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/*
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* Copyright 2020 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#import "GoogleDataTransport/GDTCCTLibrary/Private/GDTCCTCompressionHelper.h"
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#import <zlib.h>
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@implementation GDTCCTCompressionHelper
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+ (nullable NSData *)gzippedData:(NSData *)data {
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#if defined(__LP64__) && __LP64__
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// Don't support > 32bit length for 64 bit, see note in header.
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if (data.length > UINT_MAX) {
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return nil;
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}
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#endif
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enum { kChunkSize = 1024 };
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const void *bytes = [data bytes];
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NSUInteger length = [data length];
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int level = Z_DEFAULT_COMPRESSION;
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if (!bytes || !length) {
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return nil;
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}
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z_stream strm;
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bzero(&strm, sizeof(z_stream));
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int memLevel = 8; // Default.
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int windowBits = 15 + 16; // Enable gzip header instead of zlib header.
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int retCode;
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if (deflateInit2(&strm, level, Z_DEFLATED, windowBits, memLevel, Z_DEFAULT_STRATEGY) != Z_OK) {
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return nil;
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}
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// Hint the size at 1/4 the input size.
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NSMutableData *result = [NSMutableData dataWithCapacity:(length / 4)];
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unsigned char output[kChunkSize];
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// Setup the input.
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strm.avail_in = (unsigned int)length;
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strm.next_in = (unsigned char *)bytes;
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// Collect the data.
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do {
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// update what we're passing in
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strm.avail_out = kChunkSize;
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strm.next_out = output;
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retCode = deflate(&strm, Z_FINISH);
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if ((retCode != Z_OK) && (retCode != Z_STREAM_END)) {
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deflateEnd(&strm);
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return nil;
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}
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// Collect what we got.
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unsigned gotBack = kChunkSize - strm.avail_out;
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if (gotBack > 0) {
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[result appendBytes:output length:gotBack];
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}
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} while (retCode == Z_OK);
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// If the loop exits, it used all input and the stream ended.
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NSAssert(strm.avail_in == 0,
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@"Should have finished deflating without using all input, %u bytes left", strm.avail_in);
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NSAssert(retCode == Z_STREAM_END,
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@"thought we finished deflate w/o getting a result of stream end, code %d", retCode);
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// Clean up.
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deflateEnd(&strm);
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return result;
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}
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+ (BOOL)isGzipped:(NSData *)data {
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const UInt8 *bytes = (const UInt8 *)data.bytes;
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return (data.length >= 2 && bytes[0] == 0x1f && bytes[1] == 0x8b);
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}
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@end
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