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};
}
