More efficient file reads (#73)

Allows the client to handle line offsets, rather than loading the entire
file and then slicing it on the agent side.

Signed-off-by: Ben Brandt <benjamin.j.brandt@gmail.com>

Signed-off-by: Ben Brandt <benjamin.j.brandt@gmail.com>

Author: benbrandt

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## v0.4.7
+
+- More efficient file reads from the client.
+
 ## v0.4.6
 
 - Update to @anthropic-ai/claude-code@v1.0.128

package-lock.json

@@ -6,7 +6,7 @@
   "bin": {
     "claude-code-acp": "./dist/index.js"
   },
-  "version": "0.4.6",
+  "version": "0.4.7",
   "description": "An ACP-compatible coding agent powered by the Claude Code SDK (TypeScript)",
   "main": "dist/index.js",
   "type": "module",

package.json

@@ -102,15 +102,12 @@ In sessions with ${toolNames.read} always use it instead of Read as it contains
           const content = await agent.readTextFile({
             sessionId,
             path: input.abs_path,
+            line: input.offset + 1,
+            limit: input.linesToRead,
           });
 
           // Extract lines with byte limit enforcement
-          const result = extractLinesWithByteLimit(
-            content.content,
-            input.offset ?? 0,
-            input.linesToRead,
-            defaults.maxFileSize,
-          );
+          const result = extractLinesWithByteLimit(content.content, defaults.maxFileSize);
 
           // Construct informative message about what was read
           let readInfo = "";
@@ -120,11 +117,11 @@ In sessions with ${toolNames.read} always use it instead of Read as it contains
             if (result.wasLimited) {
               readInfo += `Read ${result.linesRead} lines (hit 50KB limit). `;
             } else {
-              readInfo += `Read lines ${(input.offset ?? 0) + 1}-${result.actualEndLine}. `;
+              readInfo += `Read lines ${(input.offset ?? 0) + 1}-${result.linesRead}. `;
             }
 
             if (result.wasLimited) {
-              readInfo += `Continue with offset=${result.actualEndLine}.`;
+              readInfo += `Continue with offset=${result.linesRead}.`;
             }
 
             readInfo += "</file-read-info>";

src/mcp-server.ts

@@ -5,66 +5,44 @@ describe("extractLinesWithByteLimit", () => {
   const simpleContent = "Line 1\nLine 2\nLine 3\nLine 4\nLine 5";
 
   it("should extract all lines when under byte limit", () => {
-    const result = extractLinesWithByteLimit(simpleContent, 0, 5, 1000);
+    const result = extractLinesWithByteLimit(simpleContent, 1000);
 
     expect(result.content).toBe(simpleContent);
-    expect(result.actualEndLine).toBe(4);
     expect(result.wasLimited).toBe(false);
     expect(result.linesRead).toBe(5);
   });
 
-  it("should extract partial lines with offset", () => {
-    const result = extractLinesWithByteLimit(simpleContent, 2, 2, 1000);
-
-    expect(result.content).toBe("Line 3\nLine 4");
-    expect(result.actualEndLine).toBe(3);
-    expect(result.wasLimited).toBe(false);
-    expect(result.linesRead).toBe(2);
-  });
-
   it("should limit output when exceeding byte limit", () => {
     // Create content that will exceed byte limit
     const longLine = "x".repeat(100);
     const manyLines = Array(10).fill(longLine).join("\n");
 
-    const result = extractLinesWithByteLimit(manyLines, 0, 10, 250);
+    const result = extractLinesWithByteLimit(manyLines, 250);
 
     expect(result.wasLimited).toBe(true);
-    expect(result.actualEndLine).toBe(1); // Should only get 2 lines
     expect(result.linesRead).toBe(2);
   });
 
-  it("should handle offset beyond file length", () => {
-    const result = extractLinesWithByteLimit(simpleContent, 10, 5, 1000);
-
-    expect(result.content).toBe("");
-    expect(result.actualEndLine).toBe(10);
-    expect(result.wasLimited).toBe(false);
-    expect(result.linesRead).toBe(0);
-  });
-
   it("should handle empty content", () => {
-    const result = extractLinesWithByteLimit("", 0, 10, 1000);
+    const result = extractLinesWithByteLimit("", 1000);
 
     expect(result.content).toBe("");
-    expect(result.actualEndLine).toBe(0); // Empty string splits to [""] and we process that one empty line
     expect(result.wasLimited).toBe(false);
     expect(result.linesRead).toBe(1); // We read the one empty line
   });
 
   it("should handle single line file", () => {
     const singleLine = "This is a single line without newline";
-    const result = extractLinesWithByteLimit(singleLine, 0, 10, 1000);
+    const result = extractLinesWithByteLimit(singleLine, 1000);
 
     expect(result.content).toBe(singleLine);
-    expect(result.actualEndLine).toBe(0);
     expect(result.wasLimited).toBe(false);
     expect(result.linesRead).toBe(1);
   });
 
   it("should correctly count bytes with multi-byte characters", () => {
     const unicodeContent = "Hello 世界\n你好 World\nEmoji: 🌍\nNormal line";
-    const result = extractLinesWithByteLimit(unicodeContent, 0, 10, 1000);
+    const result = extractLinesWithByteLimit(unicodeContent, 1000);
 
     expect(result.content).toBe(unicodeContent);
     expect(result.linesRead).toBe(4);
@@ -77,63 +55,25 @@ describe("extractLinesWithByteLimit", () => {
     const line3 = "c".repeat(40);
     const content = `${line1}\n${line2}\n${line3}`;
 
-    const result = extractLinesWithByteLimit(content, 0, 3, 85);
+    const result = extractLinesWithByteLimit(content, 85);
 
-    expect(result.content).toBe(`${line1}\n${line2}`);
-    expect(result.actualEndLine).toBe(1);
+    expect(result.content).toBe(`${line1}\n${line2}\n`);
     expect(result.wasLimited).toBe(true);
     expect(result.linesRead).toBe(2);
   });
 
   it("should read exactly to limit when possible", () => {
     const exactContent = "12345\n67890\n12345"; // 17 bytes total
-    const result = extractLinesWithByteLimit(exactContent, 0, 3, 17);
+    const result = extractLinesWithByteLimit(exactContent, 17);
 
     expect(result.content).toBe(exactContent);
-    expect(result.actualEndLine).toBe(2);
     expect(result.wasLimited).toBe(false);
     expect(result.linesRead).toBe(3);
   });
 
-  it("should handle reading from middle to end", () => {
-    const result = extractLinesWithByteLimit(simpleContent, 3, 100, 1000);
-
-    expect(result.content).toBe("Line 4\nLine 5");
-    expect(result.actualEndLine).toBe(4);
-    expect(result.wasLimited).toBe(false);
-    expect(result.linesRead).toBe(2);
-  });
-
-  it("should handle large content with typical parameters", () => {
-    const longContent = Array(2000).fill("Line content here").join("\n");
-    const result = extractLinesWithByteLimit(longContent, 0, 1000, 50000);
-
-    expect(result.actualEndLine).toBeLessThanOrEqual(1000); // Should be limited by line count
-  });
-
-  it("should provide correct data for partial read at start", () => {
-    const result = extractLinesWithByteLimit(simpleContent, 0, 2, 1000);
-
-    expect(result.actualEndLine).toBe(1);
-    expect(result.linesRead).toBe(2);
-  });
-
-  it("should provide correct data for partial read with offset", () => {
-    const result = extractLinesWithByteLimit(simpleContent, 1, 2, 1000);
-
-    expect(result.actualEndLine).toBe(2);
-    expect(result.linesRead).toBe(2);
-  });
-
-  it("should not add newline after last line", () => {
-    const result = extractLinesWithByteLimit("Line 1\nLine 2\nLine 3", 2, 1, 1000);
-
-    expect(result.content).toBe("Line 3"); // No trailing newline
-  });
-
   it("should handle Windows-style line endings", () => {
     const windowsContent = "Line 1\r\nLine 2\r\nLine 3";
-    const result = extractLinesWithByteLimit(windowsContent, 0, 3, 1000);
+    const result = extractLinesWithByteLimit(windowsContent, 1000);
 
     // Note: split("\n") will keep the \r characters
     expect(result.content).toBe("Line 1\r\nLine 2\r\nLine 3");
@@ -145,29 +85,18 @@ describe("extractLinesWithByteLimit", () => {
     const largeLine = "x".repeat(1000);
     const largeContent = Array(110).fill(largeLine).join("\n");
 
-    const result = extractLinesWithByteLimit(largeContent, 0, 200, 50000);
+    const result = extractLinesWithByteLimit(largeContent, 50000);
 
     expect(result.wasLimited).toBe(true);
-    expect(result.actualEndLine).toBeLessThan(50); // Should stop well before 200 lines
-  });
-
-  it("should handle line limit of 0", () => {
-    const result = extractLinesWithByteLimit(simpleContent, 0, 0, 1000);
-
-    expect(result.content).toBe("");
-    expect(result.actualEndLine).toBe(0);
-    expect(result.linesRead).toBe(0);
-    expect(result.wasLimited).toBe(false);
   });
 
   it("should allow at least one line even if it exceeds byte limit", () => {
     const veryLongLine = "x".repeat(100000); // 100KB line
-    const result = extractLinesWithByteLimit(veryLongLine, 0, 1, 50000);
+    const result = extractLinesWithByteLimit(veryLongLine, 50000);
 
     // Should return the line even though it exceeds the byte limit
     // because we always allow at least one line if no lines have been added yet
     expect(result.content).toBe(veryLongLine);
-    expect(result.actualEndLine).toBe(0);
     expect(result.linesRead).toBe(1);
     expect(result.wasLimited).toBe(false);
   });

src/tests/extract-lines.test.ts

@@ -125,7 +125,6 @@ export function applyEnvironmentSettings(settings: ManagedSettings): void {
 
 export interface ExtractLinesResult {
   content: string;
-  actualEndLine: number;
   wasLimited: boolean;
   linesRead: number;
 }
@@ -134,100 +133,55 @@ export interface ExtractLinesResult {
  * Extracts lines from file content with byte limit enforcement.
  *
  * @param fullContent - The complete file content
- * @param linesToSkip - Starting line number (0-based)
- * @param linesToRead - Maximum number of lines to read
  * @param maxContentLength - Maximum number of UTF-16 Code Units to return
  * @returns Object containing extracted content and metadata
  */
 export function extractLinesWithByteLimit(
   fullContent: string,
-  linesToSkip: number,
-  linesToRead: number,
   maxContentLength: number,
 ): ExtractLinesResult {
-  if (fullContent === "" || linesToRead === 0) {
-    if (linesToSkip === 0 && linesToRead > 0) {
-      return {
-        content: "",
-        actualEndLine: 0,
-        wasLimited: false,
-        linesRead: 1,
-      };
-    } else {
-      return {
-        content: "",
-        actualEndLine: linesToSkip,
-        wasLimited: false,
-        linesRead: 0,
-      };
-    }
+  if (fullContent === "") {
+    return {
+      content: "",
+      wasLimited: false,
+      linesRead: 1,
+    };
   }
 
   let linesSeen = 0;
   let index = 0;
-
-  while (linesSeen < linesToSkip) {
-    const nextIndex = fullContent.indexOf("\n", index);
-
-    // There were not enough lines to skip.
-    if (nextIndex < 0) {
-      return {
-        content: "",
-        actualEndLine: linesToSkip,
-        wasLimited: false,
-        linesRead: 0,
-      };
-    }
-
-    linesSeen += 1;
-    index = nextIndex + 1;
-  }
-
-  // We've successfully skipped over all the lines we were supposed to.
-  // Now we can actually start reading!
-  const startIndex = index;
   linesSeen = 0;
 
   let contentLength = 0;
   let wasLimited = false;
 
-  while (linesSeen < linesToRead) {
+  while (true) {
     const nextIndex = fullContent.indexOf("\n", index);
 
     if (nextIndex < 0) {
       // Last line in file (no trailing newline)
-      const newContentLength = fullContent.length - startIndex;
-      if (linesSeen > 0 && newContentLength > maxContentLength) {
+      if (linesSeen > 0 && fullContent.length > maxContentLength) {
         wasLimited = true;
         break;
       }
       linesSeen += 1;
-      contentLength = newContentLength;
+      contentLength = fullContent.length;
       break;
     } else {
       // Line with newline - include up to the newline
-      const newContentLength = nextIndex + 1 - startIndex;
+      const newContentLength = nextIndex + 1;
       if (linesSeen > 0 && newContentLength > maxContentLength) {
         wasLimited = true;
         break;
       }
       linesSeen += 1;
       contentLength = newContentLength;
-      index = nextIndex + 1;
-    }
-  }
-
-  // If we ended with a newline and we stopped due to byte limit or line limit (not end of file), remove the trailing newline
-  if (contentLength > 0 && fullContent[startIndex + contentLength - 1] === "\n") {
-    // Check if there's more content after our current position that we didn't read
-    if (startIndex + contentLength < fullContent.length) {
-      contentLength -= 1;
+      index = newContentLength;
     }
   }
 
   return {
-    content: fullContent.slice(startIndex, startIndex + contentLength),
-    actualEndLine: linesSeen > 0 ? linesToSkip + linesSeen - 1 : linesToSkip,
+    content: fullContent.slice(0, contentLength),
     wasLimited,
     linesRead: linesSeen,
   };