//
//  GZIP.m
//
//  Version 1.2.1
//
//  Created by Nick Lockwood on 03/06/2012.
//  Copyright (C) 2012 Charcoal Design
//
//  Distributed under the permissive zlib License
//  Get the latest version from here:
//
//  https://github.com/nicklockwood/GZIP
//
//  This software is provided 'as-is', without any express or implied
//  warranty.  In no event will the authors be held liable for any damages
//  arising from the use of this software.
//
//  Permission is granted to anyone to use this software for any purpose,
//  including commercial applications, and to alter it and redistribute it
//  freely, subject to the following restrictions:
//
//  1. The origin of this software must not be misrepresented; you must not
//  claim that you wrote the original software. If you use this software
//  in a product, an acknowledgment in the product documentation would be
//  appreciated but is not required.
//
//  2. Altered source versions must be plainly marked as such, and must not be
//  misrepresented as being the original software.
//
//  3. This notice may not be removed or altered from any source distribution.
//


#import "NSData+GZip.h"
#import <zlib.h>


#pragma clang diagnostic ignored "-Wcast-qual"


@implementation NSData (GZIP)

- (NSData *)gzippedDataWithCompressionLevel:(float)level
{
    if (self.length == 0 || [self isGzippedData])
    {
        return self;
    }
    
    z_stream stream;
    stream.zalloc = Z_NULL;
    stream.zfree = Z_NULL;
    stream.opaque = Z_NULL;
    stream.avail_in = (uint)self.length;
    stream.next_in = (Bytef *)(void *)self.bytes;
    stream.total_out = 0;
    stream.avail_out = 0;
    
    static const NSUInteger ChunkSize = 16384;
    
    NSMutableData *output = nil;
    int compression = (level < 0.0f)? Z_DEFAULT_COMPRESSION: (int)(roundf(level * 9));
    if (deflateInit2(&stream, compression, Z_DEFLATED, 31, 8, Z_DEFAULT_STRATEGY) == Z_OK)
    {
        output = [NSMutableData dataWithLength:ChunkSize];
        while (stream.avail_out == 0)
        {
            if (stream.total_out >= output.length)
            {
                output.length += ChunkSize;
            }
            stream.next_out = (uint8_t *)output.mutableBytes + stream.total_out;
            stream.avail_out = (uInt)(output.length - stream.total_out);
            deflate(&stream, Z_FINISH);
        }
        deflateEnd(&stream);
        output.length = stream.total_out;
    }
    
    return output;
}

- (NSData *)gzippedData
{
    return [self gzippedDataWithCompressionLevel:-1.0f];
}

- (NSData *)gunzippedData
{
    if (self.length == 0 || ![self isGzippedData])
    {
        return self;
    }
    
    z_stream stream;
    stream.zalloc = Z_NULL;
    stream.zfree = Z_NULL;
    stream.avail_in = (uint)self.length;
    stream.next_in = (Bytef *)self.bytes;
    stream.total_out = 0;
    stream.avail_out = 0;
    
    NSMutableData *output = nil;
    if (inflateInit2(&stream, 47) == Z_OK)
    {
        int status = Z_OK;
        output = [NSMutableData dataWithCapacity:self.length * 2];
        while (status == Z_OK)
        {
            if (stream.total_out >= output.length)
            {
                output.length += self.length / 2;
            }
            stream.next_out = (uint8_t *)output.mutableBytes + stream.total_out;
            stream.avail_out = (uInt)(output.length - stream.total_out);
            status = inflate (&stream, Z_SYNC_FLUSH);
        }
        if (inflateEnd(&stream) == Z_OK)
        {
            if (status == Z_STREAM_END)
            {
                output.length = stream.total_out;
            }
        }
    }
    
    return output;
}

- (BOOL)isGzippedData
{
    const UInt8 *bytes = (const UInt8 *)self.bytes;
    return (self.length >= 2 && bytes[0] == 0x1f && bytes[1] == 0x8b);
}

@end
