我用這個方法來編碼對象的C的base64字符串,但該應用有時墜毀:爲什麼這個Objective-C代碼會引發一個malloc錯誤?
- (NSString *) base64Encode
{
//Point to start of the data and set buffer sizes
int inLength = [self length];
int outLength = ((((inLength * 4)/3)/4)*4) + (((inLength * 4)/3)%4 ? 4 : 0);
const char *inputBuffer = [self bytes];
char *outputBuffer = malloc(outLength);
outputBuffer[outLength] = 0;
//64 digit code
static char Encode[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz/";
//start the count
int cycle = 0;
int inpos = 0;
int outpos = 0;
char temp;
//Pad the last to bytes, the outbuffer must always be a multiple of 4
outputBuffer[outLength-1] = '=';
outputBuffer[outLength-2] = '=';
/* http://en.wikipedia.org/wiki/Base64
Text content M a n
ASCII 77 97 110
8 Bit pattern 01001101 01100001 01101110
6 Bit pattern 010011 010110 000101 101110
Index 19 22 5 46
Base64-encoded T W F u
*/
while (inpos < inLength){
switch (cycle) {
case 0:
outputBuffer[outpos++] = Encode[(inputBuffer[inpos]&0xFC)>>2];
cycle = 1;
break;
case 1:
temp = (inputBuffer[inpos++]&0x03)<<4;
outputBuffer[outpos] = Encode[temp];
cycle = 2;
break;
case 2:
outputBuffer[outpos++] = Encode[temp|(inputBuffer[inpos]&0xF0)>> 4];
temp = (inputBuffer[inpos++]&0x0F)<<2;
outputBuffer[outpos] = Encode[temp];
cycle = 3;
break;
case 3:
outputBuffer[outpos++] = Encode[temp|(inputBuffer[inpos]&0xC0)>>6];
cycle = 4;
break;
case 4:
outputBuffer[outpos++] = Encode[inputBuffer[inpos++]&0x3f];
cycle = 0;
break;
default:
cycle = 0;
break;
}
}
NSString *pictemp = [NSString stringWithUTF8String:outputBuffer];
free(outputBuffer);
return pictemp;
}
錯誤是:
malloc: *** error for object 0x164084: incorrect checksum for freed object - object was probably modified after being freed.
,當我調試,它在此行中停止:
free(outputBuffer);
你知道是什麼導致了這裏的崩潰?
你應該啓用Guard Malloc(alt + cmd + R,tab「Diagnostics」,選中「Enable Guard Malloc」)來查看你是否有緩衝區溢出。 – zneak
簡單的激光:爲什麼?因爲它含有大量的語法糖! –