--- /dev/null
+package scanner
+
+import (
+ "bytes"
+ "fmt"
+ "os"
+ "unicode"
+ "unicode/utf8"
+
+ "github.com/hashicorp/hcl/json/token"
+)
+
+// eof represents a marker rune for the end of the reader.
+const eof = rune(0)
+
+// Scanner defines a lexical scanner
+type Scanner struct {
+ buf *bytes.Buffer // Source buffer for advancing and scanning
+ src []byte // Source buffer for immutable access
+
+ // Source Position
+ srcPos token.Pos // current position
+ prevPos token.Pos // previous position, used for peek() method
+
+ lastCharLen int // length of last character in bytes
+ lastLineLen int // length of last line in characters (for correct column reporting)
+
+ tokStart int // token text start position
+ tokEnd int // token text end position
+
+ // Error is called for each error encountered. If no Error
+ // function is set, the error is reported to os.Stderr.
+ Error func(pos token.Pos, msg string)
+
+ // ErrorCount is incremented by one for each error encountered.
+ ErrorCount int
+
+ // tokPos is the start position of most recently scanned token; set by
+ // Scan. The Filename field is always left untouched by the Scanner. If
+ // an error is reported (via Error) and Position is invalid, the scanner is
+ // not inside a token.
+ tokPos token.Pos
+}
+
+// New creates and initializes a new instance of Scanner using src as
+// its source content.
+func New(src []byte) *Scanner {
+ // even though we accept a src, we read from a io.Reader compatible type
+ // (*bytes.Buffer). So in the future we might easily change it to streaming
+ // read.
+ b := bytes.NewBuffer(src)
+ s := &Scanner{
+ buf: b,
+ src: src,
+ }
+
+ // srcPosition always starts with 1
+ s.srcPos.Line = 1
+ return s
+}
+
+// next reads the next rune from the bufferred reader. Returns the rune(0) if
+// an error occurs (or io.EOF is returned).
+func (s *Scanner) next() rune {
+ ch, size, err := s.buf.ReadRune()
+ if err != nil {
+ // advance for error reporting
+ s.srcPos.Column++
+ s.srcPos.Offset += size
+ s.lastCharLen = size
+ return eof
+ }
+
+ if ch == utf8.RuneError && size == 1 {
+ s.srcPos.Column++
+ s.srcPos.Offset += size
+ s.lastCharLen = size
+ s.err("illegal UTF-8 encoding")
+ return ch
+ }
+
+ // remember last position
+ s.prevPos = s.srcPos
+
+ s.srcPos.Column++
+ s.lastCharLen = size
+ s.srcPos.Offset += size
+
+ if ch == '\n' {
+ s.srcPos.Line++
+ s.lastLineLen = s.srcPos.Column
+ s.srcPos.Column = 0
+ }
+
+ // debug
+ // fmt.Printf("ch: %q, offset:column: %d:%d\n", ch, s.srcPos.Offset, s.srcPos.Column)
+ return ch
+}
+
+// unread unreads the previous read Rune and updates the source position
+func (s *Scanner) unread() {
+ if err := s.buf.UnreadRune(); err != nil {
+ panic(err) // this is user fault, we should catch it
+ }
+ s.srcPos = s.prevPos // put back last position
+}
+
+// peek returns the next rune without advancing the reader.
+func (s *Scanner) peek() rune {
+ peek, _, err := s.buf.ReadRune()
+ if err != nil {
+ return eof
+ }
+
+ s.buf.UnreadRune()
+ return peek
+}
+
+// Scan scans the next token and returns the token.
+func (s *Scanner) Scan() token.Token {
+ ch := s.next()
+
+ // skip white space
+ for isWhitespace(ch) {
+ ch = s.next()
+ }
+
+ var tok token.Type
+
+ // token text markings
+ s.tokStart = s.srcPos.Offset - s.lastCharLen
+
+ // token position, initial next() is moving the offset by one(size of rune
+ // actually), though we are interested with the starting point
+ s.tokPos.Offset = s.srcPos.Offset - s.lastCharLen
+ if s.srcPos.Column > 0 {
+ // common case: last character was not a '\n'
+ s.tokPos.Line = s.srcPos.Line
+ s.tokPos.Column = s.srcPos.Column
+ } else {
+ // last character was a '\n'
+ // (we cannot be at the beginning of the source
+ // since we have called next() at least once)
+ s.tokPos.Line = s.srcPos.Line - 1
+ s.tokPos.Column = s.lastLineLen
+ }
+
+ switch {
+ case isLetter(ch):
+ lit := s.scanIdentifier()
+ if lit == "true" || lit == "false" {
+ tok = token.BOOL
+ } else if lit == "null" {
+ tok = token.NULL
+ } else {
+ s.err("illegal char")
+ }
+ case isDecimal(ch):
+ tok = s.scanNumber(ch)
+ default:
+ switch ch {
+ case eof:
+ tok = token.EOF
+ case '"':
+ tok = token.STRING
+ s.scanString()
+ case '.':
+ tok = token.PERIOD
+ ch = s.peek()
+ if isDecimal(ch) {
+ tok = token.FLOAT
+ ch = s.scanMantissa(ch)
+ ch = s.scanExponent(ch)
+ }
+ case '[':
+ tok = token.LBRACK
+ case ']':
+ tok = token.RBRACK
+ case '{':
+ tok = token.LBRACE
+ case '}':
+ tok = token.RBRACE
+ case ',':
+ tok = token.COMMA
+ case ':':
+ tok = token.COLON
+ case '-':
+ if isDecimal(s.peek()) {
+ ch := s.next()
+ tok = s.scanNumber(ch)
+ } else {
+ s.err("illegal char")
+ }
+ default:
+ s.err("illegal char: " + string(ch))
+ }
+ }
+
+ // finish token ending
+ s.tokEnd = s.srcPos.Offset
+
+ // create token literal
+ var tokenText string
+ if s.tokStart >= 0 {
+ tokenText = string(s.src[s.tokStart:s.tokEnd])
+ }
+ s.tokStart = s.tokEnd // ensure idempotency of tokenText() call
+
+ return token.Token{
+ Type: tok,
+ Pos: s.tokPos,
+ Text: tokenText,
+ }
+}
+
+// scanNumber scans a HCL number definition starting with the given rune
+func (s *Scanner) scanNumber(ch rune) token.Type {
+ zero := ch == '0'
+ pos := s.srcPos
+
+ s.scanMantissa(ch)
+ ch = s.next() // seek forward
+ if ch == 'e' || ch == 'E' {
+ ch = s.scanExponent(ch)
+ return token.FLOAT
+ }
+
+ if ch == '.' {
+ ch = s.scanFraction(ch)
+ if ch == 'e' || ch == 'E' {
+ ch = s.next()
+ ch = s.scanExponent(ch)
+ }
+ return token.FLOAT
+ }
+
+ if ch != eof {
+ s.unread()
+ }
+
+ // If we have a larger number and this is zero, error
+ if zero && pos != s.srcPos {
+ s.err("numbers cannot start with 0")
+ }
+
+ return token.NUMBER
+}
+
+// scanMantissa scans the mantissa beginning from the rune. It returns the next
+// non decimal rune. It's used to determine wheter it's a fraction or exponent.
+func (s *Scanner) scanMantissa(ch rune) rune {
+ scanned := false
+ for isDecimal(ch) {
+ ch = s.next()
+ scanned = true
+ }
+
+ if scanned && ch != eof {
+ s.unread()
+ }
+ return ch
+}
+
+// scanFraction scans the fraction after the '.' rune
+func (s *Scanner) scanFraction(ch rune) rune {
+ if ch == '.' {
+ ch = s.peek() // we peek just to see if we can move forward
+ ch = s.scanMantissa(ch)
+ }
+ return ch
+}
+
+// scanExponent scans the remaining parts of an exponent after the 'e' or 'E'
+// rune.
+func (s *Scanner) scanExponent(ch rune) rune {
+ if ch == 'e' || ch == 'E' {
+ ch = s.next()
+ if ch == '-' || ch == '+' {
+ ch = s.next()
+ }
+ ch = s.scanMantissa(ch)
+ }
+ return ch
+}
+
+// scanString scans a quoted string
+func (s *Scanner) scanString() {
+ braces := 0
+ for {
+ // '"' opening already consumed
+ // read character after quote
+ ch := s.next()
+
+ if ch == '\n' || ch < 0 || ch == eof {
+ s.err("literal not terminated")
+ return
+ }
+
+ if ch == '"' {
+ break
+ }
+
+ // If we're going into a ${} then we can ignore quotes for awhile
+ if braces == 0 && ch == '$' && s.peek() == '{' {
+ braces++
+ s.next()
+ } else if braces > 0 && ch == '{' {
+ braces++
+ }
+ if braces > 0 && ch == '}' {
+ braces--
+ }
+
+ if ch == '\\' {
+ s.scanEscape()
+ }
+ }
+
+ return
+}
+
+// scanEscape scans an escape sequence
+func (s *Scanner) scanEscape() rune {
+ // http://en.cppreference.com/w/cpp/language/escape
+ ch := s.next() // read character after '/'
+ switch ch {
+ case 'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', '"':
+ // nothing to do
+ case '0', '1', '2', '3', '4', '5', '6', '7':
+ // octal notation
+ ch = s.scanDigits(ch, 8, 3)
+ case 'x':
+ // hexademical notation
+ ch = s.scanDigits(s.next(), 16, 2)
+ case 'u':
+ // universal character name
+ ch = s.scanDigits(s.next(), 16, 4)
+ case 'U':
+ // universal character name
+ ch = s.scanDigits(s.next(), 16, 8)
+ default:
+ s.err("illegal char escape")
+ }
+ return ch
+}
+
+// scanDigits scans a rune with the given base for n times. For example an
+// octal notation \184 would yield in scanDigits(ch, 8, 3)
+func (s *Scanner) scanDigits(ch rune, base, n int) rune {
+ for n > 0 && digitVal(ch) < base {
+ ch = s.next()
+ n--
+ }
+ if n > 0 {
+ s.err("illegal char escape")
+ }
+
+ // we scanned all digits, put the last non digit char back
+ s.unread()
+ return ch
+}
+
+// scanIdentifier scans an identifier and returns the literal string
+func (s *Scanner) scanIdentifier() string {
+ offs := s.srcPos.Offset - s.lastCharLen
+ ch := s.next()
+ for isLetter(ch) || isDigit(ch) || ch == '-' {
+ ch = s.next()
+ }
+
+ if ch != eof {
+ s.unread() // we got identifier, put back latest char
+ }
+
+ return string(s.src[offs:s.srcPos.Offset])
+}
+
+// recentPosition returns the position of the character immediately after the
+// character or token returned by the last call to Scan.
+func (s *Scanner) recentPosition() (pos token.Pos) {
+ pos.Offset = s.srcPos.Offset - s.lastCharLen
+ switch {
+ case s.srcPos.Column > 0:
+ // common case: last character was not a '\n'
+ pos.Line = s.srcPos.Line
+ pos.Column = s.srcPos.Column
+ case s.lastLineLen > 0:
+ // last character was a '\n'
+ // (we cannot be at the beginning of the source
+ // since we have called next() at least once)
+ pos.Line = s.srcPos.Line - 1
+ pos.Column = s.lastLineLen
+ default:
+ // at the beginning of the source
+ pos.Line = 1
+ pos.Column = 1
+ }
+ return
+}
+
+// err prints the error of any scanning to s.Error function. If the function is
+// not defined, by default it prints them to os.Stderr
+func (s *Scanner) err(msg string) {
+ s.ErrorCount++
+ pos := s.recentPosition()
+
+ if s.Error != nil {
+ s.Error(pos, msg)
+ return
+ }
+
+ fmt.Fprintf(os.Stderr, "%s: %s\n", pos, msg)
+}
+
+// isHexadecimal returns true if the given rune is a letter
+func isLetter(ch rune) bool {
+ return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' || ch >= 0x80 && unicode.IsLetter(ch)
+}
+
+// isHexadecimal returns true if the given rune is a decimal digit
+func isDigit(ch rune) bool {
+ return '0' <= ch && ch <= '9' || ch >= 0x80 && unicode.IsDigit(ch)
+}
+
+// isHexadecimal returns true if the given rune is a decimal number
+func isDecimal(ch rune) bool {
+ return '0' <= ch && ch <= '9'
+}
+
+// isHexadecimal returns true if the given rune is an hexadecimal number
+func isHexadecimal(ch rune) bool {
+ return '0' <= ch && ch <= '9' || 'a' <= ch && ch <= 'f' || 'A' <= ch && ch <= 'F'
+}
+
+// isWhitespace returns true if the rune is a space, tab, newline or carriage return
+func isWhitespace(ch rune) bool {
+ return ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r'
+}
+
+// digitVal returns the integer value of a given octal,decimal or hexadecimal rune
+func digitVal(ch rune) int {
+ switch {
+ case '0' <= ch && ch <= '9':
+ return int(ch - '0')
+ case 'a' <= ch && ch <= 'f':
+ return int(ch - 'a' + 10)
+ case 'A' <= ch && ch <= 'F':
+ return int(ch - 'A' + 10)
+ }
+ return 16 // larger than any legal digit val
+}
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