OP#792 initial commit after fork

cmd/httprange.go

@@ -0,0 +1,197 @@
+// Copyright (c) 2015-2021 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+const (
+	byteRangePrefix = "bytes="
+)
+
+// HTTPRangeSpec represents a range specification as supported by S3 GET
+// object request.
+//
+// Case 1: Not present -> represented by a nil RangeSpec
+// Case 2: bytes=1-10 (absolute start and end offsets) -> RangeSpec{false, 1, 10}
+// Case 3: bytes=10- (absolute start offset with end offset unspecified) -> RangeSpec{false, 10, -1}
+// Case 4: bytes=-30 (suffix length specification) -> RangeSpec{true, -30, -1}
+type HTTPRangeSpec struct {
+	// Does the range spec refer to a suffix of the object?
+	IsSuffixLength bool
+
+	// Start and end offset specified in range spec
+	Start, End int64
+}
+
+// GetLength - get length of range
+func (h *HTTPRangeSpec) GetLength(resourceSize int64) (rangeLength int64, err error) {
+	switch {
+	case resourceSize < 0:
+		return 0, errors.New("Resource size cannot be negative")
+
+	case h == nil:
+		rangeLength = resourceSize
+
+	case h.IsSuffixLength:
+		specifiedLen := -h.Start
+		rangeLength = min(specifiedLen, resourceSize)
+
+	case h.Start >= resourceSize:
+		return 0, InvalidRange{
+			OffsetBegin:  h.Start,
+			OffsetEnd:    h.End,
+			ResourceSize: resourceSize,
+		}
+
+	case h.End > -1:
+		end := h.End
+		if resourceSize <= end {
+			end = resourceSize - 1
+		}
+		rangeLength = end - h.Start + 1
+
+	case h.End == -1:
+		rangeLength = resourceSize - h.Start
+
+	default:
+		return 0, errors.New("Unexpected range specification case")
+	}
+
+	return rangeLength, nil
+}
+
+// GetOffsetLength computes the start offset and length of the range
+// given the size of the resource
+func (h *HTTPRangeSpec) GetOffsetLength(resourceSize int64) (start, length int64, err error) {
+	if h == nil {
+		// No range specified, implies whole object.
+		return 0, resourceSize, nil
+	}
+
+	length, err = h.GetLength(resourceSize)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	start = h.Start
+	if h.IsSuffixLength {
+		start = max(resourceSize+h.Start, 0)
+	}
+	return start, length, nil
+}
+
+// Parse a HTTP range header value into a HTTPRangeSpec
+func parseRequestRangeSpec(rangeString string) (hrange *HTTPRangeSpec, err error) {
+	// Return error if given range string doesn't start with byte range prefix.
+	if !strings.HasPrefix(rangeString, byteRangePrefix) {
+		return nil, fmt.Errorf("'%s' does not start with '%s'", rangeString, byteRangePrefix)
+	}
+
+	// Trim byte range prefix.
+	byteRangeString := strings.TrimPrefix(rangeString, byteRangePrefix)
+
+	// Check if range string contains delimiter '-', else return error. eg. "bytes=8"
+	sepIndex := strings.Index(byteRangeString, "-")
+	if sepIndex == -1 {
+		return nil, fmt.Errorf("'%s' does not have a valid range value", rangeString)
+	}
+
+	offsetBeginString := byteRangeString[:sepIndex]
+	offsetBegin := int64(-1)
+	// Convert offsetBeginString only if its not empty.
+	if len(offsetBeginString) > 0 {
+		if offsetBeginString[0] == '+' {
+			return nil, fmt.Errorf("Byte position ('%s') must not have a sign", offsetBeginString)
+		} else if offsetBegin, err = strconv.ParseInt(offsetBeginString, 10, 64); err != nil {
+			return nil, fmt.Errorf("'%s' does not have a valid first byte position value", rangeString)
+		} else if offsetBegin < 0 {
+			return nil, fmt.Errorf("First byte position is negative ('%d')", offsetBegin)
+		}
+	}
+
+	offsetEndString := byteRangeString[sepIndex+1:]
+	offsetEnd := int64(-1)
+	// Convert offsetEndString only if its not empty.
+	if len(offsetEndString) > 0 {
+		if offsetEndString[0] == '+' {
+			return nil, fmt.Errorf("Byte position ('%s') must not have a sign", offsetEndString)
+		} else if offsetEnd, err = strconv.ParseInt(offsetEndString, 10, 64); err != nil {
+			return nil, fmt.Errorf("'%s' does not have a valid last byte position value", rangeString)
+		} else if offsetEnd < 0 {
+			return nil, fmt.Errorf("Last byte position is negative ('%d')", offsetEnd)
+		}
+	}
+
+	switch {
+	case offsetBegin > -1 && offsetEnd > -1:
+		if offsetBegin > offsetEnd {
+			return nil, errInvalidRange
+		}
+		return &HTTPRangeSpec{false, offsetBegin, offsetEnd}, nil
+	case offsetBegin > -1:
+		return &HTTPRangeSpec{false, offsetBegin, -1}, nil
+	case offsetEnd > -1:
+		if offsetEnd == 0 {
+			return nil, errInvalidRange
+		}
+		return &HTTPRangeSpec{true, -offsetEnd, -1}, nil
+	default:
+		// rangeString contains first and last byte positions missing. eg. "bytes=-"
+		return nil, fmt.Errorf("'%s' does not have valid range value", rangeString)
+	}
+}
+
+// String returns stringified representation of range for a particular resource size.
+func (h *HTTPRangeSpec) String(resourceSize int64) string {
+	if h == nil {
+		return ""
+	}
+	off, length, err := h.GetOffsetLength(resourceSize)
+	if err != nil {
+		return ""
+	}
+	return fmt.Sprintf("%d-%d", off, off+length-1)
+}
+
+// ToHeader returns the Range header value.
+func (h *HTTPRangeSpec) ToHeader() (string, error) {
+	if h == nil {
+		return "", nil
+	}
+	start := strconv.Itoa(int(h.Start))
+	end := strconv.Itoa(int(h.End))
+	switch {
+	case h.Start >= 0 && h.End >= 0:
+		if h.Start > h.End {
+			return "", errInvalidRange
+		}
+	case h.IsSuffixLength:
+		end = strconv.Itoa(int(h.Start * -1))
+		start = ""
+	case h.Start > -1:
+		end = ""
+	default:
+		return "", errors.New("does not have valid range value")
+	}
+	return fmt.Sprintf("bytes=%s-%s", start, end), nil
+}