示例#1
0
// Number minifies a given byte slice containing a number (see parse.Number) and removes superfluous characters.
func Number(num []byte) []byte {
	// omit first + and register mantissa start and end, whether it's negative and the exponent
	neg := false
	start := 0
	dot := -1
	end := len(num)
	exp := int64(0)
	if 0 < len(num) && (num[0] == '+' || num[0] == '-') {
		if num[0] == '-' {
			neg = true
			start++
		} else {
			num = num[1:]
			end--
		}
	}
	for i := 0; i < len(num); i++ {
		c := num[i]
		if c == '.' {
			dot = i
		} else if c == 'e' || c == 'E' {
			end = i
			i++
			if i < len(num) && num[i] == '+' {
				i++
			}
			var ok bool
			if exp, ok = strconv.ParseInt(num[i:]); !ok {
				return num
			}
			break
		}
	}
	if dot == -1 {
		dot = end
	}

	// trim leading zeros but leave at least one digit
	for start < end-1 && num[start] == '0' {
		start++
	}
	// trim trailing zeros
	i := end - 1
	for ; i > dot; i-- {
		if num[i] != '0' {
			end = i + 1
			break
		}
	}
	if i == dot {
		end = dot
		if start == end {
			num[start] = '0'
			return num[start : start+1]
		}
	} else if start == end-1 && num[start] == '0' {
		return num[start:end]
	}

	// shorten mantissa by increasing/decreasing the exponent
	if end == dot {
		for i := end - 1; i >= start; i-- {
			if num[i] != '0' {
				exp += int64(end - i - 1)
				end = i + 1
				break
			}
		}
	} else {
		exp -= int64(end - dot - 1)
		if start == dot {
			for i = dot + 1; i < end; i++ {
				if num[i] != '0' {
					copy(num[dot:], num[i:end])
					end -= i - dot
					break
				}
			}
		} else {
			copy(num[dot:], num[dot+1:end])
			end--
		}
	}

	// append the exponent or change the mantissa to incorporate the exponent
	relExp := exp + int64(end-start) // exp when the first non-zero digit is directly after the dot
	n := strconv.LenInt(exp)         // number of exp digits
	if exp == 0 {
		if neg {
			start--
			num[start] = '-'
		}
		return num[start:end]
	} else if int(relExp)+n+1 < 0 || 2 < exp { // add exponent for exp 3 and higher and where a lower exp really makes it shorter
		num[end] = 'e'
		end++
		if exp < 0 {
			num[end] = '-'
			end++
			exp = -exp
		}
		for i := end + n - 1; i >= end; i-- {
			num[i] = byte(exp%10) + '0'
			exp /= 10
		}
		end += n
	} else if exp < 0 { // omit exponent
		if relExp > 0 {
			copy(num[start+int(relExp)+1:], num[start+int(relExp):end])
			num[start+int(relExp)] = '.'
			end++
		} else {
			copy(num[start-int(relExp)+1:], num[start:end])
			num[start] = '.'
			for i := 1; i < -int(relExp)+1; i++ {
				num[start+i] = '0'
			}
			end -= int(relExp) - 1
		}
	} else { // for exponent 1 and 2
		num[end] = '0'
		if exp == 2 {
			num[end+1] = '0'
		}
		end += int(exp)
	}

	if neg {
		start--
		num[start] = '-'
	}
	return num[start:end]
}
示例#2
0
// Number minifies a given byte slice containing a number (see parse.Number) and removes superfluous characters.
func Number(num []byte, prec int) []byte {
	// omit first + and register mantissa start and end, whether it's negative and the exponent
	neg := false
	start := 0
	dot := -1
	end := len(num)
	origExp := 0
	if 0 < end && (num[0] == '+' || num[0] == '-') {
		if num[0] == '-' {
			neg = true
		}
		start++
	}
	for i, c := range num[start:] {
		if c == '.' {
			dot = start + i
		} else if c == 'e' || c == 'E' {
			end = start + i
			i += start + 1
			if i < len(num) && num[i] == '+' {
				i++
			}
			if tmpOrigExp, n := strconv.ParseInt(num[i:]); n > 0 && tmpOrigExp >= int64(MinInt) && tmpOrigExp <= int64(MaxInt) {
				// range checks for when int is 32 bit
				origExp = int(tmpOrigExp)
			} else {
				return num
			}
			break
		}
	}
	if dot == -1 {
		dot = end
	}

	// trim leading zeros but leave at least one digit
	for start < end-1 && num[start] == '0' {
		start++
	}
	// trim trailing zeros
	i := end - 1
	for ; i > dot; i-- {
		if num[i] != '0' {
			end = i + 1
			break
		}
	}
	if i == dot {
		end = dot
		if start == end {
			num[start] = '0'
			return num[start : start+1]
		}
	} else if start == end-1 && num[start] == '0' {
		return num[start:end]
	}

	// n is the number of significant digits
	// normExp would be the exponent if it were normalised (0.1 <= f < 1)
	n := 0
	normExp := 0
	if dot == start {
		for i = dot + 1; i < end; i++ {
			if num[i] != '0' {
				n = end - i
				normExp = dot - i + 1
				break
			}
		}
	} else if dot == end {
		normExp = end - start
		for i = end - 1; i >= start; i-- {
			if num[i] != '0' {
				n = i + 1 - start
				end = i + 1
				break
			}
		}
	} else {
		n = end - start - 1
		normExp = dot - start
	}

	if origExp < 0 && (normExp < MinInt-origExp || normExp-n < MinInt-origExp) || origExp > 0 && (normExp > MaxInt-origExp || normExp-n > MaxInt-origExp) {
		return num
	}
	normExp += origExp

	// intExp would be the exponent if it were an integer
	intExp := normExp - n
	lenIntExp := 1
	if intExp <= -10 || intExp >= 10 {
		lenIntExp = strconv.LenInt(int64(intExp))
	}

	// there are three cases to consider when printing the number
	// case 1: without decimals and with an exponent (large numbers)
	// case 2: with decimals and without an exponent (around zero)
	// case 3: without decimals and with a negative exponent (small numbers)
	if normExp >= n {
		// case 1
		if dot < end {
			if dot == start {
				start = end - n
			} else {
				// TODO: copy the other part if shorter?
				//fmt.Println("COPY1", end-dot-1)
				copy(num[dot:], num[dot+1:end])
				end--
			}
		}
		if normExp >= n+3 {
			num[end] = 'e'
			end++
			for i := end + lenIntExp - 1; i >= end; i-- {
				num[i] = byte(intExp%10) + '0'
				intExp /= 10
			}
			end += lenIntExp
		} else if normExp == n+2 {
			num[end] = '0'
			num[end+1] = '0'
			end += 2
		} else if normExp == n+1 {
			num[end] = '0'
			end++
		}
	} else if normExp >= -lenIntExp-1 {
		// case 2
		zeroes := -normExp
		newDot := 0
		if zeroes > 0 {
			// dot placed at the front and add zeroes
			newDot = end - n - zeroes - 1
			if newDot != dot {
				d := start - newDot
				if d > 0 {
					if dot < end {
						// copy original digits behind the dot backwards
						//fmt.Println("COPY2", end-dot-1)
						copy(num[dot+1+d:], num[dot+1:end])
						if dot > start {
							// copy original digits before the dot backwards
							//fmt.Println("COPY3a", dot-start)
							copy(num[start+d+1:], num[start:dot])
						}
					} else if dot > start {
						// copy original digits before the dot backwards
						//fmt.Println("COPY3b", dot-start)
						copy(num[start+d:], num[start:dot])
					}
					newDot = start
					end += d
				} else {
					start += -d
				}
				num[newDot] = '.'
				for i := 0; i < zeroes; i++ {
					num[newDot+1+i] = '0'
				}
			}
		} else {
			// placed in the middle
			if dot == start {
				// TODO: try if placing at the end reduces copying
				// when there are zeroes after the dot
				dot = end - n - 1
				start = dot
			} else if dot >= end {
				// TODO: try if placing at the start reduces copying
				// when input has no dot in it
				dot = end
				end++
			}
			newDot = start + normExp
			if newDot > dot {
				// copy digits forwards
				//fmt.Println("COPY4", newDot-dot)
				copy(num[dot:], num[dot+1:newDot+1])
			} else if newDot < dot {
				// copy digits backwards
				//fmt.Println("COPY5", dot-newDot)
				copy(num[newDot+1:], num[newDot:dot])
			}
			num[newDot] = '.'
		}

		// apply precision
		dot = newDot
		if prec > -1 && dot+1+prec < end {
			end = dot + 1 + prec
			inc := num[end] >= '5'
			if inc || num[end-1] == '0' {
				for i := end - 1; i > start; i-- {
					if i == dot {
						end--
					} else if inc {
						if num[i] == '9' {
							end--
						} else {
							num[i]++
							inc = false
							break
						}
					} else if i > dot && num[i] == '0' {
						end--
					}
				}
			}
			if dot == start && end == start+1 {
				if inc {
					num[start] = '1'
				} else {
					num[start] = '0'
				}
			} else if inc {
				if num[start] == '9' {
					num[start] = '0'
					copy(num[start+1:], num[start:end])
					end++
					num[start] = '1'
				} else {
					num[start]++
				}
			}
		}
	} else {
		// case 3
		if dot < end {
			if dot == start {
				//fmt.Println("COPY6", n)
				copy(num[start:], num[end-n:end])
				end = start + n
			} else {
				//fmt.Println("COPY7", end-dot-1)
				copy(num[dot:], num[dot+1:end])
				end--
			}
		}
		num[end] = 'e'
		num[end+1] = '-'
		end += 2
		intExp = -intExp
		for i := end + lenIntExp - 1; i >= end; i-- {
			num[i] = byte(intExp%10) + '0'
			intExp /= 10
		}
		end += lenIntExp
	}

	if neg {
		start--
		num[start] = '-'
	}
	return num[start:end]
}