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arf/file/file.go

119 lines
3.2 KiB
Go

package file
import "os"
import "log"
import "bufio"
var logger = log.New(os.Stderr, "", 0)
// File represents a read only file that can print out formatted errors.
type File struct {
path string
file *os.File
reader *bufio.Reader
currentLine int
currentColumn int
lines [][]byte
}
// Open opens the file specified by path and returns a new File struct.
func Open (path string) (file *File, err error) {
file = &File {
path: path,
lines: [][]byte { []byte { } },
}
file.file, err = os.OpenFile(path, os.O_RDONLY, 0660)
if err != nil { return }
file.reader = bufio.NewReader(file.file)
return
}
// Stat returns the FileInfo structure describing file. If there is an error, it
// will be of type *PathError.
func (file *File) Stat () (fileInfo os.FileInfo, err error) {
return file.file.Stat()
}
// Read reads up to len(bytes) bytes from the File and stores them in bytes. It
// returns the number of bytes read and any error encountered. At end of file,
// Read returns 0, io.EOF. This method stores all data read into the file struct
// so it can be used later for error reporting.
func (file *File) Read (bytes []byte) (amountRead int, err error) {
amountRead, err = file.reader.Read(bytes)
// store the character in the file
for _, char := range bytes {
if char == '\n' {
file.lines = append(file.lines, []byte { })
file.currentLine ++
file.currentColumn = 0
} else {
file.lines[file.currentLine] = append (
file.lines[file.currentLine],
bytes...)
file.currentColumn ++
}
}
return
}
// Close closes the file. After the file is closed, data that has been read will
// still be retained, and errors can be reported.
func (file *File) Close () {
file.file.Close()
}
// mistake prints an informational message about a mistake that the user made.
func (file *File) mistake (column, row, width int, message, symbol string) {
logger.Print(symbol)
// print information about the location of the mistake
if width > 0 {
logger.Print(" ", row + 1, ":", column + 1)
}
logger.Println(" in", file.path)
if width > 0 {
// print erroneous line
logger.Println(file.lines[row])
// print an arrow with a tail spanning the width of the mistake
for column > 0 {
logger.Print(" ")
column --
}
for width > 1 {
logger.Print("-")
}
logger.Println("^")
}
logger.Println(message)
}
// Error prints an error at row and column spanning width amount of runes, and
// a message describing the error. If width is zero, neither the line nor the
// location information is printed.
func (file *File) Error (column, row, width int, message string) {
file.mistake(column, row, width, message, "ERR")
}
// Warn prints a warning at row and column spanning width amount of runes, and
// a message describing the error. If width is zero, neither the line nor the
// location information is printed.
func (file *File) Warn (column, row, width int, message string) {
file.mistake(column, row, width, message, "!!!")
}
// Location returns a location struct describing the current position inside of
// the file. This can be stored and used to print errors.
func (file *File) Location () (location Location) {
return Location {
file: file,
row: file.currentLine,
column: file.currentColumn,
}
}