diff options
Diffstat (limited to 'pkg/buffer/view.go')
-rw-r--r-- | pkg/buffer/view.go | 391 |
1 files changed, 0 insertions, 391 deletions
diff --git a/pkg/buffer/view.go b/pkg/buffer/view.go deleted file mode 100644 index 00652d675..000000000 --- a/pkg/buffer/view.go +++ /dev/null @@ -1,391 +0,0 @@ -// Copyright 2020 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package buffer - -import ( - "fmt" - "io" -) - -// View is a non-linear buffer. -// -// All methods are thread compatible. -// -// +stateify savable -type View struct { - data bufferList - size int64 - pool pool -} - -// TrimFront removes the first count bytes from the buffer. -func (v *View) TrimFront(count int64) { - if count >= v.size { - v.advanceRead(v.size) - } else { - v.advanceRead(count) - } -} - -// ReadAt implements io.ReaderAt.ReadAt. -func (v *View) ReadAt(p []byte, offset int64) (int, error) { - var ( - skipped int64 - done int64 - ) - for buf := v.data.Front(); buf != nil && done < int64(len(p)); buf = buf.Next() { - needToSkip := int(offset - skipped) - if sz := buf.ReadSize(); sz <= needToSkip { - skipped += int64(sz) - continue - } - - // Actually read data. - n := copy(p[done:], buf.ReadSlice()[needToSkip:]) - skipped += int64(needToSkip) - done += int64(n) - } - if int(done) < len(p) || offset+done == v.size { - return int(done), io.EOF - } - return int(done), nil -} - -// advanceRead advances the view's read index. -// -// Precondition: there must be sufficient bytes in the buffer. -func (v *View) advanceRead(count int64) { - for buf := v.data.Front(); buf != nil && count > 0; { - sz := int64(buf.ReadSize()) - if sz > count { - // There is still data for reading. - buf.ReadMove(int(count)) - v.size -= count - count = 0 - break - } - - // Consume the whole buffer. - oldBuf := buf - buf = buf.Next() // Iterate. - v.data.Remove(oldBuf) - oldBuf.Reset() - v.pool.put(oldBuf) - - // Update counts. - count -= sz - v.size -= sz - } - if count > 0 { - panic(fmt.Sprintf("advanceRead still has %d bytes remaining", count)) - } -} - -// Truncate truncates the view to the given bytes. -// -// This will not grow the view, only shrink it. If a length is passed that is -// greater than the current size of the view, then nothing will happen. -// -// Precondition: length must be >= 0. -func (v *View) Truncate(length int64) { - if length < 0 { - panic("negative length provided") - } - if length >= v.size { - return // Nothing to do. - } - for buf := v.data.Back(); buf != nil && v.size > length; buf = v.data.Back() { - sz := int64(buf.ReadSize()) - if after := v.size - sz; after < length { - // Truncate the buffer locally. - left := (length - after) - buf.write = buf.read + int(left) - v.size = length - break - } - - // Drop the buffer completely; see above. - v.data.Remove(buf) - buf.Reset() - v.pool.put(buf) - v.size -= sz - } -} - -// Grow grows the given view to the number of bytes, which will be appended. If -// zero is true, all these bytes will be zero. If zero is false, then this is -// the caller's responsibility. -// -// Precondition: length must be >= 0. -func (v *View) Grow(length int64, zero bool) { - if length < 0 { - panic("negative length provided") - } - for v.size < length { - buf := v.data.Back() - - // Is there some space in the last buffer? - if buf == nil || buf.Full() { - buf = v.pool.get() - v.data.PushBack(buf) - } - - // Write up to length bytes. - sz := buf.WriteSize() - if int64(sz) > length-v.size { - sz = int(length - v.size) - } - - // Zero the written section; note that this pattern is - // specifically recognized and optimized by the compiler. - if zero { - for i := buf.write; i < buf.write+sz; i++ { - buf.data[i] = 0 - } - } - - // Advance the index. - buf.WriteMove(sz) - v.size += int64(sz) - } -} - -// Prepend prepends the given data. -func (v *View) Prepend(data []byte) { - // Is there any space in the first buffer? - if buf := v.data.Front(); buf != nil && buf.read > 0 { - // Fill up before the first write. - avail := buf.read - bStart := 0 - dStart := len(data) - avail - if avail > len(data) { - bStart = avail - len(data) - dStart = 0 - } - n := copy(buf.data[bStart:], data[dStart:]) - data = data[:dStart] - v.size += int64(n) - buf.read -= n - } - - for len(data) > 0 { - // Do we need an empty buffer? - buf := v.pool.get() - v.data.PushFront(buf) - - // The buffer is empty; copy last chunk. - avail := len(buf.data) - bStart := 0 - dStart := len(data) - avail - if avail > len(data) { - bStart = avail - len(data) - dStart = 0 - } - - // We have to put the data at the end of the current - // buffer in order to ensure that the next prepend will - // correctly fill up the beginning of this buffer. - n := copy(buf.data[bStart:], data[dStart:]) - data = data[:dStart] - v.size += int64(n) - buf.read = len(buf.data) - n - buf.write = len(buf.data) - } -} - -// Append appends the given data. -func (v *View) Append(data []byte) { - for done := 0; done < len(data); { - buf := v.data.Back() - - // Ensure there's a buffer with space. - if buf == nil || buf.Full() { - buf = v.pool.get() - v.data.PushBack(buf) - } - - // Copy in to the given buffer. - n := copy(buf.WriteSlice(), data[done:]) - done += n - buf.WriteMove(n) - v.size += int64(n) - } -} - -// Flatten returns a flattened copy of this data. -// -// This method should not be used in any performance-sensitive paths. It may -// allocate a fresh byte slice sufficiently large to contain all the data in -// the buffer. This is principally for debugging. -// -// N.B. Tee data still belongs to this view, as if there is a single buffer -// present, then it will be returned directly. This should be used for -// temporary use only, and a reference to the given slice should not be held. -func (v *View) Flatten() []byte { - if buf := v.data.Front(); buf == nil { - return nil // No data at all. - } else if buf.Next() == nil { - return buf.ReadSlice() // Only one buffer. - } - data := make([]byte, 0, v.size) // Need to flatten. - for buf := v.data.Front(); buf != nil; buf = buf.Next() { - // Copy to the allocated slice. - data = append(data, buf.ReadSlice()...) - } - return data -} - -// Size indicates the total amount of data available in this view. -func (v *View) Size() int64 { - return v.size -} - -// Copy makes a strict copy of this view. -func (v *View) Copy() (other View) { - for buf := v.data.Front(); buf != nil; buf = buf.Next() { - other.Append(buf.ReadSlice()) - } - return -} - -// Apply applies the given function across all valid data. -func (v *View) Apply(fn func([]byte)) { - for buf := v.data.Front(); buf != nil; buf = buf.Next() { - fn(buf.ReadSlice()) - } -} - -// Merge merges the provided View with this one. -// -// The other view will be appended to v, and other will be empty after this -// operation completes. -func (v *View) Merge(other *View) { - // Copy over all buffers. - for buf := other.data.Front(); buf != nil; buf = other.data.Front() { - other.data.Remove(buf) - v.data.PushBack(buf) - } - - // Adjust sizes. - v.size += other.size - other.size = 0 -} - -// WriteFromReader writes to the buffer from an io.Reader. -// -// A minimum read size equal to unsafe.Sizeof(unintptr) is enforced, -// provided that count is greater than or equal to unsafe.Sizeof(uintptr). -func (v *View) WriteFromReader(r io.Reader, count int64) (int64, error) { - var ( - done int64 - n int - err error - ) - for done < count { - buf := v.data.Back() - - // Ensure we have an empty buffer. - if buf == nil || buf.Full() { - buf = v.pool.get() - v.data.PushBack(buf) - } - - // Is this less than the minimum batch? - if buf.WriteSize() < minBatch && (count-done) >= int64(minBatch) { - tmp := make([]byte, minBatch) - n, err = r.Read(tmp) - v.Append(tmp[:n]) - done += int64(n) - if err != nil { - break - } - continue - } - - // Limit the read, if necessary. - sz := buf.WriteSize() - if left := count - done; int64(sz) > left { - sz = int(left) - } - - // Pass the relevant portion of the buffer. - n, err = r.Read(buf.WriteSlice()[:sz]) - buf.WriteMove(n) - done += int64(n) - v.size += int64(n) - if err == io.EOF { - err = nil // Short write allowed. - break - } else if err != nil { - break - } - } - return done, err -} - -// ReadToWriter reads from the buffer into an io.Writer. -// -// N.B. This does not consume the bytes read. TrimFront should -// be called appropriately after this call in order to do so. -// -// A minimum write size equal to unsafe.Sizeof(unintptr) is enforced, -// provided that count is greater than or equal to unsafe.Sizeof(uintptr). -func (v *View) ReadToWriter(w io.Writer, count int64) (int64, error) { - var ( - done int64 - n int - err error - ) - offset := 0 // Spill-over for batching. - for buf := v.data.Front(); buf != nil && done < count; buf = buf.Next() { - // Has this been consumed? Skip it. - sz := buf.ReadSize() - if sz <= offset { - offset -= sz - continue - } - sz -= offset - - // Is this less than the minimum batch? - left := count - done - if sz < minBatch && left >= int64(minBatch) && (v.size-done) >= int64(minBatch) { - tmp := make([]byte, minBatch) - n, err = v.ReadAt(tmp, done) - w.Write(tmp[:n]) - done += int64(n) - offset = n - sz // Reset below. - if err != nil { - break - } - continue - } - - // Limit the write if necessary. - if int64(sz) >= left { - sz = int(left) - } - - // Perform the actual write. - n, err = w.Write(buf.ReadSlice()[offset : offset+sz]) - done += int64(n) - if err != nil { - break - } - - // Reset spill-over. - offset = 0 - } - return done, err -} |