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make NewBufRead etc. idempotent

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R=rsc
DELTA=63  (59 added, 0 deleted, 4 changed)
OCL=27143
CL=27143
This commit is contained in:
Rob Pike 2009-04-06 21:42:14 -07:00
parent ac6ebfdea9
commit ee19695cfc
2 changed files with 63 additions and 4 deletions
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20
src/lib/bufio.go
View file

@ -54,12 +54,18 @@ type BufRead struct {
} }
// NewBufReadSize creates a new BufRead whose buffer has the specified size, // NewBufReadSize creates a new BufRead whose buffer has the specified size,
// which must be greater than zero. // which must be greater than zero. If the argument io.Read is already a
// BufRead with large enough size, it returns the underlying BufRead.
// It returns the BufRead and any error. // It returns the BufRead and any error.
func NewBufReadSize(rd io.Read, size int) (b *BufRead, err *os.Error) { func NewBufReadSize(rd io.Read, size int) (*BufRead, *os.Error) {
if size <= 0 { if size <= 0 {
return nil, BadBufSize return nil, BadBufSize
} }
// Is it already a BufRead?
b, ok := rd.(*BufRead);
if ok && len(b.buf) >= size {
return b, nil
}
b = new(BufRead); b = new(BufRead);
b.buf = make([]byte, size); b.buf = make([]byte, size);
b.rd = rd; b.rd = rd;
@ -381,12 +387,18 @@ type BufWrite struct {
} }
// NewBufWriteSize creates a new BufWrite whose buffer has the specified size, // NewBufWriteSize creates a new BufWrite whose buffer has the specified size,
// which must be greater than zero. // which must be greater than zero. If the argument io.Write is already a
// BufWrite with large enough size, it returns the underlying BufWrite.
// It returns the BufWrite and any error. // It returns the BufWrite and any error.
func NewBufWriteSize(wr io.Write, size int) (b *BufWrite, err *os.Error) { func NewBufWriteSize(wr io.Write, size int) (*BufWrite, *os.Error) {
if size <= 0 { if size <= 0 {
return nil, BadBufSize return nil, BadBufSize
} }
// Is it already a BufWrite?
b, ok := wr.(*BufWrite);
if ok && len(b.buf) >= size {
return b, nil
}
b = new(BufWrite); b = new(BufWrite);
b.buf = make([]byte, size); b.buf = make([]byte, size);
b.wr = wr; b.wr = wr;

47
src/lib/bufio_test.go
View file

@ -330,3 +330,50 @@ func TestBufWrite(t *testing.T) {
} }
} }
func TestNewBufReadSizeIdempotent(t *testing.T) {
const BufSize = 1000;
b, err := NewBufReadSize(newByteReader(io.StringBytes("hello world")), BufSize);
if err != nil {
t.Error("NewBufReadSize create fail", err);
}
// Does it recognize itself?
b1, err2 := NewBufReadSize(b, BufSize);
if err2 != nil {
t.Error("NewBufReadSize #2 create fail", err2);
}
if b1 != b {
t.Error("NewBufReadSize did not detect underlying BufRead");
}
// Does it wrap if existing buffer is too small?
b2, err3 := NewBufReadSize(b, 2*BufSize);
if err3 != nil {
t.Error("NewBufReadSize #3 create fail", err3);
}
if b2 == b {
t.Error("NewBufReadSize did not enlarge buffer");
}
}
func TestNewBufWriteSizeIdempotent(t *testing.T) {
const BufSize = 1000;
b, err := NewBufWriteSize(newByteWriter(), BufSize);
if err != nil {
t.Error("NewBufWriteSize create fail", err);
}
// Does it recognize itself?
b1, err2 := NewBufWriteSize(b, BufSize);
if err2 != nil {
t.Error("NewBufWriteSize #2 create fail", err2);
}
if b1 != b {
t.Error("NewBufWriteSize did not detect underlying BufWrite");
}
// Does it wrap if existing buffer is too small?
b2, err3 := NewBufWriteSize(b, 2*BufSize);
if err3 != nil {
t.Error("NewBufWriteSize #3 create fail", err3);
}
if b2 == b {
t.Error("NewBufWriteSize did not enlarge buffer");
}
}