doc: make sure that calls to .read() are looped

The 'readable' event assumes that calls to readable.read() happens
within that event handler until readable.read() returns null.

Fixes: https://github.com/nodejs/node/issues/20503
PR-URL: https://github.com/nodejs/node/pull/25375
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 15 insertions, 6 deletions

diff --git a/doc/api/crypto.md b/doc/api/crypto.md
index 2605393878..54bbf7794e 100644
--- a/doc/api/crypto.md
+++ b/doc/api/crypto.md
@@ -200,9 +200,10 @@ const cipher = crypto.createCipheriv(algorithm, key, iv);
 
 let encrypted = '';
 cipher.on('readable', () => {
-  const data = cipher.read();
-  if (data)
-    encrypted += data.toString('hex');
+  let chunk;
+  while (null !== (chunk = cipher.read())) {
+    encrypted += chunk.toString('hex');
+  }
 });
 cipher.on('end', () => {
   console.log(encrypted);
@@ -383,9 +384,9 @@ const decipher = crypto.createDecipheriv(algorithm, key, iv);
 
 let decrypted = '';
 decipher.on('readable', () => {
-  const data = decipher.read();
-  if (data)
-    decrypted += data.toString('utf8');
+  while (null !== (chunk = decipher.read())) {
+    decrypted += chunk.toString('utf8');
+  }
 });
 decipher.on('end', () => {
   console.log(decrypted);
@@ -941,6 +942,8 @@ const crypto = require('crypto');
 const hash = crypto.createHash('sha256');
 
 hash.on('readable', () => {
+  // Only one element is going to be produced by the
+  // hash stream.
   const data = hash.read();
   if (data) {
     console.log(data.toString('hex'));
@@ -1033,6 +1036,8 @@ const crypto = require('crypto');
 const hmac = crypto.createHmac('sha256', 'a secret');
 
 hmac.on('readable', () => {
+  // Only one element is going to be produced by the
+  // hash stream.
   const data = hmac.read();
   if (data) {
     console.log(data.toString('hex'));
@@ -1762,6 +1767,8 @@ const hash = crypto.createHash('sha256');
 
 const input = fs.createReadStream(filename);
 input.on('readable', () => {
+  // Only one element is going to be produced by the
+  // hash stream.
   const data = input.read();
   if (data)
     hash.update(data);
@@ -1807,6 +1814,8 @@ const hmac = crypto.createHmac('sha256', 'a secret');
 
 const input = fs.createReadStream(filename);
 input.on('readable', () => {
+  // Only one element is going to be produced by the
+  // hash stream.
   const data = input.read();
   if (data)
     hmac.update(data);