better io.ByteBuffer implementation:
- more light-weight
- better buffer management
- added test cases
R=r
DELTA=227 (167 added, 35 deleted, 25 changed)
OCL=28252
CL=28289
diff --git a/src/lib/io/bytebuffer.go b/src/lib/io/bytebuffer.go
index 9c78e85..011166e 100644
--- a/src/lib/io/bytebuffer.go
+++ b/src/lib/io/bytebuffer.go
@@ -11,11 +11,8 @@
"os";
)
-
-// TODO(r): Do better memory management.
-
func bytecopy(dst []byte, doff int, src []byte, soff int, count int) {
- for i := 0; i < count; i++ {
+ for ; count > 0; count-- {
dst[doff] = src[soff];
doff++;
soff++;
@@ -26,79 +23,68 @@
// connected to a buffer of bytes.
// The zero value for ByteBuffer is an empty buffer ready to use.
type ByteBuffer struct {
- buf []byte;
- off int; // Read from here
- len int; // Write to here
- cap int;
+ buf []byte; // contents are the bytes buf[off : len(buf)]
+ off int; // read at &buf[off], write at &buf[len(buf)]
+}
+
+// Data returns the contents of the unread portion of the buffer;
+// len(b.Data()) == b.Len().
+func (b *ByteBuffer) Data() []byte {
+ return b.buf[b.off : len(b.buf)]
+}
+
+// Len returns the number of bytes of the unread portion of the buffer;
+// b.Len() == len(b.Data()).
+func (b *ByteBuffer) Len() int {
+ return len(b.buf) - b.off
}
// Reset resets the buffer so it has no content.
func (b *ByteBuffer) Reset() {
- b.off = 0;
- b.len = 0;
+ b.off = len(b.buf)
}
// Write appends the contents of p to the buffer. The return
-// value is the length of p; err is always nil.
+// value n is the length of p; err is always nil.
func (b *ByteBuffer) Write(p []byte) (n int, err os.Error) {
- plen := len(p);
- if len(b.buf) == 0 {
- b.cap = plen + 1024;
- b.buf = make([]byte, b.cap);
- b.len = 0;
+ m := b.Len();
+ n = len(p);
+
+ if len(b.buf) + n > cap(b.buf) {
+ // not enough space at end
+ buf := b.buf;
+ if m + n > cap(b.buf) {
+ // not enough space anywhere
+ buf = make([]byte, 2*cap(b.buf) + n)
+ }
+ bytecopy(buf, 0, b.buf, b.off, m);
+ b.buf = buf;
+ b.off = 0
}
- if b.len + plen > b.cap {
- b.cap = 2*(b.cap + plen);
- nb := make([]byte, b.cap);
- bytecopy(nb, 0, b.buf, 0, b.len);
- b.buf = nb;
- }
- bytecopy(b.buf, b.len, p, 0, plen);
- b.len += plen;
- return plen, nil;
+
+ b.buf = b.buf[0 : b.off + m + n];
+ bytecopy(b.buf, b.off + m, p, 0, n);
+ return n, nil
}
// Read reads the next len(p) bytes from the buffer or until the buffer
-// is drained. The return value is the number of bytes read; err is always nil.
+// is drained. The return value n is the number of bytes read; err is always nil.
func (b *ByteBuffer) Read(p []byte) (n int, err os.Error) {
- plen := len(p);
- if len(b.buf) == 0 {
- return 0, nil
- }
- if b.off == b.len { // empty buffer
- b.Reset();
- return 0, nil
- }
- if plen > b.len - b.off {
- plen = b.len - b.off
- }
- bytecopy(p, 0, b.buf, b.off, plen);
- b.off += plen;
- return plen, nil;
-}
+ m := b.Len();
+ n = len(p);
-// Len returns the length of the underlying buffer.
-func (b *ByteBuffer) Len() int {
- return b.len
-}
+ if n > m {
+ // more bytes requested than available
+ n = m
+ }
-// Off returns the location within the buffer of the next byte to be read.
-func (b *ByteBuffer) Off() int {
- return b.off
-}
-
-// Data returns the contents of the unread portion of the buffer.
-func (b *ByteBuffer) Data() []byte {
- return b.buf[b.off:b.len]
+ bytecopy(p, 0, b.buf, b.off, n);
+ b.off += n;
+ return n, nil
}
// NewByteBufferFromArray creates and initializes a new ByteBuffer
// with buf as its initial contents.
func NewByteBufferFromArray(buf []byte) *ByteBuffer {
- b := new(ByteBuffer);
- b.buf = buf;
- b.off = 0;
- b.len = len(buf);
- b.cap = len(buf);
- return b;
+ return &ByteBuffer{buf, 0};
}
diff --git a/src/lib/io/bytebuffer_test.go b/src/lib/io/bytebuffer_test.go
new file mode 100644
index 0000000..6a4f3c9
--- /dev/null
+++ b/src/lib/io/bytebuffer_test.go
@@ -0,0 +1,146 @@
+// Copyright 2009 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 io
+
+import (
+ "io";
+ "rand";
+ "testing";
+)
+
+
+const N = 10000; // make this bigger for a larger (and slower) test
+var data []byte; // test data for write tests
+
+
+func init() {
+ data = make([]byte, N);
+ for i := 0; i < len(data); i++ {
+ data[i] = 'a' + byte(i % 26)
+ }
+}
+
+
+// Verify that contents of buf match the string s.
+func check(t *testing.T, testname string, buf *ByteBuffer, s string) {
+ if buf.Len() != len(buf.Data()) {
+ t.Errorf("%s: buf.Len() == %d, len(buf.Data()) == %d\n", testname, buf.Len(), len(buf.Data()))
+ }
+
+ if buf.Len() != len(s) {
+ t.Errorf("%s: buf.Len() == %d, len(s) == %d\n", testname, buf.Len(), len(s))
+ }
+
+ if string(buf.Data()) != s {
+ t.Errorf("%s: string(buf.Data()) == %q, s == %q\n", testname, string(buf.Data()), s)
+ }
+}
+
+
+// Fill buf through n writes of fub.
+// The initial contents of buf corresponds to the string s;
+// the result is the final contents of buf returned as a string.
+func fill(t *testing.T, testname string, buf *ByteBuffer, s string, n int, fub []byte) string {
+ check(t, testname + " (fill 1)", buf, s);
+ for ; n > 0; n-- {
+ m, err := buf.Write(fub);
+ if m != len(fub) {
+ t.Errorf(testname + " (fill 2): m == %d, expected %d\n", m, len(fub));
+ }
+ if err != nil {
+ t.Errorf(testname + " (fill 3): err should always be nil, found err == %s\n", err);
+ }
+ s += string(fub);
+ check(t, testname + " (fill 4)", buf, s);
+ }
+ return s;
+}
+
+
+// Empty buf through repeated reads into fub.
+// The initial contents of buf corresponds to the string s.
+func empty(t *testing.T, testname string, buf *ByteBuffer, s string, fub []byte) {
+ check(t, testname + " (empty 1)", buf, s);
+
+ for {
+ n, err := buf.Read(fub);
+ if n == 0 {
+ break;
+ }
+ if err != nil {
+ t.Errorf(testname + " (empty 2): err should always be nil, found err == %s\n", err);
+ }
+ s = s[n : len(s)];
+ check(t, testname + " (empty 3)", buf, s);
+ }
+
+ check(t, testname + " (empty 4)", buf, "");
+}
+
+
+func TestBasicOperations(t *testing.T) {
+ var buf ByteBuffer;
+
+ for i := 0; i < 5; i++ {
+ check(t, "TestBasicOperations (1)", &buf, "");
+
+ buf.Reset();
+ check(t, "TestBasicOperations (2)", &buf, "");
+
+ n, err := buf.Write(data[0 : 1]);
+ if n != 1 {
+ t.Errorf("wrote 1 byte, but n == %d\n", n);
+ }
+ if err != nil {
+ t.Errorf("err should always be nil, but err == %s\n", err);
+ }
+ check(t, "TestBasicOperations (3)", &buf, "a");
+
+ n, err = buf.Write(data[1 : 26]);
+ if n != 25 {
+ t.Errorf("wrote 25 bytes, but n == %d\n", n);
+ }
+ check(t, "TestBasicOperations (4)", &buf, string(data[0 : 26]));
+
+ empty(t, "TestBasicOperations (5)", &buf, string(data[0 : 26]), make([]byte, 5));
+ empty(t, "TestBasicOperations (6)", &buf, "", make([]byte, 100));
+ }
+}
+
+
+func TestLargeWrites(t *testing.T) {
+ var buf ByteBuffer;
+ for i := 3; i < 30; i += 3 {
+ s := fill(t, "TestLargeWrites (1)", &buf, "", 5, data);
+ empty(t, "TestLargeWrites (2)", &buf, s, make([]byte, len(data)/i));
+ }
+ check(t, "TestLargeWrites (3)", &buf, "");
+}
+
+
+func TestLargeReads(t *testing.T) {
+ var buf ByteBuffer;
+ for i := 3; i < 30; i += 3 {
+ s := fill(t, "TestLargeReads (1)", &buf, "", 5, data[0 : len(data)/i]);
+ empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(data)));
+ }
+ check(t, "TestLargeReads (3)", &buf, "");
+}
+
+
+func TestMixedReadsAndWrites(t *testing.T) {
+ var buf ByteBuffer;
+ s := "";
+ for i := 0; i < 50; i++ {
+ wlen := rand.Intn(len(data));
+ s = fill(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, data[0 : wlen]);
+
+ rlen := rand.Intn(len(data));
+ fub := make([]byte, rlen);
+ n, err := buf.Read(fub);
+ s = s[n : len(s)];
+ }
+ empty(t, "TestMixedReadsAndWrites (2)", &buf, s, make([]byte, buf.Len()));
+}
