如何從Kotlin中的Header獲取原始檔案擴展名

我有一個擴展名未知的檔案。有沒有辦法通過檔案頭找到擴展的型別？

uj5u.com熱心網友回復：

你有一個好的猜測嗎？每種格式都沒有使用一個標準檔案頭。有些（如 .txt）沒有標題。其他人都有自己的自定義標題。有時即使是標題也不夠——不同型別的 .wav 和 .bmp 檔案有多個子標題。如果您有一個猜測，您可以使用該格式具有的任何標頭來測驗該猜測，但如果您甚至沒有猜測，您將無處可去。

檔案的標頭不是元資料，它只是（通常）檔案的前 N ??個位元組。

uj5u.com熱心網友回復：

用法：

GetFileHeader.isPDF(filename)

GetFileHeader 類用 java 撰寫，但您可以在 kotlin 中使用它

public class GetFileHeader {
    private static final int PDF_MAGIC[] = new int[] { 0x25, 0x50, 0x44, 0x46};
    private static final int DOC1_MAGIC[] = new int[] { 0xd0, 0xcf, 0x11, 0xe0, 0xa1, 0xb1, 0x1a, 0xe1};
    private static final int DOC2_MAGIC[] = new int[] { 0x0d, 0x44, 0x4f, 0x43};
    private static final int DOC3_MAGIC[] = new int[] { 0xcf, 0x11, 0xe0, 0xa1, 0xb1,0x1a, 0xe1, 0x00};
    private static final int DOC4_MAGIC[] = new int[] { 0xdb, 0xa5, 0x2d, 0x00};
    private static final int DOC5_MAGIC[] = new int[] { 0xec, 0xa5, 0xc1, 0x00};
    private static final int DOCX1_MAGIC[] = new int[] { 0x50, 0x4b, 0x03, 0x04};
    private static final int DOCX2_MAGIC[] = new int[] { 0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x06, 0x00};

    public static boolean isPDF(File filename) throws Exception {
        FileInputStream ins = new FileInputStream(filename);
        try {
            for(int i = 0; i < PDF_MAGIC.length;   i) {
                if(ins.read() != PDF_MAGIC[i]) {
                    return false;
                }
            }
            return true;
        } finally {
            ins.close();
        }
    }
    public static boolean isDoc1(File filename) throws Exception {
        FileInputStream ins = new FileInputStream(filename);
        try {
            for(int i = 0; i < DOC1_MAGIC.length;   i) {
                if(ins.read() != DOC1_MAGIC[i]) {
                    return false;
                }
            }
            return true;
        } finally {
            ins.close();
        }
    }
    public static boolean isDoc2(File filename) throws Exception {
        FileInputStream ins = new FileInputStream(filename);
        try {
            for(int i = 0; i < DOC2_MAGIC.length;   i) {
                if(ins.read() != DOC2_MAGIC[i]) {
                    return false;
                }
            }
            return true;
        } finally {
            ins.close();
        }
    }
    public static boolean isDoc3(File filename) throws Exception {
        FileInputStream ins = new FileInputStream(filename);
        try {
            for(int i = 0; i < DOC3_MAGIC.length;   i) {
                if(ins.read() != DOC3_MAGIC[i]) {
                    return false;
                }
            }
            return true;
        } finally {
            ins.close();
        }
    }
    public static boolean isDoc4(File filename) throws Exception {
        FileInputStream ins = new FileInputStream(filename);
        try {
            for(int i = 0; i < DOC4_MAGIC.length;   i) {
                if(ins.read() != DOC4_MAGIC[i]) {
                    return false;
                }
            }
            return true;
        } finally {
            ins.close();
        }
    }
    public static boolean isDoc5(File filename) throws Exception {
        FileInputStream ins = new FileInputStream(filename);
        try {
            for(int i = 0; i < DOC5_MAGIC.length;   i) {
                if(ins.read() != DOC5_MAGIC[i]) {
                    return false;
                }
            }
            return true;
        } finally {
            ins.close();
        }
    }
    public static boolean isDocX1(File filename) throws Exception {
        FileInputStream ins = new FileInputStream(filename);
        try {
            for(int i = 0; i < DOCX1_MAGIC.length;   i) {
                if(ins.read() != DOCX1_MAGIC[i]) {
                    return false;
                }
            }
            return true;
        } finally {
            ins.close();
        }
    }
    public static boolean isDocX2(File filename) throws Exception {
        FileInputStream ins = new FileInputStream(filename);
        try {
            for(int i = 0; i < DOCX2_MAGIC.length;   i) {
                if(ins.read() != DOCX2_MAGIC[i]) {
                    return false;
                }
            }
            return true;
        } finally {
            ins.close();
        }
    }

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