indexの作成・dumpを実装

src/constants.ts

@@ -4,3 +4,4 @@ export const CWD = process.cwd();
 
 export const GIT_DIR = join(process.cwd(), ".git");
 export const GIT_OBJECTS = join(GIT_DIR, "objects");
+export const GIT_INDEX = join(GIT_DIR, "index");

src/models/git-index.ts

@@ -1,33 +1,37 @@
-import { stat } from "node:fs/promises";
+import { createHash } from "node:crypto";
+import { stat, writeFile } from "node:fs/promises";
+
+import { GIT_INDEX } from "../constants.js";
 import { exists } from "../functions/exists.js";
 
 interface Entry {
   cTimeSec: number;
   cTimeNanoSec: number;
   mTimeSec: number;
   mTimeNanoSec: number;
-  device: number,
-  inode: number,
-  mode: number,
-  uId: number,
-  gId: number,
-  size: number,
-  hash: string,
-  flag: boolean,
-  length: number,
-  filePath: string,
+  device: number;
+  inode: number;
+  mode: number;
+  uId: number;
+  gId: number;
+  size: number;
+  hash: string;
+  flag: boolean;
+  length: number;
+  filePath: string;
 }
 
 export class GitIndex {
   private entries: Array<Entry>;
+  private readonly VERSION = 2;
 
   constructor(private readonly gitIndexPath: string) {
     this.entries = [];
   }
-  
+
   public initialize = async (): Promise<void> => {
-    await this.readEntries();
-  }
+    await this.parseEntries();
+  };
 
   public clearEntry = (): void => {
     this.entries = [];
@@ -54,27 +58,63 @@ export class GitIndex {
       filePath: filePath,
     };
 
-    this.entries.push(entry)
+    this.entries.push(entry);
+  };
+
+  public dumpIndex = async (): Promise<void> => {
+    const headerBuffer = this.createHeaderBuffer();
+    const entriesBuffer = this.createEntriesBuffer();
+    const checkSumBuffer = this.createCheckSumBuffer(entriesBuffer);
+
+    const indexBuffer = Buffer.concat([
+      Uint8Array.from(headerBuffer),
+      Uint8Array.from(entriesBuffer),
+      Uint8Array.from(checkSumBuffer),
+    ]);
+
+    await writeFile(GIT_INDEX, Uint8Array.from(indexBuffer));
+  };
+
+  private parseEntries = async (): Promise<void> => {
+    if (await exists(this.gitIndexPath)) return;
+
+    console.log(this.gitIndexPath);
+  };
+
+  private createCheckSumBuffer = (entriesBuffer: Buffer): Buffer => {
+    const hash = createHash("sha1")
+      .update(Uint8Array.from(entriesBuffer))
+      .digest("hex");
+    return Buffer.from(hash);
+  };
+
+  private createHeaderBuffer = (): Buffer => {
+    const headerBuffer = Buffer.alloc(12);
+    // https://www.w3schools.com/nodejs/met_buffer_write.asp
+    headerBuffer.write("DIRC", 0, 2);
+    headerBuffer.writeUInt32BE(2, 4);
+    headerBuffer.writeUInt32BE(this.entries.length, 8);
+    return headerBuffer;
   };
 
   private createEntriesBuffer = (): Buffer => {
     const buffers: Array<Buffer> = [];
-  
+
     for (const entry of this.entries) {
       const entryBuffer = this.createEntryBuffer(entry);
       buffers.push(entryBuffer);
     }
-  
+
     return Buffer.concat([Uint8Array.from(buffers)]);
-  }
-  
+  };
+
   private createEntryBuffer = (entry: Entry): Buffer => {
     let entryBufferLength = 64 + entry.length;
-    entryBufferLength += 8 - (entryBufferLength % 8); 
-  
+    entryBufferLength += 8 - (entryBufferLength % 8);
+
     const entryBuffer = Buffer.alloc(entryBufferLength);
     let offset = 0;
-  
+
     offset = this.writeUInt32BE(entryBuffer, entry.cTimeSec, offset);
     offset = this.writeUInt32BE(entryBuffer, entry.cTimeNanoSec, offset);
     offset = this.writeUInt32BE(entryBuffer, entry.mTimeSec, offset);
@@ -85,37 +125,28 @@ export class GitIndex {
     offset = this.writeUInt32BE(entryBuffer, entry.uId, offset);
     offset = this.writeUInt32BE(entryBuffer, entry.gId, offset);
     offset = this.writeUInt32BE(entryBuffer, entry.size, offset);
-  
+
     Buffer.from(entry.hash, "hex").copy(Uint8Array.from(entryBuffer), offset);
     offset += 20;
 
+    // 今回の実装範囲でflagの内容を読む・作成する必要はないと判断したため，全て0とする
+    // https://learn.microsoft.com/ja-jp/archive/msdn-magazine/2017/august/devops-git-internals-architecture-and-index-files#%E3%82%A4%E3%83%B3%E3%83%87%E3%83%83%E3%82%AF%E3%82%B9%E3%81%AE%E3%81%97%E3%81%8F%E3%81%BF
     offset += 2;
-  
+
     entryBuffer.writeUInt16BE(entry.length, offset);
     offset += 2;
-
-    Buffer.from(entry.filePath).copy(Uint8Array.from(entryBuffer), offset);
-
-    return entryBuffer;
-  }
-
-  private writeUInt32BE = (buffer: Buffer, value: number, offset: number): number => {
-    buffer.writeUInt32BE(value, offset);
-    return offset + 4;
-  }
-
-
-  public dumpIndex = (): void => {
 
-    const headerBuffer = '';
-    const entriesBuffer = this.createEntriesBuffer()
+    Buffer.from(entry.filePath).copy(Uint8Array.from(entryBuffer), offset);
 
-    console.log(this.entries);
+    return entryBuffer;
   };
 
-  private parseEntries = async (): Promise<void> => {
-    if (await exists(this.gitIndexPath)) return;
-
-    console.log(this.gitIndexPath);
+  private writeUInt32BE = (
+    buffer: Buffer,
+    value: number,
+    offset: number,
+  ): number => {
+    buffer.writeUInt32BE(value, offset);
+    return offset + 4;
   };
 }