gotosocial/vendor/codeberg.org/gruf/go-fastpath/v2/path.go

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package fastpath
import (
"unsafe"
)
// Clean: see Builder.Clean(). Analogous to path.Clean().
func Clean(path string) string {
return (&Builder{}).Clean(path)
}
// Join: see Builder.Join(). Analogous to path.Join().
func Join(elems ...string) string {
return (&Builder{}).Join(elems...)
}
// Builder provides a means of cleaning and joining system paths,
// while retaining a singular underlying byte buffer for performance.
type Builder struct {
// B is the underlying byte buffer
B []byte
dd int // pos of last '..' appended to builder
abs bool // abs stores whether path passed to first .Append() is absolute
set bool // set stores whether b.abs has been set i.e. not first call to .Append()
}
// Reset resets the Builder object
func (b *Builder) Reset() {
b.B = b.B[:0]
b.dd = 0
b.abs = false
b.set = false
}
// Len returns the number of accumulated bytes in the Builder
func (b Builder) Len() int {
return len(b.B)
}
// Cap returns the capacity of the underlying Builder buffer
func (b Builder) Cap() int {
return cap(b.B)
}
// Bytes returns the accumulated path bytes.
func (b Builder) Bytes() []byte {
return b.B
}
// String returns the accumulated path string.
func (b Builder) String() string {
return *(*string)(unsafe.Pointer(&b.B))
}
// Absolute returns whether current path is absolute (not relative).
func (b Builder) Absolute() bool {
return b.abs
}
// SetAbsolute converts the current path to-or-from absolute.
func (b *Builder) SetAbsolute(enabled bool) {
if !b.set {
// Ensure 1B avail
b.Guarantee(1)
if enabled {
// Set empty 'abs'
b.appendByte('/')
b.abs = true
} else {
// Set empty 'rel'
b.appendByte('.')
b.abs = false
}
b.set = true
return
}
if !enabled && b.abs {
// set && absolute
// -> update
b.abs = false
// If empty, set to '.' (empty rel path)
if len(b.B) == 0 || (len(b.B) == 1 && b.B[0] == '/') {
b.Guarantee(1)
b.B = b.B[:1]
b.B[0] = '.'
return
}
if b.B[0] != '/' {
// No need to change
return
}
if len(b.B) > 1 {
// Shift bytes 1 left
copy(b.B, b.B[1:])
}
// and drop the '/' prefix'
b.B = b.B[:len(b.B)-1]
} else if enabled && !b.abs {
// set && !absolute
// -> update
b.abs = true
// Ensure 1B avail
b.Guarantee(1)
// If empty, set to '/' (empty abs path)
if len(b.B) == 0 || (len(b.B) == 1 && b.B[0] == '.') {
b.Guarantee(1)
b.B = b.B[:1]
b.B[0] = '/'
return
}
// Increase length
l := len(b.B)
b.B = b.B[:l+1]
// Shift bytes 1 right
copy(b.B[1:], b.B[:l])
// Set first byte '/'
b.B[0] = '/'
}
}
// AppendBytes adds and cleans the supplied path bytes to the
// builder's internal buffer, growing the buffer if necessary
// to accomodate the extra path length.
func (b *Builder) AppendBytes(path []byte) {
if len(path) == 0 {
return
}
b.Guarantee(len(path) + 1)
b.append(*(*string)(unsafe.Pointer(&b)))
}
// Append adds and cleans the supplied path string to the
// builder's internal buffer, growing the buffer if necessary
// to accomodate the extra path length.
func (b *Builder) Append(path string) {
if len(path) == 0 {
return
}
b.Guarantee(len(path) + 1)
b.append(path)
}
// Clean creates the shortest possible functional equivalent
// to the supplied path, resetting the builder before performing
// this operation. The builder object is NOT reset after return.
func (b *Builder) Clean(path string) string {
if path == "" {
return "."
}
b.Reset()
b.Guarantee(len(path) + 1)
b.append(path)
return string(b.B)
}
// Join connects and cleans multiple paths, resetting the builder before
// performing this operation and returning the shortest possible combination
// of all the supplied paths. The builder object is NOT reset after return.
func (b *Builder) Join(elems ...string) string {
var size int
for _, elem := range elems {
size += len(elem)
}
if size == 0 {
return ""
}
b.Reset()
b.Guarantee(size + 1)
for _, elem := range elems {
if elem == "" {
continue
}
b.append(elem)
}
return string(b.B)
}
// append performs the main logic of 'Append()' but without an empty path check or preallocation.
func (b *Builder) append(path string) {
if !b.set {
// Set if absolute or not
b.abs = path[0] == '/'
b.set = true
} else if !b.abs && len(b.B) == 1 && b.B[0] == '.' {
// Empty non-abs path segment, drop
// the period so not prefixed './'
b.B = b.B[:0]
}
for i := 0; i < len(path); {
switch {
// Empty path segment
case path[i] == '/':
i++
// Singular '.' path segment, treat as empty
case path[i] == '.' && (i+1 == len(path) || path[i+1] == '/'):
i++
// Backtrack segment
case path[i] == '.' && path[i+1] == '.' && (i+2 == len(path) || path[i+2] == '/'):
i += 2
switch {
// Check if it's possible to backtrack with
// our current state of the buffer. i.e. is
// our buffer length longer than the last
// '..' we placed?
case len(b.B) > b.dd:
b.backtrack()
// If we reached here, need to check if
// we can append '..' to the path buffer,
// which is ONLY when path is NOT absolute
case !b.abs:
if len(b.B) > 0 {
b.appendByte('/')
}
b.appendByte('.')
b.appendByte('.')
b.dd = len(b.B)
}
default:
if (b.abs && len(b.B) != 1) || (!b.abs && len(b.B) > 0) {
// Append path separator
b.appendByte('/')
}
// Append slice up to next '/'
i += b.appendSlice(path[i:])
}
}
if len(b.B) > 0 {
return
}
if b.abs {
// Empty absolute path => /
b.appendByte('/')
} else {
// Empty relative path => .
b.appendByte('.')
}
}
// Guarantee ensures there is at least the requested size
// free bytes available in the buffer, reallocating if necessary
func (b *Builder) Guarantee(size int) {
if size > cap(b.B)-len(b.B) {
nb := make([]byte, 2*cap(b.B)+size)
copy(nb, b.B)
b.B = nb[:len(b.B)]
}
}
// Truncate reduces the length of the buffer by the requested
// number of bytes. If the byte slice is *effectively* empty,
// i.e. absolute and "/" or relative and ".", it won't be truncated.
func (b *Builder) Truncate(size int) {
if len(b.B) == 0 {
return
}
if len(b.B) == 1 && ((b.abs && b.B[0] == '/') ||
(!b.abs && b.B[0] == '.')) {
// *effectively* empty
return
}
// Truncate requested bytes
b.B = b.B[:len(b.B)-size]
}
// appendByte appends the supplied byte to the end of
// the buffer. appending is achieved by continually reslicing the
// buffer and setting the next byte-at-index, this is safe as guarantee()
// will have been called beforehand
func (b *Builder) appendByte(c byte) {
b.B = b.B[:len(b.B)+1]
b.B[len(b.B)-1] = c
}
// appendSlice appends the supplied string slice to
// the end of the buffer and returns the number of indices
// we were able to iterate before hitting a path separator '/'.
// appending is achieved by continually reslicing the buffer
// and setting the next byte-at-index, this is safe as guarantee()
// will have been called beforehand
func (b *Builder) appendSlice(slice string) int {
i := 0
for i < len(slice) && slice[i] != '/' {
b.B = b.B[:len(b.B)+1]
b.B[len(b.B)-1] = slice[i]
i++
}
return i
}
// backtrack reduces the end of the buffer back to the last
// separating '/', or end of buffer
func (b *Builder) backtrack() {
b.B = b.B[:len(b.B)-1]
for len(b.B)-1 > b.dd && b.B[len(b.B)-1] != '/' {
b.B = b.B[:len(b.B)-1]
}
if len(b.B) > 0 {
b.B = b.B[:len(b.B)-1]
}
}