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// Copyright (c) 2012 The Go Authors. All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// 
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package check

import (
    "fmt"
    "runtime"
    "time"
)

var memStats runtime.MemStats

// testingB is a type passed to Benchmark functions to manage benchmark
// timing and to specify the number of iterations to run.
type timer struct {
    start     time.Time // Time test or benchmark started
    duration  time.Duration
    N         int
    bytes     int64
    timerOn   bool
    benchTime time.Duration
    // The initial states of memStats.Mallocs and memStats.TotalAlloc.
    startAllocs uint64
    startBytes  uint64
    // The net total of this test after being run.
    netAllocs uint64
    netBytes  uint64
}

// StartTimer starts timing a test. This function is called automatically
// before a benchmark starts, but it can also used to resume timing after
// a call to StopTimer.
func (c *C) StartTimer() {
    if !c.timerOn {
        c.start = time.Now()
        c.timerOn = true

        runtime.ReadMemStats(&memStats)
        c.startAllocs = memStats.Mallocs
        c.startBytes = memStats.TotalAlloc
    }
}

// StopTimer stops timing a test. This can be used to pause the timer
// while performing complex initialization that you don't
// want to measure.
func (c *C) StopTimer() {
    if c.timerOn {
        c.duration += time.Now().Sub(c.start)
        c.timerOn = false
        runtime.ReadMemStats(&memStats)
        c.netAllocs += memStats.Mallocs - c.startAllocs
        c.netBytes += memStats.TotalAlloc - c.startBytes
    }
}

// ResetTimer sets the elapsed benchmark time to zero.
// It does not affect whether the timer is running.
func (c *C) ResetTimer() {
    if c.timerOn {
        c.start = time.Now()
        runtime.ReadMemStats(&memStats)
        c.startAllocs = memStats.Mallocs
        c.startBytes = memStats.TotalAlloc
    }
    c.duration = 0
    c.netAllocs = 0
    c.netBytes = 0
}

// SetBytes informs the number of bytes that the benchmark processes
// on each iteration. If this is called in a benchmark it will also
// report MB/s.
func (c *C) SetBytes(n int64) {
    c.bytes = n
}

func (c *C) nsPerOp() int64 {
    if c.N <= 0 {
        return 0
    }
    return c.duration.Nanoseconds() / int64(c.N)
}

func (c *C) mbPerSec() float64 {
    if c.bytes <= 0 || c.duration <= 0 || c.N <= 0 {
        return 0
    }
    return (float64(c.bytes) * float64(c.N) / 1e6) / c.duration.Seconds()
}

func (c *C) timerString() string {
    if c.N <= 0 {
        return fmt.Sprintf("%3.3fs", float64(c.duration.Nanoseconds())/1e9)
    }
    mbs := c.mbPerSec()
    mb := ""
    if mbs != 0 {
        mb = fmt.Sprintf("\t%7.2f MB/s", mbs)
    }
    nsop := c.nsPerOp()
    ns := fmt.Sprintf("%10d ns/op", nsop)
    if c.N > 0 && nsop < 100 {
        // The format specifiers here make sure that
        // the ones digits line up for all three possible formats.
        if nsop < 10 {
            ns = fmt.Sprintf("%13.2f ns/op", float64(c.duration.Nanoseconds())/float64(c.N))
        } else {
            ns = fmt.Sprintf("%12.1f ns/op", float64(c.duration.Nanoseconds())/float64(c.N))
        }
    }
    memStats := ""
    if c.benchMem {
        allocedBytes := fmt.Sprintf("%8d B/op", int64(c.netBytes)/int64(c.N))
        allocs := fmt.Sprintf("%8d allocs/op", int64(c.netAllocs)/int64(c.N))
        memStats = fmt.Sprintf("\t%s\t%s", allocedBytes, allocs)
    }
    return fmt.Sprintf("%8d\t%s%s%s", c.N, ns, mb, memStats)
}

func min(x, y int) int {
    if x > y {
        return y
    }
    return x
}

func max(x, y int) int {
    if x < y {
        return y
    }
    return x
}

// roundDown10 rounds a number down to the nearest power of 10.
func roundDown10(n int) int {
    var tens = 0
    // tens = floor(log_10(n))
    for n > 10 {
        n = n / 10
        tens++
    }
    // result = 10^tens
    result := 1
    for i := 0; i < tens; i++ {
        result *= 10
    }
    return result
}

// roundUp rounds x up to a number of the form [1eX, 2eX, 5eX].
func roundUp(n int) int {
    base := roundDown10(n)
    if n < (2 * base) {
        return 2 * base
    }
    if n < (5 * base) {
        return 5 * base
    }
    return 10 * base
}