fs: make offset, position & length args in fh.read() optional

PR-URL: #51087Fixes: #47183 Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Vinícius Lourenço Claro Cardoso <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: James M Snell <[email protected]>

Author: pulkit-30

doc/api/fs.md

@@ -385,11 +385,14 @@ added: v10.0.0
 * `buffer`{Buffer|TypedArray|DataView} A buffer that will be filled with the
  file data read.
 * `offset`{integer} The location in the buffer at which to start filling.
-* `length`{integer} The number of bytes to read.
-* `position`{integer|null} The location where to begin reading data from the
- file. If `null`, data will be read from the current file position, and
- the position will be updated. If `position` is an integer, the current
- file position will remain unchanged.
+ **Default:** `0`
+* `length`{integer} The number of bytes to read. **Default:**
+`buffer.byteLength- offset`
+* `position`{integer|bigint|null} The location where to begin reading data
+ from the file. If `null` or `-1`, data will be read from the current file
+ position, and the position will be updated. If `position` is a non-negative
+ integer, the current file position will remain unchanged.
+ **Default:**: `null`
 * Returns:{Promise} Fulfills upon success with an object with two properties:
  * `bytesRead`{integer} The number of bytes read
  * `buffer`{Buffer|TypedArray|DataView} A reference to the passed in `buffer`

lib/internal/fs/promises.js

@@ -642,7 +642,7 @@ async function read(handle, bufferOrParams, offset, length, position){
 validateInteger(offset,'offset',0);
 }
 
-length|=0;
+length??=buffer.byteLength-offset;
 
 if(length===0)
 return{__proto__: null,bytesRead: length, buffer };

test/parallel/test-fs-promises-file-handle-read.js

@@ -14,7 +14,7 @@ const assert = require('assert');
 consttmpDir=tmpdir.path;
 
 asyncfunctionread(fileHandle,buffer,offset,length,position,options){
-returnoptions.useConf ?
+returnoptions?.useConf ?
 fileHandle.read({ buffer, offset, length, position }) :
 fileHandle.read(buffer,offset,length,position);
 }
@@ -96,6 +96,21 @@ async function validateReadLength(len){
 assert.strictEqual(bytesRead,len);
 }
 
+asyncfunctionvalidateReadWithNoOptions(byte){
+constbuf=Buffer.alloc(byte);
+constfilePath=fixtures.path('x.txt');
+constfileHandle=awaitopen(filePath,'r');
+letresponse=awaitfileHandle.read(buf);
+assert.strictEqual(response.bytesRead,byte);
+response=awaitread(fileHandle,buf,0,undefined,0);
+assert.strictEqual(response.bytesRead,byte);
+response=awaitread(fileHandle,buf,0,null,0);
+assert.strictEqual(response.bytesRead,byte);
+response=awaitread(fileHandle,buf,0,undefined,0,{useConf: true});
+assert.strictEqual(response.bytesRead,byte);
+response=awaitread(fileHandle,buf,0,null,0,{useConf: true});
+assert.strictEqual(response.bytesRead,byte);
+}
 
 (asyncfunction(){
 tmpdir.refresh();
@@ -109,4 +124,6 @@ async function validateReadLength(len){
 awaitvalidateReadWithPositionZero();
 awaitvalidateReadLength(0);
 awaitvalidateReadLength(1);
+awaitvalidateReadWithNoOptions(0);
+awaitvalidateReadWithNoOptions(1);
 })().then(common.mustCall());