front_end/third_party/source-map-scopes-codec/package/src/encode/encoder.ts - devtools/devtools-frontend - Git at Google

 // Copyright 2025 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import {
   EncodedTag,
   GeneratedRangeFlags,
   OriginalScopeFlags,
 } from "../codec.js";
 import type { GeneratedRange, OriginalScope, ScopeInfo } from "../scopes.ts";
 import { encodeSigned, encodeUnsigned } from "../vlq.js";
 import { comparePositions } from "../util.js";

 const DEFAULT_SCOPE_STATE = {
   line: 0,
   column: 0,
   name: 0,
   kind: 0,
   variable: 0,
 };

 const DEFAULT_RANGE_STATE = {
   line: 0,
   column: 0,
   defScopeIdx: 0,
 };

 export class Encoder {
   readonly #info: ScopeInfo;
   readonly #names: string[];

   // Hash map to resolve indices of strings in the "names" array. Otherwise we'd have
   // to use 'indexOf' for every name we want to encode.
   readonly #namesToIndex = new Map<string, number>();

   readonly #scopeState = { ...DEFAULT_SCOPE_STATE };
   readonly #rangeState = { ...DEFAULT_RANGE_STATE };
   #encodedItems: string[] = [];
   #currentItem: string = "";

   #scopeToCount = new Map<OriginalScope, number>();
   #scopeCounter = 0;

   constructor(info: ScopeInfo, names: string[]) {
     this.#info = info;
     this.#names = names;

     for (let i = 0; i < names.length; ++i) {
       this.#namesToIndex.set(names[i], i);
     }
   }

   encode(): string {
     this.#encodedItems = [];
     this.#info.scopes.forEach((scope) => {
       this.#scopeState.line = 0;
       this.#scopeState.column = 0;
       this.#encodeOriginalScope(scope);
     });
     this.#info.ranges.forEach((range) => {
       this.#encodeGeneratedRange(range);
     });

     return this.#encodedItems.join(",");
   }

   #encodeOriginalScope(scope: OriginalScope | null): void {
     if (scope === null) {
       this.#encodedItems.push(EncodedTag.EMPTY);
       return;
     }

     this.#encodeOriginalScopeStart(scope);
     this.#encodeOriginalScopeVariables(scope);
     scope.children.forEach((child) => this.#encodeOriginalScope(child));
     this.#encodeOriginalScopeEnd(scope);
   }

   #encodeOriginalScopeStart(scope: OriginalScope) {
     const { line, column } = scope.start;
     this.#verifyPositionWithScopeState(line, column);

     let flags = 0;
     const encodedLine = line - this.#scopeState.line;
     const encodedColumn = encodedLine === 0
       ? column - this.#scopeState.column
       : column;
     this.#scopeState.line = line;
     this.#scopeState.column = column;

     let encodedName: number | undefined;
     if (scope.name !== undefined) {
       flags |= OriginalScopeFlags.HAS_NAME;
       const nameIdx = this.#resolveNamesIdx(scope.name);
       encodedName = nameIdx - this.#scopeState.name;
       this.#scopeState.name = nameIdx;
     }

     let encodedKind: number | undefined;
     if (scope.kind !== undefined) {
       flags |= OriginalScopeFlags.HAS_KIND;
       const kindIdx = this.#resolveNamesIdx(scope.kind);
       encodedKind = kindIdx - this.#scopeState.kind;
       this.#scopeState.kind = kindIdx;
     }

     if (scope.isStackFrame) flags |= OriginalScopeFlags.IS_STACK_FRAME;

     this.#encodeTag(EncodedTag.ORIGINAL_SCOPE_START).#encodeUnsigned(flags)
       .#encodeUnsigned(encodedLine).#encodeUnsigned(encodedColumn);
     if (encodedName !== undefined) this.#encodeSigned(encodedName);
     if (encodedKind !== undefined) this.#encodeSigned(encodedKind);
     this.#finishItem();

     this.#scopeToCount.set(scope, this.#scopeCounter++);
   }

   #encodeOriginalScopeVariables(scope: OriginalScope) {
     if (scope.variables.length === 0) return;

     this.#encodeTag(EncodedTag.ORIGINAL_SCOPE_VARIABLES);

     for (const variable of scope.variables) {
       const idx = this.#resolveNamesIdx(variable);
       this.#encodeSigned(idx - this.#scopeState.variable);
       this.#scopeState.variable = idx;
     }

     this.#finishItem();
   }

   #encodeOriginalScopeEnd(scope: OriginalScope) {
     const { line, column } = scope.end;
     this.#verifyPositionWithScopeState(line, column);

     const encodedLine = line - this.#scopeState.line;
     const encodedColumn = encodedLine === 0
       ? column - this.#scopeState.column
       : column;

     this.#scopeState.line = line;
     this.#scopeState.column = column;

     this.#encodeTag(EncodedTag.ORIGINAL_SCOPE_END).#encodeUnsigned(encodedLine)
       .#encodeUnsigned(encodedColumn).#finishItem();
   }

   #encodeGeneratedRange(range: GeneratedRange): void {
     this.#encodeGeneratedRangeStart(range);
     this.#encodeGeneratedRangeBindings(range);
     this.#encodeGeneratedRangeSubRangeBindings(range);
     this.#encodeGeneratedRangeCallSite(range);
     range.children.forEach((child) => this.#encodeGeneratedRange(child));
     this.#encodeGeneratedRangeEnd(range);
   }

   #encodeGeneratedRangeStart(range: GeneratedRange) {
     const { line, column } = range.start;
     this.#verifyPositionWithRangeState(line, column);

     let flags = 0;
     const encodedLine = line - this.#rangeState.line;
     let encodedColumn = column - this.#rangeState.column;
     if (encodedLine > 0) {
       flags |= GeneratedRangeFlags.HAS_LINE;
       encodedColumn = column;
     }

     this.#rangeState.line = line;
     this.#rangeState.column = column;

     let encodedDefinition;
     if (range.originalScope) {
       const definitionIdx = this.#scopeToCount.get(range.originalScope);
       if (definitionIdx === undefined) {
         throw new Error("Unknown OriginalScope for definition!");
       }

       flags |= GeneratedRangeFlags.HAS_DEFINITION;

       encodedDefinition = definitionIdx - this.#rangeState.defScopeIdx;
       this.#rangeState.defScopeIdx = definitionIdx;
     }

     if (range.isStackFrame) flags |= GeneratedRangeFlags.IS_STACK_FRAME;
     if (range.isHidden) flags |= GeneratedRangeFlags.IS_HIDDEN;

     this.#encodeTag(EncodedTag.GENERATED_RANGE_START).#encodeUnsigned(flags);
     if (encodedLine > 0) this.#encodeUnsigned(encodedLine);
     this.#encodeUnsigned(encodedColumn);
     if (encodedDefinition !== undefined) this.#encodeSigned(encodedDefinition);
     this.#finishItem();
   }

   #encodeGeneratedRangeSubRangeBindings(range: GeneratedRange) {
     if (range.values.length === 0) return;

     for (let i = 0; i < range.values.length; ++i) {
       const value = range.values[i];
       if (!Array.isArray(value) || value.length <= 1) {
         continue;
       }

       this.#encodeTag(EncodedTag.GENERATED_RANGE_SUBRANGE_BINDING)
         .#encodeUnsigned(i);

       let lastLine = range.start.line;
       let lastColumn = range.start.column;
       for (let j = 1; j < value.length; ++j) {
         const subRange = value[j];
         const prevSubRange = value[j - 1];

         if (comparePositions(prevSubRange.to, subRange.from) !== 0) {
           throw new Error("Sub-range bindings must not have gaps");
         }

         const encodedLine = subRange.from.line - lastLine;
         const encodedColumn = encodedLine === 0
           ? subRange.from.column - lastColumn
           : subRange.from.column;
         if (encodedLine < 0 || encodedColumn < 0) {
           throw new Error("Sub-range bindings must be sorted");
         }

         lastLine = subRange.from.line;
         lastColumn = subRange.from.column;

         const binding = subRange.value === undefined
           ? 0
           : this.#resolveNamesIdx(subRange.value) + 1;
         this.#encodeUnsigned(binding).#encodeUnsigned(encodedLine)
           .#encodeUnsigned(encodedColumn);
       }
       this.#finishItem();
     }
   }

   #encodeGeneratedRangeBindings(range: GeneratedRange) {
     if (range.values.length === 0) return;

     if (!range.originalScope) {
       throw new Error("Range has binding expressions but no OriginalScope");
     } else if (range.originalScope.variables.length !== range.values.length) {
       throw new Error(
         "Range's binding expressions don't match OriginalScopes' variables",
       );
     }

     this.#encodeTag(EncodedTag.GENERATED_RANGE_BINDINGS);
     for (const val of range.values) {
       if (val === null || val === undefined) {
         this.#encodeUnsigned(0);
       } else if (typeof val === "string") {
         this.#encodeUnsigned(this.#resolveNamesIdx(val) + 1);
       } else {
         const initialValue = val[0];
         const binding = initialValue.value === undefined
           ? 0
           : this.#resolveNamesIdx(initialValue.value) + 1;
         this.#encodeUnsigned(binding);
       }
     }
     this.#finishItem();
   }

   #encodeGeneratedRangeCallSite(range: GeneratedRange) {
     if (!range.callSite) return;
     const { sourceIndex, line, column } = range.callSite;

     // TODO: Throw if stackFrame flag is set or OriginalScope index is invalid or no generated range is here.

     this.#encodeTag(EncodedTag.GENERATED_RANGE_CALL_SITE).#encodeUnsigned(
       sourceIndex,
     ).#encodeUnsigned(line).#encodeUnsigned(column).#finishItem();
   }

   #encodeGeneratedRangeEnd(range: GeneratedRange) {
     const { line, column } = range.end;
     this.#verifyPositionWithRangeState(line, column);

     let flags = 0;
     const encodedLine = line - this.#rangeState.line;
     let encodedColumn = column - this.#rangeState.column;
     if (encodedLine > 0) {
       flags |= GeneratedRangeFlags.HAS_LINE;
       encodedColumn = column;
     }

     this.#rangeState.line = line;
     this.#rangeState.column = column;

     this.#encodeTag(EncodedTag.GENERATED_RANGE_END);
     if (encodedLine > 0) this.#encodeUnsigned(encodedLine);
     this.#encodeUnsigned(encodedColumn).#finishItem();
   }

   #resolveNamesIdx(name: string): number {
     const index = this.#namesToIndex.get(name);
     if (index !== undefined) return index;

     const addedIndex = this.#names.length;
     this.#names.push(name);
     this.#namesToIndex.set(name, addedIndex);
     return addedIndex;
   }

   #verifyPositionWithScopeState(line: number, column: number) {
     if (
       this.#scopeState.line > line ||
       (this.#scopeState.line === line && this.#scopeState.column > column)
     ) {
       throw new Error(
         `Attempting to encode scope item (${line}, ${column}) that precedes the last encoded scope item (${this.#scopeState.line}, ${this.#scopeState.column})`,
       );
     }
   }

   #verifyPositionWithRangeState(line: number, column: number) {
     if (
       this.#rangeState.line > line ||
       (this.#rangeState.line === line && this.#rangeState.column > column)
     ) {
       throw new Error(
         `Attempting to encode range item that precedes the last encoded range item (${line}, ${column})`,
       );
     }
   }

   #encodeTag(tag: EncodedTag): this {
     this.#currentItem += tag;
     return this;
   }

   #encodeSigned(n: number): this {
     this.#currentItem += encodeSigned(n);
     return this;
   }

   #encodeUnsigned(n: number): this {
     this.#currentItem += encodeUnsigned(n);
     return this;
   }

   #finishItem(): void {
     this.#encodedItems.push(this.#currentItem);
     this.#currentItem = "";
   }
 }
	// Copyright 2025 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import {
	EncodedTag,
	GeneratedRangeFlags,
	OriginalScopeFlags,
	} from "../codec.js";
	import type { GeneratedRange, OriginalScope, ScopeInfo } from "../scopes.ts";
	import { encodeSigned, encodeUnsigned } from "../vlq.js";
	import { comparePositions } from "../util.js";

	const DEFAULT_SCOPE_STATE = {
	line: 0,
	column: 0,
	name: 0,
	kind: 0,
	variable: 0,
	};

	const DEFAULT_RANGE_STATE = {
	line: 0,
	column: 0,
	defScopeIdx: 0,
	};

	export class Encoder {
	readonly #info: ScopeInfo;
	readonly #names: string[];

	// Hash map to resolve indices of strings in the "names" array. Otherwise we'd have
	// to use 'indexOf' for every name we want to encode.
	readonly #namesToIndex = new Map<string, number>();

	readonly #scopeState = { ...DEFAULT_SCOPE_STATE };
	readonly #rangeState = { ...DEFAULT_RANGE_STATE };
	#encodedItems: string[] = [];
	#currentItem: string = "";

	#scopeToCount = new Map<OriginalScope, number>();
	#scopeCounter = 0;

	constructor(info: ScopeInfo, names: string[]) {
	this.#info = info;
	this.#names = names;

	for (let i = 0; i < names.length; ++i) {
	this.#namesToIndex.set(names[i], i);
	}
	}

	encode(): string {
	this.#encodedItems = [];
	this.#info.scopes.forEach((scope) => {
	this.#scopeState.line = 0;
	this.#scopeState.column = 0;
	this.#encodeOriginalScope(scope);
	});
	this.#info.ranges.forEach((range) => {
	this.#encodeGeneratedRange(range);
	});

	return this.#encodedItems.join(",");
	}

	#encodeOriginalScope(scope: OriginalScope \| null): void {
	if (scope === null) {
	this.#encodedItems.push(EncodedTag.EMPTY);
	return;
	}

	this.#encodeOriginalScopeStart(scope);
	this.#encodeOriginalScopeVariables(scope);
	scope.children.forEach((child) => this.#encodeOriginalScope(child));
	this.#encodeOriginalScopeEnd(scope);
	}

	#encodeOriginalScopeStart(scope: OriginalScope) {
	const { line, column } = scope.start;
	this.#verifyPositionWithScopeState(line, column);

	let flags = 0;
	const encodedLine = line - this.#scopeState.line;
	const encodedColumn = encodedLine === 0
	? column - this.#scopeState.column
	: column;
	this.#scopeState.line = line;
	this.#scopeState.column = column;

	let encodedName: number \| undefined;
	if (scope.name !== undefined) {
	flags \|= OriginalScopeFlags.HAS_NAME;
	const nameIdx = this.#resolveNamesIdx(scope.name);
	encodedName = nameIdx - this.#scopeState.name;
	this.#scopeState.name = nameIdx;
	}

	let encodedKind: number \| undefined;
	if (scope.kind !== undefined) {
	flags \|= OriginalScopeFlags.HAS_KIND;
	const kindIdx = this.#resolveNamesIdx(scope.kind);
	encodedKind = kindIdx - this.#scopeState.kind;
	this.#scopeState.kind = kindIdx;
	}

	if (scope.isStackFrame) flags \|= OriginalScopeFlags.IS_STACK_FRAME;

	this.#encodeTag(EncodedTag.ORIGINAL_SCOPE_START).#encodeUnsigned(flags)
	.#encodeUnsigned(encodedLine).#encodeUnsigned(encodedColumn);
	if (encodedName !== undefined) this.#encodeSigned(encodedName);
	if (encodedKind !== undefined) this.#encodeSigned(encodedKind);
	this.#finishItem();

	this.#scopeToCount.set(scope, this.#scopeCounter++);
	}

	#encodeOriginalScopeVariables(scope: OriginalScope) {
	if (scope.variables.length === 0) return;

	this.#encodeTag(EncodedTag.ORIGINAL_SCOPE_VARIABLES);

	for (const variable of scope.variables) {
	const idx = this.#resolveNamesIdx(variable);
	this.#encodeSigned(idx - this.#scopeState.variable);
	this.#scopeState.variable = idx;
	}

	this.#finishItem();
	}

	#encodeOriginalScopeEnd(scope: OriginalScope) {
	const { line, column } = scope.end;
	this.#verifyPositionWithScopeState(line, column);

	const encodedLine = line - this.#scopeState.line;
	const encodedColumn = encodedLine === 0
	? column - this.#scopeState.column
	: column;

	this.#scopeState.line = line;
	this.#scopeState.column = column;

	this.#encodeTag(EncodedTag.ORIGINAL_SCOPE_END).#encodeUnsigned(encodedLine)
	.#encodeUnsigned(encodedColumn).#finishItem();
	}

	#encodeGeneratedRange(range: GeneratedRange): void {
	this.#encodeGeneratedRangeStart(range);
	this.#encodeGeneratedRangeBindings(range);
	this.#encodeGeneratedRangeSubRangeBindings(range);
	this.#encodeGeneratedRangeCallSite(range);
	range.children.forEach((child) => this.#encodeGeneratedRange(child));
	this.#encodeGeneratedRangeEnd(range);
	}

	#encodeGeneratedRangeStart(range: GeneratedRange) {
	const { line, column } = range.start;
	this.#verifyPositionWithRangeState(line, column);

	let flags = 0;
	const encodedLine = line - this.#rangeState.line;
	let encodedColumn = column - this.#rangeState.column;
	if (encodedLine > 0) {
	flags \|= GeneratedRangeFlags.HAS_LINE;
	encodedColumn = column;
	}

	this.#rangeState.line = line;
	this.#rangeState.column = column;

	let encodedDefinition;
	if (range.originalScope) {
	const definitionIdx = this.#scopeToCount.get(range.originalScope);
	if (definitionIdx === undefined) {
	throw new Error("Unknown OriginalScope for definition!");
	}

	flags \|= GeneratedRangeFlags.HAS_DEFINITION;

	encodedDefinition = definitionIdx - this.#rangeState.defScopeIdx;
	this.#rangeState.defScopeIdx = definitionIdx;
	}

	if (range.isStackFrame) flags \|= GeneratedRangeFlags.IS_STACK_FRAME;
	if (range.isHidden) flags \|= GeneratedRangeFlags.IS_HIDDEN;

	this.#encodeTag(EncodedTag.GENERATED_RANGE_START).#encodeUnsigned(flags);
	if (encodedLine > 0) this.#encodeUnsigned(encodedLine);
	this.#encodeUnsigned(encodedColumn);
	if (encodedDefinition !== undefined) this.#encodeSigned(encodedDefinition);
	this.#finishItem();
	}

	#encodeGeneratedRangeSubRangeBindings(range: GeneratedRange) {
	if (range.values.length === 0) return;

	for (let i = 0; i < range.values.length; ++i) {
	const value = range.values[i];
	if (!Array.isArray(value) \|\| value.length <= 1) {
	continue;
	}

	this.#encodeTag(EncodedTag.GENERATED_RANGE_SUBRANGE_BINDING)
	.#encodeUnsigned(i);

	let lastLine = range.start.line;
	let lastColumn = range.start.column;
	for (let j = 1; j < value.length; ++j) {
	const subRange = value[j];
	const prevSubRange = value[j - 1];

	if (comparePositions(prevSubRange.to, subRange.from) !== 0) {
	throw new Error("Sub-range bindings must not have gaps");
	}

	const encodedLine = subRange.from.line - lastLine;
	const encodedColumn = encodedLine === 0
	? subRange.from.column - lastColumn
	: subRange.from.column;
	if (encodedLine < 0 \|\| encodedColumn < 0) {
	throw new Error("Sub-range bindings must be sorted");
	}

	lastLine = subRange.from.line;
	lastColumn = subRange.from.column;

	const binding = subRange.value === undefined
	? 0
	: this.#resolveNamesIdx(subRange.value) + 1;
	this.#encodeUnsigned(binding).#encodeUnsigned(encodedLine)
	.#encodeUnsigned(encodedColumn);
	}
	this.#finishItem();
	}
	}

	#encodeGeneratedRangeBindings(range: GeneratedRange) {
	if (range.values.length === 0) return;

	if (!range.originalScope) {
	throw new Error("Range has binding expressions but no OriginalScope");
	} else if (range.originalScope.variables.length !== range.values.length) {
	throw new Error(
	"Range's binding expressions don't match OriginalScopes' variables",
	);
	}

	this.#encodeTag(EncodedTag.GENERATED_RANGE_BINDINGS);
	for (const val of range.values) {
	if (val === null \|\| val === undefined) {
	this.#encodeUnsigned(0);
	} else if (typeof val === "string") {
	this.#encodeUnsigned(this.#resolveNamesIdx(val) + 1);
	} else {
	const initialValue = val[0];
	const binding = initialValue.value === undefined
	? 0
	: this.#resolveNamesIdx(initialValue.value) + 1;
	this.#encodeUnsigned(binding);
	}
	}
	this.#finishItem();
	}

	#encodeGeneratedRangeCallSite(range: GeneratedRange) {
	if (!range.callSite) return;
	const { sourceIndex, line, column } = range.callSite;

	// TODO: Throw if stackFrame flag is set or OriginalScope index is invalid or no generated range is here.

	this.#encodeTag(EncodedTag.GENERATED_RANGE_CALL_SITE).#encodeUnsigned(
	sourceIndex,
	).#encodeUnsigned(line).#encodeUnsigned(column).#finishItem();
	}

	#encodeGeneratedRangeEnd(range: GeneratedRange) {
	const { line, column } = range.end;
	this.#verifyPositionWithRangeState(line, column);

	let flags = 0;
	const encodedLine = line - this.#rangeState.line;
	let encodedColumn = column - this.#rangeState.column;
	if (encodedLine > 0) {
	flags \|= GeneratedRangeFlags.HAS_LINE;
	encodedColumn = column;
	}

	this.#rangeState.line = line;
	this.#rangeState.column = column;

	this.#encodeTag(EncodedTag.GENERATED_RANGE_END);
	if (encodedLine > 0) this.#encodeUnsigned(encodedLine);
	this.#encodeUnsigned(encodedColumn).#finishItem();
	}

	#resolveNamesIdx(name: string): number {
	const index = this.#namesToIndex.get(name);
	if (index !== undefined) return index;

	const addedIndex = this.#names.length;
	this.#names.push(name);
	this.#namesToIndex.set(name, addedIndex);
	return addedIndex;
	}

	#verifyPositionWithScopeState(line: number, column: number) {
	if (
	this.#scopeState.line > line \|\|
	(this.#scopeState.line === line && this.#scopeState.column > column)
	) {
	throw new Error(
	`Attempting to encode scope item (${line}, ${column}) that precedes the last encoded scope item (${this.#scopeState.line}, ${this.#scopeState.column})`,
	);
	}
	}

	#verifyPositionWithRangeState(line: number, column: number) {
	if (
	this.#rangeState.line > line \|\|
	(this.#rangeState.line === line && this.#rangeState.column > column)
	) {
	throw new Error(
	`Attempting to encode range item that precedes the last encoded range item (${line}, ${column})`,
	);
	}
	}

	#encodeTag(tag: EncodedTag): this {
	this.#currentItem += tag;
	return this;
	}

	#encodeSigned(n: number): this {
	this.#currentItem += encodeSigned(n);
	return this;
	}

	#encodeUnsigned(n: number): this {
	this.#currentItem += encodeUnsigned(n);
	return this;
	}

	#finishItem(): void {
	this.#encodedItems.push(this.#currentItem);
	this.#currentItem = "";
	}
	}