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file.go
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file.go
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// Package file encapsulates the file abstractions used by the ast & parser.
//
package file
import (
"fmt"
"strings"
)
// Idx is a compact encoding of a source position within a file set.
// It can be converted into a Position for a more convenient, but much
// larger, representation.
type Idx int
// Position describes an arbitrary source position
// including the filename, line, and column location.
type Position struct {
Filename string // The filename where the error occurred, if any
Offset int // The src offset
Line int // The line number, starting at 1
Column int // The column number, starting at 1 (The character count)
}
// A Position is valid if the line number is > 0.
func (self *Position) isValid() bool {
return self.Line > 0
}
// String returns a string in one of several forms:
//
// file:line:column A valid position with filename
// line:column A valid position without filename
// file An invalid position with filename
// - An invalid position without filename
//
func (self *Position) String() string {
str := self.Filename
if self.isValid() {
if str != "" {
str += ":"
}
str += fmt.Sprintf("%d:%d", self.Line, self.Column)
}
if str == "" {
str = "-"
}
return str
}
// FileSet
// A FileSet represents a set of source files.
type FileSet struct {
files []*_file
last *_file
}
// AddFile adds a new file with the given filename and src.
//
// This an internal method, but exported for cross-package use.
func (self *FileSet) AddFile(filename, src string) int {
base := self.nextBase()
file := &_file{
filename: filename,
src: src,
base: base,
}
self.files = append(self.files, file)
self.last = file
return base
}
func (self *FileSet) nextBase() int {
if self.last == nil {
return 1
}
return self.last.base + len(self.last.src) + 1
}
// Position converts an Idx in the FileSet into a Position.
func (self *FileSet) Position(idx Idx) *Position {
position := &Position{}
for _, file := range self.files {
if idx <= Idx(file.base+len(file.src)) {
offset := int(idx) - file.base
src := file.src[:offset]
position.Filename = file.filename
position.Offset = offset
position.Line = 1 + strings.Count(src, "\n")
if index := strings.LastIndex(src, "\n"); index >= 0 {
position.Column = offset - index
} else {
position.Column = 1 + len(src)
}
}
}
return position
}
type _file struct {
filename string
src string
base int // This will always be 1 or greater
}