STOR-519: Add db-connect, a SQL over HTTPS server

vendor/github.com/mitchellh/go-server-timing/header.go

@@ -0,0 +1,129 @@
+package servertiming
+
+import (
+	"fmt"
+	"net/http"
+	"regexp"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/golang/gddo/httputil/header"
+)
+
+// HeaderKey is the specified key for the Server-Timing header.
+const HeaderKey = "Server-Timing"
+
+// Header represents a collection of metrics that can be encoded as
+// a Server-Timing header value.
+//
+// The functions for working with metrics are concurrency-safe to make
+// it easy to record metrics from goroutines. If you want to avoid the
+// lock overhead, you can access the Metrics field directly.
+//
+// The functions for working with metrics are also usable on a nil
+// Header pointer. This allows functions that use FromContext to get the
+// *Header value to skip nil-checking and use it as normal. On a nil
+// *Header, Metrics are not recorded.
+type Header struct {
+	// Metrics is the list of metrics in the header.
+	Metrics []*Metric
+
+	// The lock that is held when Metrics is being modified. This
+	// ONLY NEEDS TO BE SET WHEN working with Metrics directly. If using
+	// the functions on the struct, the lock is managed automatically.
+	sync.Mutex
+}
+
+// ParseHeader parses a Server-Timing header value.
+func ParseHeader(input string) (*Header, error) {
+	// Split the comma-separated list of metrics
+	rawMetrics := header.ParseList(headerParams(input))
+
+	// Parse the list of metrics. We can pre-allocate the length of the
+	// comma-separated list of metrics since at most it will be that and
+	// most likely it will be that length.
+	metrics := make([]*Metric, 0, len(rawMetrics))
+	for _, raw := range rawMetrics {
+		var m Metric
+		m.Name, m.Extra = header.ParseValueAndParams(headerParams(raw))
+
+		// Description
+		if v, ok := m.Extra[paramNameDesc]; ok {
+			m.Desc = v
+			delete(m.Extra, paramNameDesc)
+		}
+
+		// Duration. This is treated as a millisecond value since that
+		// is what modern browsers are treating it as. If the parsing of
+		// an integer fails, the set value remains in the Extra field.
+		if v, ok := m.Extra[paramNameDur]; ok {
+			m.Duration, _ = time.ParseDuration(v + "ms")
+			delete(m.Extra, paramNameDur)
+		}
+
+		metrics = append(metrics, &m)
+	}
+
+	return &Header{Metrics: metrics}, nil
+}
+
+// NewMetric creates a new Metric and adds it to this header.
+func (h *Header) NewMetric(name string) *Metric {
+	return h.Add(&Metric{Name: name})
+}
+
+// Add adds the given metric to the header.
+//
+// This function is safe to call concurrently.
+func (h *Header) Add(m *Metric) *Metric {
+	if h == nil {
+		return m
+	}
+
+	h.Lock()
+	defer h.Unlock()
+	h.Metrics = append(h.Metrics, m)
+	return m
+}
+
+// String returns the valid Server-Timing header value that can be
+// sent in an HTTP response.
+func (h *Header) String() string {
+	parts := make([]string, 0, len(h.Metrics))
+	for _, m := range h.Metrics {
+		parts = append(parts, m.String())
+	}
+
+	return strings.Join(parts, ",")
+}
+
+// Specified server-timing-param-name values.
+const (
+	paramNameDesc = "desc"
+	paramNameDur  = "dur"
+)
+
+// headerParams is a helper function that takes a header value and turns
+// it into the expected argument format for the httputil/header library
+// functions..
+func headerParams(s string) (http.Header, string) {
+	const key = "Key"
+	return http.Header(map[string][]string{
+		key: {s},
+	}), key
+}
+
+var reNumber = regexp.MustCompile(`^\d+\.?\d*$`)
+
+// headerEncodeParam encodes a key/value pair as a proper `key=value`
+// syntax, using double-quotes if necessary.
+func headerEncodeParam(key, value string) string {
+	// The only case we currently don't quote is numbers. We can make this
+	// smarter in the future.
+	if reNumber.MatchString(value) {
+		return fmt.Sprintf(`%s=%s`, key, value)
+	}
+
+	return fmt.Sprintf(`%s=%q`, key, value)
+}