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Diffstat (limited to 'core/parse/dispenser.go')
-rw-r--r-- | core/parse/dispenser.go | 251 |
1 files changed, 0 insertions, 251 deletions
diff --git a/core/parse/dispenser.go b/core/parse/dispenser.go deleted file mode 100644 index 08aa6e76d..000000000 --- a/core/parse/dispenser.go +++ /dev/null @@ -1,251 +0,0 @@ -package parse - -import ( - "errors" - "fmt" - "io" - "strings" -) - -// Dispenser is a type that dispenses tokens, similarly to a lexer, -// except that it can do so with some notion of structure and has -// some really convenient methods. -type Dispenser struct { - filename string - tokens []token - cursor int - nesting int -} - -// NewDispenser returns a Dispenser, ready to use for parsing the given input. -func NewDispenser(filename string, input io.Reader) Dispenser { - return Dispenser{ - filename: filename, - tokens: allTokens(input), - cursor: -1, - } -} - -// NewDispenserTokens returns a Dispenser filled with the given tokens. -func NewDispenserTokens(filename string, tokens []token) Dispenser { - return Dispenser{ - filename: filename, - tokens: tokens, - cursor: -1, - } -} - -// Next loads the next token. Returns true if a token -// was loaded; false otherwise. If false, all tokens -// have been consumed. -func (d *Dispenser) Next() bool { - if d.cursor < len(d.tokens)-1 { - d.cursor++ - return true - } - return false -} - -// NextArg loads the next token if it is on the same -// line. Returns true if a token was loaded; false -// otherwise. If false, all tokens on the line have -// been consumed. It handles imported tokens correctly. -func (d *Dispenser) NextArg() bool { - if d.cursor < 0 { - d.cursor++ - return true - } - if d.cursor >= len(d.tokens) { - return false - } - if d.cursor < len(d.tokens)-1 && - d.tokens[d.cursor].file == d.tokens[d.cursor+1].file && - d.tokens[d.cursor].line+d.numLineBreaks(d.cursor) == d.tokens[d.cursor+1].line { - d.cursor++ - return true - } - return false -} - -// NextLine loads the next token only if it is not on the same -// line as the current token, and returns true if a token was -// loaded; false otherwise. If false, there is not another token -// or it is on the same line. It handles imported tokens correctly. -func (d *Dispenser) NextLine() bool { - if d.cursor < 0 { - d.cursor++ - return true - } - if d.cursor >= len(d.tokens) { - return false - } - if d.cursor < len(d.tokens)-1 && - (d.tokens[d.cursor].file != d.tokens[d.cursor+1].file || - d.tokens[d.cursor].line+d.numLineBreaks(d.cursor) < d.tokens[d.cursor+1].line) { - d.cursor++ - return true - } - return false -} - -// NextBlock can be used as the condition of a for loop -// to load the next token as long as it opens a block or -// is already in a block. It returns true if a token was -// loaded, or false when the block's closing curly brace -// was loaded and thus the block ended. Nested blocks are -// not supported. -func (d *Dispenser) NextBlock() bool { - if d.nesting > 0 { - d.Next() - if d.Val() == "}" { - d.nesting-- - return false - } - return true - } - if !d.NextArg() { // block must open on same line - return false - } - if d.Val() != "{" { - d.cursor-- // roll back if not opening brace - return false - } - d.Next() - if d.Val() == "}" { - // Open and then closed right away - return false - } - d.nesting++ - return true -} - -// IncrNest adds a level of nesting to the dispenser. -func (d *Dispenser) IncrNest() { - d.nesting++ - return -} - -// Val gets the text of the current token. If there is no token -// loaded, it returns empty string. -func (d *Dispenser) Val() string { - if d.cursor < 0 || d.cursor >= len(d.tokens) { - return "" - } - return d.tokens[d.cursor].text -} - -// Line gets the line number of the current token. If there is no token -// loaded, it returns 0. -func (d *Dispenser) Line() int { - if d.cursor < 0 || d.cursor >= len(d.tokens) { - return 0 - } - return d.tokens[d.cursor].line -} - -// File gets the filename of the current token. If there is no token loaded, -// it returns the filename originally given when parsing started. -func (d *Dispenser) File() string { - if d.cursor < 0 || d.cursor >= len(d.tokens) { - return d.filename - } - if tokenFilename := d.tokens[d.cursor].file; tokenFilename != "" { - return tokenFilename - } - return d.filename -} - -// Args is a convenience function that loads the next arguments -// (tokens on the same line) into an arbitrary number of strings -// pointed to in targets. If there are fewer tokens available -// than string pointers, the remaining strings will not be changed -// and false will be returned. If there were enough tokens available -// to fill the arguments, then true will be returned. -func (d *Dispenser) Args(targets ...*string) bool { - enough := true - for i := 0; i < len(targets); i++ { - if !d.NextArg() { - enough = false - break - } - *targets[i] = d.Val() - } - return enough -} - -// RemainingArgs loads any more arguments (tokens on the same line) -// into a slice and returns them. Open curly brace tokens also indicate -// the end of arguments, and the curly brace is not included in -// the return value nor is it loaded. -func (d *Dispenser) RemainingArgs() []string { - var args []string - - for d.NextArg() { - if d.Val() == "{" { - d.cursor-- - break - } - args = append(args, d.Val()) - } - - return args -} - -// ArgErr returns an argument error, meaning that another -// argument was expected but not found. In other words, -// a line break or open curly brace was encountered instead of -// an argument. -func (d *Dispenser) ArgErr() error { - if d.Val() == "{" { - return d.Err("Unexpected token '{', expecting argument") - } - return d.Errf("Wrong argument count or unexpected line ending after '%s'", d.Val()) -} - -// SyntaxErr creates a generic syntax error which explains what was -// found and what was expected. -func (d *Dispenser) SyntaxErr(expected string) error { - msg := fmt.Sprintf("%s:%d - Syntax error: Unexpected token '%s', expecting '%s'", d.File(), d.Line(), d.Val(), expected) - return errors.New(msg) -} - -// EOFErr returns an error indicating that the dispenser reached -// the end of the input when searching for the next token. -func (d *Dispenser) EOFErr() error { - return d.Errf("Unexpected EOF") -} - -// Err generates a custom parse error with a message of msg. -func (d *Dispenser) Err(msg string) error { - msg = fmt.Sprintf("%s:%d - Parse error: %s", d.File(), d.Line(), msg) - return errors.New(msg) -} - -// Errf is like Err, but for formatted error messages -func (d *Dispenser) Errf(format string, args ...interface{}) error { - return d.Err(fmt.Sprintf(format, args...)) -} - -// numLineBreaks counts how many line breaks are in the token -// value given by the token index tknIdx. It returns 0 if the -// token does not exist or there are no line breaks. -func (d *Dispenser) numLineBreaks(tknIdx int) int { - if tknIdx < 0 || tknIdx >= len(d.tokens) { - return 0 - } - return strings.Count(d.tokens[tknIdx].text, "\n") -} - -// isNewLine determines whether the current token is on a different -// line (higher line number) than the previous token. It handles imported -// tokens correctly. If there isn't a previous token, it returns true. -func (d *Dispenser) isNewLine() bool { - if d.cursor < 1 { - return true - } - if d.cursor > len(d.tokens)-1 { - return false - } - return d.tokens[d.cursor-1].file != d.tokens[d.cursor].file || - d.tokens[d.cursor-1].line+d.numLineBreaks(d.cursor-1) < d.tokens[d.cursor].line -} |