// 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]
}
// 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]
}