runtime: improve atoi implementation

- Adds overflow checks
- Adds parsing of negative integers
- Adds boolean return value to signal parsing errors
- Adds atoi32 for parsing of integers that fit in an int32
- Adds tests

Handling of errors to provide error messages
at the call sites is left to future CLs.

Updates #17718

Change-Id: I3cacd0ab1230b9efc5404c68edae7304d39bcbc0
Reviewed-on: https://go-review.googlesource.com/32390
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 94 insertions, 0 deletions

diff --git a/src/runtime/string_test.go b/src/runtime/string_test.go
index ef0b01c237..fcfc52291f 100644
--- a/src/runtime/string_test.go
+++ b/src/runtime/string_test.go
@@ -279,3 +279,97 @@ func TestString2Slice(t *testing.T) {
 		t.Errorf("extra runes not zeroed")
 	}
 }
+
+const intSize = 32 << (^uint(0) >> 63)
+
+type atoi64Test struct {
+	in  string
+	out int64
+	ok  bool
+}
+
+var atoi64tests = []atoi64Test{
+	{"", 0, false},
+	{"0", 0, true},
+	{"-0", 0, true},
+	{"1", 1, true},
+	{"-1", -1, true},
+	{"12345", 12345, true},
+	{"-12345", -12345, true},
+	{"012345", 12345, true},
+	{"-012345", -12345, true},
+	{"12345x", 0, false},
+	{"-12345x", 0, false},
+	{"98765432100", 98765432100, true},
+	{"-98765432100", -98765432100, true},
+	{"20496382327982653440", 0, false},
+	{"-20496382327982653440", 0, false},
+	{"9223372036854775807", 1<<63 - 1, true},
+	{"-9223372036854775807", -(1<<63 - 1), true},
+	{"9223372036854775808", 0, false},
+	{"-9223372036854775808", -1 << 63, true},
+	{"9223372036854775809", 0, false},
+	{"-9223372036854775809", 0, false},
+}
+
+func TestAtoi(t *testing.T) {
+	switch intSize {
+	case 32:
+		for i := range atoi32tests {
+			test := &atoi32tests[i]
+			out, ok := runtime.Atoi(test.in)
+			if test.out != int32(out) || test.ok != ok {
+				t.Errorf("atoi(%q) = (%v, %v) want (%v, %v)",
+					test.in, out, ok, test.out, test.ok)
+			}
+		}
+	case 64:
+		for i := range atoi64tests {
+			test := &atoi64tests[i]
+			out, ok := runtime.Atoi(test.in)
+			if test.out != int64(out) || test.ok != ok {
+				t.Errorf("atoi(%q) = (%v, %v) want (%v, %v)",
+					test.in, out, ok, test.out, test.ok)
+			}
+		}
+	}
+}
+
+type atoi32Test struct {
+	in  string
+	out int32
+	ok  bool
+}
+
+var atoi32tests = []atoi32Test{
+	{"", 0, false},
+	{"0", 0, true},
+	{"-0", 0, true},
+	{"1", 1, true},
+	{"-1", -1, true},
+	{"12345", 12345, true},
+	{"-12345", -12345, true},
+	{"012345", 12345, true},
+	{"-012345", -12345, true},
+	{"12345x", 0, false},
+	{"-12345x", 0, false},
+	{"987654321", 987654321, true},
+	{"-987654321", -987654321, true},
+	{"2147483647", 1<<31 - 1, true},
+	{"-2147483647", -(1<<31 - 1), true},
+	{"2147483648", 0, false},
+	{"-2147483648", -1 << 31, true},
+	{"2147483649", 0, false},
+	{"-2147483649", 0, false},
+}
+
+func TestAtoi32(t *testing.T) {
+	for i := range atoi32tests {
+		test := &atoi32tests[i]
+		out, ok := runtime.Atoi32(test.in)
+		if test.out != out || test.ok != ok {
+			t.Errorf("atoi32(%q) = (%v, %v) want (%v, %v)",
+				test.in, out, ok, test.out, test.ok)
+		}
+	}
+}