зеркало из https://github.com/mozilla/gecko-dev.git
158 строки
4.4 KiB
Java
158 строки
4.4 KiB
Java
/*
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* Copyright (C) 2013 Square, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.squareup.picasso;
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import java.io.BufferedInputStream;
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import java.io.IOException;
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import java.io.InputStream;
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/**
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* An input stream wrapper that supports unlimited independent cursors for
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* marking and resetting. Each cursor is a token, and it's the caller's
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* responsibility to keep track of these.
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*/
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final class MarkableInputStream extends InputStream {
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private final InputStream in;
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private long offset;
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private long reset;
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private long limit;
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private long defaultMark = -1;
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public MarkableInputStream(InputStream in) {
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if (!in.markSupported()) {
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in = new BufferedInputStream(in);
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}
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this.in = in;
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}
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/** Marks this place in the stream so we can reset back to it later. */
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@Override public void mark(int readLimit) {
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defaultMark = savePosition(readLimit);
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}
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/**
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* Returns an opaque token representing the current position in the stream.
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* Call {@link #reset(long)} to return to this position in the stream later.
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* It is an error to call {@link #reset(long)} after consuming more than
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* {@code readLimit} bytes from this stream.
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*/
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public long savePosition(int readLimit) {
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long offsetLimit = offset + readLimit;
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if (limit < offsetLimit) {
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setLimit(offsetLimit);
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}
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return offset;
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}
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/**
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* Makes sure that the underlying stream can backtrack the full range from
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* {@code reset} thru {@code limit}. Since we can't call {@code mark()}
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* without also adjusting the reset-to-position on the underlying stream this
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* method resets first and then marks the union of the two byte ranges. On
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* buffered streams this additional cursor motion shouldn't result in any
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* additional I/O.
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*/
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private void setLimit(long limit) {
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try {
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if (reset < offset && offset <= this.limit) {
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in.reset();
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in.mark((int) (limit - reset));
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skip(reset, offset);
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} else {
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reset = offset;
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in.mark((int) (limit - offset));
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}
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this.limit = limit;
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} catch (IOException e) {
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throw new IllegalStateException("Unable to mark: " + e);
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}
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}
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/** Resets the stream to the most recent {@link #mark mark}. */
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@Override public void reset() throws IOException {
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reset(defaultMark);
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}
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/** Resets the stream to the position recorded by {@code token}. */
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public void reset(long token) throws IOException {
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if (offset > limit || token < reset) {
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throw new IOException("Cannot reset");
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}
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in.reset();
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skip(reset, token);
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offset = token;
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}
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/** Skips {@code target - current} bytes and returns. */
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private void skip(long current, long target) throws IOException {
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while (current < target) {
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long skipped = in.skip(target - current);
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if (skipped == 0) {
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if (read() == -1) {
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break; // EOF
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} else {
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skipped = 1;
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}
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}
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current += skipped;
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}
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}
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@Override public int read() throws IOException {
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int result = in.read();
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if (result != -1) {
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offset++;
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}
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return result;
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}
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@Override public int read(byte[] buffer) throws IOException {
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int count = in.read(buffer);
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if (count != -1) {
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offset += count;
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}
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return count;
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}
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@Override public int read(byte[] buffer, int offset, int length) throws IOException {
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int count = in.read(buffer, offset, length);
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if (count != -1) {
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this.offset += count;
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}
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return count;
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}
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@Override public long skip(long byteCount) throws IOException {
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long skipped = in.skip(byteCount);
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offset += skipped;
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return skipped;
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}
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@Override public int available() throws IOException {
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return in.available();
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}
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@Override public void close() throws IOException {
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in.close();
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}
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@Override public boolean markSupported() {
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return in.markSupported();
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}
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}
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