1 files changed, 266 insertions, 0 deletions
diff --git a/src/sort/search_test.go b/src/sort/search_test.go
new file mode 100644
index 0000000..49813ea
--- /dev/null
+++ b/src/sort/search_test.go
@@ -0,0 +1,266 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort_test
+
+import (
+	"runtime"
+	. "sort"
+	stringspkg "strings"
+	"testing"
+)
+
+func f(a []int, x int) func(int) bool {
+	return func(i int) bool {
+		return a[i] >= x
+	}
+}
+
+var data = []int{0: -10, 1: -5, 2: 0, 3: 1, 4: 2, 5: 3, 6: 5, 7: 7, 8: 11, 9: 100, 10: 100, 11: 100, 12: 1000, 13: 10000}
+
+var tests = []struct {
+	name string
+	n    int
+	f    func(int) bool
+	i    int
+}{
+	{"empty", 0, nil, 0},
+	{"1 1", 1, func(i int) bool { return i >= 1 }, 1},
+	{"1 true", 1, func(i int) bool { return true }, 0},
+	{"1 false", 1, func(i int) bool { return false }, 1},
+	{"1e9 991", 1e9, func(i int) bool { return i >= 991 }, 991},
+	{"1e9 true", 1e9, func(i int) bool { return true }, 0},
+	{"1e9 false", 1e9, func(i int) bool { return false }, 1e9},
+	{"data -20", len(data), f(data, -20), 0},
+	{"data -10", len(data), f(data, -10), 0},
+	{"data -9", len(data), f(data, -9), 1},
+	{"data -6", len(data), f(data, -6), 1},
+	{"data -5", len(data), f(data, -5), 1},
+	{"data 3", len(data), f(data, 3), 5},
+	{"data 11", len(data), f(data, 11), 8},
+	{"data 99", len(data), f(data, 99), 9},
+	{"data 100", len(data), f(data, 100), 9},
+	{"data 101", len(data), f(data, 101), 12},
+	{"data 10000", len(data), f(data, 10000), 13},
+	{"data 10001", len(data), f(data, 10001), 14},
+	{"descending a", 7, func(i int) bool { return []int{99, 99, 59, 42, 7, 0, -1, -1}[i] <= 7 }, 4},
+	{"descending 7", 1e9, func(i int) bool { return 1e9-i <= 7 }, 1e9 - 7},
+	{"overflow", 2e9, func(i int) bool { return false }, 2e9},
+}
+
+func TestSearch(t *testing.T) {
+	for _, e := range tests {
+		i := Search(e.n, e.f)
+		if i != e.i {
+			t.Errorf("%s: expected index %d; got %d", e.name, e.i, i)
+		}
+	}
+}
+
+func TestFind(t *testing.T) {
+	str1 := []string{"foo"}
+	str2 := []string{"ab", "ca"}
+	str3 := []string{"mo", "qo", "vo"}
+	str4 := []string{"ab", "ad", "ca", "xy"}
+
+	// slice with repeating elements
+	strRepeats := []string{"ba", "ca", "da", "da", "da", "ka", "ma", "ma", "ta"}
+
+	// slice with all element equal
+	strSame := []string{"xx", "xx", "xx"}
+
+	tests := []struct {
+		data      []string
+		target    string
+		wantPos   int
+		wantFound bool
+	}{
+		{[]string{}, "foo", 0, false},
+		{[]string{}, "", 0, false},
+
+		{str1, "foo", 0, true},
+		{str1, "bar", 0, false},
+		{str1, "zx", 1, false},
+
+		{str2, "aa", 0, false},
+		{str2, "ab", 0, true},
+		{str2, "ad", 1, false},
+		{str2, "ca", 1, true},
+		{str2, "ra", 2, false},
+
+		{str3, "bb", 0, false},
+		{str3, "mo", 0, true},
+		{str3, "nb", 1, false},
+		{str3, "qo", 1, true},
+		{str3, "tr", 2, false},
+		{str3, "vo", 2, true},
+		{str3, "xr", 3, false},
+
+		{str4, "aa", 0, false},
+		{str4, "ab", 0, true},
+		{str4, "ac", 1, false},
+		{str4, "ad", 1, true},
+		{str4, "ax", 2, false},
+		{str4, "ca", 2, true},
+		{str4, "cc", 3, false},
+		{str4, "dd", 3, false},
+		{str4, "xy", 3, true},
+		{str4, "zz", 4, false},
+
+		{strRepeats, "da", 2, true},
+		{strRepeats, "db", 5, false},
+		{strRepeats, "ma", 6, true},
+		{strRepeats, "mb", 8, false},
+
+		{strSame, "xx", 0, true},
+		{strSame, "ab", 0, false},
+		{strSame, "zz", 3, false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.target, func(t *testing.T) {
+			cmp := func(i int) int {
+				return stringspkg.Compare(tt.target, tt.data[i])
+			}
+
+			pos, found := Find(len(tt.data), cmp)
+			if pos != tt.wantPos || found != tt.wantFound {
+				t.Errorf("Find got (%v, %v), want (%v, %v)", pos, found, tt.wantPos, tt.wantFound)
+			}
+		})
+	}
+}
+
+// log2 computes the binary logarithm of x, rounded up to the next integer.
+// (log2(0) == 0, log2(1) == 0, log2(2) == 1, log2(3) == 2, etc.)
+func log2(x int) int {
+	n := 0
+	for p := 1; p < x; p += p {
+		// p == 2**n
+		n++
+	}
+	// p/2 < x <= p == 2**n
+	return n
+}
+
+func TestSearchEfficiency(t *testing.T) {
+	n := 100
+	step := 1
+	for exp := 2; exp < 10; exp++ {
+		// n == 10**exp
+		// step == 10**(exp-2)
+		max := log2(n)
+		for x := 0; x < n; x += step {
+			count := 0
+			i := Search(n, func(i int) bool { count++; return i >= x })
+			if i != x {
+				t.Errorf("n = %d: expected index %d; got %d", n, x, i)
+			}
+			if count > max {
+				t.Errorf("n = %d, x = %d: expected <= %d calls; got %d", n, x, max, count)
+			}
+		}
+		n *= 10
+		step *= 10
+	}
+}
+
+// Smoke tests for convenience wrappers - not comprehensive.
+
+var fdata = []float64{0: -3.14, 1: 0, 2: 1, 3: 2, 4: 1000.7}
+var sdata = []string{0: "f", 1: "foo", 2: "foobar", 3: "x"}
+
+var wrappertests = []struct {
+	name   string
+	result int
+	i      int
+}{
+	{"SearchInts", SearchInts(data, 11), 8},
+	{"SearchFloat64s", SearchFloat64s(fdata, 2.1), 4},
+	{"SearchStrings", SearchStrings(sdata, ""), 0},
+	{"IntSlice.Search", IntSlice(data).Search(0), 2},
+	{"Float64Slice.Search", Float64Slice(fdata).Search(2.0), 3},
+	{"StringSlice.Search", StringSlice(sdata).Search("x"), 3},
+}
+
+func TestSearchWrappers(t *testing.T) {
+	for _, e := range wrappertests {
+		if e.result != e.i {
+			t.Errorf("%s: expected index %d; got %d", e.name, e.i, e.result)
+		}
+	}
+}
+
+func runSearchWrappers() {
+	SearchInts(data, 11)
+	SearchFloat64s(fdata, 2.1)
+	SearchStrings(sdata, "")
+	IntSlice(data).Search(0)
+	Float64Slice(fdata).Search(2.0)
+	StringSlice(sdata).Search("x")
+}
+
+func TestSearchWrappersDontAlloc(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Skip("skipping; GOMAXPROCS>1")
+	}
+	allocs := testing.AllocsPerRun(100, runSearchWrappers)
+	if allocs != 0 {
+		t.Errorf("expected no allocs for runSearchWrappers, got %v", allocs)
+	}
+}
+
+func BenchmarkSearchWrappers(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		runSearchWrappers()
+	}
+}
+
+// Abstract exhaustive test: all sizes up to 100,
+// all possible return values. If there are any small
+// corner cases, this test exercises them.
+func TestSearchExhaustive(t *testing.T) {
+	for size := 0; size <= 100; size++ {
+		for targ := 0; targ <= size; targ++ {
+			i := Search(size, func(i int) bool { return i >= targ })
+			if i != targ {
+				t.Errorf("Search(%d, %d) = %d", size, targ, i)
+			}
+		}
+	}
+}
+
+// Abstract exhaustive test for Find.
+func TestFindExhaustive(t *testing.T) {
+	// Test Find for different sequence sizes and search targets.
+	// For each size, we have a (unmaterialized) sequence of integers:
+	//   2,4...size*2
+	// And we're looking for every possible integer between 1 and size*2 + 1.
+	for size := 0; size <= 100; size++ {
+		for x := 1; x <= size*2+1; x++ {
+			var wantFound bool
+			var wantPos int
+
+			cmp := func(i int) int {
+				// Encodes the unmaterialized sequence with elem[i] == (i+1)*2
+				return x - (i+1)*2
+			}
+			pos, found := Find(size, cmp)
+
+			if x%2 == 0 {
+				wantPos = x/2 - 1
+				wantFound = true
+			} else {
+				wantPos = x / 2
+				wantFound = false
+			}
+			if found != wantFound || pos != wantPos {
+				t.Errorf("Find(%d, %d): got (%v, %v), want (%v, %v)", size, x, pos, found, wantPos, wantFound)
+			}
+		}
+	}
+}