Adding upstream version 0.28.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tools/filesystem/internal/s3blob/s3/head_object.go

@@ -0,0 +1,89 @@
+package s3
+
+import (
+	"context"
+	"net/http"
+	"strconv"
+	"time"
+)
+
+// https://docs.aws.amazon.com/AmazonS3/latest/API/API_HeadObject.html#API_HeadObject_ResponseElements
+type HeadObjectResponse struct {
+	// Metadata is the extra data that is stored with the S3 object (aka. the "x-amz-meta-*" header values).
+	//
+	// The map keys are normalized to lower-case.
+	Metadata map[string]string `json:"metadata"`
+
+	// LastModified date and time when the object was last modified.
+	LastModified time.Time `json:"lastModified"`
+
+	// CacheControl specifies caching behavior along the request/reply chain.
+	CacheControl string `json:"cacheControl"`
+
+	// ContentDisposition specifies presentational information for the object.
+	ContentDisposition string `json:"contentDisposition"`
+
+	// ContentEncoding indicates what content encodings have been applied to the object
+	// and thus what decoding mechanisms must be applied to obtain the
+	// media-type referenced by the Content-Type header field.
+	ContentEncoding string `json:"contentEncoding"`
+
+	// ContentLanguage indicates the language the content is in.
+	ContentLanguage string `json:"contentLanguage"`
+
+	// ContentType is a standard MIME type describing the format of the object data.
+	ContentType string `json:"contentType"`
+
+	// ContentRange is the portion of the object usually returned in the response for a GET request.
+	ContentRange string `json:"contentRange"`
+
+	// ETag is an opaque identifier assigned by a web
+	// server to a specific version of a resource found at a URL.
+	ETag string `json:"etag"`
+
+	// ContentLength is size of the body in bytes.
+	ContentLength int64 `json:"contentLength"`
+}
+
+// load parses and load the header values into the current HeadObjectResponse fields.
+func (o *HeadObjectResponse) load(headers http.Header) {
+	o.LastModified, _ = time.Parse(time.RFC1123, headers.Get("Last-Modified"))
+	o.CacheControl = headers.Get("Cache-Control")
+	o.ContentDisposition = headers.Get("Content-Disposition")
+	o.ContentEncoding = headers.Get("Content-Encoding")
+	o.ContentLanguage = headers.Get("Content-Language")
+	o.ContentType = headers.Get("Content-Type")
+	o.ContentRange = headers.Get("Content-Range")
+	o.ETag = headers.Get("ETag")
+	o.ContentLength, _ = strconv.ParseInt(headers.Get("Content-Length"), 10, 0)
+	o.Metadata = extractMetadata(headers)
+}
+
+// HeadObject sends a HEAD request for a single object to check its
+// existence and to retrieve its metadata.
+//
+// https://docs.aws.amazon.com/AmazonS3/latest/API/API_HeadObject.html
+func (s3 *S3) HeadObject(ctx context.Context, key string, optFuncs ...func(*http.Request)) (*HeadObjectResponse, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodHead, s3.URL(key), nil)
+	if err != nil {
+		return nil, err
+	}
+
+	// apply optional request funcs
+	for _, fn := range optFuncs {
+		if fn != nil {
+			fn(req)
+		}
+	}
+
+	resp, err := s3.SignAndSend(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	result := &HeadObjectResponse{}
+	result.load(resp.Header)
+
+	return result, nil
+}