//

//  GTMNSData+zlib.m

//

//  Copyright 2007-2008 Google Inc.

//

//  Licensed under the Apache License, Version 2.0 (the "License"); you may not

//  use this file except in compliance with the License.  You may obtain a copy

//  of the License at

// 

//  http://www.apache.org/licenses/LICENSE-2.0

// 

//  Unless required by applicable law or agreed to in writing, software

//  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

//  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the

//  License for the specific language governing permissions and limitations under

//  the License.

//

#import "GTMNSData+zlib.h"

#import <zlib.h>

#import "GTMDefines.h"

#define kChunkSize 1024

@interface NSData (GTMZlibAdditionsPrivate)

+ (NSData *)gtm_dataByCompressingBytes:(const void *)bytes

                                length:(NSUInteger)length

                      compressionLevel:(int)level

                               useGzip:(BOOL)useGzip;

@end

@implementation NSData (GTMZlibAdditionsPrivate)

+ (NSData *)gtm_dataByCompressingBytes:(const void *)bytes

                                length:(NSUInteger)length

                      compressionLevel:(int)level

                               useGzip:(BOOL)useGzip {

  if (!bytes || !length) {

    return nil;

  }

  // TODO: support 64bit inputs

  // avail_in is a uInt, so if length > UINT_MAX we actually need to loop

  // feeding the data until we've gotten it all in.  not supporting this

  // at the moment.

  _GTMDevAssert(length <= UINT_MAX, @"Currently don't support >32bit lengths");

  if (level == Z_DEFAULT_COMPRESSION) {

    // the default value is actually outside the range, so we have to let it

    // through specifically.

  } else if (level < Z_BEST_SPEED) {

    level = Z_BEST_SPEED;

  } else if (level > Z_BEST_COMPRESSION) {

    level = Z_BEST_COMPRESSION;

  }

  z_stream strm;

  bzero(&strm, sizeof(z_stream));

  int windowBits = 15; // the default

  int memLevel = 8; // the default

  if (useGzip) {

    windowBits += 16; // enable gzip header instead of zlib header

  }

  int retCode;

  if ((retCode = deflateInit2(&strm, level, Z_DEFLATED, windowBits,

                              memLevel, Z_DEFAULT_STRATEGY)) != Z_OK) {

    // COV_NF_START - no real way to force this in a unittest (we guard all args)

    _GTMDevLog(@"Failed to init for deflate w/ level %d, error %d",

               level, retCode);

    return nil;

    // COV_NF_END

  }

  // hint the size at 1/4 the input size

  NSMutableData *result = [NSMutableData dataWithCapacity:(length/4)];

  unsigned char output[kChunkSize];

  // setup the input

  strm.avail_in = (unsigned int)length;

  strm.next_in = (unsigned char*)bytes;

  // loop to collect the data

  do {

    // update what we're passing in

    strm.avail_out = kChunkSize;

    strm.next_out = output;

    retCode = deflate(&strm, Z_FINISH);

    if ((retCode != Z_OK) && (retCode != Z_STREAM_END)) {

      // COV_NF_START - no real way to force this in a unittest

      // (in inflate, we can feed bogus/truncated data to test, but an error

      // here would be some internal issue w/in zlib, and there isn't any real

      // way to test it)

      _GTMDevLog(@"Error trying to deflate some of the payload, error %d",

                 retCode);

      deflateEnd(&strm);

      return nil;

      // COV_NF_END

    }

    // collect what we got

    unsigned gotBack = kChunkSize - strm.avail_out;

    if (gotBack > 0) {

      [result appendBytes:output length:gotBack];

    }

  } while (retCode == Z_OK);

  // if the loop exits, we used all input and the stream ended

  _GTMDevAssert(strm.avail_in == 0,

                @"thought we finished deflate w/o using all input, %u bytes left",

                strm.avail_in);

  _GTMDevAssert(retCode == Z_STREAM_END,

                @"thought we finished deflate w/o getting a result of stream end, code %d",

                retCode);

  // clean up

  deflateEnd(&strm);

  return result;

} // gtm_dataByCompressingBytes:length:compressionLevel:useGzip:

@end

@implementation NSData (GTMZLibAdditions)

+ (NSData *)gtm_dataByGzippingBytes:(const void *)bytes

                             length:(NSUInteger)length {

  return [self gtm_dataByCompressingBytes:bytes

                                   length:length

                         compressionLevel:Z_DEFAULT_COMPRESSION

                                  useGzip:YES];

} // gtm_dataByGzippingBytes:length:

+ (NSData *)gtm_dataByGzippingData:(NSData *)data {

  return [self gtm_dataByCompressingBytes:[data bytes]

                                   length:[data length]

                         compressionLevel:Z_DEFAULT_COMPRESSION

                                  useGzip:YES];

} // gtm_dataByGzippingData:

+ (NSData *)gtm_dataByGzippingBytes:(const void *)bytes

                             length:(NSUInteger)length

                   compressionLevel:(int)level {

  return [self gtm_dataByCompressingBytes:bytes

                                   length:length

                         compressionLevel:level

                                  useGzip:YES];

} // gtm_dataByGzippingBytes:length:level:

+ (NSData *)gtm_dataByGzippingData:(NSData *)data

                  compressionLevel:(int)level {

  return [self gtm_dataByCompressingBytes:[data bytes]

                                   length:[data length]

                         compressionLevel:level

                                  useGzip:YES];

} // gtm_dataByGzippingData:level:

+ (NSData *)gtm_dataByDeflatingBytes:(const void *)bytes

                              length:(NSUInteger)length {

  return [self gtm_dataByCompressingBytes:bytes

                                   length:length

                         compressionLevel:Z_DEFAULT_COMPRESSION

                                  useGzip:NO];

} // gtm_dataByDeflatingBytes:length:

+ (NSData *)gtm_dataByDeflatingData:(NSData *)data {

  return [self gtm_dataByCompressingBytes:[data bytes]

                                   length:[data length]

                         compressionLevel:Z_DEFAULT_COMPRESSION

                                  useGzip:NO];

} // gtm_dataByDeflatingData:

+ (NSData *)gtm_dataByDeflatingBytes:(const void *)bytes

                              length:(NSUInteger)length

                    compressionLevel:(int)level {

  return [self gtm_dataByCompressingBytes:bytes

                                   length:length

                         compressionLevel:level

                                  useGzip:NO];

} // gtm_dataByDeflatingBytes:length:level:

+ (NSData *)gtm_dataByDeflatingData:(NSData *)data

                   compressionLevel:(int)level {

  return [self gtm_dataByCompressingBytes:[data bytes]

                                   length:[data length]

                         compressionLevel:level

                                  useGzip:NO];

} // gtm_dataByDeflatingData:level:

+ (NSData *)gtm_dataByInflatingBytes:(const void *)bytes

                              length:(NSUInteger)length {

  if (!bytes || !length) {

    return nil;

  }

  // TODO: support 64bit inputs

  // avail_in is a uInt, so if length > UINT_MAX we actually need to loop

  // feeding the data until we've gotten it all in.  not supporting this

  // at the moment.

  _GTMDevAssert(length <= UINT_MAX, @"Currently don't support >32bit lengths");

  z_stream strm;

  bzero(&strm, sizeof(z_stream));

  // setup the input

  strm.avail_in = (unsigned int)length;

  strm.next_in = (unsigned char*)bytes;

  int windowBits = 15; // 15 to enable any window size

  windowBits += 32; // and +32 to enable zlib or gzip header detection.

  int retCode;

  if ((retCode = inflateInit2(&strm, windowBits)) != Z_OK) {

    // COV_NF_START - no real way to force this in a unittest (we guard all args)

    _GTMDevLog(@"Failed to init for inflate, error %d", retCode);

    return nil;

    // COV_NF_END

  }

  // hint the size at 4x the input size

  NSMutableData *result = [NSMutableData dataWithCapacity:(length*4)];

  unsigned char output[kChunkSize];

  // loop to collect the data

  do {

    // update what we're passing in

    strm.avail_out = kChunkSize;

    strm.next_out = output;

    retCode = inflate(&strm, Z_NO_FLUSH);

    if ((retCode != Z_OK) && (retCode != Z_STREAM_END)) {

      _GTMDevLog(@"Error trying to inflate some of the payload, error %d",

                 retCode);

      inflateEnd(&strm);

      return nil;

    }

    // collect what we got

    unsigned gotBack = kChunkSize - strm.avail_out;

    if (gotBack > 0) {

      [result appendBytes:output length:gotBack];

    }

  } while (retCode == Z_OK);

  // make sure there wasn't more data tacked onto the end of a valid compressed

  // stream.

  if (strm.avail_in != 0) {

    _GTMDevLog(@"thought we finished inflate w/o using all input, %u bytes left",

               strm.avail_in);

    result = nil;

  }

  // the only way out of the loop was by hitting the end of the stream

  _GTMDevAssert(retCode == Z_STREAM_END,

                @"thought we finished inflate w/o getting a result of stream end, code %d",

                retCode);

  // clean up

  inflateEnd(&strm);

  return result;

} // gtm_dataByInflatingBytes:length:

+ (NSData *)gtm_dataByInflatingData:(NSData *)data {

  return [self gtm_dataByInflatingBytes:[data bytes]

                                 length:[data length]];

} // gtm_dataByInflatingData:

@end