54 lines
1.5 KiB
Java
54 lines
1.5 KiB
Java
/*
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* Copyright 2019 Zhou Pengfei
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* SPDX-License-Identifier: Apache-2.0
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*/
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package org.signal.glide.apng.decode;
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import android.text.TextUtils;
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import org.signal.glide.apng.io.APNGReader;
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import java.io.IOException;
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/**
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* @Description: Length (长度) 4字节 指定数据块中数据域的长度，其长度不超过(231－1)字节
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* Chunk Type Code (数据块类型码) 4字节 数据块类型码由ASCII字母(A-Z和a-z)组成
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* Chunk Data (数据块数据) 可变长度 存储按照Chunk Type Code指定的数据
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* CRC (循环冗余检测) 4字节 存储用来检测是否有错误的循环冗余码
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* @Link https://www.w3.org/TR/PNG
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* @Author: pengfei.zhou
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* @CreateDate: 2019/3/27
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*/
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class Chunk {
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int length;
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int fourcc;
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int crc;
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int offset;
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static int fourCCToInt(String fourCC) {
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if (TextUtils.isEmpty(fourCC) || fourCC.length() != 4) {
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return 0xbadeffff;
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}
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return (fourCC.charAt(0) & 0xff)
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| (fourCC.charAt(1) & 0xff) << 8
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| (fourCC.charAt(2) & 0xff) << 16
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| (fourCC.charAt(3) & 0xff) << 24
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;
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}
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void parse(APNGReader reader) throws IOException {
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int available = reader.available();
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innerParse(reader);
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int offset = available - reader.available();
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if (offset > length) {
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throw new IOException("Out of chunk area");
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} else if (offset < length) {
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reader.skip(length - offset);
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}
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}
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void innerParse(APNGReader reader) throws IOException {
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}
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}
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