclusive.
*
* @param start a user-supplied index identifying a starting position in an array, list or string
* @param end a user-supplied index identifying a ending position in an array, list or string
* @param size the size of that array, list or string
* @throws IndexOutOfBoundsException if either index is negative or is greater than {@code size},
* or if {@code end} is less than {@code start}
* @throws IllegalArgumentException if {@code size} is negative
*/
public static void checkPositionIndexes(int start, int end, int size) {
// Carefully optimized for execution by hotspot (explanatory comment above)
if (start < 0 || end < start || end > size) {
throw new IndexOutOfBoundsException(badPositionIndexes(start, end, size));
}
}
private static String badPositionIndexes(int start, int end, int size) {
if (start < 0 || start > size) {
return badPositionIndex(start, size, "start index");
}
if (end < 0 || end > size) {
return badPositionIndex(end, size, "end index");
}
// end < start
return format("end index (%s) must not be less than start index (%s)", end, start);
}
private static String badPositionIndex(int index, int size, String desc) {
if (index < 0) {
return format("%s (%s) must not be negative", desc, index);
} else if (size < 0) {
throw new IllegalArgumentException("negative size: " + size);
} else { // index > size
return format("%s (%s) must not be greater than size (%s)", desc, index, size);
}
}
/**
* Substitutes each {@code %s} in {@code template} with an argument. These are matched by
* position: the first {@code %s} gets {@code args[0]}, etc. If there are more arguments than
* placeholders, the unmatched arguments will be appended to the end of the formatted message in
* square braces.
*
* @param template a non-null string containing 0 or more {@code %s} placeholders.
* @param args the arguments to be substituted into the message template. Arguments are converted
* to strings using {@link String#valueOf(Object)}. Arguments can be null.
*/
// Note that this is somewhat-improperly used from Verify.java as well.
static String format(String template, Object... args) {
template = String.valueOf(template); // null -> "null"
// start substituting the arguments into the '%s' placeholders
StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
int templateStart = 0;
int i = 0;
while (i < args.length) {
int placeholderStart = template.indexOf("%s", templateStart);
if (placeholderStart == -1) {
break;
}
builder.append(template, templateStart, placeholderStart);
builder.append(args[i++]);
templateStart = placeholderStart + 2;
}
builder.append(template, templateStart, template.length());
// if we run out of placeholders, append the extra args in square braces
if (i < args.length) {
builder.append(" [");
builder.append(args[i++]);
while (i < args.length) {
builder.append(", ");
builder.append(args[i++]);
}
builder.append(']');
}
return builder.toString();
}
}