1 files changed, 116 insertions, 0 deletions
diff --git a/errors/debug_stack.go b/errors/debug_stack.go
new file mode 100755
index 00000000..fa77ddc8
--- /dev/null
+++ b/errors/debug_stack.go
@@ -0,0 +1,116 @@
+// +build debug
+
+package errors
+
+import (
+	"bytes"
+	"fmt"
+	"runtime"
+	"strings"
+)
+
+type stack struct {
+	callers []uintptr
+	// TODO(adg): add time of creation
+}
+
+func (e *Error) populateStack() {
+	e.callers = callers()
+
+	e2, ok := e.Err.(*Error)
+	if !ok {
+		return
+	}
+
+	i := 0
+
+	ok = false
+	for ; i < len(e.callers) && i < len(e2.callers); i++ {
+		// check for similar
+		if e.callers[len(e.callers)-1-i] != e2.callers[len(e2.callers)-1-i] {
+			break
+		}
+		ok = true
+	}
+
+	if ok { //we have common PCs
+		e2Head := e2.callers[:len(e2.callers)-i]
+		eTail := e.callers
+
+		e.callers = make([]uintptr, len(e2Head)+len(eTail))
+
+		copy(e.callers, e2Head)
+		copy(e.callers[len(e2Head):], eTail)
+
+		e2.callers = nil
+	}
+}
+
+// frame returns the nth frame, with the frame at top of stack being 0.
+func frame(callers []uintptr, n int) runtime.Frame {
+	frames := runtime.CallersFrames(callers)
+	var f runtime.Frame
+	for i := len(callers) - 1; i >= n; i-- {
+		var ok bool
+		f, ok = frames.Next()
+		if !ok {
+			break
+		}
+	}
+	return f
+}
+
+func (e *Error) printStack(b *bytes.Buffer) {
+	c := callers()
+
+	var prev string
+	var diff bool
+	for i := 0; i < len(e.callers); i++ {
+		pc := e.callers[len(e.callers)-i-1] // get current PC
+		fn := runtime.FuncForPC(pc)         // get function by pc
+		name := fn.Name()
+
+		if !diff && i < len(c) {
+			ppc := c[len(c)-i-1]
+			pname := runtime.FuncForPC(ppc).Name()
+			if name == pname {
+				continue
+			}
+			diff = true
+		}
+
+		if name == prev {
+			continue
+		}
+
+		trim := 0
+		for {
+			j := strings.IndexAny(name[trim:], "./")
+			if j < 0 {
+				break
+			}
+			if !strings.HasPrefix(prev, name[:j+trim]) {
+				break
+			}
+			trim += j + 1 // skip over the separator
+		}
+
+		// Do the printing.
+		appendStrToBuf(b, Separator)
+		file, line := fn.FileLine(pc)
+		fmt.Fprintf(b, "%v:%d: ", file, line)
+		if trim > 0 {
+			b.WriteString("...")
+		}
+		b.WriteString(name[trim:])
+
+		prev = name
+	}
+}
+
+func callers() []uintptr {
+	var stk [64]uintptr
+	const skip = 4
+	n := runtime.Callers(skip, stk[:])
+	return stk[:n]
+}