Add new module

src/autocontext/context.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"fmt"
+	"errors"
+	"regexp"
+	"net/http"
+	"strings"
+	"sync"
+	"runtime"
+)
+
+var (
+	contextMutex sync.Mutex
+	contextData  = make(map[string]map[string]interface{})
+	regexServeHTTP = regexp.MustCompile("\\.ServeHTTP\\(0x[a-fA-F0-9]+, 0x[a-fA-F0-9]+, 0x[a-fA-F0-9]+, (0x[a-fA-F0-9]+)\\)")
+)
+
+// Set value in context
+func Set(r *http.Request, key string, val interface{}) {
+	contextMutex.Lock()
+	defer contextMutex.Unlock()
+	addr := fmt.Sprintf("%p", r)
+	if _, ok := contextData[addr]; !ok {
+		contextData[addr] = make(map[string]interface{})
+	}
+	contextData[addr][key] = val
+}
+
+// Get value from context
+func Get(r *http.Request, key string) interface{} {
+	addr := fmt.Sprintf("%p", r)
+	contextMutex.Lock()
+	defer contextMutex.Unlock()
+	if m, ok := contextData[addr]; ok {
+		return m[key]
+	}
+	return nil
+}
+
+// GetAuto ruturns value from current *http.Request context. It is automatically extracted from stacktrace. 
+func GetAuto(key string) interface{} {
+	addr, err := getRequestAddress()
+	if err != nil {
+		return nil
+	}
+	contextMutex.Lock()
+	defer contextMutex.Unlock()
+	if m, ok := contextData[addr]; ok {
+		return m[key]
+	}
+	return nil
+}
+
+// Reset function removes specific context busket from map
+func Reset(r *http.Request) {
+	contextMutex.Lock()
+	defer contextMutex.Unlock()
+	addr := fmt.Sprintf("%p", r)
+	if _, ok := contextData[addr]; ok {
+		delete(contextData, addr)
+	}
+}
+
+// getRequestAddress this function extracts *http.Request address from the go-lang stacktrace string.
+func getRequestAddress() (string, error) {
+	trace := make([]byte, 2048)
+	count := runtime.Stack(trace, true)
+	//fmt.Printf("Stack of %d bytes: %s\n", count, trace)
+	pos := strings.Index(string(trace),"\n\n")
+	if pos > 0 {
+		// we are interested only in first goroutene
+		trace = trace[0:pos]
+		//fmt.Printf("Stack bytes: %s\n", trace)
+	}
+	match := regexServeHTTP.FindStringSubmatch(string(trace))
+	if len(match) != 2 {
+		return "", errors.New("Failed to find *http.Request address")
+	}
+	fmt.Printf("*** extracted address from stacktrace: %s\n", match[1])
+	return match[1], nil
+}