gtsocial-umbx

path.go (7418B)

---

 package fastpath
 
 import (
 	"unsafe"
 )
 
 // allocate these just once
 var (
 	dot    = []byte(dotStr)
 	dotStr = "."
 )
 
 type Builder struct {
 	B   []byte // B is the underlying byte buffer
 	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()
 }
 
 // NewBuilder returns a new Builder object using the
 // supplied byte slice as the underlying buffer
 func NewBuilder(b []byte) Builder {
 	if b != nil {
 		b = b[:0]
 	}
 	return Builder{
 		B:  b,
 		dd: 0,
 
 		abs: false,
 		set: false,
 	}
 }
 
 // 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 {
 	if len(b.B) < 1 {
 		return dot
 	}
 	return b.B
 }
 
 // String returns the accumulated path string.
 func (b *Builder) String() string {
 	if len(b.B) < 1 {
 		return dotStr
 	}
 	return string(b.B)
 }
 
 // StringPtr returns a ptr to the accumulated path string.
 //
 // Please note the underlying byte slice for this string is
 // tied to the builder, so any changes will result in the
 // returned string changing. Consider using .String() if
 // this is undesired behaviour.
 func (b *Builder) StringPtr() string {
 	if len(b.B) < 1 {
 		return dotStr
 	}
 	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 / from absolute
 func (b *Builder) SetAbsolute(val bool) {
 	if !b.set {
 		if val {
 			// .Append() has not been
 			// called, add a '/' and set abs
 			b.Guarantee(1)
 			b.appendByte('/')
 			b.abs = true
 		}
 
 		// Set as having been set
 		b.set = true
 		return
 	}
 
 	if !val && b.abs {
 		// Already set and absolute. Update
 		b.abs = false
 
 		// If not empty (i.e. not just '/'),
 		// then shift bytes 1 left
 		if len(b.B) > 1 {
 			copy(b.B, b.B[1:])
 		}
 
 		// Truncate 1 byte. In the case of empty,
 		// i.e. just '/' then it will drop this
 		b.truncate(1)
 	} else if val && !b.abs {
 		// Already set but NOT abs. Update
 		b.abs = true
 
 		// Guarantee 1 byte available
 		b.Guarantee(1)
 
 		// If empty, just append '/'
 		if len(b.B) < 1 {
 			b.appendByte('/')
 			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] = '/'
 	}
 }
 
 // Append 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) Append(p []byte) {
 	b.AppendString(*(*string)(unsafe.Pointer(&p)))
 }
 
 // AppendString 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) AppendString(path string) {
 	defer func() {
 		// If buffer is empty, and an absolute
 		// path, ensure it starts with a '/'
 		if len(b.B) < 1 && b.abs {
 			b.appendByte('/')
 		}
 	}()
 
 	// Empty path, nothing to do
 	if len(path) == 0 {
 		return
 	}
 
 	// Guarantee at least the total length
 	// of supplied path available in the buffer
 	b.Guarantee(len(path))
 
 	// Try store if absolute
 	if !b.set {
 		b.abs = len(path) > 0 && path[0] == '/'
 		b.set = true
 	}
 
 	i := 0
 	for 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()
 				// b.cp = b.lp
 				// b.lp = 0
 
 			// 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)
 				// b.lp = lp - 2
 				// b.cp = b.dd
 			}
 
 		default:
 			if (b.abs && len(b.B) != 1) || (!b.abs && len(b.B) > 0) {
 				b.appendByte('/')
 			}
 			// b.lp = b.cp
 			// b.cp = len(b.B)
 			i += b.appendSlice(path[i:])
 		}
 	}
 }
 
 // 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 {
 	b.Reset()
 	b.AppendString(path)
 	return b.String()
 }
 
 // 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(base string, paths ...string) string {
 	b.Reset()
 	b.AppendString(base)
 	size := len(base)
 	for i := 0; i < len(paths); i++ {
 		b.AppendString(paths[i])
 		size += len(paths[i])
 	}
 	if size < 1 {
 		return ""
 	} else if len(b.B) < 1 {
 		return dotStr
 	}
 	return string(b.B)
 }
 
 // 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 builder is set to absolute, the first
 // byte (i.e. '/') will never be truncated
 func (b *Builder) Truncate(size int) {
 	// If absolute and just '/', do nothing
 	if b.abs && len(b.B) == 1 {
 		return
 	}
 
 	// Truncate requested bytes
 	b.truncate(size)
 }
 
 // truncate reduces the length of the buffer by the requested
 // size, no sanity checks are performed
 func (b *Builder) truncate(size int) {
 	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]
 	}
 }