blog/go/fonts/font/reader.go

package font

import (
	"bytes"
	"encoding/binary"
	"io"
	"os"
)

type Reader interface {
	Read([]byte) (int, error)
	Close() error
	ReadInt8() (int8, error)
	ReadInt16() (int16, error)
	ReadInt32() (int32, error)
	ReadInt64() (int64, error)
	ReadUint8() (uint8, error)
	ReadUint16() (uint16, error)
	ReadUint32() (uint32, error)
	ReadUint64() (uint64, error)
	ReadString(int) (string, error)
	ReadBytes(int) ([]byte, error)
	Seek(int64, int) (int64, error)
	Size() (int64, error)
}

type reader struct {
	path string
	fp   *os.File
}

func NewReader(file string) (Reader, error) {
	fp, err := os.OpenFile(file, os.O_RDONLY, os.ModePerm)
	if err != nil {
		return nil, err
	}
	r := &reader{
		fp:   fp,
		path: file,
	}
	return r, nil
}

func (r *reader) Read(p []byte) (int, error) {
	if r.fp == nil {
		return 0, nil
	}
	return r.fp.Read(p)
}

func (r *reader) Close() error {
	if r.fp != nil {
		return r.fp.Close()
	}
	return nil
}

func (r *reader) ReadCloser() io.ReadCloser {
	return r
}

func (r *reader) ReadInt8() (int8, error) {
	buff := make([]byte, 1)
	_, err := r.fp.Read(buff)
	if err != nil {
		return 0, err
	}
	reader := bytes.NewReader(buff)
	n := int8(0)
	return n, binary.Read(reader, binary.LittleEndian, &n)
}

func (r *reader) ReadInt16() (int16, error) {
	buff := make([]byte, 2)
	_, err := r.fp.Read(buff)
	if err != nil {
		return 0, err
	}
	reader := bytes.NewReader(buff)
	n := int16(0)
	return n, binary.Read(reader, binary.LittleEndian, &n)
}

func (r *reader) ReadInt32() (int32, error) {
	buff := make([]byte, 4)
	_, err := r.fp.Read(buff)
	if err != nil {
		return 0, err
	}
	reader := bytes.NewReader(buff)
	n := int32(0)
	return n, binary.Read(reader, binary.LittleEndian, &n)
}

func (r *reader) ReadInt64() (int64, error) {
	buff := make([]byte, 8)
	_, err := r.fp.Read(buff)
	if err != nil {
		return 0, err
	}
	reader := bytes.NewReader(buff)
	n := int64(0)
	return n, binary.Read(reader, binary.LittleEndian, &n)
}

func (r *reader) ReadUint8() (uint8, error) {
	buff := make([]byte, 1)
	_, err := r.fp.Read(buff)
	if err != nil {
		return 0, err
	}
	return uint8(buff[0]), nil
}

func (r *reader) ReadUint16() (uint16, error) {
	buff := make([]byte, 2)
	_, err := r.fp.Read(buff)
	if err != nil {
		return 0, err
	}
	return binary.BigEndian.Uint16(buff), nil
}

func (r *reader) ReadUint32() (uint32, error) {
	buff := make([]byte, 4)
	_, err := r.fp.Read(buff)
	if err != nil {
		return 0, err
	}
	return binary.BigEndian.Uint32(buff), nil
}

func (r *reader) ReadUint64() (uint64, error) {
	buff := make([]byte, 8)
	_, err := r.fp.Read(buff)
	if err != nil {
		return 0, err
	}
	return binary.BigEndian.Uint64(buff), nil
}

func (r *reader) ReadString(len int) (string, error) {
	buff := make([]byte, len)
	_, err := r.fp.Read(buff)
	if err != nil {
		return "", err
	}
	return string(buff), nil
}

func (r *reader) ReadBytes(len int) ([]byte, error) {
	buff := make([]byte, len)
	_, err := r.fp.Read(buff)
	if err != nil {
		return []byte{}, err
	}
	return buff, nil
}

func (r *reader) Seek(offset int64, whence int) (int64, error) {
	return r.fp.Seek(offset, whence)
}

func (r *reader) Size() (int64, error) {
	fi, err := r.fp.Stat()
	if err != nil {
		return 0, err
	}
	return fi.Size(), nil
}