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453 lines (422 loc) · 12.3 KB
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Copy pathvars.go
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453 lines (422 loc) · 12.3 KB
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package js
import (
"bytes"
"sort"
"github.com/tdewolff/parse/v2/js"
)
const identStartLen = 54
const identContinueLen = 64
type renamer struct {
identStart []byte
identContinue []byte
identOrder map[byte]int
reserved map[string]struct{}
rename bool
}
func newRenamer(rename, useCharFreq bool) *renamer {
reserved := make(map[string]struct{}, len(js.Keywords))
for name := range js.Keywords {
reserved[name] = struct{}{}
}
identStart := []byte("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$")
identContinue := []byte("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$0123456789")
if useCharFreq {
// sorted based on character frequency of a collection of JS samples
identStart = []byte("etnsoiarclduhmfpgvbjy_wOxCEkASMFTzDNLRPHIBV$WUKqYGXQZJ")
identContinue = []byte("etnsoiarcldu14023hm8f6pg57v9bjy_wOxCEkASMFTzDNLRPHIBV$WUKqYGXQZJ")
}
if len(identStart) != identStartLen || len(identContinue) != identContinueLen {
panic("bad identStart or identContinue lengths")
}
identOrder := map[byte]int{}
for i, c := range identStart {
identOrder[c] = i
}
return &renamer{
identStart: identStart,
identContinue: identContinue,
identOrder: identOrder,
reserved: reserved,
rename: rename,
}
}
func (r *renamer) renameScope(scope js.Scope) {
if !r.rename {
return
}
i := 0
// keep function argument declaration order to improve GZIP compression
sort.Sort(js.VarsByUses(scope.Declared[scope.NumFuncArgs:]))
for _, v := range scope.Declared {
v.Data = r.getName(v.Data, i)
i++
for r.isReserved(v.Data, scope.Undeclared) {
v.Data = r.getName(v.Data, i)
i++
}
}
}
func (r *renamer) isReserved(name []byte, undeclared js.VarArray) bool {
if 1 < len(name) { // there are no keywords or known globals that are one character long
if _, ok := r.reserved[string(name)]; ok {
return true
}
}
for _, v := range undeclared {
for v.Link != nil {
v = v.Link
}
if bytes.Equal(v.Data, name) {
return true
}
}
return false
}
func (r *renamer) getIndex(name []byte) int {
index := 0
NameLoop:
for i := len(name) - 1; 0 <= i; i-- {
chars := r.identContinue
if i == 0 {
chars = r.identStart
index *= identStartLen
} else {
index *= identContinueLen
}
for j, c := range chars {
if name[i] == c {
index += j
continue NameLoop
}
}
return -1
}
for n := 0; n < len(name)-1; n++ {
offset := identStartLen
for i := 0; i < n; i++ {
offset *= identContinueLen
}
index += offset
}
return index
}
func (r *renamer) getName(name []byte, index int) []byte {
// Generate new names for variables where the last character is (a-zA-Z$_) and others are (a-zA-Z).
// Thus we can have 54 one-character names and 52*54=2808 two-character names for every branch leaf.
// That is sufficient for virtually all input.
// one character
if index < identStartLen {
name[0] = r.identStart[index]
return name[:1]
}
index -= identStartLen
// two characters or more
n := 2
for {
offset := identStartLen
for i := 0; i < n-1; i++ {
offset *= identContinueLen
}
if index < offset {
break
}
index -= offset
n++
}
if cap(name) < n {
name = make([]byte, n)
} else {
name = name[:n]
}
name[0] = r.identStart[index%identStartLen]
index /= identStartLen
for i := 1; i < n; i++ {
name[i] = r.identContinue[index%identContinueLen]
index /= identContinueLen
}
return name
}
////////////////////////////////////////////////////////////////
func hasDefines(v *js.VarDecl) bool {
for _, item := range v.List {
if item.Default != nil {
return true
}
}
return false
}
func bindingVars(ibinding js.IBinding) (vs []*js.Var) {
switch binding := ibinding.(type) {
case *js.Var:
vs = append(vs, binding)
case *js.BindingArray:
for _, item := range binding.List {
if item.Binding != nil {
vs = append(vs, bindingVars(item.Binding)...)
}
}
if binding.Rest != nil {
vs = append(vs, bindingVars(binding.Rest)...)
}
case *js.BindingObject:
for _, item := range binding.List {
if item.Value.Binding != nil {
vs = append(vs, bindingVars(item.Value.Binding)...)
}
}
if binding.Rest != nil {
vs = append(vs, binding.Rest)
}
}
return
}
func addDefinition(decl *js.VarDecl, binding js.IBinding, value js.IExpr, forward bool) {
if decl.TokenType != js.ErrorToken {
// see if not already defined in variable declaration list
// if forward is set, binding=value comes before decl, otherwise the reverse holds true
vars := bindingVars(binding)
// remove variables in destination
RemoveVarsLoop:
for _, vbind := range vars {
for i, item := range decl.List {
if v, ok := item.Binding.(*js.Var); ok && item.Default == nil && v == vbind {
v.Uses--
decl.List = append(decl.List[:i], decl.List[i+1:]...)
continue RemoveVarsLoop
}
}
if value != nil {
// variable declaration must be somewhere else, find and remove it
for _, decl2 := range decl.Scope.Func.VarDecls {
if !decl2.InForInOf {
for i, item := range decl2.List {
if v, ok := item.Binding.(*js.Var); ok && item.Default == nil && v == vbind {
v.Uses--
decl2.List = append(decl2.List[:i], decl2.List[i+1:]...)
continue RemoveVarsLoop
}
}
}
}
}
}
}
// add declaration to destination
item := js.BindingElement{Binding: binding, Default: value}
if forward {
decl.List = append([]js.BindingElement{item}, decl.List...)
} else {
decl.List = append(decl.List, item)
}
}
func mergeVarDecls(dst, src *js.VarDecl, forward bool) {
// Merge var declarations by moving declarations from src to dst. If forward is set, src comes first and dst after, otherwise the order is reverse.
if forward {
// reverse order so we can iterate from beginning to end, sometimes addDefinition may remove another declaration in the src list
n := len(src.List) - 1
for j := 0; j < len(src.List)/2; j++ {
src.List[j], src.List[n-j] = src.List[n-j], src.List[j]
}
}
for j := 0; j < len(src.List); j++ {
addDefinition(dst, src.List[j].Binding, src.List[j].Default, forward)
}
src.List = src.List[:0]
}
func mergeVarDeclExprStmt(decl *js.VarDecl, exprStmt *js.ExprStmt, forward bool) bool {
// Merge var declarations with an assignment expression. If forward is set than expr comes first and decl after, otherwise the order is reverse.
if decl2, ok := exprStmt.Value.(*js.VarDecl); ok {
// this happens when a variable declarations is converted to an expression due to hoisting
mergeVarDecls(decl, decl2, forward)
return true
} else if commaExpr, ok := exprStmt.Value.(*js.CommaExpr); ok {
n := 0
for i := 0; i < len(commaExpr.List); i++ {
item := commaExpr.List[i]
if forward {
item = commaExpr.List[len(commaExpr.List)-i-1]
}
if src, ok := item.(*js.VarDecl); ok {
// this happens when a variable declarations is converted to an expression due to hoisting
mergeVarDecls(decl, src, forward)
n++
continue
} else if binaryExpr, ok := item.(*js.BinaryExpr); ok && binaryExpr.Op == js.EqToken {
if v, ok := binaryExpr.X.(*js.Var); ok && v.Decl == js.VariableDecl {
addDefinition(decl, v, binaryExpr.Y, forward)
n++
continue
}
}
break
}
merge := n == len(commaExpr.List)
if !forward {
commaExpr.List = commaExpr.List[n:]
} else {
commaExpr.List = commaExpr.List[:len(commaExpr.List)-n]
}
return merge
} else if binaryExpr, ok := exprStmt.Value.(*js.BinaryExpr); ok && binaryExpr.Op == js.EqToken {
if v, ok := binaryExpr.X.(*js.Var); ok && v.Decl == js.VariableDecl {
addDefinition(decl, v, binaryExpr.Y, forward)
return true
}
}
return false
}
func (m *jsMinifier) countHoistLength(ibinding js.IBinding) int {
if !m.o.KeepVarNames {
return len(bindingVars(ibinding)) * 2 // assume that var name will be of length one, +1 for the comma
}
n := 0
for _, v := range bindingVars(ibinding) {
n += len(v.Data) + 1 // +1 for the comma when added to other declaration
}
return n
}
func (m *jsMinifier) hoistVars(body *js.BlockStmt) {
// Hoist all variable declarations in the current module/function scope to the variable
// declaration that reduces file size the most. All other declarations are converted to
// expressions and their variable names are copied to the only remaining declaration.
// This is possible because an ArrayBindingPattern and ObjectBindingPattern can be converted to
// an ArrayLiteral or ObjectLiteral respectively, as they are supersets of the BindingPatterns.
if 1 < len(body.Scope.VarDecls) {
// Select which variable declarations will be hoisted (convert to expression) and which not
best := 0
scores := make([]int, len(body.Scope.VarDecls)) // savings if hoisting target
hoist := make([]bool, len(body.Scope.VarDecls))
for i, varDecl := range body.Scope.VarDecls {
hoist[i] = true
if varDecl.InForInOf {
continue
}
// variable names in for-in or for-of cannot be removed
n := 0 // total number of vars with decls
score := 3 // "var"
nArrays := 0 // of which lhs arrays
nObjects := 0 // of which lhs objects
hasDefinitions := false
for j, item := range varDecl.List {
if item.Default != nil {
// move arrays/objects to the front (saves a space)
if _, ok := item.Binding.(*js.BindingObject); ok {
if j != 0 && nArrays == 0 && nObjects == 0 {
varDecl.List[0], varDecl.List[j] = varDecl.List[j], varDecl.List[0]
}
nObjects++
} else if _, ok := item.Binding.(*js.BindingArray); ok {
if j != 0 && nArrays == 0 && nObjects == 0 {
varDecl.List[0], varDecl.List[j] = varDecl.List[j], varDecl.List[0]
}
nArrays++
}
score -= m.countHoistLength(item.Binding) // var names and commas
hasDefinitions = true
n++
}
}
if nArrays == 0 && nObjects == 0 {
score++ // required space after var
}
if !hasDefinitions && varDecl.InFor {
score-- // semicolon can be reused
}
if nObjects != 0 && !varDecl.InFor && nObjects == n {
// required parenthesis around braces to not confound it with a block statement
score -= 2
}
if score < scores[best] || body.Scope.VarDecls[best].InForInOf {
// select var decl that reduces the least when hoist target
best = i
}
if score < 0 {
// don't hoist if it increases the amount of characters
hoist[i] = false
}
scores[i] = score
}
if body.Scope.VarDecls[best].InForInOf {
// no savings possible
return
}
decl := body.Scope.VarDecls[best]
if 10000 < len(decl.List) {
return
}
hoist[best] = false
// get original declarations
orig := []*js.Var{}
for _, item := range decl.List {
orig = append(orig, bindingVars(item.Binding)...)
}
// hoist other variable declarations in this function scope but don't initialize yet
j := 0
for i, varDecl := range body.Scope.VarDecls {
if hoist[i] {
varDecl.TokenType = js.ErrorToken
for _, item := range varDecl.List {
refs := bindingVars(item.Binding)
bindingElements := make([]js.BindingElement, 0, len(refs))
DeclaredLoop:
for _, ref := range refs {
for _, v := range orig {
if ref == v {
continue DeclaredLoop
}
}
bindingElements = append(bindingElements, js.BindingElement{Binding: ref, Default: nil})
orig = append(orig, ref)
s := decl.Scope
for s != nil && s != s.Func {
s.AddUndeclared(ref)
s = s.Parent
}
if item.Default != nil {
ref.Uses++
}
}
if i < best {
// prepend
decl.List = append(decl.List[:j], append(bindingElements, decl.List[j:]...)...)
j += len(bindingElements)
} else {
// append
decl.List = append(decl.List, bindingElements...)
}
}
}
}
// rearrange to put array/object first
var prevRefs []*js.Var
BeginArrayObject:
for i, item := range decl.List {
refs := bindingVars(item.Binding)
if _, ok := item.Binding.(*js.Var); !ok {
if i != 0 {
interferes := false
if item.Default != nil {
InterferenceLoop:
for _, ref := range refs {
for _, v := range prevRefs {
if ref == v {
interferes = true
break InterferenceLoop
}
}
}
}
if !interferes {
decl.List[0], decl.List[i] = decl.List[i], decl.List[0]
break BeginArrayObject
}
} else {
break BeginArrayObject
}
}
if item.Default != nil {
prevRefs = append(prevRefs, refs...)
}
}
}
}