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fmt/print: remove a TODO regarding printing renamed byte slices.

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the solution must work around a weakness in the reflection library:
there is no way to do type-safe conversions under reflection.

R=rsc
CC=golang-dev
https://golang.org/cl/2000041
This commit is contained in:
Rob Pike 2010-08-17 08:34:40 +10:00
parent 69fe3dd754
commit 316961c172
2 changed files with 18 additions and 3 deletions
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3
src/pkg/fmt/fmt_test.go
View file

@ -334,8 +334,7 @@ var fmttests = []fmtTest{
fmtTest{"%X", renamedUint64(17), "11"},
fmtTest{"%o", renamedUintptr(18), "22"},
fmtTest{"%x", renamedString("thing"), "7468696e67"},
// TODO: It would be nice if this one worked, but it's hard.
// fmtTest{"%q", renamedBytes([]byte("hello")), `"hello"`},
fmtTest{"%q", renamedBytes([]byte("hello")), `"hello"`},
fmtTest{"%v", renamedFloat(11), "11"},
fmtTest{"%v", renamedFloat32(22), "22"},
fmtTest{"%v", renamedFloat64(33), "33"},

18
src/pkg/fmt/print.go
View file

@ -697,6 +697,22 @@ BigSwitch:
return p.printField(value.Interface(), verb, plus, goSyntax, depth+1)
}
case reflect.ArrayOrSliceValue:
// Byte slices are special.
if f.Type().(reflect.ArrayOrSliceType).Elem().Kind() == reflect.Uint8 {
// We know it's a slice of bytes, but we also know it does not have static type
// []byte, or it would have been caught above. Therefore we cannot convert
// it directly in the (slightly) obvious way: f.Interface().([]byte); it doesn't have
// that type, and we can't write an expression of the right type and do a
// conversion because we don't have a static way to write the right type.
// So we build a slice by hand. This is a rare case but it would be nice
// if reflection could help a little more.
bytes := make([]byte, f.Len())
for i := range bytes {
bytes[i] = byte(f.Elem(i).(*reflect.UintValue).Get())
}
p.fmtBytes(bytes, verb, goSyntax, depth, field)
return verb == 's'
}
if goSyntax {
p.buf.WriteString(reflect.Typeof(field).String())
p.buf.WriteByte('{')
@ -804,7 +820,7 @@ func (p *pp) doPrintf(format string, a []interface{}) {
i += w
// percent is special - absorbs no operand
if c == '%' {
p.buf.WriteByte('%') // TODO: should we bother with width & prec?
p.buf.WriteByte('%') // We ignore width and prec.
continue
}
if fieldnum >= len(a) { // out of operands