package com.alibaba.fastjson.util;

import java.lang.ref.SoftReference;
import java.nio.charset.CharsetDecoder;

public class ThreadLocalCache {

    public final static int                                 CHARS_CACH_INIT_SIZE = 1024;                                    // 1k;
    public final static int                                 CHARS_CACH_MAX_SIZE  = 1024 * 128;                              // 1k;
    private final static ThreadLocal<SoftReference<char[]>> charsBufLocal        = new ThreadLocal<SoftReference<char[]>>();

    private final static ThreadLocal<CharsetDecoder>        decoderLocal         = new ThreadLocal<CharsetDecoder>();

    public static CharsetDecoder getUTF8Decoder() {
        CharsetDecoder decoder = decoderLocal.get();
        if (decoder == null) {
            decoder = new UTF8Decoder();
            decoderLocal.set(decoder);
        }
        return decoder;
    }

    public static void clearChars() {
        charsBufLocal.set(null);
    }

    public static char[] getChars(int length) {
        SoftReference<char[]> ref = charsBufLocal.get();

        if (ref == null) {
            return allocate(length);
        }

        char[] chars = ref.get();

        if (chars == null) {
            return allocate(length);
        }

        if (chars.length < length) {
            chars = allocate(length);
        }

        return chars;
    }

    private static char[] allocate(int length) {
        int allocateLength = getAllocateLength(CHARS_CACH_INIT_SIZE, CHARS_CACH_MAX_SIZE, length);

        if (allocateLength <= CHARS_CACH_MAX_SIZE) {
            char[] chars = new char[allocateLength];
            charsBufLocal.set(new SoftReference<char[]>(chars));
            return chars;
        }

        return new char[length];
    }

    private static int getAllocateLength(int init, int max, int length) {
        int value = init;
        for (;;) {
            if (value >= length) {
                return value;
            }

            value *= 2;

            if (value > max) {
                break;
            }
        }

        return length;
    }

    // /////////
    public final static int                                 BYTES_CACH_INIT_SIZE = 1024;                                    // 1k;
    public final static int                                 BYTeS_CACH_MAX_SIZE  = 1024 * 128;                              // 1k;
    private final static ThreadLocal<SoftReference<byte[]>> bytesBufLocal        = new ThreadLocal<SoftReference<byte[]>>();

    public static void clearBytes() {
        bytesBufLocal.set(null);
    }

    public static byte[] getBytes(int length) {
        SoftReference<byte[]> ref = bytesBufLocal.get();

        if (ref == null) {
            return allocateBytes(length);
        }

        byte[] bytes = ref.get();

        if (bytes == null) {
            return allocateBytes(length);
        }

        if (bytes.length < length) {
            bytes = allocateBytes(length);
        }

        return bytes;
    }

    private static byte[] allocateBytes(int length) {
        int allocateLength = getAllocateLength(CHARS_CACH_INIT_SIZE, CHARS_CACH_MAX_SIZE, length);

        if (allocateLength <= CHARS_CACH_MAX_SIZE) {
            byte[] chars = new byte[allocateLength];
            bytesBufLocal.set(new SoftReference<byte[]>(chars));
            return chars;
        }

        return new byte[length];
    }

}