// All data should have been read.
		_, err := r.ReadByte()
		if err != io.EOF {
			t.Errorf("#%d: got error %v; want EOF", rno, err)
		}
	}
}

// Test that UnreadRune fails if the preceding operation was not a ReadRune.
func TestUnreadRuneError(t *testing.T) {
	buf := make([]byte, 3) // All runes in this test are 3 bytes long
	r := NewReader(&StringReader{data: []string{"日本語日本語日本語"}})
	if r.UnreadRune() == nil {

// big.zip that contains big.file, which contains 2³²-1 zeros.
// The big.zip file is interesting because it has no zip64 header,
// much like the innermost zip files in the well-known 42.zip.
//
// biggest.zip was generated by changing isZip64 to use > uint32max
// instead of >= uint32max and then running this program:
//
//	package main
//
//	import (
//		"archive/zip"
//		"bytes"
//		"io"
//		"log"

func nestedCall(f func()) {
	// callback(x) calls goCallback(x)
	callbackMutex.Lock()
	callbackToken++
	i := callbackToken
	callbackFuncs[i] = f
	callbackMutex.Unlock()

	// Pass the address of i because the C function was written to
	// take a pointer.  We could pass an int if we felt like
	// rewriting the C code.
	C.callback(unsafe.Pointer(&i))

	callbackMutex.Lock()
	delete(callbackFuncs, i)
	callbackMutex.Unlock()
}

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package asm

import (
	"fmt"
	"internal/abi"
	"strconv"
	"strings"
	"text/scanner"

	"cmd/asm/internal/arch"
	"cmd/asm/internal/flags"
	"cmd/asm/internal/lex"
	"cmd/internal/obj"
	"cmd/internal/obj/ppc64"
	"cmd/internal/obj/riscv"
	"cmd/internal/obj/x86"
	"cmd/internal/sys"
)

	"Path":  "/doc/asm"
}-->

<h2 id="introduction">A Quick Guide to Go's Assembler</h2>

<p>
This document is a quick outline of the unusual form of assembly language used by the <code>gc</code> Go compiler.
The document is not comprehensive.
</p>

<p>
The assembler is based on the input style of the Plan 9 assemblers, which is documented in detail
<a href="https://9p.io/sys/doc/asm.html">elsewhere</a>.

// The difference between MRC and MCR is represented by a bit high in the word, not
// in the usual way by the opcode itself. Asm must use AMRC for both instructions, so
// we return the opcode for MRC so that asm doesn't need to import obj/arm.
func ARMMRCOffset(op obj.As, cond string, x0, x1, x2, x3, x4, x5 int64) (offset int64, op0 obj.As, ok bool) {
	op1 := int64(0)
	if op == arm.AMRC {

// If the most recent read or write operation on the buffer was
// not a successful [Buffer.ReadRune], UnreadRune returns an error.  (In this regard
// it is stricter than [Buffer.UnreadByte], which will unread the last byte
// from any read operation.)
func (b *Buffer) UnreadRune() error {
	if b.lastRead <= opInvalid {
		return errors.New("bytes.Buffer: UnreadRune: previous operation was not a successful ReadRune")
	}

// license that can be found in the LICENSE file.

package lex

import (
	"go/build/constraint"
	"io"
	"os"
	"strings"
	"text/scanner"
	"unicode"

	"cmd/asm/internal/flags"
	"cmd/internal/objabi"
	"cmd/internal/src"
)

// A Tokenizer is a simple wrapping of text/scanner.Scanner, configured
// for our purposes and made a TokenReader. It forms the lowest level,

	}

	if !bytes.Equal(b[14:26], make([]byte, 12)) { // FileHeader.{CRC32,CompressSize,UncompressedSize} all zero.
		t.Errorf("unexpected crc, compress and uncompressed size to be 0 was: %v", b[14:26])
	}

	binary.LittleEndian.PutUint32(sig[:], uint32(dataDescriptorSignature))
	if bytes.Contains(b, sig[:]) {
		t.Error("there should be no data descriptor")
	}
}

		// non-ASCII rune.
		return width, data[0:width], nil
	}

	// We know it's an error: we have width==1 and implicitly r==utf8.RuneError.
	// Is the error because there wasn't a full rune to be decoded?
	// FullRune distinguishes correctly between erroneous and incomplete encodings.
	if !atEOF && !utf8.FullRune(data) {
		// Incomplete; get more bytes.
		return 0, nil, nil
	}