实现基础的206 partial content缓存

internal/caches/reader_partial_file.go

@@ -0,0 +1,142 @@
+package caches
+
+import (
+	"encoding/binary"
+	"errors"
+	rangeutils "github.com/TeaOSLab/EdgeNode/internal/utils/ranges"
+	"github.com/iwind/TeaGo/types"
+	"io"
+	"os"
+	"strings"
+)
+
+type PartialFileReader struct {
+	*FileReader
+
+	ranges    *PartialRanges
+	rangePath string
+}
+
+func NewPartialFileReader(fp *os.File) *PartialFileReader {
+	// range path
+	var path = fp.Name()
+	var dotIndex = strings.LastIndex(path, ".")
+	var rangePath = ""
+	if dotIndex < 0 {
+		rangePath = path + "@ranges.cache"
+	} else {
+		rangePath = path[:dotIndex] + "@ranges" + path[dotIndex:]
+	}
+
+	return &PartialFileReader{
+		FileReader: NewFileReader(fp),
+		rangePath:  rangePath,
+	}
+}
+
+func (this *PartialFileReader) Init() error {
+	return this.InitAutoDiscard(true)
+}
+
+func (this *PartialFileReader) InitAutoDiscard(autoDiscard bool) error {
+	if this.openFile != nil {
+		this.meta = this.openFile.meta
+		this.header = this.openFile.header
+	}
+
+	isOk := false
+
+	if autoDiscard {
+		defer func() {
+			if !isOk {
+				_ = this.discard()
+			}
+		}()
+	}
+
+	// 读取Range
+	ranges, err := NewPartialRangesFromFile(this.rangePath)
+	if err != nil {
+		return errors.New("read ranges failed: " + err.Error())
+	}
+	this.ranges = ranges
+
+	var buf = this.meta
+	if len(buf) == 0 {
+		buf = make([]byte, SizeMeta)
+		ok, err := this.readToBuff(this.fp, buf)
+		if err != nil {
+			return err
+		}
+		if !ok {
+			return ErrNotFound
+		}
+		this.meta = buf
+	}
+
+	this.expiresAt = int64(binary.BigEndian.Uint32(buf[:SizeExpiresAt]))
+
+	status := types.Int(string(buf[SizeExpiresAt : SizeExpiresAt+SizeStatus]))
+	if status < 100 || status > 999 {
+		return errors.New("invalid status")
+	}
+	this.status = status
+
+	// URL
+	urlLength := binary.BigEndian.Uint32(buf[SizeExpiresAt+SizeStatus : SizeExpiresAt+SizeStatus+SizeURLLength])
+
+	// header
+	headerSize := int(binary.BigEndian.Uint32(buf[SizeExpiresAt+SizeStatus+SizeURLLength : SizeExpiresAt+SizeStatus+SizeURLLength+SizeHeaderLength]))
+	if headerSize == 0 {
+		return nil
+	}
+	this.headerSize = headerSize
+	this.headerOffset = int64(SizeMeta) + int64(urlLength)
+
+	// body
+	this.bodyOffset = this.headerOffset + int64(headerSize)
+	bodySize := int(binary.BigEndian.Uint64(buf[SizeExpiresAt+SizeStatus+SizeURLLength+SizeHeaderLength : SizeExpiresAt+SizeStatus+SizeURLLength+SizeHeaderLength+SizeBodyLength]))
+	if bodySize == 0 {
+		isOk = true
+		return nil
+	}
+	this.bodySize = int64(bodySize)
+
+	// read header
+	if this.openFileCache != nil && len(this.header) == 0 {
+		if headerSize > 0 && headerSize <= 512 {
+			this.header = make([]byte, headerSize)
+			_, err := this.fp.Seek(this.headerOffset, io.SeekStart)
+			if err != nil {
+				return err
+			}
+			_, err = this.readToBuff(this.fp, this.header)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	isOk = true
+
+	return nil
+}
+
+// ContainsRange 是否包含某些区间内容
+// 这里的 r 是已经经过格式化的
+func (this *PartialFileReader) ContainsRange(r rangeutils.Range) bool {
+	return this.ranges.Contains(r.Start(), r.End())
+}
+
+// MaxLength 获取区间最大长度
+func (this *PartialFileReader) MaxLength() int64 {
+	if this.bodySize > 0 {
+		return this.bodySize
+	}
+	return this.ranges.Max() + 1
+}
+
+func (this *PartialFileReader) discard() error {
+	_ = os.Remove(this.rangePath)
+	return this.FileReader.discard()
+}