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bytes: add Next method to Buffer, simplify Read.

R=r
CC=golang-dev
https://golang.org/cl/980043
This commit is contained in:
Russ Cox 2010-04-26 10:02:01 -07:00
parent 9f69ab39f0
commit 78551a9b43
2 changed files with 47 additions and 6 deletions

View File

@ -196,17 +196,23 @@ func (b *Buffer) Read(p []byte) (n int, err os.Error) {
b.Truncate(0)
return 0, os.EOF
}
m := b.Len()
n = len(p)
n = copy(p, b.buf[b.off:])
b.off += n
return
}
// Next returns a slice containing the next n bytes from the buffer,
// advancing the buffer as if the bytes had been returned by Read.
// If there are fewer than n bytes in the buffer, Next returns the entire buffer.
// The slice is only valid until the next call to a read or write method.
func (b *Buffer) Next(n int) []byte {
m := b.Len()
if n > m {
// more bytes requested than available
n = m
}
copy(p, b.buf[b.off:b.off+n])
data := b.buf[b.off : b.off+n]
b.off += n
return n, err
return data
}
// ReadByte reads and returns the next byte from the buffer.

View File

@ -264,6 +264,7 @@ func TestWriteTo(t *testing.T) {
}
}
func TestRuneIO(t *testing.T) {
const NRune = 1000
// Built a test array while we write the data
@ -297,3 +298,37 @@ func TestRuneIO(t *testing.T) {
}
}
}
func TestNext(t *testing.T) {
b := []byte{0, 1, 2, 3, 4}
tmp := make([]byte, 5)
for i := 0; i <= 5; i++ {
for j := i; j <= 5; j++ {
for k := 0; k <= 6; k++ {
// 0 <= i <= j <= 5; 0 <= k <= 6
// Check that if we start with a buffer
// of length j at offset i and ask for
// Next(k), we get the right bytes.
buf := NewBuffer(b[0:j])
n, _ := buf.Read(tmp[0:i])
if n != i {
t.Fatalf("Read %d returned %d", i, n)
}
bb := buf.Next(k)
want := k
if want > j-i {
want = j - i
}
if len(bb) != want {
t.Fatalf("in %d,%d: len(Next(%d)) == %d", i, j, k, len(bb))
}
for l, v := range bb {
if v != byte(l+i) {
t.Fatalf("in %d,%d: Next(%d)[%d] = %d, want %d", i, j, k, l, v, l+i)
}
}
}
}
}
}