//
//  GTMNSData+Hex.m
//
//  Copyright 2009 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+Hex.h"
#import "GTMDefines.h"

@implementation NSData (GTMHexAdditions)

+ (NSData *)gtm_dataWithHexString:(NSString *)hexString {
  NSData *hexData = [hexString dataUsingEncoding:NSASCIIStringEncoding];
  const char *hexBuf = [hexData bytes];
  NSUInteger hexLen = [hexData length];

  // This indicates an error converting to ASCII.
  if (hexString && !hexData) {
    return nil;
  }

  if ((hexLen % 2) != 0) {
    return nil;
  }

  NSMutableData *binaryData = [NSMutableData dataWithLength:(hexLen / 2)];
  unsigned char *binaryPtr = [binaryData mutableBytes];
  unsigned char value = 0;
  for (NSUInteger i = 0; i < hexLen; i++) {
    char c = hexBuf[i];

    if (!isxdigit(c)) {
      return nil;
    }

    if (isdigit(c)) {
      value += c - '0';
    } else if (islower(c)) {
      value += 10 + c - 'a';
    } else {
      value += 10 + c - 'A';
    }

    if (i & 1) {
      *binaryPtr++ = value;
      value = 0;
    } else {
      value <<= 4;
    }
  }

  return [NSData dataWithData:binaryData];
}

- (NSString *)gtm_hexString {
  static const char kHexTable[] =
    "000102030405060708090a0b0c0d0e0f"
    "101112131415161718191a1b1c1d1e1f"
    "202122232425262728292a2b2c2d2e2f"
    "303132333435363738393a3b3c3d3e3f"
    "404142434445464748494a4b4c4d4e4f"
    "505152535455565758595a5b5c5d5e5f"
    "606162636465666768696a6b6c6d6e6f"
    "707172737475767778797a7b7c7d7e7f"
    "808182838485868788898a8b8c8d8e8f"
    "909192939495969798999a9b9c9d9e9f"
    "a0a1a2a3a4a5a6a7a8a9aaabacadaeaf"
    "b0b1b2b3b4b5b6b7b8b9babbbcbdbebf"
    "c0c1c2c3c4c5c6c7c8c9cacbcccdcecf"
    "d0d1d2d3d4d5d6d7d8d9dadbdcdddedf"
    "e0e1e2e3e4e5e6e7e8e9eaebecedeeef"
    "f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";

  const unsigned char *binaryPtr = [self bytes];
  NSUInteger binaryLen = [self length];

  NSMutableData *hexData = [NSMutableData dataWithLength:(2 * binaryLen)];
  char *hexPtr = [hexData mutableBytes];

  for (NSUInteger i = 0; i < binaryLen; i++) {
    *hexPtr++ = kHexTable[(*binaryPtr)*2];
    *hexPtr++ = kHexTable[(*binaryPtr)*2 + 1];
    ++binaryPtr;
  }

  return [[[NSString alloc] initWithData:hexData
                                encoding:NSASCIIStringEncoding] autorelease];
}

@end