mirror of
https://github.com/kubernetes-sigs/prometheus-adapter.git
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a293b2bf94
Travis seems to be having issues pulling deps, so we'll have to check in the vendor directory and prevent the makefile from trying to regenerate it normally.
121 lines
3.1 KiB
Go
121 lines
3.1 KiB
Go
// Copyright (c) 2012-2015 Ugorji Nwoke. All rights reserved.
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// Use of this source code is governed by a MIT license found in the LICENSE file.
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package codec
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// All non-std package dependencies live in this file,
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// so porting to different environment is easy (just update functions).
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func pruneSignExt(v []byte, pos bool) (n int) {
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if len(v) < 2 {
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} else if pos && v[0] == 0 {
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for ; v[n] == 0 && n+1 < len(v) && (v[n+1]&(1<<7) == 0); n++ {
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}
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} else if !pos && v[0] == 0xff {
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for ; v[n] == 0xff && n+1 < len(v) && (v[n+1]&(1<<7) != 0); n++ {
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}
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}
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return
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}
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// validate that this function is correct ...
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// culled from OGRE (Object-Oriented Graphics Rendering Engine)
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// function: halfToFloatI (http://stderr.org/doc/ogre-doc/api/OgreBitwise_8h-source.html)
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func halfFloatToFloatBits(yy uint16) (d uint32) {
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y := uint32(yy)
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s := (y >> 15) & 0x01
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e := (y >> 10) & 0x1f
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m := y & 0x03ff
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if e == 0 {
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if m == 0 { // plu or minus 0
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return s << 31
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}
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// Denormalized number -- renormalize it
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for (m & 0x00000400) == 0 {
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m <<= 1
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e -= 1
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}
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e += 1
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const zz uint32 = 0x0400
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m &= ^zz
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} else if e == 31 {
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if m == 0 { // Inf
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return (s << 31) | 0x7f800000
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}
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return (s << 31) | 0x7f800000 | (m << 13) // NaN
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}
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e = e + (127 - 15)
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m = m << 13
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return (s << 31) | (e << 23) | m
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}
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// GrowCap will return a new capacity for a slice, given the following:
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// - oldCap: current capacity
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// - unit: in-memory size of an element
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// - num: number of elements to add
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func growCap(oldCap, unit, num int) (newCap int) {
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// appendslice logic (if cap < 1024, *2, else *1.25):
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// leads to many copy calls, especially when copying bytes.
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// bytes.Buffer model (2*cap + n): much better for bytes.
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// smarter way is to take the byte-size of the appended element(type) into account
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// maintain 3 thresholds:
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// t1: if cap <= t1, newcap = 2x
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// t2: if cap <= t2, newcap = 1.75x
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// t3: if cap <= t3, newcap = 1.5x
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// else newcap = 1.25x
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//
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// t1, t2, t3 >= 1024 always.
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// i.e. if unit size >= 16, then always do 2x or 1.25x (ie t1, t2, t3 are all same)
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//
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// With this, appending for bytes increase by:
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// 100% up to 4K
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// 75% up to 8K
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// 50% up to 16K
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// 25% beyond that
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// unit can be 0 e.g. for struct{}{}; handle that appropriately
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var t1, t2, t3 int // thresholds
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if unit <= 1 {
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t1, t2, t3 = 4*1024, 8*1024, 16*1024
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} else if unit < 16 {
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t3 = 16 / unit * 1024
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t1 = t3 * 1 / 4
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t2 = t3 * 2 / 4
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} else {
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t1, t2, t3 = 1024, 1024, 1024
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}
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var x int // temporary variable
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// x is multiplier here: one of 5, 6, 7 or 8; incr of 25%, 50%, 75% or 100% respectively
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if oldCap <= t1 { // [0,t1]
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x = 8
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} else if oldCap > t3 { // (t3,infinity]
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x = 5
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} else if oldCap <= t2 { // (t1,t2]
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x = 7
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} else { // (t2,t3]
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x = 6
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}
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newCap = x * oldCap / 4
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if num > 0 {
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newCap += num
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}
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// ensure newCap is a multiple of 64 (if it is > 64) or 16.
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if newCap > 64 {
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if x = newCap % 64; x != 0 {
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x = newCap / 64
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newCap = 64 * (x + 1)
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}
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} else {
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if x = newCap % 16; x != 0 {
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x = newCap / 16
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newCap = 16 * (x + 1)
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}
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}
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return
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}
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