cmpConstGen.go

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // This program generates a test to verify that the standard comparison
     6  // operators properly handle one const operand. The test file should be
     7  // generated with a known working version of go.
     8  // launch with `go run cmpConstGen.go` a file called cmpConst.go
     9  // will be written into the parent directory containing the tests
    10  
    11  package main
    12  
    13  import (
    14  	"bytes"
    15  	"fmt"
    16  	"go/format"
    17  	"log"
    18  	"math/big"
    19  	"sort"
    20  )
    21  
    22  const (
    23  	maxU64 = (1 << 64) - 1
    24  	maxU32 = (1 << 32) - 1
    25  	maxU16 = (1 << 16) - 1
    26  	maxU8  = (1 << 8) - 1
    27  
    28  	maxI64 = (1 << 63) - 1
    29  	maxI32 = (1 << 31) - 1
    30  	maxI16 = (1 << 15) - 1
    31  	maxI8  = (1 << 7) - 1
    32  
    33  	minI64 = -(1 << 63)
    34  	minI32 = -(1 << 31)
    35  	minI16 = -(1 << 15)
    36  	minI8  = -(1 << 7)
    37  )
    38  
    39  func cmp(left *big.Int, op string, right *big.Int) bool {
    40  	switch left.Cmp(right) {
    41  	case -1: // less than
    42  		return op == "<" || op == "<=" || op == "!="
    43  	case 0: // equal
    44  		return op == "==" || op == "<=" || op == ">="
    45  	case 1: // greater than
    46  		return op == ">" || op == ">=" || op == "!="
    47  	}
    48  	panic("unexpected comparison value")
    49  }
    50  
    51  func inRange(typ string, val *big.Int) bool {
    52  	min, max := &big.Int{}, &big.Int{}
    53  	switch typ {
    54  	case "uint64":
    55  		max = max.SetUint64(maxU64)
    56  	case "uint32":
    57  		max = max.SetUint64(maxU32)
    58  	case "uint16":
    59  		max = max.SetUint64(maxU16)
    60  	case "uint8":
    61  		max = max.SetUint64(maxU8)
    62  	case "int64":
    63  		min = min.SetInt64(minI64)
    64  		max = max.SetInt64(maxI64)
    65  	case "int32":
    66  		min = min.SetInt64(minI32)
    67  		max = max.SetInt64(maxI32)
    68  	case "int16":
    69  		min = min.SetInt64(minI16)
    70  		max = max.SetInt64(maxI16)
    71  	case "int8":
    72  		min = min.SetInt64(minI8)
    73  		max = max.SetInt64(maxI8)
    74  	default:
    75  		panic("unexpected type")
    76  	}
    77  	return cmp(min, "<=", val) && cmp(val, "<=", max)
    78  }
    79  
    80  func getValues(typ string) []*big.Int {
    81  	Uint := func(v uint64) *big.Int { return big.NewInt(0).SetUint64(v) }
    82  	Int := func(v int64) *big.Int { return big.NewInt(0).SetInt64(v) }
    83  	values := []*big.Int{
    84  		// limits
    85  		Uint(maxU64),
    86  		Uint(maxU64 - 1),
    87  		Uint(maxI64 + 1),
    88  		Uint(maxI64),
    89  		Uint(maxI64 - 1),
    90  		Uint(maxU32 + 1),
    91  		Uint(maxU32),
    92  		Uint(maxU32 - 1),
    93  		Uint(maxI32 + 1),
    94  		Uint(maxI32),
    95  		Uint(maxI32 - 1),
    96  		Uint(maxU16 + 1),
    97  		Uint(maxU16),
    98  		Uint(maxU16 - 1),
    99  		Uint(maxI16 + 1),
   100  		Uint(maxI16),
   101  		Uint(maxI16 - 1),
   102  		Uint(maxU8 + 1),
   103  		Uint(maxU8),
   104  		Uint(maxU8 - 1),
   105  		Uint(maxI8 + 1),
   106  		Uint(maxI8),
   107  		Uint(maxI8 - 1),
   108  		Uint(0),
   109  		Int(minI8 + 1),
   110  		Int(minI8),
   111  		Int(minI8 - 1),
   112  		Int(minI16 + 1),
   113  		Int(minI16),
   114  		Int(minI16 - 1),
   115  		Int(minI32 + 1),
   116  		Int(minI32),
   117  		Int(minI32 - 1),
   118  		Int(minI64 + 1),
   119  		Int(minI64),
   120  
   121  		// other possibly interesting values
   122  		Uint(1),
   123  		Int(-1),
   124  		Uint(0xff << 56),
   125  		Uint(0xff << 32),
   126  		Uint(0xff << 24),
   127  	}
   128  	sort.Slice(values, func(i, j int) bool { return values[i].Cmp(values[j]) == -1 })
   129  	var ret []*big.Int
   130  	for _, val := range values {
   131  		if !inRange(typ, val) {
   132  			continue
   133  		}
   134  		ret = append(ret, val)
   135  	}
   136  	return ret
   137  }
   138  
   139  func sigString(v *big.Int) string {
   140  	var t big.Int
   141  	t.Abs(v)
   142  	if v.Sign() == -1 {
   143  		return "neg" + t.String()
   144  	}
   145  	return t.String()
   146  }
   147  
   148  func main() {
   149  	types := []string{
   150  		"uint64", "uint32", "uint16", "uint8",
   151  		"int64", "int32", "int16", "int8",
   152  	}
   153  
   154  	w := new(bytes.Buffer)
   155  	fmt.Fprintf(w, "// Code generated by gen/cmpConstGen.go. DO NOT EDIT.\n\n")
   156  	fmt.Fprintf(w, "package main;\n")
   157  	fmt.Fprintf(w, "import (\"testing\"; \"reflect\"; \"runtime\";)\n")
   158  	fmt.Fprintf(w, "// results show the expected result for the elements left of, equal to and right of the index.\n")
   159  	fmt.Fprintf(w, "type result struct{l, e, r bool}\n")
   160  	fmt.Fprintf(w, "var (\n")
   161  	fmt.Fprintf(w, "	eq = result{l: false, e: true, r: false}\n")
   162  	fmt.Fprintf(w, "	ne = result{l: true, e: false, r: true}\n")
   163  	fmt.Fprintf(w, "	lt = result{l: true, e: false, r: false}\n")
   164  	fmt.Fprintf(w, "	le = result{l: true, e: true, r: false}\n")
   165  	fmt.Fprintf(w, "	gt = result{l: false, e: false, r: true}\n")
   166  	fmt.Fprintf(w, "	ge = result{l: false, e: true, r: true}\n")
   167  	fmt.Fprintf(w, ")\n")
   168  
   169  	operators := []struct{ op, name string }{
   170  		{"<", "lt"},
   171  		{"<=", "le"},
   172  		{">", "gt"},
   173  		{">=", "ge"},
   174  		{"==", "eq"},
   175  		{"!=", "ne"},
   176  	}
   177  
   178  	for _, typ := range types {
   179  		// generate a slice containing valid values for this type
   180  		fmt.Fprintf(w, "\n// %v tests\n", typ)
   181  		values := getValues(typ)
   182  		fmt.Fprintf(w, "var %v_vals = []%v{\n", typ, typ)
   183  		for _, val := range values {
   184  			fmt.Fprintf(w, "%v,\n", val.String())
   185  		}
   186  		fmt.Fprintf(w, "}\n")
   187  
   188  		// generate test functions
   189  		for _, r := range values {
   190  			// TODO: could also test constant on lhs.
   191  			sig := sigString(r)
   192  			for _, op := range operators {
   193  				// no need for go:noinline because the function is called indirectly
   194  				fmt.Fprintf(w, "func %v_%v_%v(x %v) bool { return x %v %v; }\n", op.name, sig, typ, typ, op.op, r.String())
   195  			}
   196  		}
   197  
   198  		// generate a table of test cases
   199  		fmt.Fprintf(w, "var %v_tests = []struct{\n", typ)
   200  		fmt.Fprintf(w, "	idx int // index of the constant used\n")
   201  		fmt.Fprintf(w, "	exp result // expected results\n")
   202  		fmt.Fprintf(w, "	fn  func(%v) bool\n", typ)
   203  		fmt.Fprintf(w, "}{\n")
   204  		for i, r := range values {
   205  			sig := sigString(r)
   206  			for _, op := range operators {
   207  				fmt.Fprintf(w, "{idx: %v,", i)
   208  				fmt.Fprintf(w, "exp: %v,", op.name)
   209  				fmt.Fprintf(w, "fn:  %v_%v_%v},\n", op.name, sig, typ)
   210  			}
   211  		}
   212  		fmt.Fprintf(w, "}\n")
   213  	}
   214  
   215  	// emit the main function, looping over all test cases
   216  	fmt.Fprintf(w, "// TestComparisonsConst tests results for comparison operations against constants.\n")
   217  	fmt.Fprintf(w, "func TestComparisonsConst(t *testing.T) {\n")
   218  	for _, typ := range types {
   219  		fmt.Fprintf(w, "for i, test := range %v_tests {\n", typ)
   220  		fmt.Fprintf(w, "	for j, x := range %v_vals {\n", typ)
   221  		fmt.Fprintf(w, "		want := test.exp.l\n")
   222  		fmt.Fprintf(w, "		if j == test.idx {\nwant = test.exp.e\n}")
   223  		fmt.Fprintf(w, "		else if j > test.idx {\nwant = test.exp.r\n}\n")
   224  		fmt.Fprintf(w, "		if test.fn(x) != want {\n")
   225  		fmt.Fprintf(w, "			fn := runtime.FuncForPC(reflect.ValueOf(test.fn).Pointer()).Name()\n")
   226  		fmt.Fprintf(w, "			t.Errorf(\"test failed: %%v(%%v) != %%v [type=%v i=%%v j=%%v idx=%%v]\", fn, x, want, i, j, test.idx)\n", typ)
   227  		fmt.Fprintf(w, "		}\n")
   228  		fmt.Fprintf(w, "	}\n")
   229  		fmt.Fprintf(w, "}\n")
   230  	}
   231  	fmt.Fprintf(w, "}\n")
   232  
   233  	// gofmt result
   234  	b := w.Bytes()
   235  	src, err := format.Source(b)
   236  	if err != nil {
   237  		fmt.Printf("%s\n", b)
   238  		panic(err)
   239  	}
   240  
   241  	// write to file
   242  	err = os.WriteFile("../cmpConst_test.go", src, 0666)
   243  	if err != nil {
   244  		log.Fatalf("can't write output: %v\n", err)
   245  	}
   246  }
   247
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