Commit 0f6db15c authored by Aaron Jacobs's avatar Aaron Jacobs

buffer: give OutMessage's public API a makeover.

Use int where appropriate, fix up documentation, and clarify. Delete the
implementation where it will soon need to change.
parent 10bc0e76
......@@ -23,14 +23,9 @@ import (
"github.com/jacobsa/fuse/internal/fusekernel"
)
const outHeaderSize = unsafe.Sizeof(fusekernel.OutHeader{})
// OutMessage structs begin life with Len() == OutMessageInitialSize.
const OutMessageInitialSize = outHeaderSize
// We size out messages to be large enough to hold a header for the response
// plus the largest read that may come in.
const outMessageSize = outHeaderSize + MaxReadSize
// OutMessageHeaderSize is the size of the leading header in every
// properly-constructed OutMessage. Reset brings the message back to this size.
const OutMessageHeaderSize = unsafe.Sizeof(fusekernel.OutHeader{})
// OutMessage provides a mechanism for constructing a single contiguous fuse
// message from multiple segments, where the first segment is always a
......@@ -38,8 +33,6 @@ const outMessageSize = outHeaderSize + MaxReadSize
//
// Must be initialized with Reset.
type OutMessage struct {
offset uintptr
storage [outMessageSize]byte
}
// Make sure alignment works out correctly, at least for the header.
......@@ -53,57 +46,30 @@ func init() {
}
}
// Reset the message so that it is ready to be used again. Afterward, the
// contents are solely a zeroed header.
func (m *OutMessage) Reset() {
m.offset = OutMessageInitialSize
memclr(unsafe.Pointer(&m.storage), OutMessageInitialSize)
}
// Reset resets m so that it's ready to be used again. Afterward, the contents
// are solely a zeroed fusekernel.OutHeader struct.
func (m *OutMessage) Reset()
// Return a pointer to the header at the start of the message.
func (b *OutMessage) OutHeader() (h *fusekernel.OutHeader) {
h = (*fusekernel.OutHeader)(unsafe.Pointer(&b.storage))
return
}
// OutHeader returns a pointer to the header at the start of the message.
func (m *OutMessage) OutHeader() (h *fusekernel.OutHeader)
// Grow the buffer by the supplied number of bytes, returning a pointer to the
// start of the new segment, which is zeroed. If there is no space left, return
// the nil pointer.
func (b *OutMessage) Grow(size uintptr) (p unsafe.Pointer) {
p = b.GrowNoZero(size)
if p != nil {
memclr(p, size)
}
// Grow grows m's buffer by the given number of bytes, returning a pointer to
// the start of the new segment, which is guaranteed to be zeroed. If there is
// insufficient space, it returns nil.
func (b *OutMessage) Grow(n int) (p unsafe.Pointer)
return
}
// GrowNoZero is equivalent to Grow, except the new segment is not zeroed. Use
// with caution!
func (b *OutMessage) GrowNoZero(n int) (p unsafe.Pointer)
// Equivalent to Grow, except the new segment is not zeroed. Use with caution!
func (b *OutMessage) GrowNoZero(size uintptr) (p unsafe.Pointer) {
if outMessageSize-b.offset < size {
return
}
p = unsafe.Pointer(uintptr(unsafe.Pointer(&b.storage)) + b.offset)
b.offset += size
return
}
// Shrink to the supplied size. Panic if the size is greater than Len() or less
// than OutMessageInitialSize.
func (b *OutMessage) ShrinkTo(n uintptr) {
if n < OutMessageInitialSize || n > b.offset {
panic(fmt.Sprintf("ShrinkTo(%d) out of range for offset %d", n, b.offset))
}
b.offset = n
}
// ShrinkTo shrinks m to the given size. It panics if the size is greater than
// Len() or less than OutMessageHeaderSize.
func (b *OutMessage) ShrinkTo(n int)
// Equivalent to growing by the length of p, then copying p over the new
// segment. Panics if there is not enough room available.
// Append is equivalent to growing by len(src), then copying src over the new
// segment. Int panics if there is not enough room available.
func (b *OutMessage) Append(src []byte) {
p := b.GrowNoZero(uintptr(len(src)))
p := b.GrowNoZero(len(src))
if p == nil {
panic(fmt.Sprintf("Can't grow %d bytes", len(src)))
}
......@@ -114,10 +80,9 @@ func (b *OutMessage) Append(src []byte) {
return
}
// Equivalent to growing by the length of s, then copying s over the new
// segment. Panics if there is not enough room available.
// AppendString is like Append, but accepts string input.
func (b *OutMessage) AppendString(src string) {
p := b.GrowNoZero(uintptr(len(src)))
p := b.GrowNoZero(len(src))
if p == nil {
panic(fmt.Sprintf("Can't grow %d bytes", len(src)))
}
......@@ -128,12 +93,13 @@ func (b *OutMessage) AppendString(src string) {
return
}
// Return the current size of the buffer.
// Len returns the current size of the message, including the leading header.
func (b *OutMessage) Len() int {
return int(b.offset)
}
// Return a reference to the current contents of the buffer.
// Bytes returns a reference to the current contents of the buffer, including
// the leading header.
func (b *OutMessage) Bytes() []byte {
return b.storage[:int(b.offset)]
}
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