C# implementation of atof; replacement when necessary for float.TryPars; approximately 2.4x faster

gistfile1.txt

private float atof(char[] num, ref int index) {
			float integerPart = 0;
			float fractionPart = 0;
			float divisorForFraction = 1;
			float sign = 1;
			char numIndex;

			/*Take care of +/- sign*/
			if (num [index] == '-') {
				index++;
				sign = -1;
			} else if (num [index] == '+') {
				index++;
			}

			// integer part
			while (true) {
				numIndex = num [index++];
				if (numIndex >= '0' && numIndex <= '9') {
					integerPart = integerPart * 10 + (numIndex - '0');
				} else if (numIndex == '.') {
					break;
				} else {
					return sign * (integerPart + fractionPart / divisorForFraction);
				}
			}

			// fraction part
			while (true) {
				numIndex = num [index++];
				if (numIndex >= '0' && numIndex <= '9') {
					fractionPart = fractionPart * 10 + (numIndex - '0');
					divisorForFraction *= 10;
				} else {
					if (numIndex == 'E') {
						// E part
						float ePart = 0;
						bool eNegative = false;
						if (num [index] == '-') {
							index++;
							eNegative = true;
						} else if (num [index] == '+') {
							index++;
						}

						while (true) {
							numIndex = num [index++];
							if (numIndex >= '0' && numIndex <= '9') {
								ePart = ePart * 10 + (numIndex - '0');
							} else {
								break;
							}
						}

						float eMult = 10.0f;
						while (ePart > 1) {
							eMult *= 10.0f;
							ePart--;
						}

						return ( eNegative ? 
							(sign * (integerPart + fractionPart / divisorForFraction)) / eMult :
							(sign * (integerPart + fractionPart / divisorForFraction)) * eMult
						);
					}
					return sign * (integerPart + fractionPart / divisorForFraction);
				}
			}
		}