// Copyright 2009 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 fmt_test

import (
	"bufio"
	"bytes"
	"errors"
	. "fmt"
	"io"
	"math"
	"reflect"
	"regexp"
	"strings"
	"testing"
	"testing/iotest"
	"unicode/utf8"
)

type ScanTest struct {
	text string
	in   any
	out  any
}

type ScanfTest struct {
	format string
	text   string
	in     any
	out    any
}

type ScanfMultiTest struct {
	format string
	text   string
	in     []any
	out    []any
	err    string
}

var (
	boolVal              bool
	intVal               int
	int8Val              int8
	int16Val             int16
	int32Val             int32
	int64Val             int64
	uintVal              uint
	uint8Val             uint8
	uint16Val            uint16
	uint32Val            uint32
	uint64Val            uint64
	uintptrVal           uintptr
	float32Val           float32
	float64Val           float64
	stringVal            string
	bytesVal             []byte
	runeVal              rune
	complex64Val         complex64
	complex128Val        complex128
	renamedBoolVal       renamedBool
	renamedIntVal        renamedInt
	renamedInt8Val       renamedInt8
	renamedInt16Val      renamedInt16
	renamedInt32Val      renamedInt32
	renamedInt64Val      renamedInt64
	renamedUintVal       renamedUint
	renamedUint8Val      renamedUint8
	renamedUint16Val     renamedUint16
	renamedUint32Val     renamedUint32
	renamedUint64Val     renamedUint64
	renamedUintptrVal    renamedUintptr
	renamedStringVal     renamedString
	renamedBytesVal      renamedBytes
	renamedFloat32Val    renamedFloat32
	renamedFloat64Val    renamedFloat64
	renamedComplex64Val  renamedComplex64
	renamedComplex128Val renamedComplex128
)

// Xs accepts any non-empty run of the verb character
type Xs string

func (x *Xs) Scan(state ScanState, verb rune) error {
	tok, err := state.Token(true, func(r rune) bool { return r == verb })
	if err != nil {
		return err
	}
	s := string(tok)
	if !regexp.MustCompile("^" + string(verb) + "+$").MatchString(s) {
		return errors.New("syntax error for xs")
	}
	*x = Xs(s)
	return nil
}

var xVal Xs

// IntString accepts an integer followed immediately by a string.
// It tests the embedding of a scan within a scan.
type IntString struct {
	i int
	s string
}

func (s *IntString) Scan(state ScanState, verb rune) error {
	if _, err := Fscan(state, &s.i); err != nil {
		return err
	}

	tok, err := state.Token(true, nil)
	if err != nil {
		return err
	}
	s.s = string(tok)
	return nil
}

var intStringVal IntString

var scanTests = []ScanTest{
	// Basic types
	{"T\n", &boolVal, true},  // boolean test vals toggle to be sure they are written
	{"F\n", &boolVal, false}, // restored to zero value
	{"21\n", &intVal, 21},
	{"2_1\n", &intVal, 21},
	{"0\n", &intVal, 0},
	{"000\n", &intVal, 0},
	{"0x10\n", &intVal, 0x10},
	{"0x_1_0\n", &intVal, 0x10},
	{"-0x10\n", &intVal, -0x10},
	{"0377\n", &intVal, 0377},
	{"0_3_7_7\n", &intVal, 0377},
	{"0o377\n", &intVal, 0377},
	{"0o_3_7_7\n", &intVal, 0377},
	{"-0377\n", &intVal, -0377},
	{"-0o377\n", &intVal, -0377},
	{"0\n", &uintVal, uint(0)},
	{"000\n", &uintVal, uint(0)},
	{"0x10\n", &uintVal, uint(0x10)},
	{"0377\n", &uintVal, uint(0377)},
	{"22\n", &int8Val, int8(22)},
	{"23\n", &int16Val, int16(23)},
	{"24\n", &int32Val, int32(24)},
	{"25\n", &int64Val, int64(25)},
	{"127\n", &int8Val, int8(127)},
	{"-21\n", &intVal, -21},
	{"-22\n", &int8Val, int8(-22)},
	{"-23\n", &int16Val, int16(-23)},
	{"-24\n", &int32Val, int32(-24)},
	{"-25\n", &int64Val, int64(-25)},
	{"-128\n", &int8Val, int8(-128)},
	{"+21\n", &intVal, +21},
	{"+22\n", &int8Val, int8(+22)},
	{"+23\n", &int16Val, int16(+23)},
	{"+24\n", &int32Val, int32(+24)},
	{"+25\n", &int64Val, int64(+25)},
	{"+127\n", &int8Val, int8(+127)},
	{"26\n", &uintVal, uint(26)},
	{"27\n", &uint8Val, uint8(27)},
	{"28\n", &uint16Val, uint16(28)},
	{"29\n", &uint32Val, uint32(29)},
	{"30\n", &uint64Val, uint64(30)},
	{"31\n", &uintptrVal, uintptr(31)},
	{"255\n", &uint8Val, uint8(255)},
	{"32767\n", &int16Val, int16(32767)},
	{"2.3\n", &float64Val, 2.3},
	{"2.3e1\n", &float32Val, float32(2.3e1)},
	{"2.3e2\n", &float64Val, 2.3e2},
	{"2.3p2\n", &float64Val, 2.3 * 4},
	{"2.3p+2\n", &float64Val, 2.3 * 4},
	{"2.3p+66\n", &float64Val, 2.3 * (1 << 66)},
	{"2.3p-66\n", &float64Val, 2.3 / (1 << 66)},
	{"0x2.3p-66\n", &float64Val, float64(0x23) / (1 << 70)},
	{"2_3.4_5\n", &float64Val, 23.45},
	{"2.35\n", &stringVal, "2.35"},
	{"2345678\n", &bytesVal, []byte("2345678")},
	{"(3.4e1-2i)\n", &complex128Val, 3.4e1 - 2i},
	{"-3.45e1-3i\n", &complex64Val, complex64(-3.45e1 - 3i)},
	{"-.45e1-1e2i\n", &complex128Val, complex128(-.45e1 - 100i)},
	{"-.4_5e1-1E2i\n", &complex128Val, complex128(-.45e1 - 100i)},
	{"0x1.0p1+0x1.0P2i\n", &complex128Val, complex128(2 + 4i)},
	{"-0x1p1-0x1p2i\n", &complex128Val, complex128(-2 - 4i)},
	{"-0x1ep-1-0x1p2i\n", &complex128Val, complex128(-15 - 4i)},
	{"-0x1_Ep-1-0x1p0_2i\n", &complex128Val, complex128(-15 - 4i)},
	{"hello\n", &stringVal, "hello"},

	// Carriage-return followed by newline. (We treat \r\n as \n always.)
	{"hello\r\n", &stringVal, "hello"},
	{"27\r\n", &uint8Val, uint8(27)},

	// Renamed types
	{"true\n", &renamedBoolVal, renamedBool(true)},
	{"F\n", &renamedBoolVal, renamedBool(false)},
	{"101\n", &renamedIntVal, renamedInt(101)},
	{"102\n", &renamedIntVal, renamedInt(102)},
	{"103\n", &renamedUintVal, renamedUint(103)},
	{"104\n", &renamedUintVal, renamedUint(104)},
	{"105\n", &renamedInt8Val, renamedInt8(105)},
	{"106\n", &renamedInt16Val, renamedInt16(106)},
	{"107\n", &renamedInt32Val, renamedInt32(107)},
	{"108\n", &renamedInt64Val, renamedInt64(108)},
	{"109\n", &renamedUint8Val, renamedUint8(109)},
	{"110\n", &renamedUint16Val, renamedUint16(110)},
	{"111\n", &renamedUint32Val, renamedUint32(111)},
	{"112\n", &renamedUint64Val, renamedUint64(112)},
	{"113\n", &renamedUintptrVal, renamedUintptr(113)},
	{"114\n", &renamedStringVal, renamedString("114")},
	{"115\n", &renamedBytesVal, renamedBytes([]byte("115"))},

	// Custom scanners.
	{"  vvv ", &xVal, Xs("vvv")},
	{" 1234hello", &intStringVal, IntString{1234, "hello"}},

	// Fixed bugs
	{"2147483648\n", &int64Val, int64(2147483648)}, // was: integer overflow
}

var scanfTests = []ScanfTest{
	{"%v", "TRUE\n", &boolVal, true},
	{"%t", "false\n", &boolVal, false},
	{"%v", "-71\n", &intVal, -71},
	{"%v", "-7_1\n", &intVal, -71},
	{"%v", "0b111\n", &intVal, 7},
	{"%v", "0b_1_1_1\n", &intVal, 7},
	{"%v", "0377\n", &intVal, 0377},
	{"%v", "0_3_7_7\n", &intVal, 0377},
	{"%v", "0o377\n", &intVal, 0377},
	{"%v", "0o_3_7_7\n", &intVal, 0377},
	{"%v", "0x44\n", &intVal, 0x44},
	{"%v", "0x_4_4\n", &intVal, 0x44},
	{"%d", "72\n", &intVal, 72},
	{"%c", "a\n", &runeVal, 'a'},
	{"%c", "\u5072\n", &runeVal, '\u5072'},
	{"%c", "\u1234\n", &runeVal, '\u1234'},
	{"%d", "73\n", &int8Val, int8(73)},
	{"%d", "+74\n", &int16Val, int16(74)},
	{"%d", "75\n", &int32Val, int32(75)},
	{"%d", "76\n", &int64Val, int64(76)},
	{"%b", "1001001\n", &intVal, 73},
	{"%o", "075\n", &intVal, 075},
	{"%x", "a75\n", &intVal, 0xa75},
	{"%v", "71\n", &uintVal, uint(71)},
	{"%d", "72\n", &uintVal, uint(72)},
	{"%d", "7_2\n", &uintVal, uint(7)}, // only %v takes underscores
	{"%d", "73\n", &uint8Val, uint8(73)},
	{"%d", "74\n", &uint16Val, uint16(74)},
	{"%d", "75\n", &uint32Val, uint32(75)},
	{"%d", "76\n", &uint64Val, uint64(76)},
	{"%d", "77\n", &uintptrVal, uintptr(77)},
	{"%b", "1001001\n", &uintVal, uint(73)},
	{"%b", "100_1001\n", &uintVal, uint(4)},
	{"%o", "075\n", &uintVal, uint(075)},
	{"%o", "07_5\n", &uintVal, uint(07)}, // only %v takes underscores
	{"%x", "a75\n", &uintVal, uint(0xa75)},
	{"%x", "A75\n", &uintVal, uint(0xa75)},
	{"%x", "A7_5\n", &uintVal, uint(0xa7)}, // only %v takes underscores
	{"%U", "U+1234\n", &intVal, int(0x1234)},
	{"%U", "U+4567\n", &uintVal, uint(0x4567)},

	{"%e", "2.3\n", &float64Val, 2.3},
	{"%E", "2.3e1\n", &float32Val, float32(2.3e1)},
	{"%f", "2.3e2\n", &float64Val, 2.3e2},
	{"%g", "2.3p2\n", &float64Val, 2.3 * 4},
	{"%G", "2.3p+2\n", &float64Val, 2.3 * 4},
	{"%v", "2.3p+66\n", &float64Val, 2.3 * (1 << 66)},
	{"%f", "2.3p-66\n", &float64Val, 2.3 / (1 << 66)},
	{"%G", "0x2.3p-66\n", &float64Val, float64(0x23) / (1 << 70)},
	{"%E", "2_3.4_5\n", &float64Val, 23.45},

	// Strings
	{"%s", "using-%s\n", &stringVal, "using-%s"},
	{"%x", "7573696e672d2578\n", &stringVal, "using-%x"},
	{"%X", "7573696E672D2558\n", &stringVal, "using-%X"},
	{"%q", `"quoted\twith\\do\u0075bl\x65s"` + "\n", &stringVal, "quoted\twith\\doubles"},
	{"%q", "`quoted with backs`\n", &stringVal, "quoted with backs"},

	// Byte slices
	{"%s", "bytes-%s\n", &bytesVal, []byte("bytes-%s")},
	{"%x", "62797465732d2578\n", &bytesVal, []byte("bytes-%x")},
	{"%X", "62797465732D2558\n", &bytesVal, []byte("bytes-%X")},
	{"%q", `"bytes\rwith\vdo\u0075bl\x65s"` + "\n", &bytesVal, []byte("bytes\rwith\vdoubles")},
	{"%q", "`bytes with backs`\n", &bytesVal, []byte("bytes with backs")},

	// Renamed types
	{"%v\n", "true\n", &renamedBoolVal, renamedBool(true)},
	{"%t\n", "F\n", &renamedBoolVal, renamedBool(false)},
	{"%v", "101\n", &renamedIntVal, renamedInt(101)},
	{"%c", "\u0101\n", &renamedIntVal, renamedInt('\u0101')},
	{"%o", "0146\n", &renamedIntVal, renamedInt(102)},
	{"%v", "103\n", &renamedUintVal, renamedUint(103)},
	{"%d", "104\n", &renamedUintVal, renamedUint(104)},
	{"%d", "105\n", &renamedInt8Val, renamedInt8(105)},
	{"%d", "106\n", &renamedInt16Val, renamedInt16(106)},
	{"%d", "107\n", &renamedInt32Val, renamedInt32(107)},
	{"%d", "108\n", &renamedInt64Val, renamedInt64(108)},
	{"%x", "6D\n", &renamedUint8Val, renamedUint8(109)},
	{"%o", "0156\n", &renamedUint16Val, renamedUint16(110)},
	{"%d", "111\n", &renamedUint32Val, renamedUint32(111)},
	{"%d", "112\n", &renamedUint64Val, renamedUint64(112)},
	{"%d", "113\n", &renamedUintptrVal, renamedUintptr(113)},
	{"%s", "114\n", &renamedStringVal, renamedString("114")},
	{"%q", "\"1155\"\n", &renamedBytesVal, renamedBytes([]byte("1155"))},
	{"%g", "116e1\n", &renamedFloat32Val, renamedFloat32(116e1)},
	{"%g", "-11.7e+1", &renamedFloat64Val, renamedFloat64(-11.7e+1)},
	{"%g", "11+6e1i\n", &renamedComplex64Val, renamedComplex64(11 + 6e1i)},
	{"%g", "-11.+7e+1i", &renamedComplex128Val, renamedComplex128(-11. + 7e+1i)},

	// Interesting formats
	{"here is\tthe value:%d", "here is   the\tvalue:118\n", &intVal, 118},
	{"%% %%:%d", "% %:119\n", &intVal, 119},
	{"%d%%", "42%", &intVal, 42}, // %% at end of string.

	// Corner cases
	{"%x", "FFFFFFFF\n", &uint32Val, uint32(0xFFFFFFFF)},

	// Custom scanner.
	{"%s", "  sss ", &xVal, Xs("sss")},
	{"%2s", "sssss", &xVal, Xs("ss")},

	// Fixed bugs
	{"%d\n", "27\n", &intVal, 27},         // ok
	{"%d\n", "28 \n", &intVal, 28},        // was: "unexpected newline"
	{"%v", "0", &intVal, 0},               // was: "EOF"; 0 was taken as base prefix and not counted.
	{"%v", "0", &uintVal, uint(0)},        // was: "EOF"; 0 was taken as base prefix and not counted.
	{"%c", " ", &uintVal, uint(' ')},      // %c must accept a blank.
	{"%c", "\t", &uintVal, uint('\t')},    // %c must accept any space.
	{"%c", "\n", &uintVal, uint('\n')},    // %c must accept any space.
	{"%d%%", "23%\n", &uintVal, uint(23)}, // %% matches literal %.
	{"%%%d", "%23\n", &uintVal, uint(23)}, // %% matches literal %.

	// space handling
	{"%d", "27", &intVal, 27},
	{"%d", "27 ", &intVal, 27},
	{"%d", " 27", &intVal, 27},
	{"%d", " 27 ", &intVal, 27},

	{"X%d", "X27", &intVal, 27},
	{"X%d", "X27 ", &intVal, 27},
	{"X%d", "X 27", &intVal, 27},
	{"X%d", "X 27 ", &intVal, 27},

	{"X %d", "X27", &intVal, nil},  // expected space in input to match format
	{"X %d", "X27 ", &intVal, nil}, // expected space in input to match format
	{"X %d", "X 27", &intVal, 27},
	{"X %d", "X 27 ", &intVal, 27},

	{"%dX", "27X", &intVal, 27},
	{"%dX", "27 X", &intVal, nil}, // input does not match format
	{"%dX", " 27X", &intVal, 27},
	{"%dX", " 27 X", &intVal, nil}, // input does not match format

	{"%d X", "27X", &intVal, nil}, // expected space in input to match format
	{"%d X", "27 X", &intVal, 27},
	{"%d X", " 27X", &intVal, nil}, // expected space in input to match format
	{"%d X", " 27 X", &intVal, 27},

	{"X %d X", "X27X", &intVal, nil},  // expected space in input to match format
	{"X %d X", "X27 X", &intVal, nil}, // expected space in input to match format
	{"X %d X", "X 27X", &intVal, nil}, // expected space in input to match format
	{"X %d X", "X 27 X", &intVal, 27},

	{"X %s X", "X27X", &stringVal, nil},  // expected space in input to match format
	{"X %s X", "X27 X", &stringVal, nil}, // expected space in input to match format
	{"X %s X", "X 27X", &stringVal, nil}, // unexpected EOF
	{"X %s X", "X 27 X", &stringVal, "27"},

	{"X%sX", "X27X", &stringVal, nil},   // unexpected EOF
	{"X%sX", "X27 X", &stringVal, nil},  // input does not match format
	{"X%sX", "X 27X", &stringVal, nil},  // unexpected EOF
	{"X%sX", "X 27 X", &stringVal, nil}, // input does not match format

	{"X%s", "X27", &stringVal, "27"},
	{"X%s", "X27 ", &stringVal, "27"},
	{"X%s", "X 27", &stringVal, "27"},
	{"X%s", "X 27 ", &stringVal, "27"},

	{"X%dX", "X27X", &intVal, 27},
	{"X%dX", "X27 X", &intVal, nil}, // input does not match format
	{"X%dX", "X 27X", &intVal, 27},
	{"X%dX", "X 27 X", &intVal, nil}, // input does not match format

	{"X%dX", "X27X", &intVal, 27},
	{"X%dX", "X27X ", &intVal, 27},
	{"X%dX", " X27X", &intVal, nil},  // input does not match format
	{"X%dX", " X27X ", &intVal, nil}, // input does not match format

	{"X%dX\n", "X27X", &intVal, 27},
	{"X%dX \n", "X27X ", &intVal, 27},
	{"X%dX\n", "X27X\n", &intVal, 27},
	{"X%dX\n", "X27X \n", &intVal, 27},

	{"X%dX \n", "X27X", &intVal, 27},
	{"X%dX \n", "X27X ", &intVal, 27},
	{"X%dX \n", "X27X\n", &intVal, 27},
	{"X%dX \n", "X27X \n", &intVal, 27},

	{"X%c", "X\n", &runeVal, '\n'},
	{"X%c", "X \n", &runeVal, ' '},
	{"X %c", "X!", &runeVal, nil},  // expected space in input to match format
	{"X %c", "X\n", &runeVal, nil}, // newline in input does not match format
	{"X %c", "X !", &runeVal, '!'},
	{"X %c", "X \n", &runeVal, '\n'},

	{" X%dX", "X27X", &intVal, nil},  // expected space in input to match format
	{" X%dX", "X27X ", &intVal, nil}, // expected space in input to match format
	{" X%dX", " X27X", &intVal, 27},
	{" X%dX", " X27X ", &intVal, 27},

	{"X%dX ", "X27X", &intVal, 27},
	{"X%dX ", "X27X ", &intVal, 27},
	{"X%dX ", " X27X", &intVal, nil},  // input does not match format
	{"X%dX ", " X27X ", &intVal, nil}, // input does not match format

	{" X%dX ", "X27X", &intVal, nil},  // expected space in input to match format
	{" X%dX ", "X27X ", &intVal, nil}, // expected space in input to match format
	{" X%dX ", " X27X", &intVal, 27},
	{" X%dX ", " X27X ", &intVal, 27},

	{"%d\nX", "27\nX", &intVal, 27},
	{"%dX\n X", "27X\n X", &intVal, 27},
}

var overflowTests = []ScanTest{
	{"128", &int8Val, 0},
	{"32768", &int16Val, 0},
	{"-129", &int8Val, 0},
	{"-32769", &int16Val, 0},
	{"256", &uint8Val, 0},
	{"65536", &uint16Val, 0},
	{"1e100", &float32Val, 0},
	{"1e500", &float64Val, 0},
	{"(1e100+0i)", &complex64Val, 0},
	{"(1+1e100i)", &complex64Val, 0},
	{"(1-1e500i)", &complex128Val, 0},
}

var truth bool
var i, j, k int
var f float64
var s, t string
var c complex128
var x, y Xs
var z IntString
var r1, r2, r3 rune

var multiTests = []ScanfMultiTest{
	{"", "", []any{}, []any{}, ""},
	{"%d", "23", args(&i), args(23), ""},
	{"%2s%3s", "22333", args(&s, &t), args("22", "333"), ""},
	{"%2d%3d", "44555", args(&i, &j), args(44, 555), ""},
	{"%2d.%3d", "66.777", args(&i, &j), args(66, 777), ""},
	{"%d, %d", "23, 18", args(&i, &j), args(23, 18), ""},
	{"%3d22%3d", "33322333", args(&i, &j), args(333, 333), ""},
	{"%6vX=%3fY", "3+2iX=2.5Y", args(&c, &f), args((3 + 2i), 2.5), ""},
	{"%d%s", "123abc", args(&i, &s), args(123, "abc"), ""},
	{"%c%c%c", "2\u50c2X", args(&r1, &r2, &r3), args('2', '\u50c2', 'X'), ""},
	{"%5s%d", " 1234567 ", args(&s, &i), args("12345", 67), ""},
	{"%5s%d", " 12 34 567 ", args(&s, &i), args("12", 34), ""},

	// Custom scanners.
	{"%e%f", "eefffff", args(&x, &y), args(Xs("ee"), Xs("fffff")), ""},
	{"%4v%s", "12abcd", args(&z, &s), args(IntString{12, "ab"}, "cd"), ""},

	// Errors
	{"%t", "23 18", args(&i), nil, "bad verb"},
	{"%d %d %d", "23 18", args(&i, &j), args(23, 18), "too few operands"},
	{"%d %d", "23 18 27", args(&i, &j, &k), args(23, 18), "too many operands"},
	{"%c", "\u0100", args(&int8Val), nil, "overflow"},
	{"X%d", "10X", args(&intVal), nil, "input does not match format"},
	{"%d%", "42%", args(&intVal), args(42), "missing verb: % at end of format string"},
	{"%d% ", "42%", args(&intVal), args(42), "too few operands for format '% '"}, // Slightly odd error, but correct.
	{"%%%d", "xxx 42", args(&intVal), args(42), "missing literal %"},
	{"%%%d", "x42", args(&intVal), args(42), "missing literal %"},
	{"%%%d", "42", args(&intVal), args(42), "missing literal %"},

	// Bad UTF-8: should see every byte.
	{"%c%c%c", "\xc2X\xc2", args(&r1, &r2, &r3), args(utf8.RuneError, 'X', utf8.RuneError), ""},

	// Fixed bugs
	{"%v%v", "FALSE23", args(&truth, &i), args(false, 23), ""},
}

var readers = []struct {
	name string
	f    func(string) io.Reader
}{
	{"StringReader", func(s string) io.Reader {
		return strings.NewReader(s)
	}},
	{"ReaderOnly", func(s string) io.Reader {
		return struct{ io.Reader }{strings.NewReader(s)}
	}},
	{"OneByteReader", func(s string) io.Reader {
		return iotest.OneByteReader(strings.NewReader(s))
	}},
	{"DataErrReader", func(s string) io.Reader {
		return iotest.DataErrReader(strings.NewReader(s))
	}},
}

func testScan(t *testing.T, f func(string) io.Reader, scan func(r io.Reader, a ...any) (int, error)) {
	for _, test := range scanTests {
		r := f(test.text)
		n, err := scan(r, test.in)
		if err != nil {
			m := ""
			if n > 0 {
				m = Sprintf(" (%d fields ok)", n)
			}
			t.Errorf("got error scanning %q: %s%s", test.text, err, m)
			continue
		}
		if n != 1 {
			t.Errorf("count error on entry %q: got %d", test.text, n)
			continue
		}
		// The incoming value may be a pointer
		v := reflect.ValueOf(test.in)
		if p := v; p.Kind() == reflect.Pointer {
			v = p.Elem()
		}
		val := v.Interface()
		if !reflect.DeepEqual(val, test.out) {
			t.Errorf("scanning %q: expected %#v got %#v, type %T", test.text, test.out, val, val)
		}
	}
}

func TestScan(t *testing.T) {
	for _, r := range readers {
		t.Run(r.name, func(t *testing.T) {
			testScan(t, r.f, Fscan)
		})
	}
}

func TestScanln(t *testing.T) {
	for _, r := range readers {
		t.Run(r.name, func(t *testing.T) {
			testScan(t, r.f, Fscanln)
		})
	}
}

func TestScanf(t *testing.T) {
	for _, test := range scanfTests {
		n, err := Sscanf(test.text, test.format, test.in)
		if err != nil {
			if test.out != nil {
				t.Errorf("Sscanf(%q, %q): unexpected error: %v", test.text, test.format, err)
			}
			continue
		}
		if test.out == nil {
			t.Errorf("Sscanf(%q, %q): unexpected success", test.text, test.format)
			continue
		}
		if n != 1 {
			t.Errorf("Sscanf(%q, %q): parsed %d field, want 1", test.text, test.format, n)
			continue
		}
		// The incoming value may be a pointer
		v := reflect.ValueOf(test.in)
		if p := v; p.Kind() == reflect.Pointer {
			v = p.Elem()
		}
		val := v.Interface()
		if !reflect.DeepEqual(val, test.out) {
			t.Errorf("Sscanf(%q, %q): parsed value %T(%#v), want %T(%#v)", test.text, test.format, val, val, test.out, test.out)
		}
	}
}

func TestScanOverflow(t *testing.T) {
	// different machines and different types report errors with different strings.
	re := regexp.MustCompile("overflow|too large|out of range|not representable")
	for _, test := range overflowTests {
		_, err := Sscan(test.text, test.in)
		if err == nil {
			t.Errorf("expected overflow scanning %q", test.text)
			continue
		}
		if !re.MatchString(err.Error()) {
			t.Errorf("expected overflow error scanning %q: %s", test.text, err)
		}
	}
}

func verifyNaN(str string, t *testing.T) {
	var f float64
	var f32 float32
	var f64 float64
	text := str + " " + str + " " + str
	n, err := Fscan(strings.NewReader(text), &f, &f32, &f64)
	if err != nil {
		t.Errorf("got error scanning %q: %s", text, err)
	}
	if n != 3 {
		t.Errorf("count error scanning %q: got %d", text, n)
	}
	if !math.IsNaN(float64(f)) || !math.IsNaN(float64(f32)) || !math.IsNaN(f64) {
		t.Errorf("didn't get NaNs scanning %q: got %g %g %g", text, f, f32, f64)
	}
}

func TestNaN(t *testing.T) {
	for _, s := range []string{"nan", "NAN", "NaN"} {
		verifyNaN(s, t)
	}
}

func verifyInf(str string, t *testing.T) {
	var f float64
	var f32 float32
	var f64 float64
	text := str + " " + str + " " + str
	n, err := Fscan(strings.NewReader(text), &f, &f32, &f64)
	if err != nil {
		t.Errorf("got error scanning %q: %s", text, err)
	}
	if n != 3 {
		t.Errorf("count error scanning %q: got %d", text, n)
	}
	sign := 1
	if str[0] == '-' {
		sign = -1
	}
	if !math.IsInf(float64(f), sign) || !math.IsInf(float64(f32), sign) || !math.IsInf(f64, sign) {
		t.Errorf("didn't get right Infs scanning %q: got %g %g %g", text, f, f32, f64)
	}
}

func TestInf(t *testing.T) {
	for _, s := range []string{"inf", "+inf", "-inf", "INF", "-INF", "+INF", "Inf", "-Inf", "+Inf"} {
		verifyInf(s, t)
	}
}

func testScanfMulti(t *testing.T, f func(string) io.Reader) {
	sliceType := reflect.TypeOf(make([]any, 1))
	for _, test := range multiTests {
		r := f(test.text)
		n, err := Fscanf(r, test.format, test.in...)
		if err != nil {
			if test.err == "" {
				t.Errorf("got error scanning (%q, %q): %q", test.format, test.text, err)
			} else if !strings.Contains(err.Error(), test.err) {
				t.Errorf("got wrong error scanning (%q, %q): %q; expected %q", test.format, test.text, err, test.err)
			}
			continue
		}
		if test.err != "" {
			t.Errorf("expected error %q error scanning (%q, %q)", test.err, test.format, test.text)
		}
		if n != len(test.out) {
			t.Errorf("count error on entry (%q, %q): expected %d got %d", test.format, test.text, len(test.out), n)
			continue
		}
		// Convert the slice of pointers into a slice of values
		resultVal := reflect.MakeSlice(sliceType, n, n)
		for i := 0; i < n; i++ {
			v := reflect.ValueOf(test.in[i]).Elem()
			resultVal.Index(i).Set(v)
		}
		result := resultVal.Interface()
		if !reflect.DeepEqual(result, test.out) {
			t.Errorf("scanning (%q, %q): expected %#v got %#v", test.format, test.text, test.out, result)
		}
	}
}

func TestScanfMulti(t *testing.T) {
	for _, r := range readers {
		t.Run(r.name, func(t *testing.T) {
			testScanfMulti(t, r.f)
		})
	}
}

func TestScanMultiple(t *testing.T) {
	var a int
	var s string
	n, err := Sscan("123abc", &a, &s)
	if n != 2 {
		t.Errorf("Sscan count error: expected 2: got %d", n)
	}
	if err != nil {
		t.Errorf("Sscan expected no error; got %s", err)
	}
	if a != 123 || s != "abc" {
		t.Errorf("Sscan wrong values: got (%d %q) expected (123 \"abc\")", a, s)
	}
	n, err = Sscan("asdf", &s, &a)
	if n != 1 {
		t.Errorf("Sscan count error: expected 1: got %d", n)
	}
	if err == nil {
		t.Errorf("Sscan expected error; got none: %s", err)
	}
	if s != "asdf" {
		t.Errorf("Sscan wrong values: got %q expected \"asdf\"", s)
	}
}

// Empty strings are not valid input when scanning a string.
func TestScanEmpty(t *testing.T) {
	var s1, s2 string
	n, err := Sscan("abc", &s1, &s2)
	if n != 1 {
		t.Errorf("Sscan count error: expected 1: got %d", n)
	}
	if err == nil {
		t.Error("Sscan <one item> expected error; got none")
	}
	if s1 != "abc" {
		t.Errorf("Sscan wrong values: got %q expected \"abc\"", s1)
	}
	n, err = Sscan("", &s1, &s2)
	if n != 0 {
		t.Errorf("Sscan count error: expected 0: got %d", n)
	}
	if err == nil {
		t.Error("Sscan <empty> expected error; got none")
	}
	// Quoted empty string is OK.
	n, err = Sscanf(`""`, "%q", &s1)
	if n != 1 {
		t.Errorf("Sscanf count error: expected 1: got %d", n)
	}
	if err != nil {
		t.Errorf("Sscanf <empty> expected no error with quoted string; got %s", err)
	}
}

func TestScanNotPointer(t *testing.T) {
	r := strings.NewReader("1")
	var a int
	_, err := Fscan(r, a)
	if err == nil {
		t.Error("expected error scanning non-pointer")
	} else if !strings.Contains(err.Error(), "pointer") {
		t.Errorf("expected pointer error scanning non-pointer, got: %s", err)
	}
}

func TestScanlnNoNewline(t *testing.T) {
	var a int
	_, err := Sscanln("1 x\n", &a)
	if err == nil {
		t.Error("expected error scanning string missing newline")
	} else if !strings.Contains(err.Error(), "newline") {
		t.Errorf("expected newline error scanning string missing newline, got: %s", err)
	}
}

func TestScanlnWithMiddleNewline(t *testing.T) {
	r := strings.NewReader("123\n456\n")
	var a, b int
	_, err := Fscanln(r, &a, &b)
	if err == nil {
		t.Error("expected error scanning string with extra newline")
	} else if !strings.Contains(err.Error(), "newline") {
		t.Errorf("expected newline error scanning string with extra newline, got: %s", err)
	}
}

// eofCounter is a special Reader that counts reads at end of file.
type eofCounter struct {
	reader   *strings.Reader
	eofCount int
}

func (ec *eofCounter) Read(b []byte) (n int, err error) {
	n, err = ec.reader.Read(b)
	if n == 0 {
		ec.eofCount++
	}
	return
}

// TestEOF verifies that when we scan, we see at most EOF once per call to a
// Scan function, and then only when it's really an EOF.
func TestEOF(t *testing.T) {
	ec := &eofCounter{strings.NewReader("123\n"), 0}
	var a int
	n, err := Fscanln(ec, &a)
	if err != nil {
		t.Error("unexpected error", err)
	}
	if n != 1 {
		t.Error("expected to scan one item, got", n)
	}
	if ec.eofCount != 0 {
		t.Error("expected zero EOFs", ec.eofCount)
		ec.eofCount = 0 // reset for next test
	}
	n, err = Fscanln(ec, &a)
	if err == nil {
		t.Error("expected error scanning empty string")
	}
	if n != 0 {
		t.Error("expected to scan zero items, got", n)
	}
	if ec.eofCount != 1 {
		t.Error("expected one EOF, got", ec.eofCount)
	}
}

// TestEOFAtEndOfInput verifies that we see an EOF error if we run out of input.
// This was a buglet: we used to get "expected integer".
func TestEOFAtEndOfInput(t *testing.T) {
	var i, j int
	n, err := Sscanf("23", "%d %d", &i, &j)
	if n != 1 || i != 23 {
		t.Errorf("Sscanf expected one value of 23; got %d %d", n, i)
	}
	if err != io.EOF {
		t.Errorf("Sscanf expected EOF; got %q", err)
	}
	n, err = Sscan("234", &i, &j)
	if n != 1 || i != 234 {
		t.Errorf("Sscan expected one value of 234; got %d %d", n, i)
	}
	if err != io.EOF {
		t.Errorf("Sscan expected EOF; got %q", err)
	}
	// Trailing space is tougher.
	n, err = Sscan("234 ", &i, &j)
	if n != 1 || i != 234 {
		t.Errorf("Sscan expected one value of 234; got %d %d", n, i)
	}
	if err != io.EOF {
		t.Errorf("Sscan expected EOF; got %q", err)
	}
}

var eofTests = []struct {
	format string
	v      any
}{
	{"%s", &stringVal},
	{"%q", &stringVal},
	{"%x", &stringVal},
	{"%v", &stringVal},
	{"%v", &bytesVal},
	{"%v", &intVal},
	{"%v", &uintVal},
	{"%v", &boolVal},
	{"%v", &float32Val},
	{"%v", &complex64Val},
	{"%v", &renamedStringVal},
	{"%v", &renamedBytesVal},
	{"%v", &renamedIntVal},
	{"%v", &renamedUintVal},
	{"%v", &renamedBoolVal},
	{"%v", &renamedFloat32Val},
	{"%v", &renamedComplex64Val},
}

func TestEOFAllTypes(t *testing.T) {
	for i, test := range eofTests {
		if _, err := Sscanf("", test.format, test.v); err != io.EOF {
			t.Errorf("#%d: %s %T not eof on empty string: %s", i, test.format, test.v, err)
		}
		if _, err := Sscanf("   ", test.format, test.v); err != io.EOF {
			t.Errorf("#%d: %s %T not eof on trailing blanks: %s", i, test.format, test.v, err)
		}
	}
}

// TestUnreadRuneWithBufio verifies that, at least when using bufio, successive
// calls to Fscan do not lose runes.
func TestUnreadRuneWithBufio(t *testing.T) {
	r := bufio.NewReader(strings.NewReader("123αb"))
	var i int
	var a string
	n, err := Fscanf(r, "%d", &i)
	if n != 1 || err != nil {
		t.Errorf("reading int expected one item, no errors; got %d %q", n, err)
	}
	if i != 123 {
		t.Errorf("expected 123; got %d", i)
	}
	n, err = Fscanf(r, "%s", &a)
	if n != 1 || err != nil {
		t.Errorf("reading string expected one item, no errors; got %d %q", n, err)
	}
	if a != "αb" {
		t.Errorf("expected αb; got %q", a)
	}
}

type TwoLines string

// Scan attempts to read two lines into the object. Scanln should prevent this
// because it stops at newline; Scan and Scanf should be fine.
func (t *TwoLines) Scan(state ScanState, verb rune) error {
	chars := make([]rune, 0, 100)
	for nlCount := 0; nlCount < 2; {
		c, _, err := state.ReadRune()
		if err != nil {
			return err
		}
		chars = append(chars, c)
		if c == '\n' {
			nlCount++
		}
	}
	*t = TwoLines(string(chars))
	return nil
}

func TestMultiLine(t *testing.T) {
	input := "abc\ndef\n"
	// Sscan should work
	var tscan TwoLines
	n, err := Sscan(input, &tscan)
	if n != 1 {
		t.Errorf("Sscan: expected 1 item; got %d", n)
	}
	if err != nil {
		t.Errorf("Sscan: expected no error; got %s", err)
	}
	if string(tscan) != input {
		t.Errorf("Sscan: expected %q; got %q", input, tscan)
	}
	// Sscanf should work
	var tscanf TwoLines
	n, err = Sscanf(input, "%s", &tscanf)
	if n != 1 {
		t.Errorf("Sscanf: expected 1 item; got %d", n)
	}
	if err != nil {
		t.Errorf("Sscanf: expected no error; got %s", err)
	}
	if string(tscanf) != input {
		t.Errorf("Sscanf: expected %q; got %q", input, tscanf)
	}
	// Sscanln should not work
	var tscanln TwoLines
	n, err = Sscanln(input, &tscanln)
	if n != 0 {
		t.Errorf("Sscanln: expected 0 items; got %d: %q", n, tscanln)
	}
	if err == nil {
		t.Error("Sscanln: expected error; got none")
	} else if err != io.ErrUnexpectedEOF {
		t.Errorf("Sscanln: expected io.ErrUnexpectedEOF (ha!); got %s", err)
	}
}

// TestLineByLineFscanf tests that Fscanf does not read past newline. Issue
// 3481.
func TestLineByLineFscanf(t *testing.T) {
	r := struct{ io.Reader }{strings.NewReader("1\n2\n")}
	var i, j int
	n, err := Fscanf(r, "%v\n", &i)
	if n != 1 || err != nil {
		t.Fatalf("first read: %d %q", n, err)
	}
	n, err = Fscanf(r, "%v\n", &j)
	if n != 1 || err != nil {
		t.Fatalf("second read: %d %q", n, err)
	}
	if i != 1 || j != 2 {
		t.Errorf("wrong values; wanted 1 2 got %d %d", i, j)
	}
}

// TestScanStateCount verifies the correct byte count is returned. Issue 8512.

// runeScanner implements the Scanner interface for TestScanStateCount.
type runeScanner struct {
	rune rune
	size int
}

func (rs *runeScanner) Scan(state ScanState, verb rune) error {
	r, size, err := state.ReadRune()
	rs.rune = r
	rs.size = size
	return err
}

func TestScanStateCount(t *testing.T) {
	var a, b, c runeScanner
	n, err := Sscanf("12➂", "%c%c%c", &a, &b, &c)
	if err != nil {
		t.Fatal(err)
	}
	if n != 3 {
		t.Fatalf("expected 3 items consumed, got %d", n)
	}
	if a.rune != '1' || b.rune != '2' || c.rune != '➂' {
		t.Errorf("bad scan rune: %q %q %q should be '1' '2' '➂'", a.rune, b.rune, c.rune)
	}
	if a.size != 1 || b.size != 1 || c.size != 3 {
		t.Errorf("bad scan size: %q %q %q should be 1 1 3", a.size, b.size, c.size)
	}
}

// RecursiveInt accepts a string matching %d.%d.%d....
// and parses it into a linked list.
// It allows us to benchmark recursive descent style scanners.
type RecursiveInt struct {
	i    int
	next *RecursiveInt
}

func (r *RecursiveInt) Scan(state ScanState, verb rune) (err error) {
	_, err = Fscan(state, &r.i)
	if err != nil {
		return
	}
	next := new(RecursiveInt)
	_, err = Fscanf(state, ".%v", next)
	if err != nil {
		if err == io.ErrUnexpectedEOF {
			err = nil
		}
		return
	}
	r.next = next
	return
}

// scanInts performs the same scanning task as RecursiveInt.Scan
// but without recurring through scanner, so we can compare
// performance more directly.
func scanInts(r *RecursiveInt, b *bytes.Buffer) (err error) {
	r.next = nil
	_, err = Fscan(b, &r.i)
	if err != nil {
		return
	}
	c, _, err := b.ReadRune()
	if err != nil {
		if err == io.EOF {
			err = nil
		}
		return
	}
	if c != '.' {
		return
	}
	next := new(RecursiveInt)
	err = scanInts(next, b)
	if err == nil {
		r.next = next
	}
	return
}

func makeInts(n int) []byte {
	var buf bytes.Buffer
	Fprintf(&buf, "1")
	for i := 1; i < n; i++ {
		Fprintf(&buf, ".%d", i+1)
	}
	return buf.Bytes()
}

func TestScanInts(t *testing.T) {
	testScanInts(t, scanInts)
	testScanInts(t, func(r *RecursiveInt, b *bytes.Buffer) (err error) {
		_, err = Fscan(b, r)
		return
	})
}

// 800 is small enough to not overflow the stack when using gccgo on a
// platform that does not support split stack.
const intCount = 800

func testScanInts(t *testing.T, scan func(*RecursiveInt, *bytes.Buffer) error) {
	r := new(RecursiveInt)
	ints := makeInts(intCount)
	buf := bytes.NewBuffer(ints)
	err := scan(r, buf)
	if err != nil {
		t.Error("unexpected error", err)
	}
	i := 1
	for ; r != nil; r = r.next {
		if r.i != i {
			t.Fatalf("bad scan: expected %d got %d", i, r.i)
		}
		i++
	}
	if i-1 != intCount {
		t.Fatalf("bad scan count: expected %d got %d", intCount, i-1)
	}
}

func BenchmarkScanInts(b *testing.B) {
	b.ResetTimer()
	ints := makeInts(intCount)
	var r RecursiveInt
	for i := b.N - 1; i >= 0; i-- {
		buf := bytes.NewBuffer(ints)
		b.StartTimer()
		scanInts(&r, buf)
		b.StopTimer()
	}
}

func BenchmarkScanRecursiveInt(b *testing.B) {
	b.ResetTimer()
	ints := makeInts(intCount)
	var r RecursiveInt
	for i := b.N - 1; i >= 0; i-- {
		buf := bytes.NewBuffer(ints)
		b.StartTimer()
		Fscan(buf, &r)
		b.StopTimer()
	}
}

func BenchmarkScanRecursiveIntReaderWrapper(b *testing.B) {
	b.ResetTimer()
	ints := makeInts(intCount)
	var r RecursiveInt
	for i := b.N - 1; i >= 0; i-- {
		buf := struct{ io.Reader }{strings.NewReader(string(ints))}
		b.StartTimer()
		Fscan(buf, &r)
		b.StopTimer()
	}
}

// Issue 9124.
// %x on bytes couldn't handle non-space bytes terminating the scan.
func TestHexBytes(t *testing.T) {
	var a, b []byte
	n, err := Sscanf("00010203", "%x", &a)
	if n != 1 || err != nil {
		t.Errorf("simple: got count, err = %d, %v; expected 1, nil", n, err)
	}
	check := func(msg string, x []byte) {
		if len(x) != 4 {
			t.Errorf("%s: bad length %d", msg, len(x))
		}
		for i, b := range x {
			if int(b) != i {
				t.Errorf("%s: bad x[%d] = %x", msg, i, x[i])
			}
		}
	}
	check("simple", a)
	a = nil

	n, err = Sscanf("00010203 00010203", "%x %x", &a, &b)
	if n != 2 || err != nil {
		t.Errorf("simple pair: got count, err = %d, %v; expected 2, nil", n, err)
	}
	check("simple pair a", a)
	check("simple pair b", b)
	a = nil
	b = nil

	n, err = Sscanf("00010203:", "%x", &a)
	if n != 1 || err != nil {
		t.Errorf("colon: got count, err = %d, %v; expected 1, nil", n, err)
	}
	check("colon", a)
	a = nil

	n, err = Sscanf("00010203:00010203", "%x:%x", &a, &b)
	if n != 2 || err != nil {
		t.Errorf("colon pair: got count, err = %d, %v; expected 2, nil", n, err)
	}
	check("colon pair a", a)
	check("colon pair b", b)
	a = nil
	b = nil

	// This one fails because there is a hex byte after the data,
	// that is, an odd number of hex input bytes.
	n, err = Sscanf("000102034:", "%x", &a)
	if n != 0 || err == nil {
		t.Errorf("odd count: got count, err = %d, %v; expected 0, error", n, err)
	}
}

func TestScanNewlinesAreSpaces(t *testing.T) {
	var a, b int
	var tests = []struct {
		name  string
		text  string
		count int
	}{
		{"newlines", "1\n2\n", 2},
		{"no final newline", "1\n2", 2},
		{"newlines with spaces ", "1  \n  2  \n", 2},
		{"no final newline with spaces", "1  \n  2", 2},
	}
	for _, test := range tests {
		n, err := Sscan(test.text, &a, &b)
		if n != test.count {
			t.Errorf("%s: expected to scan %d item(s), scanned %d", test.name, test.count, n)
		}
		if err != nil {
			t.Errorf("%s: unexpected error: %s", test.name, err)
		}
	}
}

func TestScanlnNewlinesTerminate(t *testing.T) {
	var a, b int
	var tests = []struct {
		name  string
		text  string
		count int
		ok    bool
	}{
		{"one line one item", "1\n", 1, false},
		{"one line two items with spaces ", "   1 2    \n", 2, true},
		{"one line two items no newline", "   1 2", 2, true},
		{"two lines two items", "1\n2\n", 1, false},
	}
	for _, test := range tests {
		n, err := Sscanln(test.text, &a, &b)
		if n != test.count {
			t.Errorf("%s: expected to scan %d item(s), scanned %d", test.name, test.count, n)
		}
		if test.ok && err != nil {
			t.Errorf("%s: unexpected error: %s", test.name, err)
		}
		if !test.ok && err == nil {
			t.Errorf("%s: expected error; got none", test.name)
		}
	}
}

func TestScanfNewlineMatchFormat(t *testing.T) {
	var a, b int
	var tests = []struct {
		name   string
		text   string
		format string
		count  int
		ok     bool
	}{
		{"newline in both", "1\n2", "%d\n%d\n", 2, true},
		{"newline in input", "1\n2", "%d %d", 1, false},
		{"space-newline in input", "1 \n2", "%d %d", 1, false},
		{"newline in format", "1 2", "%d\n%d", 1, false},
		{"space-newline in format", "1 2", "%d \n%d", 1, false},
		{"space-newline in both", "1 \n2", "%d \n%d", 2, true},
		{"extra space in format", "1\n2", "%d\n %d", 2, true},
		{"two extra spaces in format", "1\n2", "%d \n %d", 2, true},
		{"space vs newline 0000", "1\n2", "%d\n%d", 2, true},
		{"space vs newline 0001", "1\n2", "%d\n %d", 2, true},
		{"space vs newline 0010", "1\n2", "%d \n%d", 2, true},
		{"space vs newline 0011", "1\n2", "%d \n %d", 2, true},
		{"space vs newline 0100", "1\n 2", "%d\n%d", 2, true},
		{"space vs newline 0101", "1\n 2", "%d\n%d ", 2, true},
		{"space vs newline 0110", "1\n 2", "%d \n%d", 2, true},
		{"space vs newline 0111", "1\n 2", "%d \n %d", 2, true},
		{"space vs newline 1000", "1 \n2", "%d\n%d", 2, true},
		{"space vs newline 1001", "1 \n2", "%d\n %d", 2, true},
		{"space vs newline 1010", "1 \n2", "%d \n%d", 2, true},
		{"space vs newline 1011", "1 \n2", "%d \n %d", 2, true},
		{"space vs newline 1100", "1 \n 2", "%d\n%d", 2, true},
		{"space vs newline 1101", "1 \n 2", "%d\n %d", 2, true},
		{"space vs newline 1110", "1 \n 2", "%d \n%d", 2, true},
		{"space vs newline 1111", "1 \n 2", "%d \n %d", 2, true},
		{"space vs newline no-percent 0000", "1\n2", "1\n2", 0, true},
		{"space vs newline no-percent 0001", "1\n2", "1\n 2", 0, true},
		{"space vs newline no-percent 0010", "1\n2", "1 \n2", 0, true},
		{"space vs newline no-percent 0011", "1\n2", "1 \n 2", 0, true},
		{"space vs newline no-percent 0100", "1\n 2", "1\n2", 0, false},  // fails: space after nl in input but not pattern
		{"space vs newline no-percent 0101", "1\n 2", "1\n2 ", 0, false}, // fails: space after nl in input but not pattern
		{"space vs newline no-percent 0110", "1\n 2", "1 \n2", 0, false}, // fails: space after nl in input but not pattern
		{"space vs newline no-percent 0111", "1\n 2", "1 \n 2", 0, true},
		{"space vs newline no-percent 1000", "1 \n2", "1\n2", 0, true},
		{"space vs newline no-percent 1001", "1 \n2", "1\n 2", 0, true},
		{"space vs newline no-percent 1010", "1 \n2", "1 \n2", 0, true},
		{"space vs newline no-percent 1011", "1 \n2", "1 \n 2", 0, true},
		{"space vs newline no-percent 1100", "1 \n 2", "1\n2", 0, false}, // fails: space after nl in input but not pattern
		{"space vs newline no-percent 1101", "1 \n 2", "1\n 2", 0, true},
		{"space vs newline no-percent 1110", "1 \n 2", "1 \n2", 0, false}, // fails: space after nl in input but not pattern
		{"space vs newline no-percent 1111", "1 \n 2", "1 \n 2", 0, true},
	}
	for _, test := range tests {
		var n int
		var err error
		if strings.Contains(test.format, "%") {
			n, err = Sscanf(test.text, test.format, &a, &b)
		} else {
			n, err = Sscanf(test.text, test.format)
		}
		if n != test.count {
			t.Errorf("%s: expected to scan %d item(s), scanned %d", test.name, test.count, n)
		}
		if test.ok && err != nil {
			t.Errorf("%s: unexpected error: %s", test.name, err)
		}
		if !test.ok && err == nil {
			t.Errorf("%s: expected error; got none", test.name)
		}
	}
}

// Test for issue 12090: Was unreading at EOF, double-scanning a byte.

type hexBytes [2]byte

func (h *hexBytes) Scan(ss ScanState, verb rune) error {
	var b []byte
	_, err := Fscanf(ss, "%4x", &b)
	if err != nil {
		panic(err) // Really shouldn't happen.
	}
	copy((*h)[:], b)
	return err
}

func TestHexByte(t *testing.T) {
	var h hexBytes
	n, err := Sscanln("0123\n", &h)
	if err != nil {
		t.Fatal(err)
	}
	if n != 1 {
		t.Fatalf("expected 1 item; scanned %d", n)
	}
	if h[0] != 0x01 || h[1] != 0x23 {
		t.Fatalf("expected 0123 got %x", h)
	}
}
