1 files changed, 302 insertions, 0 deletions
diff --git a/src/runtime/print.go b/src/runtime/print.go
new file mode 100644
index 0000000..b2a642b
--- /dev/null
+++ b/src/runtime/print.go
@@ -0,0 +1,302 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+import (
+	"internal/goarch"
+	"runtime/internal/atomic"
+	"unsafe"
+)
+
+// The compiler knows that a print of a value of this type
+// should use printhex instead of printuint (decimal).
+type hex uint64
+
+func bytes(s string) (ret []byte) {
+	rp := (*slice)(unsafe.Pointer(&ret))
+	sp := stringStructOf(&s)
+	rp.array = sp.str
+	rp.len = sp.len
+	rp.cap = sp.len
+	return
+}
+
+var (
+	// printBacklog is a circular buffer of messages written with the builtin
+	// print* functions, for use in postmortem analysis of core dumps.
+	printBacklog      [512]byte
+	printBacklogIndex int
+)
+
+// recordForPanic maintains a circular buffer of messages written by the
+// runtime leading up to a process crash, allowing the messages to be
+// extracted from a core dump.
+//
+// The text written during a process crash (following "panic" or "fatal
+// error") is not saved, since the goroutine stacks will generally be readable
+// from the runtime datastructures in the core file.
+func recordForPanic(b []byte) {
+	printlock()
+
+	if atomic.Load(&panicking) == 0 {
+		// Not actively crashing: maintain circular buffer of print output.
+		for i := 0; i < len(b); {
+			n := copy(printBacklog[printBacklogIndex:], b[i:])
+			i += n
+			printBacklogIndex += n
+			printBacklogIndex %= len(printBacklog)
+		}
+	}
+
+	printunlock()
+}
+
+var debuglock mutex
+
+// The compiler emits calls to printlock and printunlock around
+// the multiple calls that implement a single Go print or println
+// statement. Some of the print helpers (printslice, for example)
+// call print recursively. There is also the problem of a crash
+// happening during the print routines and needing to acquire
+// the print lock to print information about the crash.
+// For both these reasons, let a thread acquire the printlock 'recursively'.
+
+func printlock() {
+	mp := getg().m
+	mp.locks++ // do not reschedule between printlock++ and lock(&debuglock).
+	mp.printlock++
+	if mp.printlock == 1 {
+		lock(&debuglock)
+	}
+	mp.locks-- // now we know debuglock is held and holding up mp.locks for us.
+}
+
+func printunlock() {
+	mp := getg().m
+	mp.printlock--
+	if mp.printlock == 0 {
+		unlock(&debuglock)
+	}
+}
+
+// write to goroutine-local buffer if diverting output,
+// or else standard error.
+func gwrite(b []byte) {
+	if len(b) == 0 {
+		return
+	}
+	recordForPanic(b)
+	gp := getg()
+	// Don't use the writebuf if gp.m is dying. We want anything
+	// written through gwrite to appear in the terminal rather
+	// than be written to in some buffer, if we're in a panicking state.
+	// Note that we can't just clear writebuf in the gp.m.dying case
+	// because a panic isn't allowed to have any write barriers.
+	if gp == nil || gp.writebuf == nil || gp.m.dying > 0 {
+		writeErr(b)
+		return
+	}
+
+	n := copy(gp.writebuf[len(gp.writebuf):cap(gp.writebuf)], b)
+	gp.writebuf = gp.writebuf[:len(gp.writebuf)+n]
+}
+
+func printsp() {
+	printstring(" ")
+}
+
+func printnl() {
+	printstring("\n")
+}
+
+func printbool(v bool) {
+	if v {
+		printstring("true")
+	} else {
+		printstring("false")
+	}
+}
+
+func printfloat(v float64) {
+	switch {
+	case v != v:
+		printstring("NaN")
+		return
+	case v+v == v && v > 0:
+		printstring("+Inf")
+		return
+	case v+v == v && v < 0:
+		printstring("-Inf")
+		return
+	}
+
+	const n = 7 // digits printed
+	var buf [n + 7]byte
+	buf[0] = '+'
+	e := 0 // exp
+	if v == 0 {
+		if 1/v < 0 {
+			buf[0] = '-'
+		}
+	} else {
+		if v < 0 {
+			v = -v
+			buf[0] = '-'
+		}
+
+		// normalize
+		for v >= 10 {
+			e++
+			v /= 10
+		}
+		for v < 1 {
+			e--
+			v *= 10
+		}
+
+		// round
+		h := 5.0
+		for i := 0; i < n; i++ {
+			h /= 10
+		}
+		v += h
+		if v >= 10 {
+			e++
+			v /= 10
+		}
+	}
+
+	// format +d.dddd+edd
+	for i := 0; i < n; i++ {
+		s := int(v)
+		buf[i+2] = byte(s + '0')
+		v -= float64(s)
+		v *= 10
+	}
+	buf[1] = buf[2]
+	buf[2] = '.'
+
+	buf[n+2] = 'e'
+	buf[n+3] = '+'
+	if e < 0 {
+		e = -e
+		buf[n+3] = '-'
+	}
+
+	buf[n+4] = byte(e/100) + '0'
+	buf[n+5] = byte(e/10)%10 + '0'
+	buf[n+6] = byte(e%10) + '0'
+	gwrite(buf[:])
+}
+
+func printcomplex(c complex128) {
+	print("(", real(c), imag(c), "i)")
+}
+
+func printuint(v uint64) {
+	var buf [100]byte
+	i := len(buf)
+	for i--; i > 0; i-- {
+		buf[i] = byte(v%10 + '0')
+		if v < 10 {
+			break
+		}
+		v /= 10
+	}
+	gwrite(buf[i:])
+}
+
+func printint(v int64) {
+	if v < 0 {
+		printstring("-")
+		v = -v
+	}
+	printuint(uint64(v))
+}
+
+var minhexdigits = 0 // protected by printlock
+
+func printhex(v uint64) {
+	const dig = "0123456789abcdef"
+	var buf [100]byte
+	i := len(buf)
+	for i--; i > 0; i-- {
+		buf[i] = dig[v%16]
+		if v < 16 && len(buf)-i >= minhexdigits {
+			break
+		}
+		v /= 16
+	}
+	i--
+	buf[i] = 'x'
+	i--
+	buf[i] = '0'
+	gwrite(buf[i:])
+}
+
+func printpointer(p unsafe.Pointer) {
+	printhex(uint64(uintptr(p)))
+}
+func printuintptr(p uintptr) {
+	printhex(uint64(p))
+}
+
+func printstring(s string) {
+	gwrite(bytes(s))
+}
+
+func printslice(s []byte) {
+	sp := (*slice)(unsafe.Pointer(&s))
+	print("[", len(s), "/", cap(s), "]")
+	printpointer(sp.array)
+}
+
+func printeface(e eface) {
+	print("(", e._type, ",", e.data, ")")
+}
+
+func printiface(i iface) {
+	print("(", i.tab, ",", i.data, ")")
+}
+
+// hexdumpWords prints a word-oriented hex dump of [p, end).
+//
+// If mark != nil, it will be called with each printed word's address
+// and should return a character mark to appear just before that
+// word's value. It can return 0 to indicate no mark.
+func hexdumpWords(p, end uintptr, mark func(uintptr) byte) {
+	printlock()
+	var markbuf [1]byte
+	markbuf[0] = ' '
+	minhexdigits = int(unsafe.Sizeof(uintptr(0)) * 2)
+	for i := uintptr(0); p+i < end; i += goarch.PtrSize {
+		if i%16 == 0 {
+			if i != 0 {
+				println()
+			}
+			print(hex(p+i), ": ")
+		}
+
+		if mark != nil {
+			markbuf[0] = mark(p + i)
+			if markbuf[0] == 0 {
+				markbuf[0] = ' '
+			}
+		}
+		gwrite(markbuf[:])
+		val := *(*uintptr)(unsafe.Pointer(p + i))
+		print(hex(val))
+		print(" ")
+
+		// Can we symbolize val?
+		fn := findfunc(val)
+		if fn.valid() {
+			print("<", funcname(fn), "+", hex(val-fn.entry()), "> ")
+		}
+	}
+	minhexdigits = 0
+	println()
+	printunlock()
+}