986f076276
Add a new generic container registry client via a new `container` package. Use this to create a command line utility as well as a new upload target for container registries. The code uses the github.com/containers/* project and packages to interact with container registires that is also used by skopeo, podman et al. One if the dependencies is `proglottis/gpgme` that is using cgo to bind libgpgme, so we have to add the corresponding devel package to the BuildRequires as well as installing it on CI. Checks will follow later via an integration test.
171 lines
4 KiB
Go
171 lines
4 KiB
Go
// Copyright 2014-2021 Ulrich Kunitz. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package lzma
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import (
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"errors"
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)
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// buffer provides a circular buffer of bytes. If the front index equals
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// the rear index the buffer is empty. As a consequence front cannot be
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// equal rear for a full buffer. So a full buffer has a length that is
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// one byte less the the length of the data slice.
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type buffer struct {
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data []byte
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front int
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rear int
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}
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// newBuffer creates a buffer with the given size.
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func newBuffer(size int) *buffer {
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return &buffer{data: make([]byte, size+1)}
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}
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// Cap returns the capacity of the buffer.
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func (b *buffer) Cap() int {
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return len(b.data) - 1
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}
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// Resets the buffer. The front and rear index are set to zero.
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func (b *buffer) Reset() {
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b.front = 0
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b.rear = 0
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}
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// Buffered returns the number of bytes buffered.
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func (b *buffer) Buffered() int {
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delta := b.front - b.rear
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if delta < 0 {
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delta += len(b.data)
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}
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return delta
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}
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// Available returns the number of bytes available for writing.
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func (b *buffer) Available() int {
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delta := b.rear - 1 - b.front
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if delta < 0 {
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delta += len(b.data)
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}
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return delta
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}
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// addIndex adds a non-negative integer to the index i and returns the
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// resulting index. The function takes care of wrapping the index as
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// well as potential overflow situations.
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func (b *buffer) addIndex(i int, n int) int {
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// subtraction of len(b.data) prevents overflow
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i += n - len(b.data)
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if i < 0 {
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i += len(b.data)
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}
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return i
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}
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// Read reads bytes from the buffer into p and returns the number of
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// bytes read. The function never returns an error but might return less
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// data than requested.
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func (b *buffer) Read(p []byte) (n int, err error) {
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n, err = b.Peek(p)
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b.rear = b.addIndex(b.rear, n)
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return n, err
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}
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// Peek reads bytes from the buffer into p without changing the buffer.
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// Peek will never return an error but might return less data than
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// requested.
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func (b *buffer) Peek(p []byte) (n int, err error) {
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m := b.Buffered()
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n = len(p)
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if m < n {
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n = m
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p = p[:n]
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}
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k := copy(p, b.data[b.rear:])
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if k < n {
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copy(p[k:], b.data)
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}
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return n, nil
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}
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// Discard skips the n next bytes to read from the buffer, returning the
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// bytes discarded.
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//
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// If Discards skips fewer than n bytes, it returns an error.
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func (b *buffer) Discard(n int) (discarded int, err error) {
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if n < 0 {
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return 0, errors.New("buffer.Discard: negative argument")
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}
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m := b.Buffered()
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if m < n {
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n = m
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err = errors.New(
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"buffer.Discard: discarded less bytes then requested")
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}
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b.rear = b.addIndex(b.rear, n)
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return n, err
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}
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// ErrNoSpace indicates that there is insufficient space for the Write
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// operation.
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var ErrNoSpace = errors.New("insufficient space")
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// Write puts data into the buffer. If less bytes are written than
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// requested ErrNoSpace is returned.
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func (b *buffer) Write(p []byte) (n int, err error) {
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m := b.Available()
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n = len(p)
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if m < n {
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n = m
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p = p[:m]
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err = ErrNoSpace
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}
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k := copy(b.data[b.front:], p)
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if k < n {
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copy(b.data, p[k:])
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}
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b.front = b.addIndex(b.front, n)
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return n, err
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}
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// WriteByte writes a single byte into the buffer. The error ErrNoSpace
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// is returned if no single byte is available in the buffer for writing.
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func (b *buffer) WriteByte(c byte) error {
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if b.Available() < 1 {
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return ErrNoSpace
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}
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b.data[b.front] = c
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b.front = b.addIndex(b.front, 1)
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return nil
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}
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// prefixLen returns the length of the common prefix of a and b.
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func prefixLen(a, b []byte) int {
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if len(a) > len(b) {
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a, b = b, a
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}
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for i, c := range a {
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if b[i] != c {
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return i
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}
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}
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return len(a)
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}
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// matchLen returns the length of the common prefix for the given
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// distance from the rear and the byte slice p.
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func (b *buffer) matchLen(distance int, p []byte) int {
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var n int
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i := b.rear - distance
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if i < 0 {
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if n = prefixLen(p, b.data[len(b.data)+i:]); n < -i {
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return n
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}
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p = p[n:]
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i = 0
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}
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n += prefixLen(p, b.data[i:])
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return n
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}
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