Fixes encoding array readUntil function and add encodeUntil option

Author: Ericbla

README.md

@@ -208,7 +208,12 @@ keys:
   a function. Use number for statically sized arrays.
 - `readUntil` - (either `length`, `lengthInBytes`, or `readUntil` is required)
   If `"eof"`, then this parser reads until the end of `Buffer` object. If
-  function it reads until the function returns true.
+  function it reads until the function returns true. **<u>Note</u>**: When encoding,
+  the `buffer` second parameter of `readUntil` function is the buffer already encoded
+  before this array. So no *read-ahead* is possible.
+- `encodeUntil` - a function (item, object), only used when encoding, that replaces
+  the `readUntil` function when present and allow limit the number of encoded items
+  by returning true based on *item* values or other *object* properies.
 
 ```javascript
 var parser = new Parser()

lib/binary_parser.js

@@ -898,7 +898,6 @@ Parser.prototype.generate_encodeArray = function(ctx) {
   var item = ctx.generateTmpVariable();
   var itemCounter = ctx.generateTmpVariable();
   var maxItems = ctx.generateTmpVariable();
-  var maxOffset = ctx.generateTmpVariable();
   var isHash = typeof this.options.key === "string";
 
   if (isHash) {
@@ -928,7 +927,10 @@ Parser.prototype.generate_encodeArray = function(ctx) {
   );
 
   ctx.pushCode("var {0} = 0;", itemCounter);
-  if (typeof this.options.readUntil === "function") {
+  if (
+    typeof this.options.encodeUntil === "function" ||
+    this.options.readUntil
+  ) {
     ctx.pushCode("do {");
   } else {
     ctx.pushCode("for ( ; {0} < {1}; ) {", itemCounter, maxItems);
@@ -958,9 +960,19 @@ Parser.prototype.generate_encodeArray = function(ctx) {
 
   ctx.pushCode("}"); // End of 'do {'  or 'for(...) {'
 
-  if (typeof this.options.readUntil === "function") {
+  if (typeof this.options.encodeUntil === "function") {
     ctx.pushCode(
-      " while (!({0}).call(this, {1}, {2}.toBuffer()));",
+      " while ({0} < {1} && !({2}).call(this, {3}, vars));",
+      itemCounter,
+      maxItems,
+      this.options.encodeUntil,
+      item
+    );
+  } else if (typeof this.options.readUntil === "function") {
+    ctx.pushCode(
+      " while ({0} < {1} && !({2}).call(this, {3}, {4}.toBuffer()));",
+      itemCounter,
+      maxItems,
       this.options.readUntil,
       item,
       savSmartBuffer

package.json

@@ -1,6 +1,6 @@
 {
   "name": "binary-parser-encoder",
-  "version": "1.3.2",
+  "version": "1.4.0",
   "description": "Blazing-fast binary parser builder",
   "main": "lib/binary_parser.js",
   "devDependencies": {

test/zz_encoder_bugs.js

@@ -0,0 +1,147 @@
+var assert = require("assert");
+var Parser = require("../lib/binary_parser").Parser;
+
+describe("Specific bugs testing", function() {
+  describe("Array encoder with readUntil", function() {
+    it("should limit to array length even if readUntil is never true", function() {
+      var parser = Parser.start()
+        .uint16("len")
+        .array("payloads", {
+          type: new Parser().uint8("cmd").array("params", {
+            type: new Parser().uint8("param"),
+            readUntil: function(item, buffer) {
+              return buffer.length == 2; // Stop when 2 bytes left in parsed buffer
+            }
+          }),
+          lengthInBytes: function() {
+            return this.len - 4;
+          }
+        })
+        .uint16("crc");
+
+      var buffer = Buffer.from("0008AAB1B2B3FFFF", "hex");
+      var decoded = parser.parse(buffer);
+
+      assert.deepEqual(decoded, {
+        len: 8,
+        payloads: [
+          {
+            cmd: 170,
+            params: [
+              {
+                param: 177
+              },
+              {
+                param: 178
+              },
+              {
+                param: 179
+              }
+            ]
+          }
+        ],
+        crc: 65535
+      });
+
+      var encoded;
+      // Although readUntil is never true here, the encoding will be good
+      assert.doesNotThrow(function() {
+        encoded = parser.encode(decoded);
+      });
+      assert.deepEqual(encoded, buffer);
+    });
+
+    it("is not the reverse of parsing when readUntil gives false information", function() {
+      var parser = Parser.start()
+        .uint16("len")
+        .array("payloads", {
+          type: new Parser().uint8("cmd").array("params", {
+            type: new Parser().uint8("param"),
+            readUntil: function(item, buffer) {
+              return buffer.length <= 2; // Stop when 2 bytes left in buffer
+            }
+          }),
+          lengthInBytes: function() {
+            return this.len - 4;
+          }
+        })
+        .uint16("crc");
+
+      var buffer = Buffer.from("0008AAB1B2B3FFFF", "hex");
+      var decoded = parser.parse(buffer);
+
+      assert.deepEqual(decoded, {
+        len: 8,
+        payloads: [
+          {
+            cmd: 170,
+            params: [
+              {
+                param: 177
+              },
+              {
+                param: 178
+              },
+              {
+                param: 179
+              }
+            ]
+          }
+        ],
+        crc: 0xffff
+      });
+
+      var encoded = parser.encode(decoded);
+      // Missing parms 178 and 179 as readUntil will be true at first run
+      assert.deepEqual(encoded, Buffer.from("0008AAB1FFFF", "hex"));
+    });
+
+    it("should ignore readUntil when encodeUntil is provided", function() {
+      var parser = Parser.start()
+        .uint16("len")
+        .array("payloads", {
+          type: new Parser().uint8("cmd").array("params", {
+            type: new Parser().uint8("param"),
+            readUntil: function(item, buffer) {
+              return buffer.length == 2; // Stop when 2 bytes left in buffer
+            },
+            encodeUntil: function(item, obj) {
+              return item.param === 178; // Stop encoding when value 178 is reached
+            }
+          }),
+          lengthInBytes: function() {
+            return this.len - 4;
+          }
+        })
+        .uint16("crc");
+
+      var buffer = Buffer.from("0008AAB1B2B3FFFF", "hex");
+      var decoded = parser.parse(buffer);
+
+      assert.deepEqual(decoded, {
+        len: 8,
+        payloads: [
+          {
+            cmd: 170,
+            params: [
+              {
+                param: 177
+              },
+              {
+                param: 178
+              },
+              {
+                param: 179
+              }
+            ]
+          }
+        ],
+        crc: 0xffff
+      });
+
+      var encoded = parser.encode(decoded);
+      // Missing parms 179 as encodeUntil stops at 178
+      assert.deepEqual(encoded, Buffer.from("0008AAB1B2FFFF", "hex"));
+    });
+  });
+});