make NewBufRead etc. idempotent
R=rsc
DELTA=63 (59 added, 0 deleted, 4 changed)
OCL=27143
CL=27143
diff --git a/src/lib/bufio.go b/src/lib/bufio.go
index ab70b68..3bc2d3d 100644
--- a/src/lib/bufio.go
+++ b/src/lib/bufio.go
@@ -54,12 +54,18 @@
}
// 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.
-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 {
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.buf = make([]byte, size);
b.rd = rd;
@@ -381,12 +387,18 @@
}
// 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.
-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 {
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.buf = make([]byte, size);
b.wr = wr;
diff --git a/src/lib/bufio_test.go b/src/lib/bufio_test.go
index ef97bc4..d8c77c1 100644
--- a/src/lib/bufio_test.go
+++ b/src/lib/bufio_test.go
@@ -330,3 +330,50 @@
}
}
+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");
+ }
+}
