library/src/main/java/com/bumptech/glide/util/Util.java

package com.bumptech.glide.util;

import android.annotation.TargetApi;
import android.graphics.Bitmap;
import android.os.Build;
import android.os.Looper;

import java.util.ArrayDeque;
import java.util.Queue;

/**
 * A collection of assorted utility classes.
 */
public final class Util {
    private static final char[] HEX_CHAR_ARRAY = "0123456789abcdef".toCharArray();
    // 32 bytes from sha-256 -> 64 hex chars.
    private static final char[] SHA_256_CHARS = new char[64];
    // 20 bytes from sha-1 -> 40 chars.
    private static final char[] SHA_1_CHARS = new char[40];

    private Util() {
        // Utility class.
    }

    /**
     * Returns the hex string of the given byte array representing a SHA256 hash.
     */
    public static String sha256BytesToHex(byte[] bytes) {
        return bytesToHex(bytes, SHA_256_CHARS);
    }

    /**
     * Returns the hex string of the given byte array representing a SHA1 hash.
     */
    public static String sha1BytesToHex(byte[] bytes) {
        return bytesToHex(bytes, SHA_1_CHARS);
    }

    // Taken from:
    // http://stackoverflow.com/questions/9655181/convert-from-byte-array-to-hex-string-in-java/9655275#9655275
    private static String bytesToHex(byte[] bytes, char[] hexChars) {
        int v;
        for (int j = 0; j < bytes.length; j++) {
            v = bytes[j] & 0xFF;
            hexChars[j * 2] = HEX_CHAR_ARRAY[v >>> 4];
            hexChars[j * 2 + 1] = HEX_CHAR_ARRAY[v & 0x0F];
        }
        return new String(hexChars);
    }

    /**
     * Returns the allocated byte size of the given bitmap.
     *
     * @see #getBitmapByteSize(android.graphics.Bitmap)
     *
     * @deprecated Use {@link #getBitmapByteSize(android.graphics.Bitmap)} instead. Scheduled to be removed in Glide
     * 4.0.
     */
    @Deprecated
    public static int getSize(Bitmap bitmap) {
        return getBitmapByteSize(bitmap);
    }

    /**
     * Returns the in memory size of the given {@link Bitmap} in bytes.
     */
    @TargetApi(Build.VERSION_CODES.KITKAT)
    public static int getBitmapByteSize(Bitmap bitmap) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            // Workaround for KitKat initial release NPE in Bitmap, fixed in MR1. See issue #148.
            try {
                return bitmap.getAllocationByteCount();
            } catch (NullPointerException e) {
                // Do nothing.
            }
        }
        return bitmap.getHeight() * bitmap.getRowBytes();
    }

    /**
     * Returns the in memory size of {@link android.graphics.Bitmap} with the given width, height, and
     * {@link android.graphics.Bitmap.Config}.
     */
    public static int getBitmapByteSize(int width, int height, Bitmap.Config config) {
        return width * height * getBytesPerPixel(config);
    }

    private static int getBytesPerPixel(Bitmap.Config config) {
        // A bitmap by decoding a gif has null "config" in certain environments.
        if (config == null) {
            config = Bitmap.Config.ARGB_8888;
        }

        int bytesPerPixel;
        switch (config) {
            case ALPHA_8:
                bytesPerPixel = 1;
                break;
            case RGB_565:
            case ARGB_4444:
                bytesPerPixel = 2;
                break;
            case ARGB_8888:
            default:
                bytesPerPixel = 4;
        }
        return bytesPerPixel;
    }

    /**
     * Throws an {@link java.lang.IllegalArgumentException} if called on a thread other than the main thread.
     */
    public static void assertMainThread() {
        if (!isOnMainThread()) {
            throw new IllegalArgumentException("You must call this method on the main thread");
        }
    }

    /**
     * Throws an {@link java.lang.IllegalArgumentException} if called on the main thread.
     */
    public static void assertBackgroundThread() {
        if (!isOnBackgroundThread()) {
            throw new IllegalArgumentException("YOu must call this method on a background thread");
        }
    }

    /**
     * Returns {@code true} if called on the main thread, {@code false} otherwise.
     */
    public static boolean isOnMainThread() {
        return Looper.myLooper() == Looper.getMainLooper();
    }

    /**
     * Returns {@code true} if called on the main thread, {@code false} otherwise.
     */
    public static boolean isOnBackgroundThread() {
        return !isOnMainThread();
    }

    /**
     * Creates a {@link java.util.Queue} of the given size using Glide's preferred implementation.
     */
    public static <T> Queue<T> createQueue(int size) {
        return new ArrayDeque<T>(size);
    }
}