1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
|
// Copyright 2012 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.
// MakeFunc implementation.
package reflect
import (
"internal/abi"
"unsafe"
)
// makeFuncImpl is the closure value implementing the function
// returned by MakeFunc.
// The first three words of this type must be kept in sync with
// methodValue and runtime.reflectMethodValue.
// Any changes should be reflected in all three.
type makeFuncImpl struct {
makeFuncCtxt
ftyp *funcType
fn func([]Value) []Value
}
// MakeFunc returns a new function of the given Type
// that wraps the function fn. When called, that new function
// does the following:
//
// - converts its arguments to a slice of Values.
// - runs results := fn(args).
// - returns the results as a slice of Values, one per formal result.
//
// The implementation fn can assume that the argument Value slice
// has the number and type of arguments given by typ.
// If typ describes a variadic function, the final Value is itself
// a slice representing the variadic arguments, as in the
// body of a variadic function. The result Value slice returned by fn
// must have the number and type of results given by typ.
//
// The Value.Call method allows the caller to invoke a typed function
// in terms of Values; in contrast, MakeFunc allows the caller to implement
// a typed function in terms of Values.
//
// The Examples section of the documentation includes an illustration
// of how to use MakeFunc to build a swap function for different types.
//
func MakeFunc(typ Type, fn func(args []Value) (results []Value)) Value {
if typ.Kind() != Func {
panic("reflect: call of MakeFunc with non-Func type")
}
t := typ.common()
ftyp := (*funcType)(unsafe.Pointer(t))
code := abi.FuncPCABI0(makeFuncStub)
// makeFuncImpl contains a stack map for use by the runtime
_, _, abi := funcLayout(ftyp, nil)
impl := &makeFuncImpl{
makeFuncCtxt: makeFuncCtxt{
fn: code,
stack: abi.stackPtrs,
argLen: abi.stackCallArgsSize,
regPtrs: abi.inRegPtrs,
},
ftyp: ftyp,
fn: fn,
}
return Value{t, unsafe.Pointer(impl), flag(Func)}
}
// makeFuncStub is an assembly function that is the code half of
// the function returned from MakeFunc. It expects a *callReflectFunc
// as its context register, and its job is to invoke callReflect(ctxt, frame)
// where ctxt is the context register and frame is a pointer to the first
// word in the passed-in argument frame.
func makeFuncStub()
// The first 3 words of this type must be kept in sync with
// makeFuncImpl and runtime.reflectMethodValue.
// Any changes should be reflected in all three.
type methodValue struct {
makeFuncCtxt
method int
rcvr Value
}
// makeMethodValue converts v from the rcvr+method index representation
// of a method value to an actual method func value, which is
// basically the receiver value with a special bit set, into a true
// func value - a value holding an actual func. The output is
// semantically equivalent to the input as far as the user of package
// reflect can tell, but the true func representation can be handled
// by code like Convert and Interface and Assign.
func makeMethodValue(op string, v Value) Value {
if v.flag&flagMethod == 0 {
panic("reflect: internal error: invalid use of makeMethodValue")
}
// Ignoring the flagMethod bit, v describes the receiver, not the method type.
fl := v.flag & (flagRO | flagAddr | flagIndir)
fl |= flag(v.typ.Kind())
rcvr := Value{v.typ, v.ptr, fl}
// v.Type returns the actual type of the method value.
ftyp := (*funcType)(unsafe.Pointer(v.Type().(*rtype)))
code := methodValueCallCodePtr()
// methodValue contains a stack map for use by the runtime
_, _, abi := funcLayout(ftyp, nil)
fv := &methodValue{
makeFuncCtxt: makeFuncCtxt{
fn: code,
stack: abi.stackPtrs,
argLen: abi.stackCallArgsSize,
regPtrs: abi.inRegPtrs,
},
method: int(v.flag) >> flagMethodShift,
rcvr: rcvr,
}
// Cause panic if method is not appropriate.
// The panic would still happen during the call if we omit this,
// but we want Interface() and other operations to fail early.
methodReceiver(op, fv.rcvr, fv.method)
return Value{&ftyp.rtype, unsafe.Pointer(fv), v.flag&flagRO | flag(Func)}
}
func methodValueCallCodePtr() uintptr {
return abi.FuncPCABI0(methodValueCall)
}
// methodValueCall is an assembly function that is the code half of
// the function returned from makeMethodValue. It expects a *methodValue
// as its context register, and its job is to invoke callMethod(ctxt, frame)
// where ctxt is the context register and frame is a pointer to the first
// word in the passed-in argument frame.
func methodValueCall()
// This structure must be kept in sync with runtime.reflectMethodValue.
// Any changes should be reflected in all both.
type makeFuncCtxt struct {
fn uintptr
stack *bitVector // ptrmap for both stack args and results
argLen uintptr // just args
regPtrs abi.IntArgRegBitmap
}
// moveMakeFuncArgPtrs uses ctxt.regPtrs to copy integer pointer arguments
// in args.Ints to args.Ptrs where the GC can see them.
//
// This is similar to what reflectcallmove does in the runtime, except
// that happens on the return path, whereas this happens on the call path.
//
// nosplit because pointers are being held in uintptr slots in args, so
// having our stack scanned now could lead to accidentally freeing
// memory.
//go:nosplit
func moveMakeFuncArgPtrs(ctxt *makeFuncCtxt, args *abi.RegArgs) {
for i, arg := range args.Ints {
// Avoid write barriers! Because our write barrier enqueues what
// was there before, we might enqueue garbage.
if ctxt.regPtrs.Get(i) {
*(*uintptr)(unsafe.Pointer(&args.Ptrs[i])) = arg
} else {
// We *must* zero this space ourselves because it's defined in
// assembly code and the GC will scan these pointers. Otherwise,
// there will be garbage here.
*(*uintptr)(unsafe.Pointer(&args.Ptrs[i])) = 0
}
}
}
|
