perf(parser): scan the input as bytes instead of runes
Assisted-by: GLM 5.3
This commit is contained in:
@@ -42,6 +42,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
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and shared with the encoder, which now resolves duplicate field keys with
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it. Strict decoding of an array of tables of structs runs about a quarter
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faster; marshalling structs gained the same layout without measurable cost.
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- The parser scans the input bytes in place instead of building a `[]rune`
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copy of the document: every character that drives the grammar is ASCII and
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the input is validated UTF-8 up front, so the conversion pass and its four
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bytes per rune were pure overhead. Parsing a large array-of-tables document
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runs about a fifth faster and allocates about half the memory.
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### Fixed
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+3
-1
@@ -110,7 +110,9 @@ func ParseContext(ctx context.Context, data []byte) (map[string]any, error) {
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if !utf8.Valid(data) {
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return nil, &SyntaxError{Line: 1, Msg: "input is not valid UTF-8"}
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}
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p := &parser{src: []rune(string(data)), line: 1, ctx: ctx}
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// The parser scans data in place; it only reads the buffer, and every
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// string it stores in the tree is copied out of it.
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p := &parser{src: data, line: 1, ctx: ctx}
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return p.parse()
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}
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@@ -8,6 +8,7 @@ import (
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"fmt"
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"strconv"
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"strings"
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"unicode/utf8"
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)
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// ctxCheckInterval is the number of top-level parser iterations between
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@@ -16,8 +17,15 @@ import (
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const ctxCheckInterval = 64
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// parser is a recursive-descent TOML parser producing a map[string]any tree.
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//
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// The scanner works on bytes, not runes: the input is validated UTF-8 before
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// the parser runs, every character that drives the grammar (quotes,
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// separators, newlines, bare-key characters) is ASCII, and multi-byte runes
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// matter only as string content, where they are decoded on the spot. Holding
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// the source as []rune instead would cost a conversion pass plus four bytes
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// per rune of extra memory before parsing even starts.
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type parser struct {
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src []rune
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src []byte
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pos int
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line int
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ctx context.Context
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@@ -85,10 +93,10 @@ func (p *parser) checkCtx() error {
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func (p *parser) parseTableHeader() error {
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array := false
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p.next() // consume '['
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p.pos++ // consume '['
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if !p.eof() && p.peek() == '[' {
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array = true
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p.next()
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p.pos++
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}
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key, err := p.parseKeyPath()
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@@ -100,12 +108,12 @@ func (p *parser) parseTableHeader() error {
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if p.eof() || p.peek() != ']' {
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return p.errf("expected ']' to close table header")
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}
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p.next()
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p.pos++
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if array {
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if p.eof() || p.peek() != ']' {
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return p.errf("expected ']]' to close array-of-tables header")
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}
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p.next()
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p.pos++
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}
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if array {
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@@ -218,7 +226,7 @@ func (p *parser) parseKeyValue() error {
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if p.eof() || p.peek() != '=' {
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return p.errf("expected '=' after key")
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}
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p.next()
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p.pos++
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p.skipInline()
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val, err := p.parseValue()
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@@ -227,7 +235,10 @@ func (p *parser) parseKeyValue() error {
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}
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dest := p.current
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abs := append([]string{}, p.currentPath...)
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// One allocation covers the current section plus the dotted key; a
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// top-level statement reuses it for the leaf.
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abs := make([]string, 0, len(p.currentPath)+len(key))
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abs = append(abs, p.currentPath...)
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for _, k := range key[:len(key)-1] {
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abs = append(abs, k)
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if p.frozen[pathKey(abs)] {
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@@ -301,7 +312,7 @@ func (p *parser) parseKeyPath() ([]string, error) {
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parts = append(parts, part)
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p.skipInline()
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if !p.eof() && p.peek() == '.' {
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p.next()
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p.pos++
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continue
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}
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break
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@@ -313,7 +324,7 @@ func (p *parser) parseKeyComponent() (string, error) {
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if p.eof() {
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return "", p.errf("expected a key")
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}
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switch c := p.peek(); c {
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switch p.peek() {
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case '"':
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if p.lookahead(`"""`) {
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return "", p.errf("multiline strings are not allowed in keys")
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@@ -330,13 +341,14 @@ func (p *parser) parseKeyComponent() (string, error) {
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c := p.peek()
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if (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') ||
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(c >= '0' && c <= '9') || c == '_' || c == '-' {
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p.next()
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p.pos++
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continue
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}
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break
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}
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if p.pos == start {
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return "", p.errf("invalid key character %q", string(p.peek()))
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r, _ := utf8.DecodeRune(p.src[p.pos:])
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return "", p.errf("invalid key character %q", string(r))
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}
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return string(p.src[start:p.pos]), nil
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}
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@@ -385,7 +397,7 @@ func (p *parser) parseAtom() (any, error) {
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// A date may be followed by a space and a time, forming one date-time.
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if isDateToken(tok) && !p.eof() && p.peek() == ' ' {
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if next, ok := p.peekAt(1); ok && next >= '0' && next <= '9' {
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p.next() // consume the separating space
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p.pos++ // consume the separating space
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timeStart := p.pos
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p.scanBareToken()
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tok = tok + " " + string(p.src[timeStart:p.pos])
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@@ -410,7 +422,7 @@ func (p *parser) scanBareToken() {
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c == ',' || c == ']' || c == '}' || c == '#' {
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return
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}
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p.next()
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p.pos++
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}
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}
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@@ -420,31 +432,32 @@ func (p *parser) parseBasicString() (string, error) {
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if p.lookahead(`"""`) {
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return p.parseMultilineString('"', true)
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}
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p.next() // opening quote
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p.pos++ // opening quote
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var b strings.Builder
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for {
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if p.eof() {
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return "", p.errf("unterminated string")
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}
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c := p.next()
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c := p.peek()
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switch c {
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case '"':
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p.pos++
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return b.String(), nil
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case '\n':
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return "", p.errf("unterminated string")
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case '\r':
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return "", p.errf("bare carriage return is not allowed in a string")
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case '\\':
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p.pos++
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r, err := p.readEscape()
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if err != nil {
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return "", err
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}
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b.WriteRune(r)
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default:
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if isControlRune(c) {
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return "", p.errf("control character U+%04X is not allowed in a string", c)
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if err := p.writeContentRune(&b); err != nil {
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return "", err
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}
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b.WriteRune(c)
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}
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}
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}
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@@ -453,38 +466,58 @@ func (p *parser) parseLiteralString() (string, error) {
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if p.lookahead(`'''`) {
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return p.parseMultilineString('\'', false)
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}
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p.next() // opening quote
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p.pos++ // opening quote
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var b strings.Builder
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for {
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if p.eof() {
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return "", p.errf("unterminated literal string")
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}
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c := p.next()
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if c == '\'' {
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c := p.peek()
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switch c {
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case '\'':
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p.pos++
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return b.String(), nil
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}
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if c == '\n' {
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case '\n':
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return "", p.errf("unterminated literal string")
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}
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if c == '\r' {
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case '\r':
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return "", p.errf("bare carriage return is not allowed in a string")
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default:
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if err := p.writeContentRune(&b); err != nil {
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return "", err
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}
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}
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if isControlRune(c) {
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return "", p.errf("control character U+%04X is not allowed in a string", c)
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}
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b.WriteRune(c)
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}
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}
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func (p *parser) parseMultilineString(quote rune, escapes bool) (string, error) {
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// writeContentRune appends the rune at the cursor to b and advances past it.
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// An ASCII byte, which includes every control character the grammar forbids,
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// is checked and written directly; a multi-byte rune is decoded and can never
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// be a control character.
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func (p *parser) writeContentRune(b *strings.Builder) error {
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c := p.peek()
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if c < utf8.RuneSelf {
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if isControlRune(rune(c)) {
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return p.errf("control character U+%04X is not allowed in a string", c)
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}
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p.pos++
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b.WriteByte(c)
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return nil
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}
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r, size := utf8.DecodeRune(p.src[p.pos:])
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p.pos += size
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b.WriteRune(r)
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return nil
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}
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func (p *parser) parseMultilineString(quote byte, escapes bool) (string, error) {
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p.skipN(3) // opening delimiter
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// A newline immediately after the opening delimiter is trimmed.
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if !p.eof() && p.peek() == '\r' {
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p.next()
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p.pos++
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}
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if !p.eof() && p.peek() == '\n' {
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p.line++
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p.next()
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p.pos++
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}
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var b strings.Builder
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@@ -504,31 +537,32 @@ func (p *parser) parseMultilineString(quote rune, escapes bool) (string, error)
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return "", p.errf("too many '%c' before the closing delimiter", quote)
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}
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for range n - 3 {
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b.WriteRune(quote)
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b.WriteByte(quote)
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}
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p.skipN(n)
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return b.String(), nil
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}
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for range n {
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b.WriteRune(quote)
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p.next()
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b.WriteByte(quote)
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p.pos++
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}
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continue
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}
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c := p.next()
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if c == '\n' {
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c := p.peek()
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switch {
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case c == '\n':
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p.line++
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b.WriteRune(c)
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continue
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}
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if c == '\r' {
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if !p.eof() && p.peek() == '\n' {
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b.WriteRune(c)
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p.pos++
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b.WriteByte(c)
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case c == '\r':
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if p.pos+1 < len(p.src) && p.src[p.pos+1] == '\n' {
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b.WriteByte(c)
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p.pos++
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continue
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}
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return "", p.errf("bare carriage return is not allowed in a string")
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}
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if escapes && c == '\\' {
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case escapes && c == '\\':
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p.pos++
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// Line-ending backslash trims the following whitespace/newlines.
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if p.trimLineEndingBackslash() {
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continue
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@@ -538,12 +572,11 @@ func (p *parser) parseMultilineString(quote rune, escapes bool) (string, error)
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return "", err
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}
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b.WriteRune(r)
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continue
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default:
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if err := p.writeContentRune(&b); err != nil {
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return "", err
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}
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}
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if isControlRune(c) {
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return "", p.errf("control character U+%04X is not allowed in a string", c)
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}
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b.WriteRune(c)
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}
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}
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@@ -555,7 +588,7 @@ func (p *parser) trimLineEndingBackslash() bool {
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for !p.eof() {
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c := p.peek()
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if c == ' ' || c == '\t' || c == '\r' {
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p.next()
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p.pos++
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continue
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}
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if c == '\n' {
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@@ -574,11 +607,11 @@ func (p *parser) trimLineEndingBackslash() bool {
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c := p.peek()
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if c == '\n' {
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p.line++
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p.next()
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p.pos++
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continue
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}
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if c == ' ' || c == '\t' || c == '\r' {
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p.next()
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p.pos++
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continue
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}
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break
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@@ -617,7 +650,10 @@ func (p *parser) readEscape() (rune, error) {
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case 'U':
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return p.readUnicode(8)
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default:
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return 0, p.errf("invalid escape sequence \\%c", c)
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// The byte just consumed starts a rune: the backslash before it is a
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// boundary, and the input is valid UTF-8.
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r, _ := utf8.DecodeRune(p.src[p.pos-1:])
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return 0, p.errf("invalid escape sequence \\%c", r)
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}
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}
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@@ -640,7 +676,7 @@ func (p *parser) readUnicode(n int) (rune, error) {
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// --- arrays and inline tables ---------------------------------------------
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func (p *parser) parseArray() (any, error) {
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p.next() // '['
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p.pos++ // '['
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arr := []any{}
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for {
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if err := p.skipNestedSpace(); err != nil {
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@@ -650,7 +686,7 @@ func (p *parser) parseArray() (any, error) {
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return nil, p.errf("unterminated array")
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}
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if p.peek() == ']' {
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p.next()
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p.pos++
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return arr, nil
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}
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v, err := p.parseValue()
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@@ -666,9 +702,9 @@ func (p *parser) parseArray() (any, error) {
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}
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switch p.peek() {
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case ',':
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p.next()
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p.pos++
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case ']':
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p.next()
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p.pos++
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return arr, nil
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default:
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return nil, p.errf("expected ',' or ']' in array")
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@@ -677,7 +713,7 @@ func (p *parser) parseArray() (any, error) {
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}
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func (p *parser) parseInlineTable() (any, error) {
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p.next() // '{'
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p.pos++ // '{'
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tbl := map[string]any{}
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assigned := map[string]bool{}
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// TOML 1.1 lets an inline table span lines: interior whitespace includes
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@@ -687,7 +723,7 @@ func (p *parser) parseInlineTable() (any, error) {
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return nil, err
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}
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if !p.eof() && p.peek() == '}' {
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p.next()
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p.pos++
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return tbl, nil
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}
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for {
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@@ -702,7 +738,7 @@ func (p *parser) parseInlineTable() (any, error) {
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if p.eof() || p.peek() != '=' {
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return nil, p.errf("expected '=' in inline table")
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}
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p.next()
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p.pos++
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p.skipInline()
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val, err := p.parseValue()
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if err != nil {
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@@ -745,16 +781,16 @@ func (p *parser) parseInlineTable() (any, error) {
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}
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switch p.peek() {
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case ',':
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p.next()
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p.pos++
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if err := p.skipNestedSpace(); err != nil {
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return nil, err
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}
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if !p.eof() && p.peek() == '}' {
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p.next()
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p.pos++
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return tbl, nil
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}
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case '}':
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p.next()
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p.pos++
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return tbl, nil
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default:
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return nil, p.errf("expected ',' or '}' in inline table")
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@@ -765,12 +801,12 @@ func (p *parser) parseInlineTable() (any, error) {
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// --- scanning helpers ------------------------------------------------------
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func (p *parser) eof() bool { return p.pos >= len(p.src) }
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func (p *parser) peek() rune { return p.src[p.pos] }
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func (p *parser) peek() byte { return p.src[p.pos] }
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// peekAt returns the rune at offset n from the current position and whether the
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// peekAt returns the byte at offset n from the current position and whether the
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// offset is within the source. Use it instead of indexing p.src directly when
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// the offset may sit past the end.
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func (p *parser) peekAt(n int) (rune, bool) {
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func (p *parser) peekAt(n int) (byte, bool) {
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i := p.pos + n
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if i < 0 || i >= len(p.src) {
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return 0, false
|
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@@ -778,7 +814,7 @@ func (p *parser) peekAt(n int) (rune, bool) {
|
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return p.src[i], true
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}
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func (p *parser) next() rune {
|
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func (p *parser) next() byte {
|
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c := p.src[p.pos]
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p.pos++
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return c
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@@ -792,30 +828,23 @@ func (p *parser) skipN(n int) {
|
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|
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func (p *parser) match(word string) bool {
|
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if p.lookahead(word) {
|
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p.skipN(len([]rune(word)))
|
||||
p.skipN(len(word))
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return true
|
||||
}
|
||||
return false
|
||||
}
|
||||
|
||||
// lookahead reports whether s follows the cursor. Every lookahead argument in
|
||||
// the grammar is ASCII, so comparing bytes is exact.
|
||||
func (p *parser) lookahead(s string) bool {
|
||||
r := []rune(s)
|
||||
if p.pos+len(r) > len(p.src) {
|
||||
return false
|
||||
}
|
||||
for i, c := range r {
|
||||
if p.src[p.pos+i] != c {
|
||||
return false
|
||||
}
|
||||
}
|
||||
return true
|
||||
return p.pos+len(s) <= len(p.src) && string(p.src[p.pos:p.pos+len(s)]) == s
|
||||
}
|
||||
|
||||
// skipInline consumes spaces and tabs only.
|
||||
func (p *parser) skipInline() {
|
||||
for !p.eof() {
|
||||
if c := p.peek(); c == ' ' || c == '\t' {
|
||||
p.next()
|
||||
p.pos++
|
||||
continue
|
||||
}
|
||||
break
|
||||
@@ -828,14 +857,14 @@ func (p *parser) skipNestedSpace() error {
|
||||
for !p.eof() {
|
||||
switch p.peek() {
|
||||
case ' ', '\t':
|
||||
p.next()
|
||||
p.pos++
|
||||
case '\r':
|
||||
if err := p.expectCRLF(); err != nil {
|
||||
return err
|
||||
}
|
||||
case '\n':
|
||||
p.line++
|
||||
p.next()
|
||||
p.pos++
|
||||
case '#':
|
||||
if err := p.skipComment(); err != nil {
|
||||
return err
|
||||
@@ -852,14 +881,14 @@ func (p *parser) skipBlank() error {
|
||||
for !p.eof() {
|
||||
switch p.peek() {
|
||||
case ' ', '\t':
|
||||
p.next()
|
||||
p.pos++
|
||||
case '\r':
|
||||
if err := p.expectCRLF(); err != nil {
|
||||
return err
|
||||
}
|
||||
case '\n':
|
||||
p.line++
|
||||
p.next()
|
||||
p.pos++
|
||||
case '#':
|
||||
if err := p.skipComment(); err != nil {
|
||||
return err
|
||||
@@ -872,7 +901,7 @@ func (p *parser) skipBlank() error {
|
||||
}
|
||||
|
||||
func (p *parser) skipComment() error {
|
||||
p.next() // consume '#'
|
||||
p.pos++ // consume '#'
|
||||
for !p.eof() {
|
||||
c := p.peek()
|
||||
switch {
|
||||
@@ -884,11 +913,11 @@ func (p *parser) skipComment() error {
|
||||
}
|
||||
return p.errf("bare carriage return is not allowed")
|
||||
case c == '\t':
|
||||
p.next()
|
||||
p.pos++
|
||||
case c < 0x20 || c == 0x7f:
|
||||
return p.errf("control character U+%04X is not allowed in a comment", c)
|
||||
default:
|
||||
p.next()
|
||||
p.pos++
|
||||
}
|
||||
}
|
||||
return nil
|
||||
@@ -898,7 +927,7 @@ func (p *parser) skipComment() error {
|
||||
// line feed; a bare CR is invalid.
|
||||
func (p *parser) expectCRLF() error {
|
||||
if p.pos+1 < len(p.src) && p.src[p.pos+1] == '\n' {
|
||||
p.next() // consume CR; the LF is handled by the caller
|
||||
p.pos++ // consume CR; the LF is handled by the caller
|
||||
return nil
|
||||
}
|
||||
return p.errf("bare carriage return is not allowed")
|
||||
@@ -929,10 +958,11 @@ func (p *parser) expectLineEnd() error {
|
||||
}
|
||||
if p.peek() == '\n' {
|
||||
p.line++
|
||||
p.next()
|
||||
p.pos++
|
||||
return nil
|
||||
}
|
||||
return p.errf("unexpected %q after value", string(p.peek()))
|
||||
r, _ := utf8.DecodeRune(p.src[p.pos:])
|
||||
return p.errf("unexpected %q after value", string(r))
|
||||
}
|
||||
|
||||
func (p *parser) errf(format string, args ...any) error {
|
||||
|
||||
Reference in New Issue
Block a user