ssa: SliceToArrayPointer

internal/runtime/errors.go

@@ -0,0 +1,116 @@
+// Copyright 2014 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
+
+// A boundsError represents an indexing or slicing operation gone wrong.
+type boundsError struct {
+	x int64
+	y int
+	// Values in an index or slice expression can be signed or unsigned.
+	// That means we'd need 65 bits to encode all possible indexes, from -2^63 to 2^64-1.
+	// Instead, we keep track of whether x should be interpreted as signed or unsigned.
+	// y is known to be nonnegative and to fit in an int.
+	signed bool
+	code   boundsErrorCode
+}
+
+type boundsErrorCode uint8
+
+const (
+	boundsIndex boundsErrorCode = iota // s[x], 0 <= x < len(s) failed
+
+	boundsSliceAlen // s[?:x], 0 <= x <= len(s) failed
+	boundsSliceAcap // s[?:x], 0 <= x <= cap(s) failed
+	boundsSliceB    // s[x:y], 0 <= x <= y failed (but boundsSliceA didn't happen)
+
+	boundsSlice3Alen // s[?:?:x], 0 <= x <= len(s) failed
+	boundsSlice3Acap // s[?:?:x], 0 <= x <= cap(s) failed
+	boundsSlice3B    // s[?:x:y], 0 <= x <= y failed (but boundsSlice3A didn't happen)
+	boundsSlice3C    // s[x:y:?], 0 <= x <= y failed (but boundsSlice3A/B didn't happen)
+
+	boundsConvert // (*[x]T)(s), 0 <= x <= len(s) failed
+	// Note: in the above, len(s) and cap(s) are stored in y
+)
+
+// boundsErrorFmts provide error text for various out-of-bounds panics.
+// Note: if you change these strings, you should adjust the size of the buffer
+// in boundsError.Error below as well.
+var boundsErrorFmts = [...]string{
+	boundsIndex:      "index out of range [%x] with length %y",
+	boundsSliceAlen:  "slice bounds out of range [:%x] with length %y",
+	boundsSliceAcap:  "slice bounds out of range [:%x] with capacity %y",
+	boundsSliceB:     "slice bounds out of range [%x:%y]",
+	boundsSlice3Alen: "slice bounds out of range [::%x] with length %y",
+	boundsSlice3Acap: "slice bounds out of range [::%x] with capacity %y",
+	boundsSlice3B:    "slice bounds out of range [:%x:%y]",
+	boundsSlice3C:    "slice bounds out of range [%x:%y:]",
+	boundsConvert:    "cannot convert slice with length %y to array or pointer to array with length %x",
+}
+
+// boundsNegErrorFmts are overriding formats if x is negative. In this case there's no need to report y.
+var boundsNegErrorFmts = [...]string{
+	boundsIndex:      "index out of range [%x]",
+	boundsSliceAlen:  "slice bounds out of range [:%x]",
+	boundsSliceAcap:  "slice bounds out of range [:%x]",
+	boundsSliceB:     "slice bounds out of range [%x:]",
+	boundsSlice3Alen: "slice bounds out of range [::%x]",
+	boundsSlice3Acap: "slice bounds out of range [::%x]",
+	boundsSlice3B:    "slice bounds out of range [:%x:]",
+	boundsSlice3C:    "slice bounds out of range [%x::]",
+}
+
+func (e boundsError) RuntimeError() {}
+
+func appendIntStr(b []byte, v int64, signed bool) []byte {
+	if signed && v < 0 {
+		b = append(b, '-')
+		v = -v
+	}
+	var buf [20]byte
+	b = append(b, itoa(buf[:], uint64(v))...)
+	return b
+}
+
+func (e boundsError) Error() string {
+	fmt := boundsErrorFmts[e.code]
+	if e.signed && e.x < 0 {
+		fmt = boundsNegErrorFmts[e.code]
+	}
+	// max message length is 99: "runtime error: slice bounds out of range [::%x] with capacity %y"
+	// x can be at most 20 characters. y can be at most 19.
+	b := make([]byte, 0, 100)
+	b = append(b, "runtime error: "...)
+	for i := 0; i < len(fmt); i++ {
+		c := fmt[i]
+		if c != '%' {
+			b = append(b, c)
+			continue
+		}
+		i++
+		switch fmt[i] {
+		case 'x':
+			b = appendIntStr(b, e.x, e.signed)
+		case 'y':
+			b = appendIntStr(b, int64(e.y), true)
+		}
+	}
+	return string(b)
+}
+
+func itoa(buf []byte, val uint64) []byte {
+	i := len(buf) - 1
+	for val >= 10 {
+		buf[i] = byte(val%10 + '0')
+		i--
+		val /= 10
+	}
+	buf[i] = byte(val + '0')
+	return buf[i:]
+}
+
+// failures in the conversion ([x]T)(s) or (*[x]T)(s), 0 <= x <= y, y == len(s)
+func PanicSliceConvert(x int, y int) {
+	panic(boundsError{x: int64(x), signed: true, y: y, code: boundsConvert})
+}