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Speed up BTCHexFromData by 5.5x (-85%) #114

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Speed up BTCHexFromData by 5.5x (-85%) #114

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27365f9
speed up BTCHexFromData by 85%
wjmelements Jul 14, 2018
ee9ff9d
const char arrays
wjmelements Jul 14, 2018
ba70750
no need to mask
wjmelements Jul 14, 2018
37b1f0b
ascii encoding is somewhat faster
wjmelements Jul 14, 2018
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46 changes: 31 additions & 15 deletions CoreBitcoin/BTCData.m
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Original file line number Diff line number Diff line change
Expand Up @@ -183,20 +183,36 @@ static inline int BTCFairCoinFlip() {
return [[NSData alloc] initWithBytesNoCopy:buf length:len/2];
}


NSString* BTCHexFromDataWithFormat(NSData* data, const char* format) {
if (!data) return nil;

NSUInteger length = data.length;
if (length == 0) return @"";

NSMutableData* resultdata = [NSMutableData dataWithLength:length * 2];
char *dest = resultdata.mutableBytes;
unsigned const char *src = data.bytes;
for (int i = 0; i < length; ++i) {
sprintf(dest + i*2, format, (unsigned int)(src[i]));
static const char hexValues[16] = {
'0', '1', '2', '3',
'4', '5', '6', '7',
'8', '9', 'a', 'b',
'c', 'd', 'e', 'f',
};

static const char upperHexValues[16] = {
'0', '1', '2', '3',
'4', '5', '6', '7',
'8', '9', 'A', 'B',
'C', 'D', 'E', 'F',
};

static NSString* BTCHexFromDataWithCharset(NSData* data, const char* charset) {
size_t inLength = data.length;
size_t length = inLength * 2;
uint8_t *outString = malloc(length);
const unsigned char *bytes = data.bytes;
for (uint32_t i = 0; i < inLength; i++) {
unsigned char byte = bytes[i];
outString[i*2] = charset[byte >> 4];
outString[i*2+1] = charset[byte & 0x0F];
}
return [[NSString alloc] initWithData:resultdata encoding:NSASCIIStringEncoding];
return [[NSString alloc]
initWithBytesNoCopy:outString
length:length
encoding:NSASCIIStringEncoding
freeWhenDone:YES
];
}

NSString* BTCHexStringFromData(NSData* data) { // deprecated
Expand All @@ -208,11 +224,11 @@ static inline int BTCFairCoinFlip() {
}

NSString* BTCHexFromData(NSData* data) {
return BTCHexFromDataWithFormat(data, "%02x");
return BTCHexFromDataWithCharset(data, hexValues);
}

NSString* BTCUppercaseHexFromData(NSData* data) {
return BTCHexFromDataWithFormat(data, "%02X");
return BTCHexFromDataWithCharset(data, upperHexValues);
}


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