github.com/m3db/m3@v1.5.0/src/query/util/writer/int_writer.go (about)

     1  // Copyright (c) 2019 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package writer
    22  
    23  // IntLength determines the number of digits in a base 10 integer.
    24  func IntLength(i int) int {
    25  	if i == 0 {
    26  		return 1
    27  	}
    28  
    29  	count := 0
    30  	for ; i > 0; i /= 10 {
    31  		count++
    32  	}
    33  
    34  	return count
    35  }
    36  
    37  // WriteInteger writes a base 10 integer to a buffer at a given index.
    38  //
    39  // NB: based on fmt.Printf handling of integers, specifically base 10 case.
    40  func WriteInteger(dst []byte, value, idx int) int {
    41  	// Because printing is easier right-to-left: format u into buf, ending at buf[i].
    42  	// We could make things marginally faster by splitting the 32-bit case out
    43  	// into a separate block but it's not worth the duplication, so u has 64 bits.
    44  	// Use constants for the division and modulo for more efficient code.
    45  	// Switch cases ordered by popularity.
    46  	idx = idx + IntLength(value)
    47  	finalIndex := idx
    48  	for value >= 10 {
    49  		idx--
    50  		dst[idx] = byte(48 + value%10)
    51  		next := value / 10
    52  		value = next
    53  	}
    54  
    55  	dst[idx-1] = byte(48 + value)
    56  	return finalIndex
    57  }
    58  
    59  // IntsLength determines the number of digits in a list of base 10 integers,
    60  // accounting for separators between each integer.
    61  func IntsLength(is []int) int {
    62  	// initialize length accounting for separators.
    63  	l := len(is) - 1
    64  	for _, i := range is {
    65  		l += IntLength(i)
    66  	}
    67  
    68  	return l
    69  }
    70  
    71  // WriteIntegers writes a slice of base 10 integer to a buffer at a given index,
    72  // separating each value with the given separator, returning the index at which
    73  // the write ends.
    74  //
    75  // NB: Ensure that there is sufficient space in the buffer to hold values and
    76  // separators.
    77  func WriteIntegers(dst []byte, values []int, sep byte, idx int) int {
    78  	l := len(values) - 1
    79  	for _, v := range values[:l] {
    80  		idx = WriteInteger(dst, v, idx)
    81  		dst[idx] = sep
    82  		idx++
    83  	}
    84  
    85  	idx = WriteInteger(dst, values[l], idx)
    86  	// Write the last integer.
    87  	return idx
    88  }