File transfer: New API /file/read

webapi/HTTP Range.go

@@ -0,0 +1,94 @@
+/*
+File Name:  HTTP Range.go
+Copyright:  2021 Peernet Foundation s.r.o.
+Author:     Peter Kleissner
+*/
+
+package webapi
+
+import (
+	"errors"
+	"net/textproto"
+	"strconv"
+	"strings"
+)
+
+// Fork from https://golang.org/src/net/http/fs.go
+
+// HTTPRange represents an HTTP range
+type HTTPRange struct {
+	start, length int
+}
+
+// ParseRangeHeader parses a Range header string as per RFC 7233.
+func ParseRangeHeader(s string, size int, noMultiRange bool) ([]HTTPRange, error) {
+	if s == "" {
+		return nil, nil // header not present
+	}
+	const b = "bytes="
+	if !strings.HasPrefix(s, b) {
+		return nil, errors.New("invalid range")
+	}
+	var ranges []HTTPRange
+	for _, ra := range strings.Split(s[len(b):], ",") {
+		ra = textproto.TrimString(ra)
+		if ra == "" {
+			continue
+		}
+		i := strings.Index(ra, "-")
+		if i < 0 {
+			return nil, errors.New("invalid range")
+		}
+		start, end := textproto.TrimString(ra[:i]), textproto.TrimString(ra[i+1:])
+		var r HTTPRange
+		if start == "" {
+			if size < 0 {
+				return nil, errors.New("range start relative to end not supported")
+			}
+			// If no start is specified, end specifies the
+			// range start relative to the end of the file.
+			i, err := strconv.ParseInt(end, 10, 64)
+			if err != nil {
+				return nil, errors.New("invalid range")
+			}
+			if int(i) > size {
+				i = int64(size)
+			}
+			r.start = size - int(i)
+			r.length = size - r.start
+		} else {
+			i, err := strconv.ParseInt(start, 10, 64)
+			if err != nil || i < 0 {
+				return nil, errors.New("invalid range")
+			}
+			if size > 0 && int(i) >= size {
+				// If the range begins after the size of the content, then it does not overlap. -> always return error.
+				return nil, errors.New("start out of range")
+			}
+			r.start = int(i)
+			if end == "" {
+				// If no end is specified, range extends to end of the file.
+				if size < 0 {
+					//return nil, errors.New("open range not supported")
+					r.length = -1
+				} else {
+					r.length = size - r.start
+				}
+			} else {
+				i, err := strconv.ParseInt(end, 10, 64)
+				if err != nil || r.start > int(i) {
+					return nil, errors.New("invalid range")
+				}
+				if size > 0 && int(i) >= size {
+					i = int64(size - 1)
+				}
+				r.length = int(i) - r.start + 1
+			}
+		}
+		ranges = append(ranges, r)
+		if noMultiRange && len(ranges) > 1 {
+			return nil, errors.New("multiple ranges not supported")
+		}
+	}
+	return ranges, nil
+}